Radiation Protection

RADIOLOGICAL PROTECTION

TABLE OF CONTENTS

 _ 

BASIC PHYSI CS ........... ................................. ............................ ............. .............. ............. ............ .............. ................... ............. ..... ........................ ....................... ...... ........... ................. ........ R SI Elements

.... ..... ....... ......... .... ......... ........... ....... ..... .... .... .... ..... .............. ................. ..... .... .... ..... ..... .... ....... ........ ........ ........ .......... ................... .............. ....... ..... ......... ..... ...... ......... ... .....

RS

1-

............... ...... .... ..... ...... ........ ..... ..... ........ .................. ................. .......... ........ ..... ..... ......... ......... ...... ..... ......... ............. ............. ............ ...... ..... ..... ..... ............ ......... ...... ..... ........ ..... RS

Atoms At oms

1

1- 1

Iso Is otop topes. es....... ........ ............... ............. ....... ...... ........ .... .... .... ........ ....... ........... ............... ........... .... ..... ............. ..................... .............. ................... .................. ............ .......... .......... ............ .... R S

1 -2

I

-2

Ions

............ ....... ..... .... .... .......... ...... ...... ....... .... ..... ........ ....... ......... ......... ....... ........ ........ ....... ....... .... ..... ........ ......... .......... ....... ......... ......... ......... ..... .... ............... .................. ............ ............ ......

Molec Mole cules

R S

...... .. ................. ... .......... ........... ............... ............ ....... ....... ................ ............. ...... ................ ..................... ................... ................ ...... ......... ............ ...... ........... ........ R S 1-2

Radionuclide s (radio (radio--i sotopes) ...... .......... ............. .............. .................. .............. ........ ....... ............ ........... ........... ........ ............... .................... ........... ............... R S 1 -2 'J -ypes of r adration adration .... ............ ............... ........... ........ ........ ...... ...... ........ ..... ...... ..... ...... ..... ................ ................ .... ...... ......... .......... ...... ........... ............... ........... ........ ..... ......... ..... .....RS 1-3 Acti tivity vity .......... ............... .......... ..... .... .... .... ........ ..... .... ........ .......... ....... ......... ........ ...... ...... ..... ............ ......... .... ......... ...... .... ..... ....... ...... ..... ....... .... .......... ........... ........ ....... ......... ......... .......... ..... RS 1 -5 Dec ecay ay ........... ............... ...... ..... ....... ..... ........ .......... .... ........ ......... ...... ......... ......... ......... ........... .............. .......... ....... ...... ..... .......... ............ ........... .......... ....... ............. .....···· ········ ······ ······· ····- - RS l -6

Ioni Io ni sation ... ....... ...... ..... ...... ........... ........ ...... ........ .......... ......... ......... ..... .......... ....... ..... .... .... .... ....... ..... ..... ........ .......... ........ ...... ............ ........ .... ....... ........... .... ..... ...... ........ ............... RS 1-6 ABSORPTION AND SCATIERJNG ...... .................. ................ ..... ....................... ............................................................ ......... ........... .. R SlA Sl A

RADIOGRAPIDC EQU1Pl\I EQU1Pl\IIIENT ... .......... ...... ........ ...................... ........................... ................... ........ ....... ............. ........... ..... .......... .......................... ....................... ........R S2 Gamma sources .. .......... ......... ............ ......... .... .... .... .... ..... ...... ..... .... .... .... ..... .......... ...... ............ ............. ........ ...... ......... ............. ......................... ........................... ................ ......... RS2RS2-II X -ray

sour ces..... sour  ces........... ......... ....... ................. .................. ............ ........ ...... ......... ...... ..... ....... ...... ........ ........ ........... .......... ..................... .................. ......... ..... .... ..... ..... ........... ....RS2 .RS2--4

RADIATION UNITS .............. ............. .... ........ ............................................ ..................................... ............................ lS3 Activ Act iviity

....... .... ........ ..... ..... .......... ........ ........ .................... ................... ........ ....... ..... ............. ....................... ...................... .......... ..... ................... .......................... ...... ..... ....... .... ..... ........ ..... ....RS3-

I

Dose or exposure .................. .. ....................... ..................... .. ............. ......................... ............... ..... .... ...... ........ ....... ..... ............. ............. ......... ...... ........ ...... ..... ....... ...... RS3- l

Absorbed dose (kerma) ...... .............. ...................... ................ ........ ...... .... .... .... ...... .......... ........... .......... ......... ....... .... ....... ........ .......... ....... ...... ...... ...... ...... .... ............. ....RS3-l RS3-l Dose

Dose Do se

equivallen equiva entt

RS3-- 1 RS3

........... .... ............. ............... .............. ......... ...... ....... ............ .......... ...... ...... .......... ........ .............. ................... ............ .......... ............ .... ..... ......................

rate ... .............. ....... ..... ..... .... ..... ......... ........ ........ ..... ..... ..... ......... ........ ..... ....... ........ ............ ......... ........ ............... ........ ...... ........ ....... ......... ................ ................ ............. ......... RS3 -2

BIOLOGICAL BIOLOGI CAL EFFECTS EFFECTS.............................. ............................ ... ..................... ................... ..... ............... .......................... ........................ .......... RS4

Overview .. ...... ..... ................. .................. ......... ....... .......... ..... ........... .............. ............... ............. ....... ........................ ........................ .......... .............. ........... ........ .... .... ........ ............... RS4 RS4-- l Somat So mat ie effects ..... ........... .......... .... ...... ....... ......... ................. ............. ..... ......... ...... ....... ........ ........ ...... ................. .................. ...... ............... ..... .......... ..... ........ ............. ......... RS4-l Genetic effects ......... ........... .... ..... ....... ...... ...... ....... ..... ................... ................. .............. .................. ......... ......... .......... ............ .......... ..... .......... ....... ................. .............. ............. RS4 -2 Othe herr

defi efin n itio ition n s.. .... .... .................... .................. ........... ............ .... .... ..... .............. .............. .......... ............... ..... .... .... .... .......... ........... ..... ..... ...... ........ .... ....... ......... ........ ......... ...... RS RS4 4 -2

DOSE LIMITS ............ ................ ........... ......... ..... ....... ...... ................................. ............................. ....... ......... ...................... ........................... ............ ................. .................. ..... .......... .............. RS RSS S RADIATION DET DETECTION ECTION AND MEASUREMENT ....................... ........... .................... ............... ........... .................. ............. ..... .....RS6 Dose

ratemeters rat emeters

.... ..... .... ...... ........ ..... ..... .......... ............ ..... ...... ......... ..... .... ........ .......... ........ ..... .......... ........... ......... ....... ............. ............ ........ ...... ....... ....... ........... ........... .......... RS6 RS6-- I

Per  Pe r sonal sonal dosemeters ..... ......... ....... .................... .................... ...... ........ .... .... .... ......... ........... .......... ........ .............. ................. ..... ...... ........ .......... ........ ...... ............. ................ ....... R S6-2

Pocket d osemete osemeter  r s (expos (exposure ure mete m eter  r s) s) ........... ............. .................... .................. .......... ................ ................ ............ .......... .... ....... ....... ..... ......... ............. R S6-3 Aud ibl ible e alarms alarm s ( pocket  pocket types) types).. ............... ............ ..... ........ ................. ................... ......... ................. ............ ..... ..... ......... ............. ...... .... ....... .... ........ ....... ........ ........ RS6 RS6--3 PROTECTION

AGAJNST RAD RADIA IATIO TIO N.  N..... ................. .............. .............. ............... ...... .............. ................. ............ .............. ................ ............ ......... ...... ...... ....... R S7 S7

Controll Con trolled ed and super  super -vised -vised areas ... ....... ......... ..... .... ...... .................. .......................... .................. ........ .... ......... ........... ........ ............ ....... ........... .......... .... .... ....... ..... .... .... R S7

1

The inverse squa squar  r c law .... ............ .............. ........ ......... ...... ..... ...... ...... ...... ...... .......... ...... ...... ....... .... ........ .......... .......... ............. ................. ................. ........ ......... ...... ..... ........ R S7 S7-3 -3

Sh ielding ding.. ..... ..... .... .... .... ..... ...... ................. ...................... ................... ........... ........... ............ ......... ......... .... ......... ...... ......... ......... ...................... ...................... ..... ....... ....... ..... ..............

R S7-4

H TV!TVT ... .............. .............. ....... ................ ............... ...... ........ ...... ......... ........... ........ .......... ............ ............... .............. ......... ............ ............ ............... ................. ....... ...... ........... ..... R  R S S7-5 CAL CA LCULATIO NS FOR RADIATIO N PROTECfiO N ..... ..... .......... ............... .......................................... ..................................... .......... ........R  R S7A S7 A TORAGE TO RAGE OF RADIATION SOURCES SOURCES... .................... ........................... ......... ......... ................. ............ ..... .................... .................. ........ ........ ........... ......... ..... R S8 S8 Gamma so sou u r ces ... ................ .................. ......... ......... ..... ....... ....... ...... ........................ ..... .......... ......... ....... ............... ....................... ............ ...... .......... X-ray

 _ _  _  _  _

R S8S8- l

ma ch i n cs cs........... ...................... ............ .......... ........ .... .... .... .... ..... ................ ................ ....... ...... .......... ....... ......... ......... ..... .............. ................ ...... .......... ....................... ................ R S8S8- I

TRANSPORT OF RADIOACTIVE SUBSTANCES ................................................................ ........... R S9 S9

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TABLE OF CONTENTS

 _ 

BASIC PHYSI CS ........... ................................. ............................ ............. .............. ............. ............ .............. ................... ............. ..... ........................ ....................... ...... ........... ................. ........ R SI Elements

.... ..... ....... ......... .... ......... ........... ....... ..... .... .... .... ..... .............. ................. ..... .... .... ..... ..... .... ....... ........ ........ ........ .......... ................... .............. ....... ..... ......... ..... ...... ......... ... .....

RS

1-

............... ...... .... ..... ...... ........ ..... ..... ........ .................. ................. .......... ........ ..... ..... ......... ......... ...... ..... ......... ............. ............. ............ ...... ..... ..... ..... ............ ......... ...... ..... ........ ..... RS

Atoms At oms

1

1- 1

Iso Is otop topes. es....... ........ ............... ............. ....... ...... ........ .... .... .... ........ ....... ........... ............... ........... .... ..... ............. ..................... .............. ................... .................. ............ .......... .......... ............ .... R S

1 -2

I

-2

Ions

............ ....... ..... .... .... .......... ...... ...... ....... .... ..... ........ ....... ......... ......... ....... ........ ........ ....... ....... .... ..... ........ ......... .......... ....... ......... ......... ......... ..... .... ............... .................. ............ ............ ......

Molec Mole cules

R S

...... .. ................. ... .......... ........... ............... ............ ....... ....... ................ ............. ...... ................ ..................... ................... ................ ...... ......... ............ ...... ........... ........ R S 1-2

Radionuclide s (radio (radio--i sotopes) ...... .......... ............. .............. .................. .............. ........ ....... ............ ........... ........... ........ ............... .................... ........... ............... R S 1 -2 'J -ypes of r adration adration .... ............ ............... ........... ........ ........ ...... ...... ........ ..... ...... ..... ...... ..... ................ ................ .... ...... ......... .......... ...... ........... ............... ........... ........ ..... ......... ..... .....RS 1-3 Acti tivity vity .......... ............... .......... ..... .... .... .... ........ ..... .... ........ .......... ....... ......... ........ ...... ...... ..... ............ ......... .... ......... ...... .... ..... ....... ...... ..... ....... .... .......... ........... ........ ....... ......... ......... .......... ..... RS 1 -5 Dec ecay ay ........... ............... ...... ..... ....... ..... ........ .......... .... ........ ......... ...... ......... ......... ......... ........... .............. .......... ....... ...... ..... .......... ............ ........... .......... ....... ............. .....···· ········ ······ ······· ····- - RS l -6

Ioni Io ni sation ... ....... ...... ..... ...... ........... ........ ...... ........ .......... ......... ......... ..... .......... ....... ..... .... .... .... ....... ..... ..... ........ .......... ........ ...... ............ ........ .... ....... ........... .... ..... ...... ........ ............... RS 1-6 ABSORPTION AND SCATIERJNG ...... .................. ................ ..... ....................... ............................................................ ......... ........... .. R SlA Sl A

RADIOGRAPIDC EQU1Pl\I EQU1Pl\IIIENT ... .......... ...... ........ ...................... ........................... ................... ........ ....... ............. ........... ..... .......... .......................... ....................... ........R S2 Gamma sources .. .......... ......... ............ ......... .... .... .... .... ..... ...... ..... .... .... .... ..... .......... ...... ............ ............. ........ ...... ......... ............. ......................... ........................... ................ ......... RS2RS2-II X -ray

sour ces..... sour  ces........... ......... ....... ................. .................. ............ ........ ...... ......... ...... ..... ....... ...... ........ ........ ........... .......... ..................... .................. ......... ..... .... ..... ..... ........... ....RS2 .RS2--4

RADIATION UNITS .............. ............. .... ........ ............................................ ..................................... ............................ lS3 Activ Act iviity

....... .... ........ ..... ..... .......... ........ ........ .................... ................... ........ ....... ..... ............. ....................... ...................... .......... ..... ................... .......................... ...... ..... ....... .... ..... ........ ..... ....RS3-

I

Dose or exposure .................. .. ....................... ..................... .. ............. ......................... ............... ..... .... ...... ........ ....... ..... ............. ............. ......... ...... ........ ...... ..... ....... ...... RS3- l

Absorbed dose (kerma) ...... .............. ...................... ................ ........ ...... .... .... .... ...... .......... ........... .......... ......... ....... .... ....... ........ .......... ....... ...... ...... ...... ...... .... ............. ....RS3-l RS3-l Dose

Dose Do se

equivallen equiva entt

RS3-- 1 RS3

........... .... ............. ............... .............. ......... ...... ....... ............ .......... ...... ...... .......... ........ .............. ................... ............ .......... ............ .... ..... ......................

rate ... .............. ....... ..... ..... .... ..... ......... ........ ........ ..... ..... ..... ......... ........ ..... ....... ........ ............ ......... ........ ............... ........ ...... ........ ....... ......... ................ ................ ............. ......... RS3 -2

BIOLOGICAL BIOLOGI CAL EFFECTS EFFECTS.............................. ............................ ... ..................... ................... ..... ............... .......................... ........................ .......... RS4

Overview .. ...... ..... ................. .................. ......... ....... .......... ..... ........... .............. ............... ............. ....... ........................ ........................ .......... .............. ........... ........ .... .... ........ ............... RS4 RS4-- l Somat So mat ie effects ..... ........... .......... .... ...... ....... ......... ................. ............. ..... ......... ...... ....... ........ ........ ...... ................. .................. ...... ............... ..... .......... ..... ........ ............. ......... RS4-l Genetic effects ......... ........... .... ..... ....... ...... ...... ....... ..... ................... ................. .............. .................. ......... ......... .......... ............ .......... ..... .......... ....... ................. .............. ............. RS4 -2 Othe herr

defi efin n itio ition n s.. .... .... .................... .................. ........... ............ .... .... ..... .............. .............. .......... ............... ..... .... .... .... .......... ........... ..... ..... ...... ........ .... ....... ......... ........ ......... ...... RS RS4 4 -2

DOSE LIMITS ............ ................ ........... ......... ..... ....... ...... ................................. ............................. ....... ......... ...................... ........................... ............ ................. .................. ..... .......... .............. RS RSS S RADIATION DET DETECTION ECTION AND MEASUREMENT ....................... ........... .................... ............... ........... .................. ............. ..... .....RS6 Dose

ratemeters rat emeters

.... ..... .... ...... ........ ..... ..... .......... ............ ..... ...... ......... ..... .... ........ .......... ........ ..... .......... ........... ......... ....... ............. ............ ........ ...... ....... ....... ........... ........... .......... RS6 RS6-- I

Per  Pe r sonal sonal dosemeters ..... ......... ....... .................... .................... ...... ........ .... .... .... ......... ........... .......... ........ .............. ................. ..... ...... ........ .......... ........ ...... ............. ................ ....... R S6-2

Pocket d osemete osemeter  r s (expos (exposure ure mete m eter  r s) s) ........... ............. .................... .................. .......... ................ ................ ............ .......... .... ....... ....... ..... ......... ............. R S6-3 Aud ibl ible e alarms alarm s ( pocket  pocket types) types).. ............... ............ ..... ........ ................. ................... ......... ................. ............ ..... ..... ......... ............. ...... .... ....... .... ........ ....... ........ ........ RS6 RS6--3 PROTECTION

AGAJNST RAD RADIA IATIO TIO N.  N..... ................. .............. .............. ............... ...... .............. ................. ............ .............. ................ ............ ......... ...... ...... ....... R S7 S7

Controll Con trolled ed and super  super -vised -vised areas ... ....... ......... ..... .... ...... .................. .......................... .................. ........ .... ......... ........... ........ ............ ....... ........... .......... .... .... ....... ..... .... .... R S7

1

The inverse squa squar  r c law .... ............ .............. ........ ......... ...... ..... ...... ...... ...... ...... .......... ...... ...... ....... .... ........ .......... .......... ............. ................. ................. ........ ......... ...... ..... ........ R S7 S7-3 -3

Sh ielding ding.. ..... ..... .... .... .... ..... ...... ................. ...................... ................... ........... ........... ............ ......... ......... .... ......... ...... ......... ......... ...................... ...................... ..... ....... ....... ..... ..............

