Str ucture of the Chernobyl radiation sources and e xposed population groups

Oosimetric support of the International Programme on the Health Effects of the Chernobyl Accident (IPHECA) pilot project: main results and problems

1 .A. Likhtarev , L. N . Ko vgan, V .S . Repin, I.P . L os', V .V Chumak, D .N . Novak, B .G. Sobolev, I.A. Keiro, N .I. Chepurnoy, D .N. Perevosnikov

&

L.A. t itv tnets «

Str ucture of the Chernobyl radiation sources and e xposed population groups

Th e lime-evolu tion fo r both the Chcm o byl radia- tio n sou rces and main exposedgroupsof popu la- tion involved in the acciden t in diffe ren t time- inte rval s afterthe release is shown in BoxI(1).

In .accordance with the acce p ted classifica- tion (2), it is possible to single out 4 main po st- acciden t time-peri ods wh ich diffe r both by the mainso u rceofexposu re (d ifferentrad ion uc lidcs) an dbythe population groupsexp osed:

First stage:. su p er-early Second stage: io din e

Third stage: radioacti ve trace

Fourth stage: long-lived fission and fuel radio- nuclides

Each path way of expos u re can becha racterized inmorede tail.Thus,the evo lu tionof external gam- ma exposu re can be consideredwith in 3time peri- ods(3),andthat of in ternalgammaexposu re (fr om the ingestion oft37<:,)wi thin 5timeperi ods(4).

aDepartm ent ofDosim etry and Radiation llygtene.Ukrain e ScientificCentrefo rRadia tio nMed icine,Kiev, Ukraine.

As foll owsfro m Box J, Cb c r n obylsexposu r e sources differ rather stro ngly in duration (half- life). Therefore theycan be cond itio nally divided into 3 gro ups- sho r t-lived, lon g-lived and supcr- long-lived rad iatio nsources.

The short-livedsources include: (a) externa lex- po sure from the rad ioac tive cloud and internal exposure con necte d with the inhalation of fission an d fuel radionuclidcsas fallout. Theaverage half- lifeof this typeof sourcevaries from several hours

tosevera l days;an d (b) internal thyroid exposure from the ingestion of rad ioiod inc as the resultof cons u m p tio nofcontam inated fo ods (such asmilk and fresh vegetable s) during a pe riod ofseve ral days to two monthsafter the falloutoccurred.

The main sources of long-lioed rad ia tio n expo- su re of the pop ulatio n are externalgamma-expo- su refrom the Chern obylgammasources deposited as fallout on the grou n d, an d internal exposure fro m the radioisotopes ofcaesiu m andstro ntiu m, as the result of cons u ming radioactively-con tami- nate d fo ods.

Deposi ts of238.239,210p u and24 lA m ca n be con- sidere d as super-long-livedradiation sources.Expo- sure to these radi o n ucl ideswill be responsibl efor

Box1

Chernobylradiationsources and exposedpopulationgroups(evolutionovertime)

I 11

Superearly Early

stage stace

.R..I~lnlS01IIitcunlimlnlllijaroll

Uqul~alo..

m

III IV Post-

Middle Late accident

stage stage period

SOG,....

1~

Externalexposure .137, 1 hour 1day

I - r 1

Cloud I I

[§]

1week

1.1

I"j

95Nb 1month

1.1

106Ru 144ee 134,13les

1 year 2: 3 10 50 100 500 years

I I I I I ^I I ! ! I ^{I I}

Ra~loattl.. BlpOl11l

.1 I I I I

:1

^1:1

106Ru 144ee 134,13les 90S, Pu 241Am

Internal exposure (inhalationandingestion)

Uqulaatorl

RI.ld.I~1iof_I~Iconlamlnalld ,,"al

'ChUdren wuii Ihyroldelpoluro

.Evacuees

40

1- 2monlM 1 monlN

Yllt

500 ....

Rapp.trimesl.stalist. sanit.mond.,49(1996)

rad iat ion dosesillseve ralsubsequen tge n eratio ns.

Dur in g thefi rst50..100yearsafte rtheaccident the do se co n tri bu tion of trans-u ran ium elements to the to ta l exposu re of the population will he \'t'ry sma ll, hut in the future. when the levels of dose s hum ~loSr and l:ri"Cs decrease practically 10 zero , the small levels of expo su re fro m tran s-uranium eleme ntswilldominateamon g the Chern o hylradi- atio n facto rs stillactive .

Ano therextre me lyimpo rtaut principleofclas- sification isthat of"criticallyirradiated"gro upsor sub pop u lations.