R S7-4

H TV!TVT ... .............. .............. ....... ................ ............... ...... ........ ...... ......... ........... ........ .......... ............ ............... .............. ......... ............ ............ ............... ................. ....... ...... ........... ..... R  R S S7-5 CAL CA LCULATIO NS FOR RADIATIO N PROTECfiO N ..... ..... .......... ............... .......................................... ..................................... .......... ........R  R S7A S7 A TORAGE TO RAGE OF RADIATION SOURCES SOURCES... .................... ........................... ......... ......... ................. ............ ..... .................... .................. ........ ........ ........... ......... ..... R S8 S8 Gamma so sou u r ces ... ................ .................. ......... ......... ..... ....... ....... ...... ........................ ..... .......... ......... ....... ............... ....................... ............ ...... .......... X-ray

 _ _  _  _  _

R S8S8- l

ma ch i n cs cs........... ...................... ............ .......... ........ .... .... .... .... ..... ................ ................ ....... ...... .......... ....... ......... ......... ..... .............. ................ ...... .......... ....................... ................ R S8S8- I

TRANSPORT OF RADIOACTIVE SUBSTANCES ................................................................ ........... R S9 S9

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UNIT RSl · BASIC PHYSICS

Ruane & 11 T P O'  O' N ei/1

NOTES

ELEMENTS An element is a su bs  bstt a nce tha thatt cannot cannot be  be se parated into any oth ther er cons constitu tituen entts. This statement is with r efer  efer ence ence to the chemica chemicall na narure onl nly y. 10

There are over one hund undr  r ed ed elements known to man and the these se have have b  be ecn cn plac  place ed w1thin a ta b  ble le referr ed to as the  p eriodic table elementss into group roupss and  periods table;; th is  places element with refere refe rence nce to th the eir chemi emic cal chara racte cter  r isti istic cs.

Hydroge Hydro gen n (H) is th the e lightest element and is tak en en as the ref  re f ere erenc nce e element element.. Hehu m (He), neo eon n (Ne), argo argon n {Ar), krypton (Kr) and xenon (Xe) are grouped together   because th these ese a re in ine ert gases or gases that that cann cannot ot react chemicall hemically y wit with h ot.h t.he er cle clem m en entts.

20

The halogen group incl inclu u des flu fluorine orine (F), (F), c hl hlo orin rine e (C (CII), ), bromin  bromin e (Br ) and iodine (1); these ar e very active el element ntss wh whiich readi ly combine combine with mos m ostt of th the e oth othe er elcme cments nts in th the e tab ablle. Elements r ange Elemen ange from hydrogen h ydrogen (H), with wi th an atomic numb numbe er of 1, to ur anium (U) w ith an atomic num be  berr 92  be etween these these are ali ali the the element.s element.s that that make up everything on 92;; b earth eart h.

JO

ATOMS 4

o

An atom is the the smallest part of an element that can ha hav ve th the e eleme lemen nt's t's propertie  properties. s. A li atoms of the same e lemen entt are similar in construction, how owe ever, atoms of diff erent erent elements have differ ent co constructions nstructions.. An atom is a very sm all particle which is made up from a numbe umberr of sub sub--atom atomiic  pa rtic  parti cles grouped toge t ogetther . The size of the the sub-atomic sub-atomic pa  particles rticles are smal smalt, t, w ith mo mosst of  eac ea ch ato atom m co consistin nsisting g of fr ee ee space space..

50

The su b b-atomi atomic c  parti  partic cles in the centr e (core or or nucleus) of ea ch atom contain the heavier  part  partiicles co con n sisting of of proton  protonss whi whic ch carry a  positi  positive ve char ge., and neu eutr  tr ons which carry n o cha char  r ge. ge. Protons and neutron neutronss bav  bave e an unu unussu al a ttr action action f or or each ot oth h er  and tend to to pair  pair toge togeth ther. er. TI1e TI1 e li ligh ghtter  particle  particles, s, electro ectron ns, are said to  b  be e h eld in stable or   bitss around the  bit the nu nucle cleu us  by th the e attrac attraction tion of th the e  protons in the nu nuc cleus. These orbits orbits are r eferred eferred to as s  sh hell   s , e.g .g.. K, L, M shells shells..

60

There are ot oth her sub ub-a -attom ic  particles, e.g e.g.. th the e  po  posi sitr  tr on, whic which is of sin1i sin1illar size and and m ass to the ele lec ctr on b  but ut with w ith a posi  posittive charge.

Sub--atomic particles Sub

10

•

•

so

•

Protons are th the e heav ies estt particles particl es and are fo found und i.n th the e nu nucleus. cleus. to··27 kg  positively  pos itively char gcd gcd and h ave a r est est ma mass ss of 1.673 x to kg..

They The y ar e

 Nc utro  Ncu tron n s are simi simillar in mass to a p a  pro rott on havin having g a r est est m ass of 1. 1.675 675 x 10 10""2 1 k g. ·rney have no rney no ch a r ge, ge, a r e neutra! and and are f ound ound in the the nu nucleus. cleus.

Elcctrons ar e sm sma a ll ll,, very li lig ght weight  particl es and ha have ve a r est est ma ss of  9.109 x 1011 · K g. Th They ey ha have ve a negat n egativ ive e charge charge an and d orbit orbit th the e nucleus in r estricted shell she llss acc acco or ding ding to the cules of of quantum mec echanics. hanics.

Atoms will have have the sa same me number of  pro  prottons an and d ele elec ctron tronss when the atom is in cquili cqui li brium  brium,, i .e. wh whe en it is not an ion ion.. 90

A to tomic mic number  numbe r  The atomic number or Z numbc umbcrr is the total tota l number of of prot  protons ons in th the e nucleus an and d this dcfin dcfi nes the element, e.g. Il = 1;He = 2; C = 6; O = 8.

100

' R •: n  nc c & r r o·.s m

•

h; c•

t.a..Ot..'O t.a t..'Oll

n st -1

TABLE OF CONTENTS APPOINTMENTSIRESPONSIBILITIES ..... ....... ....... ..... ........ ......... ................ ............... ...... ...... ....... ......... ........... ......... ....... ..... .... ............ .............. ........ ....... ... RSIO R a di dia ati on Protection

Advisser (RPA) ...... Advi ............. ..... ...... .......... ....... ........ .... ..... ..................... .................. ....... ..... ...... ........... ............ ........... ......... RS I O-l

Radiation Protec rotectt ion Supervisor (RPS) .. .... ...... .... ....... ..... .......... ................ ........... ........ .............. ............. ..... .... .... ...... ..... ......... .......... ......... ......... .... ....... RS 1010- 1 Classified Pe Person rson .. .......... ............. ....... ..... ............... ................. .......... ....... ........ .......... ..... ........... .......... ...... ....... ......... ........ ..... ..... ...... ...... .... .... ...... .... ...... ....... ....... .... ....... ........ ..... RS 10-1 Qualified

LOCAl,

Person

RULES

Local

&

....... ..... .... ..... ............. ................ .................... ..................... ......... .............. ...................... ............. ....... ........ ...... .......... .......... .... ......... ......... ...... ............. ........... .... RS 1 0-2

CONTINGENCY

PLANS................. PLANS............... ..... ......... ........ ............ ............. ..... ........ ..... .... ..... ................. .............. ........... .............. ..... RS RSII II

r u les ...... ....... ....... ....... ............. ........... .. ..... ..... .... .... ................ ................ ................ .................. ........ ......... ........ ......... ......... ......... ............... ............. ....... ..... .. ...... ........... ............. RS 1 1-1

Contingency plans .... ........ ...... ....................... ...................... ...... ........... ............ ......... ......... ...... ........... ................ ... ........ ........ ........... .......... ..... ..... ..... ........... ............ ..... RS 1 l- 1

PERSONAL DOSIMETRY ... ...... ....... .......................... .......................... ....... ......... .......... ...... ..... ............ ............................... .............................. ................... ................. .......... ... RS 12 Classification ......... ....................... ................. ..... ......... ......... .......... ................... ............... ............. ................ ......... ................. ................. ........ .............. ............ ......... ..... ..... ....... .... ... RS 12 12-1 -1 Medica Medi call sur veilla vei llan nce ........ .......... ....... ......... ...... ........................... ........................... .... .. .. .... ..... ......... ........ .... ....... ....... .... ...... .... ..... ....... ...... ........ ........ ........ .............. .......... .... .. RS 12 12-- 1

Dose assessments ........... ............... .... .......... .................. .............. .... .... .... ..................... ................. ................... .... ....................... ..................... ..... ............ .............. ....... RS 122-2 2 The AL ALARP ARP p  prin rinciple ciple ... .......................... ....................... .. .... ........... ............. .................... .................. ........ .......... ............ .............. ...... ............. ..................... ........ ...... .... ..... RS 12-2 Exposure/o Exposure /overexposure verexposure investigat ion ions.................................... s.................................... ... ....... .................................................. .. RS 12 12--2

The Ionising Radiation (Ou (Outtside Workers) Re Regu gullation ationss.............. ......................... .............. ................ ...... ........ .... RS 12-3 Per sonal sonal dosime dosim etry r ecords ecords ....... ..... ............ .......................... ........ .......... ..... .... ..... .......................... ....................... ....... ......... .......... ............. ......... ....... .... .... .. RS RS1 12-4

RADIATION SAFETY RELATED RELA TED CONTAC CONTACTS TS ......... ..... ........... .......... ........... ............ ........................... ........................... ......... .....APPEN APPEN DIX A

 NORMATIVE DOCUMENTS DOCUMENTS..... ..... ...... ......................... ............................... .............. ..... ......... ............. ........ ..... ...... ............. .................. .......... ......... .......APPENDIX APPENDIX B

l ·R uar.t" uar.t" •

S:.

T P O"NdJI

1-.. uc: 6 l-1/ l-1/U U(Y{Il

Ruane & 1/  T P O'Nei/1

UNIT RSl

Ruane & Il  T P O'Nei/1 ·

BASIC PHYSICS

Every radionuclid radionuclide e has a half life, th this is is the th e time time it tak es es for th the e activity to drop to one half of its initi half initial strength; this varies fr om a fr action action of a seco second nd f or some isoto p  pes es and to thousands of years for others.

OTES.. OTES

 ·IS n term which ·Act1v11y IS re1ates to the number of disintegrotions per disintegrotions  per 11nit 

10

i s mcnsur  mcnsur etf  etf  in bec becqu qucre crel   s l  (Bq)or (Bq) or Cu Curi rie e s III IIC.  A CII V i  ii)' i )'

 Natural occurring radionuclides There are two ma in radionucl radionucliides which occur natura!ly: rad rado on and rad ium ium.. R adon b adon  bas as a half life of 3.8 3.82 25 days and r adi adium has has a half lif e of 1,5 ,590 90 years. y ears.

( C  C1). 1  ).

 Radwm prorluces ratfon ratfo n

 gru..  gru

•

20

Radium 226 is no longer used for r adio adiog gr aph aphy  becaus  becausee of th thee hazards hazards presente present ed by its it s a l pha  ph a decay decay and ils gascous radioa radioacctive daughter rad radon. on. Bones ar e espect all ally y susce ptihle to rlam:ct ge: f rom rom ra rad diation emitted from radium 226.

Artificia l radionuclides Art1ficially  produ ced radionuclides have replaced natural radionuclidcs fo forr use in industria dustriall radio radiog graphy raphy.. T11ere are three three methods of produc produ cin ing g artifi artific cial ra radionuclid dionuclides: es: 30

1.

 Ne  N eutron activation (ne (neutr  utr on bo on bomb mbardment ardment in a rea reac ctor ). ).

2.

Fission produ Fission  produc ce separatio separation. n.

3.

Charged p Charged  particle article bombardment  bombardment (via high energy x -ray machine).

The Th e mos ostt widely use u sed d radioisotopes are shown in the following following tabl table e: 40

Isoto pe

To convert R/h!Ci to  pSvl/v G Bq  Bq.. d1vitf e by 37  then multrply by 10.000 .

50

Co60 Cs137 Irl92 Th170 Th1 70 Yt169 Se75

Halflife Hal flife

5.27 years 30.1 30. 1 years 74 .3 da day ys 129days 31 days 118.5 11 8.5 days

Output @ 1m 1.32 0.3 .33 3 0.48 0.0025 0.13 0.203

J.tSv//h/GBq J.tSv

Steel Steel thickness

357 89..2 89 130 0.68 34 54..86 54

50 -20 -200mm 0mm 2525 - IOOmm 6 - 90 nun up to 12 12 mm up to 17 mm 2-70 mm

Co balt 60 (Co60) (Co60) JS produ ced by bombard ing Co59 with n eutrons in a rea reac ctor. 60

 Natural iridium occ ccurs urs as two iissotop otopes, es, lr19 1 and Tr1 Tr193. 93.  bombarding Ir Ir1 191 with ne neutrons in a reac reactor .

l.r192 l.r19 2 is  produ  produced ced  by

Cae aessium 137 is one of the mos most common common products  products of nu nuclear clear fission and is generated in gr eat eat a bundance in ali nu nuclear clear react reacto or s. The main difficu diffi cult lty y is in se paratin g t hi hiss elem en entt from other fiss fissiion products product s and the uranium fuel. 70

Thulium 169 is on on e of th the e rar e earth elem leme en ts and and b  beca ecau u se it is extremely ex tremely difficu diffi cu lt t o  produce, it is generally used as an oxid oxide. e. Thall Thalliium 170 1 70 is  produc  produce ed from Th 169 by thenna th ennall neutron capture.

 Fission '  ·is the diSmtegrallon of n hcavy at omic omic nurleus illlo smaller. illlo smaller. lightcr   fr a g ments.

80

TYPES OF RADIATION

E lectromag ectromagn n et etiic radiation The electromagnetic s p  pec ectrum trum o

Ali wavcs in the th e electro electrom m agnetic s pectrum  pectrum travel in an undul a t ing fashion fashion.. Quantum th t:ory tht: ory states that these undulation undulationss ar e not con continuou tinuouss wa wa vcs vcs bur  bur consis consistt o f quanta . or   pac  p ackages kages of ener gy gy (ph (photons) trave ravellin lling g in quick succ success essiion likc likc bullets  bullets fu fue ed from a mac ma chinc gun. Each p Each pac ack  k et et of energy ha hass a co combination mbination of wave wavellengths. A wa ests of a wave. wave . TI1e wav vele elen n g th th (i. = lambda} is the distance betwecn two adjacent cr ests shortcr the wavel wavelength, th thc c mor e p  pe en etrating th the e ra ray y.

100

RS1-3

UNIT RSI · BASIC PHYSICS

Ruane & Il  T P O'Neil/ 

Mass number 

 NOTES

The mass number or  A number essentially refers to the weight of an atom and is the  A) number f or He = 4, C = 12 number of protons and neutrons in the nucleus. Mass (  10

and O

==

16.  Note that the mass number is not always twice the atomic number.

ISOTOPES 20

Elements that have the same number of protons  but differcnt numbers of ncutrons are varieties of the same element and are called isoto pes. 1 Among the 3100 or so kno"l.vn 2 clemcnts thcrc arc somc 300 diffcrcnt isotopcs, c.g. H

1

,H 1 and H 1 are thr cc isotopes

ofhydrogen H/ = deuterium, H 31== tritium. 12

13

Carbon also has three isotopes: C6 , C6 carbon 13 and carbon 14 r espectively.

14

and C

comm only r eferred to as carbon 12,

30

IONS An ion is an electrically charged partide which may be  positive (+ve) or negative (-ve). 40

50

When particles or photons of energy ( quanta)  pass through matter , ali the energy is absorbed in exciting the atoms or molecules so that electrons are ejected producing electrica! imbalance. The ejected electrons (having negative charges) are negative ions, whilst the atoms losing electrons are positive ions due to their unpaired proton (s) in each nucleus. Ions are created when x-rays, gamma rays, alpha particles,  beta particles or neutrons  pass through matter. The process of producing ions is

k.nOVI'll

a ionisation.

MOLECULES 60

When atoms bond together chemically in flXed whole number  ratios, they forrn mo/ecules. The molecule may be of the same clement, e.g. H2 (H + H), or a combination of atoms of different elements; examples: 2H + O = H20 - water  H + CI = HCI- hydrochloric acid

70

C + O = CO - carbon monoxide

c + 20 = co2 - carbon dioxide  Na + CI = NaCI - sodium chloride 80

When molecules bond together, the resultant substance is known as a compozmd.

RADIONUCLIDES (RADIO-ISOTOPES) 90

Radionuclides arc radioactive isotopes, i.e. the disintegrate  by releasing sub-atomic  particles, and also give off excess energy known as gamma radiation. Ali elements with atomic numbers higher than bismuth (atomic number 83) are radioactive and are elements which result from the decay of either uranium 235, uranium 238 or thorium 232.

100

RSI-2

UNIT RSl · BASIC PHYSICS

Ruane & 11 T P O'Nei/1 OTES

10

The wavelength in the spectrum vary from the longest waves (r adio waves) down to waves associated with cosmic radiation. X and gamma rays are much shorter  wavelength than visible and ultraviolet light. Wavelengths are measured in 9 nanometres (nm); 1 nm = 1o- m. The relationship between the wavelengths of visible light, UV light, x-r ays, gamma rays and cosmic rays ar e roughly as shown in the following table:

Electromagnetic radiation typc Vîsible light ..Ultraviolet light X-rays (conventional tubes) Gamma rays Betatrons and linear accelerators Cosmic rays

20

Wavelength in om 700-400 400 -100 0.025 -0.003 0.015 -0.001 0.001 -0.00004 < 0.000025

30

The characteristics of x-rays and ganuna rays ar e similar and they have no mass or  electrica] charge, they travel at the s peed of light and their wavelengths and photon ener gy overlap. The main difference between x-rays and gamma rays is the method by which they are  produ ced,i.e.the source of radiation. 40

50

X-r ays consist of a heterogeneous  band of wavelcngths, i.e. a band of mixed wavelengths. The wavelengths of x-rays ar e govemed  by the kinetic ener gy resul!ing from interactions between fast moving electrons and sub-atomic particles. In x-ray rnachines it is the potential difference (kV)  between a cathode and an anode (target) that govems the velocity of electroos flowing and ther efore the kinetic energy when a collision occurs. The circuitry of an x-r ay machine also aff ects wavelength . Short wavelengtb x-rays are generated when the a.c. rnodified sine wave for potentia l is at its peak. the rnedium wavelength x-rays are tbe r esult of the bu ild up to tbe peak and the fali off after the  peak. Long wavelengths are geoerated at t be start and fmish of the half cycles.

60

Radio-isotopes  pr oduce garnma rays consisting of discreet wavelengths and are constant f or a given isotope.

Properties of x-rays and gamma rays Both x-rays and ganuna rays have the following properties : 70

80

a. The bave no effect on the buman senses.  b. They have adverse effects on the body tissue and blood. c. They penetrate matter. d. They move in straight lines. e. They are part of tbe electromagnetic spectrum and ther efore travcl at the speed of  light (3 x 108 ms·l f. They obey the inverse squar e law. g. They ionise gases. h.

. They may be scattered.

1.

They effect photographic emulsion. They make certain materials fluoresce. They may be refract ed, diffracted and polarized.

 j. k. ?O

100

"'R u:.n & T P O"NciU

RSl-4

UNIT RSl  BASIC PHYSICS

Ruane & I l  T P O'Nei/1

•

NOTES

Corpuscular (particulate)radiation Corpuscular rad iation is the flow of sub-atomjc particles. These particles may or may not havc an electrica! charge. 10

This type of radiation is di fferent to x and gamma radiation by h aving mass and not travelling at the s peed of light. There are three main types of corpuscular radiation: alpha, bela and neutron radiation. AJpha radiation 20

 An al pha  partide is a lar ge sub-atomic  particle consist ing of two  protons ami two

neutr ons (the nuc Ieus of a helium atom) and therefore has a positive char ge. Alpha radiation travels comparatively slowly Ieaving the sour ce al about 16,000 km.s·' ( 10,000 miles/sec) but the particles soon slow down and only travcl a total distance of  a few ccntimetres through the air.

30

Alpha particles ionise atoms  by r emoving electrons as they pass through matter  but they do not penetrate deeply and can be stopped by a sheet of paper and human skin. The ma in hazard is that they may enter the body thr ough a cut in the skin or they may  be ingested. Beta radiation

40

50

A beta partide is a very light high s peed e1ectron or  positron and therefore may  possess a negative or positive charge.

Beta particles travel faster than al pha  particles_ They are small and lightweight and therefor e do not have a high ionising potentia l cornpared with alpha r adiation . They can travcl through 3 rneters of air or 1 mm of lead and are more penetraling than al pha  particles but they can be stopped by a few rrullimetr es of rnost solid or liqu id rnaterials. If beta rays are errutted from a radioactive source, they ar e normally  pr evented from entering the surr ounding air s pace by absorption by the mass of the r adioact ive  pellet or its surr ounding ca psule.

 Neut r on radiation 60

 Neutr on radiation simply consistsof flowing neutrons which have no electrica!charge.  Neutr ons are  produced from nuclear r eactor s, accelerators and certain radioa ctive isoto pes, e.g. califomium 252, ali of which  produ ce  fas t neutrons. These neutrons normally have to  be slowed down  by using a moderator  before they are used in radiograpby; these slower , lower energy, neutrons are called thermal neutrons

70

IlO

 Neutr on radiation can  penetrare many materials rnade from heavy elements wi th ease  but it is absorbed by many lighter materials,  particular ly those containing hydrogen. Hydrogcn has an affmity for neutr ons.

ACTIVJTY The activity of a radioactive source can be expr essed in becquer els (RlJ) or cmies (Ci); the h1gher this value, the greater the intensity of gamma rays pr oduced. The becquerel is the SI unit f or activity and is equal to one radionuclide disintegration  per second.

90

The older unit, which is still widely used, is the cunc which is equal to 3.7 x 10'0 disintcgrations per second. 1 bccquerel "' 1 disintegration per second;

3.7 x 1010 becquerels = 1 curie; therefor c: 3.7 x 1010 disintcgr ations per second = 1 curie. 100

... .;Ru:tn

TPO'f\c1U

,

h"ut 6 l..t/DGIO \

RSJ -5

Ruane &hll 

UNIT RSl · BASIC PHYSICS

TPO'NeO

For industrial radiography, it  gi"gabecquerels (G Bq):

NOTES

is usually more practica!

to

talk

m

tenns

of 

Giga = I09 10

1 gigabecquerel

==

37 gigabecquerels

10"becquer els.

=

1 curie.

20

 Note: The activity of a radioactive tsoto pe does not r elate to the  penetr ating  power of  the gamma rays  produced ; penetrating  power depends on the wavelength of the gamma rays  produ ced and this depends on the specific r ad10active element involved. For  example, cobalt GO (Co60) !Jas a vtay high pc:nt:lr ating power and may be used on steel compooents u p to 200 mm tbick , because the gamma radiation emitted bas a very short wavelength.

30

DECAY

Ternbecquere/s m11y be :ncountered . T ern - 1O" 

 Decay is the pr ocess of s pontaneous transformati on of a r adionuclide. A loss of  activity will be the result of decay and most r adionuclide will decay throu gh disintegration . Radioactive materials decay by at least one of five primary modes: 40

1. Emission of alpha particles (helium nucleus). 2. 3. 4.

50

Emission of beta particles. Electron capture or positron emission . Emission of gamma rays {photoos).

5. Spontaneous fission.

IONISATION

60

Ionisation is simply the formation of ions whic h are positively or negatively cbarged  particles.  fonising radia/ion means gamma rays, x-rays or corpuscular radiations which are capa ble of producing ions either directly or indirectly.

70

X-rays and gamma rays are photons (packets of ener gy) and since energy cannot  be destroyed it is absorbed or converted when the photons collide with matter. Some of  the energy may be absorbed by an or   biting electron which may be sufficient to r emove it fr om its orbit around the nucleus. TI1e r emainder of the energy may forma lower  energy  photon and the process is r e peatcd until ali the ener gy is either absorbed or  converted. Low energy photons will eventually decay into ultravio let light, light and heat.

80

90

Ionisation creates an unbalanced atom since at least one of the paired electrons has  been removed leaving the atom with an extra unpaired proton ; the atom tben becomes known liS <1 positivc: ion. The ejected electron is a negative char gcd  part icle and theref ore is a negative ion. These electrons move with differ ent velocitics and in diff crent directions and some will collide with other atoms which will absor   b some of the ener gy and produce low encrgy x-rays. Therefore,low ener gy seco ndary or scattere d rad iat ion will be produced.

100

<€) Ru nc & T J"

o·N.,·iU

R l -6

UNIT RSlA · ABSORPTION AND SCATTERING

Ruane & Il  T P O' Neil/ 

Compton scattering

NO  _ TES

10

This is also called the Compton effect. In this process, a photon interacts witb a free or  weakly bonded outer electron, part of the photon's ener gy is transferred to the t:lectron which is ejected. The  photon emerges from the collision as scattered rad iation of  r educed energy.

Photons

------0

,, 20

E  je cte d electron (-)

-----.... Scattered radiation 30

40

Pair production

50

This effect occurs at very high radiation energies (above 1.02 MeV). When a high energy  pboton collides with the nucleus of the atom, the energy of the photon is absorbed and produces an electr on and a positron. Very soon after, the electron and the positron collide and both ar e destr oyed  but release two photons each with ener gies of O.S MeV.

60

Collison and annihilation

Photons > 1.02 MeV

Ejected positron (+ 0

70

0 5 MeV

8 /

o

--

"""--

0.5MeV

\

Ejected electmn (-) Photons

80

9 0

100

R SI A-2

UNIT RSlA · ABSORPTION AND SCATTERING

Ruane & Il  T P O'Nei/1

The intensity of ionising r adiation is r educed by at least one of tbe f ollowiog types of  interaclion:

1\0TES

10

a.  b.

R ayleigh scattering. Photoelectric ef fect.

c. d.

Compton effect. Pair production

The extent of absorption and scattering is govemed  by the encr gy of the  pnmary radiation and the atomic number ofthe elemcnts makmg up the medium through which the r adiation is travelling. 20

Scatter ed radiation may seriously effect the quality of a radiographic imagc and ma y also increase t be radiation dose levels in the working viscinity.

Rayleigh scattering

30

In the process, photons are deflected by outer electrons but do not change in ener gy or  r elease any electrons. The photon scattering is in the forward dir ection. This pr ocess accounts for less than 20% of the total attenuation of a radiat ion beam. Rayleigh scattering is most relevant whcn dealing with low energies of radiation  passing through materials consisting of elements with a high atomic number.

40

Photons

50

60

Photoelectric effcct 70

The photoelectri c cffect is an interaction between a photon and an orbiting electron which causes an electron to be ejected. The photon is consumed and the excess cnergy imparts kinetic eoer gy to the electron. TI1is  pr ocess applies to ionising radiation of relatively low energy, e.g. less than 100 keV in steel, and also to hig ber ener gy radiation up to about 2 MeV when passing

80

thr ough materials nntaining elcments ofhigh atom jc number.

Photons 90

1()0

E jec !edelectr on (-)

V:

-·

@)J '-:: '

-

-/

RSI A-1

UNIT RS2

Ruane & Il TP O'Nei/1  NOT S

  RADIOGRAPHIC EQUIPl\fENT

•

GAMMA SOURCES 10

Sealed sources The sour ce of gamma radiation, i.e. the r adioisotope, which is rypically in d1sc or  cylindr ical form, is enclosed in a capsul e somctimes referred to as a pili.

20

30

The sources availa ble range in size and configur ation from 0.5 mm diarneter disc to a 4 mm x 4 mm cylinder. Exam ple configurations are: •

40

Thin discs: typica lly up to 3.0 mm diameter x 1.0 mrn thick. These can be stacked together .

•

Cylindrical:typically up to 4 mm in length.

•

Spherical: 0.6 - 3.0 mm diameter.

The ca psule is made fr om either 316 S12 grade stainless steel or titanium.

50

Titanium is used for Ytl69 ca psules and is an alternative to stainless steel for lr 192 and Co60.

Classification and types of exposure container  To com ply with BS 5650 (ISO 3999), apparatus for gamma r adiography is class•f ied according to the mobility of the exposure container.

 BS 5650 . 1978 : Specification for apparatus  for  gamrna rodiography.

•

60

•

•

10

C lass P- A porta ble exposur e container designed to be carried by one mao alone .

C la ss M - A mobile but not portable exposure container designed to be move d easily by a suitable meaos provided for the purpose. C lass F - A fixed installed exposur e conta iner or one with mobility restricted to the confmes of a particular working ar ea.

An ex posure container must  be provided either witb ao integral lock or with has ps through which separate  padlocks can  be fitted. The locks must be eit ber lockable without the key or an integral Iock f rom whicb the key cannot be removed when the container is in the working position . On ali exposur e containers the radiation can only  be exposed after an unlocking operation. There are a number of dif ferent designs f or containers, the most common types are: •

Shutter type (Category f ).

•

Rotating type (Category f).

•

Projection typc (Catcgory II).

80

90

 An expo sur c llead "III be fi 

 f ont! of collmJntor .

BS 5760 Categ01y 1 containers arc containers from wbich the sealed source is not removed f or exposure. C ateg01y Il container s are thosc from which the sealed sour ce is projcctcd from the container via a proje ction sheat h (guid e tube) to an e xposure head, they may operate electrically , mechanically or pneumatically . Another type of container is the torch type. l11is type of contamcr should no longt!r bc uscd bccause of r elatively high radiat ion doscs r eccived by the user and the high risk of  ovcr cx posure.

100

RSZ- 1

UNIT RS2 · RADIOGRAPHIC EQUIPl\IENT

 Ruane & 1/  T P O'Nei/1

Torch type

N O TES  BS 56 50 does no f cover  appnrnlus oper al ed by 10 removing  I he seoled  source ( r om che expo sure container by u sing a manual hand/in g d evice because ie s use is  prohib iled in cercain nationnl regulat ion s. 20

The container bouses the source within a torch assembly and also a s bort  bandle . The handle is fitted to the torch assembly, this is secured in the ma in container by a bayonet fixing. As the torch assembly is withdrawn from the container, a spring load  plunger   pushes part of the assembly down  pr oducing a shielding eff ect so as to  produce a narrow beam of radiation. handle

30

Torch type 40

Shutter type (Category 1 type to BS 5650)

50

shielding material

60

Shutter type

70

Rotating ty pe (Category 1 type to BS 5650) shielding material

rotates

8 0

9 0

L

 _ _ _

Rotating type ](){)

.J Ku:ml('& T l" O'Nt:iH

R S2-2

UNIT RS2 · RADIOGRAPHIC EQUIPMENT

Ruane & Il  T P O'Nei/1

Projection type (Category

lliOTES

10

n type BS 5650)

This type is also known as a remote control or wind out type. The sour ce is attached to a s pecial connector called a pigtail ; the pigtail and source are moved along a guide tube  by means of a cable until the source reaches the exposure head (which is fixed in the working position). The cable is driven along by means of a hand-cr anked wind out mechanism, or it can be pneumatically or electr ically controlled. The ca ble is r etractcd to retum the source to its container at the end of the exposure. The projection type can be further classified as an S -ty pe or straig ht -through type. handle

20

30 removable storage

shipping plug assembly

------

40

shieldmg material

50

sealed source Projection type

Marking of exposure containers

60

 BS3510: 1968: Specifica t ionfor a basic  symbol to de note the actual  or poten tial presenc e of ionising radimion. 70

Each exposure container must bave a metal plate  permanently fixed and indelibly marked by engraving, stam ping or other means with the following inforrnation : 1. 1l1e basic ionising radiation symbol com plying with BS 3510 (ISO 361). 2.  RADIOACTIVE in Jcrter s no less !han 10 mm in height.

3. The maximum rating ofthe container for the type ofsource tobe used. 4. BS 5650 (ISO 3999). 5. The manufacturer's type and serial number . Class M and  F containers shall  be marked with the mass of the container .

Identification of the scaled source in the ex posure container 

80

90

The user must ensure that the following inforrnation is dis played in a durable fom1, artached to the exposur e container, usually in the form of a brass disc. 1.

The chemical symbol and mass num ber of the radionuclidc.

2.

Activity and the date on wh jch this activity was measured .

3.

Idcntification number of the sealed sour ce.

Source exchangers Source exchange type contoiners or  sour ce exclrangers an: used to safely transfer  sources to and from the cxposure containers so that the uscr can rcceive new sources and retum old sources to the supplier.

100

There are a number of proprietary source exchangcrs availablc, thereforc thc specific manufacturer's instructions must  be r cad and understood beforc sourcc exchangcs arc attempted.

h\UI' 6 Ut0610l

RS2-3

UNIT RS2

Ruane & Il  T P O'Nei/ 1

•

RADIOGRAPHIC EQUIPl\iENT

Testing of isotope containers aud sealed sources

NOTES

Tests carried out on isotope containers are undertaken by designers and manufacturers, i.e. not the user. The tests which are conducted are a s follows: 10

•

Shielding efficiency.

•

Vibration.

•

Shock.

•

Endurance .

•

Kinking, crushmg and tensile.

•

Drop.

7.0

 IAEA =Intern ational Atomic  Energy  Agency . 30

Leak tests must  be carried out on sealed sources (1999 IRR Regulations state at suitable intervals) in most cases every 26 months (IAEA are recorrunending 12 monthly testing). Test methods include the following: •

•

40

Wipe test A - The container is wiped with a swab or tissue moistened with methanol or water. The activity of the residue removed is measured . The acceptable limit is 185 Bq. Bubble test B - The container is immersed in water ora suitable liquid (ethanol) and the pressure reduced to 13 kPa. No bubbles to be observed.

Additional tests should be roade when damage occurs or when maintenance is carried out which could affect the integrity of the source . R ecords of lcakage tests must be kept for two years.

so

Collimators Collimators are usually used with garnma sources during exposures for safety reasons and sometimes to improve radiograph ic quality; see Unit RS7.

X-RAY SOURCES 60

Geoeration of x-rays X-rays are  pr oduced when fast moving electrons ar e stopped or slowed down (decelerated) on collision with matter. 70

X-rays used in industrial radiography ar e  produced from electrica! machines usually referred to as x-ray sets; the x-ray sets themselves being produced from within an x-ray

tube or insert.

&O

90

100

An x-ray tube consists of an evacuatcd glass bulb, encompassing an anode (the positive electrode), and a cathode (the negat ive electr ode). The cathode conta ins a filament within a curved r e flector or focusing cu p.

) kunC" .'
RS2-4

UNIT RS2

Ruane & Il 

•

RADIOGRAPHIC EQUIPl\IENT

T P O'Nei/1 !'OOTES

10

When the filament is heated to a white hot state by a current flow of a few am peres, electrons are ernitted and are attr acted towards the anode in a concentrated  beam formed by tbe focusing cup. The beam strikes a tar get set into the anode which r esults in the release ofenergy; this energy consists ofapproximately 97-99% beat and 1-3% x-rays for conventiOnal x-ray tubes up to 300 kV. Because of the h igh amount of heat energy produ ced, the anode is made fr om cop per  to conduci away lhe beat. But, copper  bas a low melting  point, so to  preveni the copper melting, a slip of met al with a higb melting point is r ecessed into the anode at the point which is stmck by the electron beam.

20

This slip of meta l also serves nnother  purposc, because, the higher the atomic number  of the element struck by electrons, the gr eater will  bc the intensiry and energy of the x-r a ys produced . This sli p of metal, or lar get, is usually made of tungsten because of  its high melting point of 3370°C, and its high atomic number of74. The area on tbe lar get which is struck by the electrons is called the f oca!spot; this ar ea

30

should  be lar ge enough to avoid local overheating, although f rom the r adiographic image qualiry  point of view, the foca! s pot sbould be as srnall as possible to provide good definition (sharpness) on tbe radiograph. Additional cooling is requir ed to cool the anode; gas, oii or water normally  being employed for tbis purpose.

40

Tbe cooling system and the insert ar e contained together in an earthed , lead lined container , the complete unit common ly being referr ed lo as lhe x-ray tubehead. TI1e tubehead is controlled from the control panel.

Tbe x-ray equipment control panel 50

The thr ee controls that govem a radiogr aphic exposure using x-rays ar e the timer, the mA control and the k V contr ol.

mA

60

Topowcr 

To warni..ng rysum

70

Timer   ,J,e · To J raJ t  (20 m mitri,..u:m cabl lLn tlr}

ee

80

Timer  90

The timer is usua lly calibrated in mioutes. The exposur e time f or an exposure is preset; when the equipment is activated, thc timer counts down from the pre-set value. The exposur e time will partially govem how much radiatton ts going to r each the film.

Milliam ps (mA) 100

The mA controls the intensiry or quantity of x-rays. When the mA is incr eased, the curr cnt flow through the filament is increased, wh ich causes the filament to get hottcr 

"' Ru11n(' ..

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RS2-S

Ruane &

UNIT RS2 · RADIOGRAPHIC EQUIPl\IENT

11 

Nei/1 T P O' 

r esulting in an increase in the intensity of electrons released. The greater the intensity of electrons str iking the target, the greater the intensity ofthe x-rays produced.

. NOTES

10

The mA control on conven tional x-ray equipment may only a!low for a maximum o f 6 to 12 mA to  be used, the value being measured across the tube, i.e.  between the cathode and the anode. The value requ ir ed for a specific exposure is usually pr e-set on the panel, this value is usually at, or close to, the maximum mA  possi ble with the equipment for the purpose of minimising exposur e time. Kilovoltage (kV)

20

30

40

The kV govems the wavelengt h or quality of x-rays produced wh ich practically govems penetr ating power. When the kV is increased, the speed of the electron flow from the cathode to the anode is increased. Therefore, when the electrons strike the target, the kinetic energy is incr eased, which results in a r eduction of wavelength. An increase in kV, i.e. a shortening of wavelength, bas an adverse af fe   ct on the contrast and definition of a r adiographic image. Certain standard specifications,  s , states the maximum k V values for this reason. e.g. BS EN 1435 Radiog raphy ofweld 

The kV meters on the control panels for conventional x-ray equipment ar e  peak kV values measured across the tube, i.e. between the cathode and the anode. The maximum k V which can be used is  primarily govemed by the tubehead ; typical maximum values are 200 kV, 250 kV and 300 k V . The value required for a specific exposure is usually pre-set on the panel.

Pipeline crawler equipment

50

Machines have  been developed specifically for the radiographic examination of   pipeline welds using either x-ray units or gamma sources. These machine s may have a  power source attached to the radiation sour ce, i.e. battery pack or gener ator, or they may be operated r emotely via a cahle with the power source outside the pipeline. Because pipeline cr awler s are used inside the pipeline, they are not visible from the outside of the pipeline, therefor e, it is essential that suitable waming signals are given and are capable of alerting persons in the vicinity of the crawler.

60

70

Signals that operate automatically shou ld be linked by some method to the cr awler , this is normally achieved by using sensor s linked to warning lights which operate as soon as they detect ionising radiation. Crawlers available usually have an integrated audible  pre-exposure alarm and an exposure alarm.  A separate waming signal is sometimes integrated when the craw!er is in motion. The useful  beam from cr awler s should  be restricted so that the beam width does not exceed 120 mm at the cir cumfer ence of the pipe.

Any control isotope used should not exceed 100 tSv .h- 1 at the accessible surface of the  pipe when exposed.

Higb eoergy units 80

R adiography using x-ray energies of one million electr on volts (1 MeY) or greater is considered to be in the high energy range.

Electrostatic gener ators

90

The V an d e Gra ffe electro static  g enerator consists of a rapidly moving insulated belt onto which is sprayed an electric charge which is carried to a hemispherical high voltage termina l. This  produces a high voltage difference with res pect to the lowcr  end. Electr ically charged particl es are made available f or acceleration from a heated carhodc and injected into a very high vacuum tube and collimated to bombard special tar gcts and produce x-rays. ll1e tar get size is about 2.5 rnm.

100

!(":' Nurmt" & T P O"Nc..-111

R SZ-6

UNIT RS2 · RADIOGRAPHIC EQUIPl\IENT

Ruane & Il 

TP O'Neill 

Electron linear acceler ators

NO _ TES

Thesc are commonly referred to as linacs or simply linear accelerator   s. Linacs accelerate electr ons down a guide by mean s of radio fr equency (rf) voltages. Thc

voltages are applied so that tbe electrons r each an accelcration point in the field at a  precise time. The guide consists of a series of cavities which produce gaps when the rf   power is applied. With phased  power, the electrons are accelcrated along the guide to a target, the rays energy at the other side.

10

The cner gy in electron volts increases with the length of lhe tube. The foca] spots can be as small as 0.1 nun.

20

As an example, the 100 nun thick steel shell of a nuclear reactor ata power statioo in Wales was radiographed at a distance of 9 m using ultrafine grain film wilh a 20 minute exposure. Bach exposure covered 3 m of weld . Thc 4 MeV linac was mounted centrally on a r otating stand in lhe centr e of the shell. This 4 MeV was traosportable and could readily be moved wilh lifling equipment.

30

The Betatron This machine is  based on the same principle as the linac  but tbe electron guide is a spiral. Tbis means that the pafu oflhe electroos can be iocreased over a smaller overall area. 40

Betatrons can be manufactured up to 300 MeV and an Il MeV can penetrate steel up to 300 nun thick, but is noi trans portable.

Portable :>t-ray betatrons are available with energy outputs up to 6 MeV.

50

60

70

80

90

100

•·

Ru:uu: ...

1 l' O"N

·îll

RS2-7

UNIT RS3 ·RADIATION UNITS

R uane & Il  TP O'Nei/1 NOTES

ACTIVITY Applicable to gamma radiogra phy. 10

Activity is the number of nuclear disintegrations per unit time taking  place in a radioactive source, i.e.the rate at which transformations occur. SI unit: Bcquerel (Bq)

One bequerel corresponds to the decay of one radionuclide per second. 9

G Giga= 10 T

20

= Ter a = 10 

1 1

It is more  practica! for industrial radiographers to talk in terms of Gigabecquerels 12 9 (GBq), l GBq = l0 Bq; or Terabecquerls, l TBq = 10 Bq. The old unit is the Curie (Ci); this unit is often encountered.

1 Curie= 37 GBq

or

1 Curie = 3.7 x 1010 Bq

1 Bq = 27 pCi

or

1 Bq = 2.7 10 _ ,, Ci

30

DOSE OR EXPOSURE This is applicable to aU types of radiation and r elates to the incidence of radiation on living or inanimate material by accident or intent. The coulomb is rhe SI unit 

of electr ic charge.

40

SI unit: Coulomb/kilogram (Cikg) The old unit of exposure (stiH encountered) is the Rontge n (R). 3

50

One rontgen is the quantity of X or gamma radiation that will ionise 1 cm of air to give one electrostatic unit under fixed conditions. More specifically, one r ontgen is the quantity of x or gamma radiation such that the associated corpuscular emission per 0.001293 gram of air pr oduces, in air, ions canying one electrostatic unit (e.s.u.) of  electricity of either sign.

1 C/kg = 3876 R

or

1 R = 2.58 x 10-4 Clkg

ABSORBED DOSE (KERMA) 60

This is the quantity of energy imparted is also known as kemw. SI un it: gray (Gy)

1 gray = 1 J/kg (1 joule of energy absorbed by 1 kg of matter). It is more likely that industr ial radiographers will talk in terms of rnicrograys (f.lGy) or  milligrays (mGy).

6 

o = 10"   p =micr  m = mi /l i =

10  J  70

The old unit is the rad (still encountered). 1 Gy = 100 rads

or

1 rad= 10 2 Gy (10 mGy)

DOSE EQUJVALENT 80

The dose equiva /ent is a quantity observed  by multiplying the absorbed dose by a factor to allow for the diff erent effectiveness of the various ionising r adiations m causing harm to tissues, i.e. it is a value that relates to the  biologica! effect of  radiat ion.

SI unit: Sievert (Sv) 90

l sievert = 1 J/kg (1 joule of energy absorbed by 1 kg of matter ). One sievert (1 Sv) has the same  biologica} eff ectiveness as one gray ( 1 Gy) of xradiation ;  but it is noi the same f or al! types of r adiation, e.g. 1 Gy of thermal neutrons will give 3 Sv.

1 oo

It is more lik ely that industr ial r adiographers will talk in tenm of mîcr osievens (fl.Sv) or mîllîsieverts (mSv).

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RS3-1

UNIT RSJ ·RADIATION UNITS

Ruane & 11 TP O'Nei/1

The old unit is the rem (still encounter ed)

NOTES

1 Sv = 100 rcms 10

or

2

1 r em = 10· Sv (10 mSv)

Quality factor s The absorbed dose can  be converted into sieverts by multiplying by the applicable quality factor (QF). The value of the QF depends on the type of radiation absorbed. More specifically, thc biologica!effect of an absorbed dose is govemed by lhe density of ionisation caused by the radiation.

20

QF

Type of R a diation X, gamma and beta rays

1

Thermal neutrons

3

Al pha and f ast neutrons

10

30

Eff ective dose equivalent = grays x QF

Gy x QF = Sv mGy x QF = mSv 4 0

Gy x QF = Sv

 Example What is the total effect dose equivalenl if in one year a worker r eceives a garruna dose

 so

of 20 mGy, a thermal neutron dose of 5 mGy and a fast neutr on dose of 1 mGy? Total dose equivalent

absorbed dose x QF

Gamma dose equivalent

20 X 1

20mSv 60

Thermal neutron dose equivalent

5x3

15mSv Fast neutron dese equivalent

1 X J0

10 mSv 70

Total dose equivalent

45 mSv (0.045 Sv)

DOSERATE

80

Clkg, Gy and Sv are units ex pr essing an amount of r adiation which may have been received over any period of time. To control th e radia tion hazard it is necessary to know the r ate at which the radiation is being received.

 E   xampl e If a man working in an area for 2 hours receives a dose equivaJent of 4 mSv, then the dose equivalent rate is 2 mSv per hour.

,\/r//rsu!ver/5 per

hour mny lx: c prC":ued ns m::;\·flrr or  1

mSv.h" 

•

90

1 1

Similarly wc can have expo sure rat es (C.kg. s.

)

and absor bed dose rates (mGy.h"\

nre n!Jsorbed do.f c rnte 11111)'  olso bc referred tn ns the lu:rmn rntc.

100

.t; Rtunt & T f' o•r: rtU h..ut 6 J:..C/1)6/0,,

RS3-2

UNIT RS4 · BIOLOGICAL EFFECTS

Ruane & Il 

T P O'Neill 

.:'liOTES

nte emplo yer s i r es ponsiblc fo r pr ovidin g corr ect pers onnel 

OVERVIEW The ef fe  cts of radiation are divided into two classes: ( 1)  somatie effeccs in which the damage appears in the irradiated person themselv es and (2) g enelic effects which arise in the offspring of the irradiated per son as a result of radiation damage to gene ceIls in the r eproductive organs_ 

1O

protec  t iw: equipment a  nd  (or ens  ur i  ng a i  s worn w  hen 

The fundamental effect of radiation on any lîving organism is the destruction of cells. Many different k inds of celis exist in the  body. Those f orming bone, skin, rnuscle etc. ar e known as d!f!er ential cells and have reached the stage where in an adult, they do not undergo further division. The process of division in wh ich more celis are produ ced is called mitosis and the daughter cells may be mitolic or differ entiated.

requir ed.

20

Mitotic cells are rnuch mor e sensitive to radiation then differentiated cells. The effect of radiation depends on whether the whole body is irradiated or only a pa rt ofthe body. Which pact ofthe body is irradi ated also govems the eff ect. 30

For a given dose, the effect of ionising radiation will  be most noticeable if the whole  body is irradiated and least if only a small volume of skin and muscle is involved.

Because of the r ecovering process, the effects will also depend on the dose rate, i.e. the time over which a given dose is received. In general, the effect is less harmful if the dose is spread over a long time rather than r eceived in a single acute exposur e. 4 0

SOMATIC EFFECTS

Blood The  blood cells are the fu-st to suffer the effects fr om absorbed 1omsmg radiation . lnitially the production of white blood ce lis in the bone marrow is slowed down and at slightly higher received doses the same happens to the red cells. Both these changes when sufficiently severe and prolonged can be lethal and are the fu-st detectable effects of ionising radiation. Therefore, taking a blood count of individuals who work with radiation is a conunon and effective test.

50

60

Skin lfinstead ofthe whole body  being irradiated, the dose were confmed to a small volume of limb, any reaction would be greatly reduced and confmed mainly to the skin.

If an acute dose of appr oximately 400 mSv were received ther e would be a r eddening ofthe skin with per haps loss ofhair, both ofwhich would be temporary (erythema).

70

At greater doses the skin peels (desquemation) . At larger doscs still the skin blisters (wel d e squemation). Very lar ge doses would produce buming of the skin which wou!d  be very slow in healing and may develo p into malignancy, e.g. cancer cells. TI1ese effects were f airly conunon with early x-r ay experiments.

80

Eyes The eyes are partîcularly sensir ive ro ionising radiation. Cataract fonnation 1s the lik ely result of over exposure. 90

100

1

ftu2nt- & 1·P O"Ndll

R S4-l

UNIT RS4

Ruane &  /1 TPO'Nei/1 NOTES

  BIOLOGICAL EFFECTS

•

Probable eff ects of an acute radiation dose ou the whole body 10

o- 250

20

30

Probablc effcct

Acute dose (mSv)  No obvious injury.

250 - 500

Poss1 ble minor blood change.

500- 1000

Vomiting and nausea for about 1 day in 5% to 10% ofpeo ple, fatigue but no ser ious injury.

1000 - 2000

R adiation sickness in 50% ofpeo ple, pos sible _ injury.

2000- 4000

Radiation siclcness in ali, with 20% death s within 2 - 6 weck s.

4000- 6000

Over 50% deaths.

> 6000

Fatal.

GENETIC EFFECTS Very small doses of radiat ion whilst not effecting the ability of a celi to live and divide, may cause minor changes in the interna! arr angement of the cell. This can be of  considerable importance when the cells are the reproductive cells.

40

 so

The effects are to change the chromos omes or genes which are responsible for the character istics of the individual. Radiation can alter the chromosomcs in such a way tbat aftcr cell division tbe daughter cclls will be the samc as the altcr ed parent cell; this is known as mutation.  Normally mutations are a change f or the worse and can  be caused  by very small amounts of radiation. The probability of such a change depends on the dose r eceived and appears tobe in proportion to the total dose received . In general, the result of such mutarions is that the affected individual d1es at an early age or fails to repr oduce. Most mutations are bom dead. It  bas been estimated that the mutation r ate would double if the population were exposed to a dose of about 500 mSv.

60

0THER DEFINITIONS

 BS 47 27 : Pnrt 5 : Group 01  Radiol o g>• nntl r nd iol ag icnl  pllysi cs   t er minol o gy.

·

10

Acute irradiation

A term used to denote high levei irradiation of a short durat ion

Chronic irradiation

A tem1used to denote low levei inadiation of a long dur ation, either continuous or intennittent.

Deterministic ef fect

Eff ects whicb will not occur below a certain threshold level of dose. Above that threshold dose, the severity of the eff ect is dir ectly r elated to the magnitude of thc dose received and the part of the body exposed. Usually the r esults of acute r elatively high doses will ap pear within days or weeks of exposur c.

Stochastic effect

Ef fe  cts whose pr o ba bility of occurring (r ather than severity) is r egarded as a function of the a bsorbed dose withou t threshold.

 Non·stochastic ef fect

Ef fe  cts whose seventy var ics with that absorbed dose and for  which :l threshol d may occur.

8 0

90

100

RS4-2

UNIT RS6 • RADIATION DETECTION AND 1\IEASUREl\lENT

Ruane & 11 T P O'Nei/1 OTES

10

Radiation may be detected and measur ed by va rious means. TI1e terms uscd which relat e to devices used for radiation detection and measurement can be confusing and they are often misused. Tbe correct terms to use may be found in BS 4727 : Pan 5 : GroupOI . There ar e essentially three types of radiation detector used by industTial radiographer s: 1.  Radiat ion me/ers: these give the user measured quant ities of rad1ation prcscnt and are normally used by radiogr aphers to inform thcm of the exposure rate or  absorbed dose rate.

20

2.  Personal dosemeters : these ar e wom by 1111 radiogr aphers and inform them of thc absorbed dose or dose equivalent received. 3.  P ersonal audible alarniS : each radiographer may have an audible alarm which is  placed in the pocket.

30

40

Warning assemblies, wh.ich may be visible ancVor audible, may also be used to infom1  per sons in the nearby viscinity (and the radiogyaphers themselves) that ionising radiation is  being emitted and/or about to be emitted . These are not necessar ily radiation detectors.

DOSE RATEMETERS A dose ratemeter measures the rate of radiation exposure, i.e. the amount of radiation  being r eceived per unit time and permits the evaluation of the absorbed dose rate.

 Dose rtllemeter s should not  be confused with dosemeters

When dose r a temeter s are being used, the action is often terrned monitor in g and the dose ratemeter is often ref erred to as a monitor or survey meter. 50

 Monitor ing is defined a s a conlinuing procedur e for the co/le
The dose ratemeter informs tbe radiographer how much radiation he/she is receiving. Radiogra pher s need to know how much iooising radiation they ar e receiving at any  particular time to comply with the ALARP requirement and to ensure that maximum instantaneous doses are not being exceeded.

Dose ratemeter s are also used: a.  b. c. d.

al the  perimeter of controlled areas to give an assurance that the maximum  permissîble value is not being exceeded; to determine the extent of the supervised area and to monitor them; to ensure that r adio-isotopes have been retumed into their containers; to check radio-isotope container s for leakage.

70

The r esults from radiatîon monitoring of controlled areas must be recorded; the r ecords should be kept by the employer for 2 years.  Radiat ion meters uscd must bc capable of reg istering al/  the tonising radiat ion type s and energin presen t 

80

 Radwtion for S ite  Radiograph y (a book 0 11 the PCN estential reading list   stat es 14 montlts. nu! 1999  Reg ulatil/ns state thm 12 mont lr  bc  s ma y not •

90

 prat·tu ; fll , pnge 85 of ACOP .  parng•nph 353).

100

Dose ratemeters must be calibrated  by a qualified  pe rsrm when new, after rcpair . if a malfunction occurs, and al intervals not exceeding 12 months (*see note). Certificates of calibration must be issued and records should  be kept by the employer for a minimum of 2 years. As a minimum, a meter must  be used with each sourct: of radiation  being used and it must bc switcbed on during exposure. Fr equcnt check s are requir ed to ensure that the dose ratemcter is working satisfactorily and must include a battery condition check, zer oing of thc needlc and response checks. Dose r atemeters consist of ionisat ion chambers and g1ve a visual readout usually calibrated in 1-1Sv.h·1 and mSv.h·•. They must be capable of reading dose rates below 7.5  j.t Sv.h·• and above 2 mSv .h·1.

lt is possi ble t o jam a dose ratemeter if the dose levels bcing r ec;e;:Jvcd are too h1gh for  the calibration, this can r esul! in a zero reading, thcr efor e always set thc mstrument initially to detcct high lcvcls ofradiat1on aftcr carrying out a battery check.

l Ru:tiH'

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1-..ţuc b l JIOl)

RS( -1 •

UNIT RSS •  DOSE Lll\HTS

Ruane & Il  T PO'Nei/1

Any dose of ionising r adia!ion received during radiograpruc work shou ld be consider ed excessive. A II doses should be kept as low as r easonably  practicable (ALARP   principle).

OTES

10

The only method of contr ol 1s to have dose limits for specific  periods ro limit the damage caused by radiation .

Dose limits per calendar year  Whol e Body

Skin Feet

Eye

Classified per son

20 mSv

500 mSv

150 mSv

Trainee under 18 years*

6mSv

150 mSv

50 mSv

Unclassified  per son

1 mSv

50 mSv

15 mSv

Status • ,-.,(immum ngcfor a ralnee lnvolved In

20

rodiogrnphy is 16 .

30

lnst antaneous dose lirnits 1

Classified per son: 2 mSv.h· when starting or terminating an exposure. 1

Unclassified person:7.5 11Sv.h·

40

•

Additional dose limits for women Consecutive 3 month period- 13 mSv maximum . During the term ofpregnancy- 10 mSv maximum .

Action levels 50

1. Tbe IRR 1999 Regulations requires that where an accident or other occurrence t.akes place which is lîkely to result in a person receiving mor e than three tenths of any dose limit (f or classified persons this is > 6 mSv), the employer shall : a. For classified persoos, arrange for a dose assessment tobe made by the ADS irnmediately .  b. For any other  persons, arrange for the dose to be assessed by an appropriate

60

70

means as soon as possible havi.ng taken advice from the RPA .

2.

The a p proved dosimetry service must inform the cmployer and HSE as soon as a  per son's dose record exceeds 30 mSv in any one quarter.

3. The employer must also set an investigation dose Jevel. This level may  be whatever the employer wants it tobe  but must not  be more than 15 mSv. When this limit is exceeded f or the f ust tirne in any calendar year, an immediate iovestigatioo must be carried out. This dose limit shall  be written in the local rules. The action required with r egard to over exposure is dependent on the employrnent medical adviser (EMA or AD), however there is no provision in the regulations where over exposure requires automatic suspension from work.

80

90

100

R.o nt & T P O"N l"iH 1\...ur 6 24!06/U]

RS5-1

UNIT RS6

Ruane & 11 T P O' Nei/1

RADIATION DETECTION AND 1\IEASUREMENT

Iooisation cbambers

NOTES

71zcr e nr e mnny typcs of  ioni sat ion chamber .

•

A dose ratemeter contains an ionisation chamber which contains two electrodes. The  power su pply is usually a battery which is connected across thc clectrodes and an ammeter is connected in ser ies to the battery. Ionisation takes  place in the chamber  when it is exposed to r adiation.

10

Individual ions are attr acted to the electrode of opposite char ge and upon reaching the electrode, become neutra! by attracting a charge fr om the battery . This flow of current required fr om the battery is measur ed on the ammeter which can be calibrated in mSv or J1Sv. 20

Iouisation c bambers have variable accuracies  but are typically accurate tu ± 12%, exce pt in areas of Iow intensity radiation because su fficient ionisation currcnt is not generated to indicate accurately on the meter. In these ar eas of low intensity  geiger  counter   s may be used.

Geiger couoters

30

Tbese instruments contain a Geiger-Mull er tube which is a gas filled ion isation chamber and operates as a high sensitivity radiation detecting device. The voltage difference between the tu be anode and cathode and the gas within the tube, create an atmos phere wher ein any single ionisation process is multiplied into many such events. Tbis phenomenon of a single ionisation event  produ cing many ions in a fraction of a millisecond is known as gas multiplication; sophisticated electronic amplification is therefor e not r equir ed.

40

lbe resultant amplified  pulse of electr ica!ener gy can  be used to detlect a meter,

illuminate a Jamp or sound an audible alann.

Geiger counters have an accur acy of typically ± 15% pr ovided thcy are calibrated f or  the type of radiation in use. Filters may be required to distinguish different types of  radiation .

50

They are used in cases of gross contamination but ar e not intended to  be used as accurate dose rate meters, because in high r adiation intensity areas they can  block out and the meter will indicate a false z er o reading. If high radiati on dose rates are antici pated, Geiger counters should not be used . 60

Geiger counter s measure ionising radiation in counts per second.

PERSONAL DOSEMETERS Industrial radiographe r s, whilst working with ionising r adiation, must always wear a  per sonal dosemeter (fil m badge or t hermo-luminescent d osemeter ( TLD).

70

A TLD or film badge is pinned to the outside of clothing between the chest and waist ar eas. The user mu st ensure it is wom the right way round (the plastic holder s are norm ally labelledfr ont and back). Clnssified persons must  wcnr a T/..D or  film badge by / nw

Per sonal dosemeter s give information about the amount and type of radiation received over the period of tinle the dosemeter was wom.

80

Film badge dosemeter  The film badge consists of a photographic film contained in a plastic holder containing severa) metallic filtcrs and a plastic filter. The filters are used to deteTmine the type and energy of any r adiation r eceived. After a specified period of time which has been agr eed with the approved dosimetry service (ADS}, the film is taken from the holder  and sent to the ADS to  be  pr ocessed and assessed. A new film i s issued  by the employer to r eplace the used film.

90

Any ionising r adiation which has been r eceived wi ll affect the film emu lsion. When the film is  pr ocessed the degree of density represents Lhe dose Jevcls received. The ADS recor cl<; this amount and also adds it to the individual's accumula/il •e dose , th is infom1ation is also sent to the employer.

100

.:i

RJJ:.t.nc & T t• O" Null

RS6-2

UNIT RS7  PROTECTION AGAINST RADIATION

Ruane & Il 

•

T P O'Neill 

e. f.

OTES

!O

20 The distance reqwred for o constant potential  x-roy ut  may be greater.

In ali cases where radiographic equipment is de-ener g1sed {or sh1elded) by a safety system, it is essentia l that only intentiona)  positive action is tak en to re-energise the equ i pment. For exam ple, if a door is opened and an interlock cu ts off an exposure  by x-r ay equipment, then r ecommencement of the exposure must not be  possibJe Slm ply  by closing the door; it must only be achieved only by intent iona! action at the control  panel.

Using x-ray tubes oo site A typica l  pr ocedure f or erecting barriers for site r adiography using a conventional x ray tube u p to 300 kV is as follows: 1.

Erect the  barriers with waming notices approximatcly 25 metres away fr om the source of r adiarion. This distance is not specified in any Regulations but is a good  pr acticat guide to give maximum confidence that the dose Jcvels at the  barriers WJII be l ess t ban 7.5 Sv.h·'. The Inver  se Square Law will not  be r eliable for xr ay beams due to their heterogeneou s s pectra, however, if a radiation dose r ate was known at a s pecific distance from the x-ray tubehead, the minimum distance for the barrier s could be saf ely calculated by using the Inverse Law.

2.

Turn on the x-ray tu behead. Assumin g the tubehead bas  been warmed up, incr ease the kV and mA settings until the maximu m values to be used ha ve  been r eached.

3.

Monitor the dose levels at the barriers to ensur e they are not being exceedcd. 1f  the levei is excessive then the x-ray tube must be tumed off and the barrier s moved further back . Local shielding or collimation of the x-ray beam may be used if the distance to the barriers is not pr actica! to achieve without such measures.

30

 M inimum cabie l engths 20 m upto300/cV . 40

50

60

70

Time switcbes. lnterlocks operated by light beams.

Waming signals which may  be audible or visible or  both, should be  pr esent so that anyone approaching the controlled area is made aware of the potential hazard. X-ray units used for site r adiography have an integr ated waming system. An audible waming (beii, sir cn or buzzer) activates for about ten seconds to wam  peoplc in the vicinity that ionising radiation is about to  be emitted. The audible waming is usuaJly replaced by an orange flashing light when ionising radiation is being emitted.

The waming notices used ar e usually pla ced just outside the controlled area and must contain the interna tional symbol f or ionising radiation - called a tr efoil . Some of the notices must also give an ex planatioo of the significance of the barriers and waming signals. Waming notices s bould  be clearly visible to anyone ap pr oaching the controlled area. In general, no body should be within the controlled area during a rad iogr aphic exposur e. When this cannot  be avoided, e.g.  by classified  per sons comrnencing or  tenninating an exposure, then each  person should not be ex posed to an instantaneous 1

dose rate in excess of 2 mSv .h- . 80

Usiog gamma sour ces on site

90

Because the dose r ate al 1 m fr om the source will be known (via tables), and  because gamma  beams are of fixed discrete wavelengths, the safe distance {minimum d1stance from the sour ce to the  barrier s) can  be calculatcd using the Inverse Square Law. Collimation will almost certainly be used to restrict the r adîation beam, t11is will reduce the safe distance; shielding may also  be introduced if it is r equired to r educe the distance somc more.

Commuoication 100

Everybody in close proxîmity to a controlled arca must  be madc aware of what the warning signals mdicate; suitable worded s1gns placed at strategiC positions should bc u scd as a minimum to convey this information.

RS7-2

UNIT RS6

Ruane & 11 T P O' Neill 

•

RADIATION DETECTION ANO 1\tEASUREl\tENT

T bermo-Iumioescent dosemeter (TLD)

NOTE S

10

20

The TLD consists of two teflon discs containing lithium nuoride set i.n an aluminium  plate which is binary coded for identification purposes . This plate is contained within a plastic  packet and  placed in a holder similar to a film  badge but with no metallic filters. After a specified  per iod of time whtch has  been agreed with the ADS, the  plastic  pack et containing the discs is sent to the ADS to  be assessed. TI1e discs are  placed in a special oven whic b causes the discs to give off light when the temperatur e is r a ised. The intensity of light is measured to determine the amount of radiation received. The ADS records this amount and also adds it to the i.ndividual's accumul ative dose, this i.nformation is also sent to the employer. The TLD system of dose assessment is more easily automated compa red to the film  badge system and TLD's are less sensitive to envirorunental i.nfluences such as heat or  chemical fumes.

30

POCKET DOSEMETERS {EXPOSURE METERS) Pock et dosemeters may be ofthe d ir ect r eadin g type or the ind ir ect read in g type.

40

50

The quartzfibrescope (also know an a quartzfibre e/ectroscope or dosimet er) is a pen lik e device which measures the accumulative dose of ionising radiation received. A quartz fibre, wht ch acts as a pointer , is deflected along a scale (usually calibrated in 11Sv) when ionising radiation is received, the pointer remains i.n th is positjon until mor e radiation is r eceived. The reading can  be taken by holding the instrument to a light source and looki.ng thr ough the opposite end. At any time, the user can zero the readi.ng by placing the fibr esco pe into a socket on a pr oprietary device specifically usedforresett:ing purposes. The use of quartz fibrescopes  by classified per sonnel is not compulsory  by law, but may  be used by radiographers who wish to know the accumulative dose r eceived wbilst wearing the instrument over a period of rime.

Quartt fibrescopes are fragile and can give misleading readi.ngs if dr opped or k n ocked.

60

AUDIBLE ALARMS (POCKET TYPE) Radiation detectors of the audible type may  be wom  by radiographers (typically cli p ped to a  pocket) and sim ply inform the user that helshe is receiving ionising radiation. These instruments do not tell the user how much radiation is being received and do oot permanently r ecord the dose. 70

The use of audible alarms by classificd per sonnel is noi compulsory by l aw, but their use is strongly recommended when working with garruna sources.

80

90

100

h..u 6 Hf06.03

RS6-3

UNIT RS7

Ruane& 11 TP O' Nei/1 NOTES

7 days notice 10 HSE rnclo

ume raduuion is used  waive

tltis 7 day notice can be

mnde. t .e wilen le ss nouce

20

isrequtred.

 Risk a:sse ssment

if more

tilon 5 worker   s.

Fr om an industrial radiograp bers per specrive, a controlled area is an ar ea designated by the employer within which t be radiography tak es  place. If there is a likelihood that a  person 18 years of age or over wi ll exceed 3/1Oths of any relevant dose Iimit, then the area must  be designated as a contr olled area . Section 16 of the Ionising R adiations Regu lations 1999 givcs detail r egar ding the designation of controlled areas.

thereaft er  10

PROTECTION AGAINST RADIATION

CONTROLLED AND SUPERVJSED AREAS

18 days notice r o  J/SE before using rad101ion fo r tltejir .
 Requ ests tu fiSE

•

30

Cabinets or walled enclosur es are not necessarily designated as controlled a r eas if ther e is no likelibood of aoy body r eceiving mor e than 311Oths of any relevant dose Jimit Controlled ar eas for radiography work in factor ies are normally walled enclosu r es often r eferred to as radiographic cell   s or bays. For r adiogra phjc work on site, barr ier s are often erected so that ex posures may be made on components in situ. However, it is always prefer able to transport test components to wallcd enclosures which havc been specifically designed f or radiognphic work . As a second c boice, components should  be tr ansported to an area surrounded by barriers which has  been designated as a controlled area and clear ly identified as such. The purpose of the barriers/wall s is to  pr eveni access by any non-classified persons. AII controlled areas s bould  be clearly identified  by the use of waming signs and the instantaneous dose rate must not exceed 7.5 J.1Sv.h '1 outside the barrier /wall.

40

50

On site work, controlled areas m ust be completely surr ounded by means of a banier , usually bunting or r o pe, erected at waist height . The barriers must be er ected prior to any radiograpruc work comrnencing. A supervised area is designated as an area where any person is likely to be subjected to doses of ionising radiation above one thir d of the levels to be f ound in a controlled ar ea, i.e.2.5 ).1Sv.h·1 Tbis ar ea need not be enclosed by baniers or walls, unless wr itten into a company's local rul es, but it is stîll subject to contr ol by the radiographers. •

Waroing signals and safety systems 46 Ci C o60 or 1U ot l m.

a lr/926 0

Waming signals, wruch may  be audible or v isible or  both, should  be clear , unambiguous and situated so tbat any person within or approaching the contr olled area is made aware of tbe impending danger or actual presence of r adiation. Two wamings should be given, the fir st immediately prior to and the second dur ing the radiographic exposure. Ther e should  be a difference and a clear distinction  between these two warnings.

70

Waming signals must o perate automatically for ali x-r ay equipment and f or sealed source equipment where the instantaneous dose rate is gr eater than 10 mSv.min·• at 1 m from the sour ce. Exposures must not commence if the waming signals do not operate. Many fonns of safety systems ar e in use f or walled enclosur es for x-r ay or gamma source work. llte main systems available incorporate the following:

80

100

a.

Electrica! interlocks or microswitches: Thesc should be constructed and fitted so that they w îll fail-to-saf ety and ca onot  bc casily overridden. This can often  be acrueved by arranging that the equipment is cnerg1scd when the switch is r elcased r ather than wben it is depressed. R eliance must nevcr bc placed on an inter lock or  micr oswitch acting as the main on/off switch.  b. Magnetically operated switcbes. c. K ey operated swîtches: These  provide positive  protection and at the same time cnable strict administr ative control over the choice of authorised users. The operator holding the key has a  positive saf eguard against inadvcrtent exposure. Multiple key systems ar e available which cnsur e that al! door s and other saf ety devices are checked and a key withdrawn fr om each and inserted into a maste r  k eyboard. Only when the master keyboard is filled can thc control key for  energisation of the radiographic equi pmcnt be obtained and used. d _ Mechanical safe guard s, e.g. automatic doors.

.:> Ru3n & T P O'N..:ill

RS7-t

UNIT RS7 ·PROTECTION AGAINST RADIATION

R uane & Il 

TP O'Nei   /1

THE Il\TVER SE SQUARE LAW

NOTES

10

Electr omagnetic radiation, x-rays, gamma r ays and light etc., obey the inverse squar e law which states that the intensity is inversely  p r oportional to the  square of thc dist ancefrom t he source. Ther efore, the f ormula can be stated as follows:

20

wher eI =original intensity at DI. 30

12 = intensity at 02. OI = original distance.

D2 = new dista nce.

40

Pr oviding that three of the f our values are known, then the f ourth value can be calculated. Tofind I 1 when 12, D 1 and 02 ar e known,usethe f ollowing formula :

50

To fmd 12 when 11 , D 1 and D2 ar e known, use the f ollowing f ormula:

60

To find DI when 11 , 12 and D2 ar e k n owo, use the following f onnula:

70

To fmd 02 when D1, 11 and 12 ar e known , use the follow ing formula:

80

90

1()(}

RS7-J

UNIT RS7  PROTECTION AGAINST RADIATION

R uane & I  l  T P O'Nei/1  _

•

OTES

.

Calculating saf e work ing distance using gamm a sou rces From the inverse square law formula, 02 wiU be used to represent the safe working 10

distance, therefore:

20

where 11

1

= intensity at 01 in J.!Sv_h -

or source strength (GBq) x output (depends on

sour ce type)

1

12 = maximum pemtissible dose rate (7.5 ţ.tSv .h. ). 01 = 1mctr e (because outputs are given at 1 m).

30

02 = Safe distance in metres. Outputs or exposure rat efactors are usually obtained from a published table and will  be given in J.!Svlh/GBq or Rlh/Ci.

To con vc•rt  R/h/Ci 10   pSvlh/GBq . divide by 0037 .

o

40

Sour ce

50

60

Out put@ lm

Rlh/Ci

 j.tSv/h/G Bq

Cobalt 60

1.32

357

Caesium 134

0.&7

235

Caesium 137

0.33

89

Iridium 192

0.48

130

Ytter   buim 169

0.125

34

Thulium 170

0.0025

0.68

 Note: Oespite using calculations to determine safe distances, it is still necessary to cbeck radiation levels at the perimeter with a dose rate meter as an extra precaution.

Ex posure time An exposure dose can be reduced by restricting the time of an exposure. 70

80

lo order to obtain acceptable images, radiographers will have calculated their exposure time for specific ap pl ications  based on  penetra ting power of the radiation and the intensity of radiat ion available. The exposure times for the specific application cannot normally be reduced any further unless peoetr ating power and/or the radiation intensity is increased. If it is  possible (or  permissible) to do this, the radiation wtll be mor e hannful anyway. However, it is  possible to minimise the time spent close to any sour ce of radiation cinring xposur es.

SHIELDING 90

lOO

Shielding may be uscd during radiograp hic cxposurcs in order to restrict or reduce exposure to ionising radiation . Shielding may be used on site or in opcn compounds to allow a reduction in barricr distance  but it is prim ar i l y considered when dcsigning walled enclosur es for radiographic work. Rad•ographic enclosures are constructcd units which should prov1dc cffect•vc shielding from ionising radiation. The  protection is  provided  by the walls, doors etc. and their  cffcctivcness will dcpend upon the choice of materials and whcther they are acting as  primary or sccondary barrier s.

f) ku:anr &

•

r·o l'tlll

hsuor6 N/U(IJ{J )

•

RS7-4

UNIT RS7

Ruane& 11 T P O'Nei/ 1  NOTIS

 _

•

•

10

•

PROTECTION AGAINST RADIATION

Primary barriers are designed to provide protection again st the primary radiation  beam. Secondary barrier s are designed to pr ovide pr otection against scattered radiation.

When erecting compounds it is sensible to use the cheapest  building material and th is is usually concrete. Besides plain concret e, heavy concr ete made from barium sulphate is sometimes used. Lead concrete and concr ete conta ining 50% iron ar e also available_  Shielding may be introduced local to the source of radiation and may simply consist of  a sheet of lead which may be attached to a wooden board for handling r easons.

20

Sh.ielding matcrials arc choscn by taking in to consideration their cost, weight, izc and shielding effectiveness which is lar gely dependent on the density of the mat erial.

HVT/TVT 30

Shielding effectiveness is derived by taking into consideration the half value thickne ss or the t ent h value thickness of a specific material, both of which are govemed by the wavelength(s) ofradiation being used. •

•

40

Half value thickness (HVT): the thickness of a material which will r educe the exposure rate to one half . Tenth value thickness (TVT): the thickness of a material which will reduce the exposure rate to one tenth. Lead

Steel

Concr ete

Energy

50

60

70

Collimation

so

Collimation is a forrn of shielding and  provides a parallel, or near  parallel, beam of  r adiation by blocking out unwanted parts of the beam. The beam may be r estricted for  image quality r easons or safety r easons. Collimators are usually made of lead, tungsten, or similar dense material and are used to reduce the useji1l beam to the minimum size necessary f or the r equired cxposure.

A collimator for a directionat x-r ay tube may  be attached to the window of the  A pa no r amic tubehead may be converted ton 90 d ircctwnal t ubehead by nllnchin g a collîmM or  cnnt nining 11 hoie allche

tubehead and in some cases may be adjusted like a pair of curta ins. A collimator for a  panor amic x-ray tubehead consists of two bracelets, the  positions of which may  be adjusted to obtain the r equir ed useful beam. Collimator s for gamma sources are normally prepositio ncd on or ncar thc componcnt to be radiographed, th en the sourcc is placed into thc collimator, e.g. via a wind out mechanism.

way nrounrl t lle circum fer ence. tl w s  pr ovuiin g shiel ding  e,·cry -,..here exccpl in thc  / ocntion of the halP.. !00

- Hu::we /.:. 1r O"J'IIrill

RS7-5

UNIT RS7A · CALCULATIONS FOR RADIATION PROTECTIO

Ruane & 11 T P O'Nei/1

 Example 1

NOTES

What is the safe d•stance (mjnimum distance for the barriers) for a 370 GBq lr l92 source? 10

a.

 b.

From the table, output for Jrl92 is 130 ţ. Svlh/GBq a l m; ther efore:

Dz

2

J370

?O

C.

02

d.

02

X

J30 7.5

X

12

.J64t3

30

e. 02

 It is stil/ necessary to check  radiation l evcls at the  pcrimeter with n d ose rate

=

80.1 m

Therefore, the barriers must be erected at least 80.1 m fr om the source unless shielding is introduced .

mete.r .

40

 Example2 1

An x-ray unit set at 250 kV produces 6.2 mSv.h- at 1 m. How much concrete will  be 1

requir ed to reduce this to 7.5 JJSv.h" ? 1

1

a. Convert rnSv.h" to J.1Sv.h'  by multiplying by 1000:

6.2 mSv.h"1 x 1000 = 6200 )lSv.h- 1•

50

 b.

Determine how many times greater the dose rate is at 1 m compared to 7.5 ţ. Sv.h-1

:

6200 f.1Sv.h"1

60

7.5 )lSv.h"1 c.

826.6 or 827 times greater.

Determine how many HVT's are required to bring the value down to Jcss than 1 1 (which repr esents a dose rate oflessthan 7.5 ţ. Sv.h" :

70

1

827

2

3

4

5

6

7

 j413.5  j206.75,103.38j51.69 j25 .84 112.92  j6.46

8

,3.23

9

10

 jJ.62

 j0.81

Therefore, 1O HVT's would be required to r educe the dose rate to less than 7.5 J.!Sv.h-1. 80

d.

Detennine the total thickncss of concrete requir ed: 1 HVT of concrete at 250 kV = 28 mm (as dctcnnined from liVT chart). 1O x 28 mm = 280 mm of concr ete to give a dose lower than 7.5 )lSv.h"

1 •

90

100

RS7A- J

Ul\'IT RS7A

Ruane & Il  T P O' Nei/1 OTES

•

CALCULATIONS FOR RADIATION PROTECTION

 Example 3

 _

10

An lrl92 source produces a dose meter r eading which is 250 times greater than the maximum permitted dose rate. How much lead will bc required to reduce this to 7.5 J.!Sv.h-1 or less? a.

Determine how man y HVT's are requircd to bring the value down to less than 1 (which r e presentsa dose rate of less than 7.5 !lSv.h:

2

1

250

20

 jl25

3

162.5

4

5

6

[ 31.25  j 15.62 ,7.8 1  j3.9

7

8

, 1.95  j 0.97

Therefore, 8 HVT's wou1d be requir ed to reduce the dose r ate to less than 7.5 J.!Sv.h-1 •

 b. 30

Determine the total thick.ness of Jead required: 1 HVT of lead for Irl92 = 5.5 mm (as deterrnincd from HVT chart). 8 X 5.5 nun = 44 mm or lead to give a dose lower than 7.5 J.!SV.b- 1 •

 Exampl e4 40

An x-ray set operating at 250 kVp  produces 18.5 mSv/rnNmin at 1 m. If the set operates at 10 mA, how much concrete would be r equired to reduce the dose to 7.5 f.lSv. b-1 or less? a.

Convert mSv/mA/min to mSv/rnA/h by multi plying by 60:

60 x 18.5 mSv/mA/min - 11 10 mSv/rnA/h

 so  b.

Convert mSv/mA/b to mSv.h-1 by multiplying  by mA  being used (10):

10 mA x 1110 mSv/rnA/h = 11,100 mSv.h- 1 c.

Convert mSv.h-1 to f.lSv.h-1 by mu ltiplying by 1000:

60

1000 X 11,100 J.!SV.h- 1 = 11,100,000 f.lSv.h-1 d.

Determine ratio between value pr esent at 1 m at 7.5 f.lSv.h-1: 11,100,000f.1Sv.h·1 1 7.5J.!Sv.h ·

70

e.

r ·r 

Determine how many HVT's will be requir ed by using a scientific calculator : Type in 1480000 and pr ess log (this gives 6.170...); press -;- (divide) then type in 2, press lo g and finally = (equals). The answer you get s bould be 20.497..., which means 20.497 HVT's of concrete would bc required .

80

f.

90

= 1,480,000 times greater .

1 HVT of concrete at 250 kV = 28 mm (as determined fr om HVT chart). 20.497 x 28 nm1 = 574 mm of concrete to give a dose lower than 7.5 f.lSv.h- 1.

 Note: A scientific calculator could ha ve been uscd in exampl es 3 and 4 to obtain more accurate r esults, although thc r esults obtaincd do err on the side of caution.

100

i'.:· ftu:aut &: -r r O"Ndll

RS7 A -2

UNIT RS7A · CALCULATIO S FOR RADIATION PROTECTION

Ruane & Il  T P O'N ei/1

 Example 5

NOTES

10

An lr 192 source with 8 Ci output is being used to radiogra ph welds on an open ended tank made from steel with dimensions as shown in the diagram. Calculate thc safe distances from the externa!surfaces of the tank.

20

30

40

1. Source output calculation: a.

Convert Ci to GBq.

8 Ci x 37 = 296 GBq. so

b.

Calculate output at 1 m: From table output is 130 Sv/GBq for [rl92 at 1 m. 1 130 x 296 = 38480 J.tSv.h" .

2.

Work out safe work ing distance from open end:

60

Source output

MPDR 

70

 Jsl3o.666 

C.

Dm

d.

D m = 71 .6 m from th e sour ce

e.

Dm

&O

90

3.

=

from the end of the tank = 71.6 m - 2 m = 69.6 m

Work out saf e distances from the two s1des of the tank with 26 mm wall th icknesses:

a. HVT of stecl using lrl 92 is 13 mm (as dctennined fr om HVT table). Source 1 output al 1 m is 38,480 pSv.h" (alr eady known from Step /).  b. Determine how many HVT's arc present:

26 mm of stccl = 2 HVT' s (1 JIVT = 13 mm).

100

' ku.: nC" 4.: T 5• o·N('ilt  /0f.tO.l lo.:suc 6 :.1

RS7A-3

UNITRS7A · CALCULATIONSFORRADIATIONPROTECTION

Ruane & Il  T P O' N ei/1 OTES

c. Detenninc dose rate after 2 x HVT: 10

1

2

38,480 1 19,240 = 9620 J-1Sv.h"

9620

1 .

d. Detennine the safe working distance: 20

Dm =

{OutPtrt

vMPDR:

30

Dm = Jl282.66 Dm

35.8 m from the source

40

Dm fr om the sides of the tank = 35.8 m - 1.5 m = 34.3 m 4.

Work out saf e distances from the closed end of the tank with 39 mm wall thickness: a. HVT of steel using Ir192 is 13 mm (as detennined f ro   m HVT table). Source 1 output at 1 m is 38,480 J!Sv.h- (alr eady known fr om Step 1).

50

 b. Detemline how many HVT's are pr escnt:

39 mrn of steel = 3 HVT's (1 HVT = 13 mm). c. Determine dose rate after 3 x HVT: 60

1 38,480 lt 9,240

2

3

1

9620 1

4810

1

= 4810 J-1Sv.h"

70

d. Determine the saf c wor king distancc: Dm =

R

80

Dm = Dm 90

=

5  J641.33

Dm = 25.32 m from t he sour ce Dm from the closed end of the tank

= 25.32 m - 2 m = 23.32 m

100

f,.;

R u:an

& T Po

h'U(" (1 1.&/U6!0.l

Nt•U

RS7A-4

UNIT RSS ·STORAGE OF RADIATION SOURCES

 Ruane &  Il  T P

O'Nei/1

NOTES

GAMMA SOURCES 10

The Ionising Radiations Regulations require ali radioa ctive substances to be k ept in a  suitabf e r eceptacl e when not in use. When tbe suita bility of a receptacle is being considered there are a number of factor s which need to be tak en into consideration, including the environmental conditions, risk of damage, characteristics of the source, e.g. the selfheating effect in high activity sources.

The storc used for storing ganuna sour ces in their container s/r ece ptacles must be dedicated for the storage of radioactive materials and ancillary irems. Flamm able or  20

explosive material s must not be put in the store.

Signs must be placed in a prominent position to warn persons in the vicinity that the store may contain radioactive substances. The signs mu st conform to the Safety Signs Regu lations: 1980(SI 1980No. l471),BS3510 : 1968andBS5378: 1980. A suitable storc for radioactive substances should provide the following: 30

1.

Protection from the weather /environment.

2.

Resistance to fire.

3.

Shielding for non-classified  persons with an instantaneous dose rate of less than 2.5 Sv.h·' outside the storc. If this figure cannot be achieved then the ar ea may have to be designated a controfled ar ca.

4.

Ventilation .

40

5. Security.

50

60

For site radiograpby, gamma sources shielded in their containers should be stored in an isotope stor age pit (bomb pit) when not in use. This consists of a 450 mm to 600 rnm diameter  pipe approxirnately one metre long set into the ground and fitted with a lockable lid, surr ounded by an enclosur e (fence or wall) with a lockable entrance and waming signs displayed.

X-RA y MACillNES X-ray machines should  be stored under lock and key when not in use for prolonged  periods, e.g. ovemight. Keys for x-ray control panels should be held by a r esponsible  person when the equipment is not in use.

70

80

90

100

-:0 H.unc & t 1• O"NtHl

lssuc 6 UJI»tto. Ol

RS8-I

UNIT RS9 ·TRANSPORT OF RADIOACTIVE SUBSTANCES

Ruane & Il  T P O' Nei/1 OTES

The wherenbouts of source r ecor ds shoulrf be updated 10 an n dai/) bosi.t .

20

The r equi r ements for the transport of radioactive substances, includ ing sealed sources, are documcnted in R egulation 29 of IRR 1999. The SI document entitled The  Radioactive  Mat ert a l (   Road Transport)Regulations 2002 (S   I 1093), as the t itle suggests,deals wilh transportation by r oad.

The tcrm tran spor t as dcfined by IR.R 1999 encom passes tr ans pon by road, raii, sea or  air or any other form oftransportation thr ough a pu blic place, including by hand. The em ployer causing or perrnitting tr ansportation of a r a dioactive substance is r es ponsible , as far as is reasonably pr aclica ble, for ensuring that the correct reccptac le (container ) and labclling is used. Containers must  be locked during trans portation although a r adiation monitor shou ld  be switched on in case of leakage.

The veh.icle must be equipped with firefighting appliances in case of accident.

30

SI l093 requirem ents Ali carriers involvcd in the transportation of r adioactive goods must estabhsh radiation protection progranune which: a.

40

 b.

a

takes into account the rneasures to  be taken in r espect of the magmtude and likelihood of exposure.

adopts a structured and systematic approach.

Carriers must also review the radiation protection programmes at suitable intervals (not exceeding 3 years) and, where necessary, revtse these. This programme must be made available to the Secretary of State upon written requcst. 50

The carrier must also pr ovide the public , who would be in the arca of the carriage, inf orrnation regarding the carriage and emcr gency measu r es envisaged to alter, protect and assist in an emergency. This should include the res ponsible authority for  implementing emergency measures.

Leakages 60

70

Carr iers must ensure that leakage level.s on the externa! surface do not exceed: a.

4 Bq/cm2 for beta and garruna emitter s.

 b .

0.4 Bq/cm2 for alpha eminers.

Packaging Type A  packaging is used for sour ces with an activity up to a s pecificd value (A 1 (s pecial forrn) or A 2 value) which is govcmed by the type ofradioisotope.

Type 8 or C packaging is used for sour ces with an activity above a specified valuc (A 1 or A 2 value), i.e. activities greater than tbose authorised for that  package design, or a radio-nuclide or physical fonn differ enl fr om those authorised for that package design. 80

90

Sealcd sour ces more than 5 mrn in size (known as special form radioactive material) are normally used in industria l r adiogr aphy, therefore the A , values which apply are as follows for some commonly used radioisoto pcs: •

Cobalt 60

0.4 TBq

•

Cacsium 137

2TBq

•

lridium 192

1 TBq

•

Selemium 75

3TBq

•

Ynerbium 169

4TBq

Marking , labcllin g and pl aca r ding 100

Schedule 6 details thc r cquirements f or marki.ng, la belling and  placarding. Pl ac;trds display ing the word "RADJOACTI VE" (fig. 2-6 in Schcdulc 14) are rcquir ed to be

c- lhJ "r &. h)UC:

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RS9-I

UNIT RS9 · TRANSPORT OF RADIOACTIVE SUBSTANCES

Ruane & 11 T P O'Nei ll 

 placed on both sides and on the r ear of any vehicle used for transportat ion of packaged

SOTES

10

rad10active substances which have  been labelled 1-WHITE, li-YELLOW or III YELLOW (if the vehicle has no lateral walls, the signs may be fixcd dir ectly to the cargo providing they ar e visible). This labei depends on the dose rate measured at the surface and at 1 m.

The category of the  package depends on thc dose rates at thc surfacc of the  pflckage and is detemlliled fr om Table IV of Schedule 1 whilst taking into consider at 1on a Transport Index calculated in accordance wi th Schedule 5. 20

for industrial radiography using sealed sources, the Transport Index would normally  be determined  by mcasuring the dose rate 10 mSv.h·' at 1 m fr om the externa! sur face of the packa ge then multiplying by 100. The vehicle used for trans port must also bear a frreproof placard, securely posted in the cab of the vehicle and it must be v isible to the driver. The  placard mu st con tain embossed or stamped lettering with the word "RADIOACTIVE" at least 12 mrn high

30

along with additional information in lettering at least 5 mm high. The size of the placar d should be at least 12 cm square and be in the f ollowing f orm:

This vehicle is carrying

RADIOACTIVE

40

MATER IAL In case of accident get in touch at once with THE

POLICE

and [Particular s of owner /oper ator of the vehiclc]

50

Tr a ns por t documents 60

70

 IA EA = lntunationnl Atomic  E nergy Ag anc y.

80

A consignor who is trans porting radioact ive material must  possess detailed transport documents complying with applicable r egulations. If transporting radioactive materia l  by road, SI 1093 requires at least the following in formation in accordance with Schedule 20 and Schedule 21 : a. Reference to SI 1093 (2002).  b.  Name, address and telephone number of consignor. c.  Name and addr ess of consignee. d. The proper shipping name as specified in column 2 of Table VIII in Schedule 1). c. The United National Class Number "7". f. The words "RADIOACTIVE MATERJAL". g. The name or sym bol of thc radionuclide(s). h. . A description of the physical and chemical form of the mater  ial. The maximum activity in Bq. 1. The category of the package, i.e.l-WHITE. Il-YELLOW or III-YELLOW.  j. k. The Transport Index if the category of the  package is Il-YELLOW or 

IH-YELLOW. A declaration signed  by the consignor that ali contents arc accurately dcscribed in the transport documentation. m. . Any actions that are requi.red  by the carricr. Emer gency arrangements appropriate to thc n. . consignment. o. The UN number assigned to the mater ial (column 1 of Table VIII, Schedule 1).  p. The identification mark of each competent approval certificate applicable 1.

90

100

-.· RM:IItic-& l"I"O"Nt.ili lhut C. !< 'Ub/0)

RS9-2

UNIT RSIO • APPOINTl\IENTS /RESPONSIBILITIES

Ruane & Il  TP O'Nei/1 1\0TES

RADIATI ON PROTECI'ION ADVISER

(RPA)

AII companies using ionising radiations must appoint an RPA. His appointment must 10

 be notified to the Health & Safety Executive (HSE) 28 days prior to commencement date. The HSE will a pprove thc appointment in writing. The RPA must be qualified to advise the company on ali aspects of radiation hazards, safcty and protection . The RPA is not necessarily an employee.

20

Large companies or organisations may r equir e more than one RPA.

Qualifications Qualifications and ex perience should include : 30

40

a. Theoretical trainiog on the properties of ionising radiation, hazards and thc control of these to minimise exposure to ionising rad iation.  b. A detailed knowledge of ali statutory  provisions and documentation includin g k eeping up to date oo the use of ionising r adiation. c. A detailed under standing of the working pracrices of the company which he/she represents and a genera l knowledge of other similar working practices . d. The ability to communicate and  provide deta iled instructions (Local Rules) and sound advice on aU aspects of radiat ion saf ety.

Typical duties

50

a. Provision or ap prova l of Local Rules and saf ety related working instructions.  b. Provision or ap proval of detailed contingency plans. c. lnvestigation of incidents involving high doses of radiation and over ex posure. d. The selection or approval of radiation protection supervisors (RPS). e. May be involved with training and other duties involved with ionising radiation.

RADIATION PROTECTION SUPERVISOR (RPS) 60

70

RPS's are employees of the com pany a ppointed in writing. TI1er e should be one RPS to each area of working or altematively one RPS to oversee ali radiographic areas but he/she cannot  be involved in taking any of the ex posures. The name and contact details of the RPS shou ld  be posted in suitable areas and is an essential  part of the Local Rules. The employer cannot delegate r esponsibility for com pliance with the regulations to the RPS.

The person(s) appointed should have a good under standing of the r egulations and the local rules and have the authority to enf or ce them.

CLASSIFIED PERSON 80

Prior to working with radiation the JRR 1999 r equir e a  person to become classified  by the employer.

90

Per sons must be classified if they may be required to enter a conrroll ed ar ea and if  there is any likelihood that they may r eceive a dose of radiation which exceeds 3/ 1Oths of any dose limit. A person is requ ir ed to bc classified if the ionising radiauon uscd is capable of pr oducing an over dose within a few minutcs. Classified workers must be trained m the use of ionising radia tion ap paratus and ali associated ancillary equipment. Tbey sh ould also be convcr sant with the Local R u les. An employee once classified wi ll be classificd for 12 months.

1oo

To become classified the per son must be ovcr 18 years of agc and must  be certified fit to wor k w ith ionising r adiations by eithcr an cmploymcn t med i cal advisor (EMA) or  an appointed doctor (AD) and so recorded in thc hcalth r ccords.

tJ Rua nc: & T P O' N tiU htuc 6!tf06JO)

HSI0-1

UNIT RSlO

R uane & Il 

· APPOI1'4'Tl\IENTS /RESPONSIBILITIES

eil/  T P O'N  OTES

QUALIFIED PER SONS

1O

Qualified per soos are used for thc purpos e of testjng monjtoring equipment; they must  be formally trained and have the r equir ed expenise and experience to test and calibrate monitoring equipment .

Qualified persons are normally employed by equipment manufactur ers or specialist calibration or ganisations. Their appointment must bc notified to the HSE in a similar  manner as for the RPA. 20

30

40

50

60

7 0

so

90

100

RSI0-2

UNIT RSll • LOCAL RULES & CONTINGENCY PLANS

Ruane & Il  TP O'Nei   /1 1\0TES

LOCALRULES

 /}{R /999  Ref 17 - Local  worlcing prnc t ices.

 Local Rules are radiographic safety rules, typically produced in bookJet f orrn, which apply to specific work locations. 10

Some orgn isntions try to 20 bc nil ancompn ssing with tha cont enl of the Local  Rufe. . thuefore sometimes it is only nece.uory 10  tfistr ib111e the relevant paris of the Local Hul es to enrpl o yee.s. 30 •

An employer must prov ide local rules with a content and format which leaves the radiographers in no doubt regarding the operation of r adiographic equ1pmcnt and emergency  procedur es (contin gency plans).

Local Rules may differ considerably from one work location to another , e.g. the equipment being used may be diffcr ent and the contact details for emer gencies may differ. Thc RPA will normally be r es ponsible for the produ ction ofthcse Local Rules and the RPS(s) are responsible for ovcrsceing thcir implcmentation. A copy of the rules should  be k c pt at a centra l point but copies must  be cir culated to the employees involved.

 Note : The employer carriesthe responsibility f or compliance with the regulations ; this cannot be delegated to RPA's or RPS's.

Conten t of Local Ru les 1.  Names and contact details, e.g. telephooe number s, ofR PA and/or RPS. 40

50

60

2.

Description ofhow controlled area(s) and supervised area{s) are designated.

3.

Procedures for setting up barriers (site radiography).

4.

Operating instructions or ref er ence to them.

5.

Arrangerneots for keeping doses ALARP.

6. Copies of signs and notices. 7.

Contingeocy plans and use of any emergency equipment.

8.

Reportinglrecording arrangemeots for adverse incidents involving radiation.

9.

Accounting arrangements for radioactive materials.

10. Transport arrangements for radioactive materials.

I l. Storage arr angements for radioactive mater ials. 12. Procedur es f or equipment handov ers. 13. Qualificationltr aining of staff using Local Rules. 10

14. Dosirnetry arrangements for staff . 15. Monitoring arrangements and r ecords. 16. Co-operation between the client and other employer s.

80

CONTINGENCY PLANS Every employer should have written emergency procedure s to cover the action to be taken when an incident occur s with a sealed sour ce or x-ray equipment. These contingency plan s should be pr e par ed  by an RPA or by using advice fr om an RPA . Consult.ation ma y also be necessary with thc cmcr gency services and the contractor or  client.

90

R egulation 25 (w) A ssessmenr of Hazards sta tes that employees must be pr ovided with information, instruction, tra ining and equi pment lo restrict exposure to ionising radiations. A copy of the contingency  plan f or a s pecific location must  be induded in the Local Rules.

100

Rehearsals of contingency plans are r equir ed a t suita blc intervals by IRR 1999 12(2)c.

t) Ru2n r & T r O"Nrill lo>suc- (, !.4/06!0J

R Sll -1

UNIT RSll • LOCAL RULES & CONTINGENCY PLANS

Ruane & 11 T P O'Nei/1

 National Arrangement s for lnciden ts lnvolving Radioactivily (NAIR) may be involved if radiation accidents involve members of the public only at the request of the police and only after the HSE and NRPB have proved tobe unavailable .

OTES

10

TI1e emergency arrangements which can be implemented by the police, i.c. NAIR, should noi fonn any part oflhc conringency plan. The contingency plan should include:

1. The names of persons authorised to implcment the contingency plans. 20

2.

The names of persons res ponsîble for radiation safety (RPA and RPS(s)).

Typica1areas which also need 10 be covered are: 1. Situations in which work will cease immediately.

JO

2.

Positioning of barrier s and waming signs.

3.

Names and telephone numbers of the  peop1e who need immediately, i.c. RPS, RPA and clîenls.

4.

Search procedure for lost sour ces.

10

 be inforrned

5. Recovery procedures. 6.

Action requ ir ed for a sour ce involved in a fue or transport accident.

7.

Arrangements for dose assessment ofpersons involved in any accident.

8.

Evacuation pr ocedure.

9.

Prepara6on of the incident report.

40

Example contingency plan 50

The following contingency plan could  be used for locating and making safe a sealed source which has been lost in the nearby vicinity, e.g. one which bas become detached fr om a guide tube. The mnemonic device MAPTRACK may bc used:

60

Measures the radiation with a dose ratemeter to determine levcls.

M  A

Access tobe r estricted, barriers and warning signs;md lights to bc  positioned to keep dose levels to 7.5 -t Sv.h·' or lcss. Patr ol barners (only persons involved in source recovery tobe allowed through).

p

Plan a course of action prior to entering a controlled area, i.e. long haodled tongs, bags oflead shot.

T

Tell the responsible site repr esentative, e.g. senior cngineer , of  occurrence and cour se of action proposed . Inform police if public are at risk and advise them on action to be taken.

R

R cplace, ifpossible, a deta ched source. Work as a tcam, each person to r eceive a minimal exposur e (refer to table for S uur c:e Recovcl)').

A

Anenuate the radiation if the source cannot be r eplaccd using any masking material available. Check dose rates.

c

Caii for help frorn RPA ,RPS and, if r equired , NRPB.

70

HO

K 90

=

K eep the barriers in position until assistance arrives and the problem ts solved.

100

RSII -2

UNIT RSll · LOCAL RULES&CONTINGENCY PLANS

Ruane & 11 TPO' Nei/1

Emergency kit f or gamma source recovery typically consists ofthe following :

OTES

a.  b.

Survey meter . Personal audible alarm. Handling tongs- 1 m and 2 m. Tool kit- pliers, hacksaw, screwdrivers etc.. Torch . 4 to 5 bags of lead shot - 2 kg each. Tripod. Guide tube. Storage pot - if not proprietary, improvise with any lc:ad lined container.

c. d. c.

10

f. g. h. i.

20

The following table cnables dose assessments to be determined.

Sour ce Recovery- Maximum times for exposure

 Ref erence levelsfor 10 mSv to the hands at 1 mfrom a source 30

Sour ce

Activity (curies} 1 2 5

Ir192

40

50

Co60

10 20 50 100 1 2 5 10 20 50 100

Dose rate at 1m mSv 4.8 9.6 24 48 96 240 480 13.2 26.4 66 132 264 660 1320

Time allowed (mios} 120 60 25 12 6 2 1 46

23 9 4.6 2.3 0.9 0.4

60

Actions (sealed sour ces) The following actions are r equired depcnding upon the type of incident. Remember  that the detailed procedures should be documented in the contingency plans. •

70

•

80

Lost sour ce - If lost in the nearby vicin ity the MAPTRACK procedure rnay  be used  by a person authorised  by the employer (document ed in the contingency  plans), otherwise, inform the employer immedia tely. The employer is to organise the search and infom1 the HSE if it is not f ound within 24 hours. A report will be r equired under the Radioactive Substances Act 1993. Stolen sourcc or source lost in transit - Infom1 the employer ami police irnmediately. The employer to inform the HSE if it  î s not f ou nd within 24 hours.  A report will be required under the Radioactive Substances Act 1993.

Contiogency plans for x-ray uoits

90

Contingency plans f or x-ray units must  be in a wrinen f o rmat similar to thosc for sealed sour ces. TI1ey should cover a siruation when the x -ray unit is accidcntally switched on or is damaged and cannot be switched off. TI1ere is also the possi bility of  x-ray cr awlers used on pipe lines to go missing inside the pipeline' 'tne requirement to isolate a faulty x-r ay unit until rectificd  by a propcrly qualificd  person should be stTessed.

\ 00

!f an mcident occurs, the x-ray unit should not bc moved (ifpractica ble) unt1l dctaJls of  ils position have becn r ccor ded for the purposes of dose assessmcnts.

n R.u:an &: lniU' (,

T

f" O'N

UJt.1610 \

U

HSII-3

UNIT RSll · LOCAL RULES & CONTINGENCY PLANS

Ruane & Il  TP O'Neil/ 

The f ollowing mnemonic device may be used for incidents with x-ray tubes:

OTES

SLAT  10

s

Switch off the machine (by cutting off the power supply if this cannot  be achieved from the control  panel).

L

Leave everything in position until scen by 1he R PA or R.PS.

A

Ask any per sons who may have been exposed to x-r ays to remain until qucstioned by RPA or RPS otherwise obtain names, addresses and telephone numbers.

T

Tell and inf orm any person or authority who has any responsibilities in connection with the occurrence, i.e.RPA,RPS,Eng1ncers, Police,  NRPB.

20

30

40

50

60

70

80

90

100

.,_ ltu3nc: & T l' O'Neill

RSII -4

UNIT RS12 · PERSONAL DOSIMETRY

Ruane & I l  TPO'Nei/1 .

NOTES

CLASSIFICATION 10

The lonising Radiations Regulation s require a person to be classijied if they ar e likely to exceed 3/1Oths of any relevant dose Iimit. Anybody \\ ho is requircd to work in a controllcd area will fali into lhis category . In deciding wheth er a person should  be classified, consideration should  be given to the circumstances when lhere is a chance of that person receiving a significant tlosc of  radiation.

20

There are special requirements for female employees where a dose of more than 13 mSv to the abdomen in any consecutive  period of 3 months would rcquiu:: consultation with the RPA to control the exposure and ensure this level is not rca ched. A classified person should be trained in lhe use ofthe ionising radiation equipment and generator s, be conversant with a writ1en system of wor k and be aware of the dangcrs.

30

A medical is required  prior to a per son srarting work involving ionising radiation (known as a pre-employm ent medical); this is performed  by an appointed doctor (AD) oremployment medical advisor (EMA). An AD is a r egistered medica l practitioner appointed in writing by tbe HSE for the  purposes ofthe R egulations.

40

An EMA is appointed under Section 56 of the Heallh & Safety at Work etc. Act 1974.

MEDICAL SURVEILLANCE Medical surveillance includes the following:

so

a.

b. c. d.

60

Pre-employment medical examinations . Special medical examinations. Per iodic reviews of hea lth. Determination whether further dose limit conditions are appr o pnate.

AII classified per sons must have a r ecord of medical surveillance; this is called a health r ecord. Heallh recor ds must be kept for 50 years after the last cntry was made. A form which is available from HMSO (Form 2067) is normally used as the proforma for  the health r ecord and this specifies the information to be recorded and maintained for  the purposes of the Regulat ions. Medical examinations, wh ich include a blood test, are conducted by the AD or EMA . lf the r esults of the examination are satisfactory, tbe AD or EMA will then certify the

70

80

 person fit for working with ionising radiation . The employer îs r esponsible for ensuring that ali of his radiat ion worker s are subjecr to adequate medical surveillance. This includes ensuring that the AD or EMA at least r eviews the health r ecord of each employee at no more than 12 monthly intervals or  more frequently if requir ed by the AD or EMA; this is known as a periodic r eview. AD's and EMA's have been strongly advised  by the HSE to conduci medicals for site radiographers at least on an annual hasis . Thc judgcmcnt of thc EMA and AD may, allcr cxamination of dosc rccord s and au interview with the classified person, r equcst a fui! medical exammatîon, medtcal tests and exceptionally chr omosome aberrat ion tests.

90

lf the persoo changes cmployment they are still classified providing that they have  bcen certifiedfit within the  precedin g 12 months and that a co py ofthc cert•f•cahon ts kept in the new health r ecord.

100

Ruanc-

&. T P o·x

b c 6 l.t10(.,..J

ill

RS12-l

UNIT RS12

R uane & Il  T P O'Nei/1 NOTES

•

PERSONAL DOSIMETRY

DOSE ASSESSMENTS An  Approved Dosimetry S ervice (ADS) must carry out the examination of dosemeters 10

and determine thc dose received by the wearer . ·ne approved systcm gives maximum confidence of accurate assessments to accepted national standards. The ADS supply the dosemcters, assess the dose rcceived of ali significant amounts of  radiation, keeps the per son's dose rccords and u1fonns the empl oyer of doses with summaries at least once every 3 months.

20

The ADS will also include any estimatcd doses madc by the HSE in the case where a dosemet
30

The employer is responsible for distri bution and collection of dosemeter s and for  arrangements with the ADS regard ing assessments. The employer must kee p a copy of th c summary of the dose record from the ADS for  at least 2 years.

40

Dosemeter s are changed in relation to the dose likely to  bc receaved. lntervals of  l montb ar e normal  but shorter or longer periods may apply, i.e. a 3 month interval would only be appropriate where small doses are being asscssed. The dosemeter should be worn al ali times at work when there is a risk of s•gnificant occupational exposure; the whole body dosemeter is wom outside the cloth ing between waist and neck.

50

TIIE AL ARP PRINCIPLE ReguJation 6.1 states tbat every employer shall ' ...take al/ necessary  steps ro r estrict so  far as reasonably practicable the extent that persons are exposed ro ionising  radiation.'  60

70

The ideal is tbat the dose received, even  by radiation workers, should be zero. When this is not  pr act icable, then the dose should be kept as low as i r easonably  practicable (A LARP). It is possible to place a 50 rnm thick lead  box around thc radiation sour ce and the test item to totally restrict exposure but it is not practicabl e to do so

EXPOSURE/OVEREXPOSURE I NVESTIGA TIONS The IRR \999 Regulations r equires tbe employer to set a dose limit. Th1s limit may be whatever the employer wishes it tobe but must not be more than 15 mSv. lf this level is exceeded for the fust time in any calendar year, then the cmployer shall carry out an investigation immediately. The dose level must  be written into the Local Rules.

80

The investigation should be exhaustive and pr oduce a detailed r eport containing known facts, probabiliti cs and possibî!îties rclating to tc::
90

When the employer of r adiation workers  suspects that an overcxposur c has  been received by any  person, an immcdiate investigation must  be undertaken to tk t ermine whether this is a possibility . l11is ap plies to smgle incident s and to situations wh cr e an individual's accumulative dose ex.ceeds any appl icable dose Iim it.

100

RSI2-2

UNIT RS12

Ruane & Il  TP O'Nei/1

  PERSONAL DOSIMETRY

•

Unless the investigation reveals beyond r easonable doubt that an overexposure has not occurred, the following must be inf ormcd:

OTES

a. 10

 b. c.

The Health & Safety Executive. The employer of the pcr son who has r eceived an overdose (or suspected to ha ve received an overdosc). The EMA or AD as applicablc.

A detailed investigation must then be instigated by the employer and the r esults sent to the aforementioned and to the person suspected of receiving the ovcrexposur e. 20

Exposures received during medical examinations are not considcred. Any person involved with an overexposur e can continue to work in accor dance w ith any conditions imposed by the EMA or AD.

JO

THE IONISING RADIATION (OUTSIDE WORKERS) REGULATIONS The Ionising Radiation (Outside Wor ke   r s) Regulations: 1993 SI No. 2379 supplement the IRR 1999 and are intended to strengthen the radiation protection arrangements for   periparetic workers who work in aoother or ganisation's controlled area.

'Pertpate/lc·mean s gomg  40 (rom place to place .

These Regulations pr ovide an extension to the lRR 1999 for Outside Worker s ( per ipatetic radiation workers) working in other EC member states. The main requirements of these regulations ar e as follows: l. To exchange information between the outside worker's employer and the operator 

(site occupier) of the work site with r espect to controlled areas  bef ore wor k  conunences. 50

2. For estimation of doses received by Outside Workers working on the operator 's site to be roade. 3. For aU Outside Worker s to holda  Radia/ion Pa ssbook 

Radiation Passbook  60

This book contains personal details, estimated dose records, work locations and date of  medical reviews. A representative of the com pany where the wor k is per formed must enter and sign the dose assessments. The passbook is a small book (usually yellow) with the title and serial numbcr on the fr ont cover. Notes are included to assist with the entry of r ecords.

70

•

•

80

•

•

•

90

Section 1 is completed by the ADS and includes the name, address, teleph one number and fax number of the company; this page also includes and the ADS deta ils. Section 2 contains the per sonal details of the  pcrson to whom to book has  becn issued.

Scction 3 is completed to confliffi thc datcs of medical reviews and is completed  by an author ised p erson of the site operator. Section 4 confirms cumulative dose assessments for the calendar year and is completed by an authorised person of the site operator. Section 5 records the estimated doses rcceived during activities în the operators' controlled ar ea(s). This information is entercd by the authorised person of lhe Site o perator.

100

l. I.:O u 6 Z.J.!U61G

RSJ2-3

UNIT RSI2 •  PERSONAL DOSil\fETRY

R uane & 11 T P O' Neill 

OTES

PER SONAL DOSIMETRY RECORDS 1. 10

Dose recor ds must be k e pt by an ADS for 50 year s fr om the date of tht: last entry. It is the employer's r es ponsibility to ensure that these records are kept.

2. Thc health r ecord of each indiv1dual must be k ept for at lcast 50 ycar s. It is the employer 's responsibility to ensur e that these record s ar e kcpt.

20

3.

Exposure invest igation records must be k ept f or at least 2 years by the employer .

4.

A copy of any overexposur e investigation r ecords must be kept by the em ployer  f or at least 50 year s.

30

40

50

60

70

80

90

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.)Ru..nt & 1 ·r O'Ndlt

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1uu. b U.'ut..'\11

R S12-4

APPENDIX A · RADIATION SAFETY RELATED CONTACTS

Ruane & 11 T P O'Nei/1 OTES

10

Health & SafctyExecutive Level6  North Wing R ose Court 2 Southwark Br idge London SEt 9HS

Tel: 0207 717 6848 Fax: 0207 7 17 6681 20

30

 Na tional Radiologica1 Protection Board Chilton Didcot Oxon OXII ORQ

Tel: 01235 831600 Fax: 01235 833891

40

 AEA Technology pic 528.10 Unit 1

Hatwell Didcot Oxfor dshire OXII ORA 50

60

Tel: 01235 821111

ICRU Publications 791O Wooclmont Avenue Suite 800 Bethesda MD 208 14-3095 USA

Tel: {301) 657 2652 Fax: (30 1) 907 8768 70

80

!JO

100

iit' H.u2nc & 1·r O"Ndll

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