As shown in Box I, it is possibl e to sing le ou t 4 main ~rollps: (a) the po pulation co ntinuously li\"in g in the radi oactive-cou ram ina te d te rrit ori es:

(b)ch ildren andteenagers(age at thetim eofacci- dent) ,wit h irradiationofthe thyroidgla nd in May- June 1986, asthe resu lt both of inhalat ion and of consum p tion of con ta minated foods; (r) in hab it- antsevacu ate d from I'ri pjat an d seu lc urentsin

the ~lO-kIII lo ne;an d (d)liq u idators - perso nswho

part icipated in various types of cleanup work in 19 H(}-.19H7on the Cher n o hylNuclearPo we r Plant and inside the:lO-kmzone,

Box2

Structure of CentralDosimetricRegister

Storage and generalization o f the ecological and dosimetric data

Perh aps oneof the mostim po rta n tcha llengesaris- ing after the acc ide n t. was the devel opment ofa coordin at ed co m p ute r syste m fur the storage of the enor mouslyla rge flowofecologicalan d dosi- metric informat ion, an d produ ction of any re- qnircd com binationsofOll lJ Hl Idat a.Th isproble m was solved withi n the framewo rk of the Cen tral Dosimet ricRegiste r (CDR)_

StructureoftheCentralOosimetricRegister

Box 2 presents the Cent ral Dos imetri c Registe r (CDR) .a struc tu re developed in the Department of Dosimetry and Radia tion Hygiene of the USCR M (Ukraine Scie n tific Cen tre for Radiat ion Medicine}. Now the CUR isa .:l-in fo rma tio n-level struc ture .whic h hashrought together: (a) the re- su lts of direct measu rements of the Chern obyl rad ion uclid cs in the environ me n t (so il, foods, etc.): (h)the resultsofindividual and grOllp CXP(}o

su re estimatesfur the inhabitants of the radio ac- tively contaminate d terr ito ries. includi ng retro-

~ ⁽

Riskassessments

1

St

St I Administrativearea

~

¥

^St

Administrative- ¹

-I

SeUlement (ST)

l. ,

Medical-demographic Unit geographicUnil

/ _~

^{Demography E}pidemiology Protective

structure structure actions

Ecology Unit ³

•

Dose Unit

Background Accidental 137Cs.90SrSOi:

I

^{Food R}etrospective.currentdoses y-irradiation y-irradiation depositdensity contamination

External 131

1,137CS.9OS~

I

^{Total Prediction}

j-expcsure lnternalexposureexposure

-V

Analytical Unit

t

Radioecology

j-irradiaucn I Soil I foods TLO WBC ^131t Evacuees Background

I

"'Cs

l oos, I

13'Cs

1 90s

r

exposure

Localdata base

t t ⁱ _~

I

^{Health Ministry,G}oskomgydromet

I

⁰~

J

Wldhlthstatistquart.,49(1996) 41

a K

External gamma-exposure of t he population to radioactive fallout f romChernobyl

External gamma-exposu re fromreleasedradionu- elideswasoneofmost important radiatio n sources

Thyroid dosemap ofUkraine

The sp eci al map inFig.6where thewholeterritory of Ukrain e isdividedinto7dosage zones hasbeen developed tosu p port the ep idem iological studyof radiation-indu cedthyroid cancer (8).Both the re- sults of direct measureme nts and retrospective modelestimateswere usedtocreate this map.

- informati on on the dens ity of soil con tamina- tionbyI'7CS;

geogra p h ica lcoordin a tes of the se ttleme n ts rei- ative to the Chem o byl Nuclear Power Plant; and

lo cation of theradioactivetraces.

The observahl e value can he described by the em pirical form:

D(og<) ~Ko 0 exp (-b ⁰ age),

(I) whe re D_tagf) = average dose fora particul ar age

grou p (cGy)

=scaling factor, describing the 13I1 intake ;

~ parameter, referring to the thy- roid doseforinfants;

b =ageparamet er(vear:').

Thelog normaldistributionof individualdoses wasassume d,withdistinctparametersfor eachage gro up.As anexa m ple,in Fig.3the valuesofmea- suredindividualdo ses and estimated average doses fo r each age-groupof thepopulationof onesettle- ment are shown .The se data demonstrate a good corre latio n between the doses ,as estimated based on the modelassumpti on and using the resul tsof directmeasurements.Italso provesthatit is possi- ble to reconstructthedosesin those age-grou ps for which direct measurements of 1311 activity in the thyroidglandhave notbeen made.

The next stage in the recon struction of doses received bythe population in areas in which thy- roid mo nitoring has not been carried out, is the extrapolation ofthe scalin g factor K in the age- model fo ronesettlem entto alarger territo ry.The extrapolation procedure devel oped was based on thedata for 137Csfallout an d spherical coord inates relative to theCh e rno bylNuclearPowerPlant.

The resulting3-dimensionaldistribution of thy- roid doses for ch ild re n born in 1986 an d ad u lts (over 18 ye a rs) for Chern igov distri ct ispresented in Figs4& 5.

Theindividuali zationof groupthyroiddose es- timat esis aspeci alproblemwhich can besolvedby the analysis of human behaviour.Suchresearchis being carried out now,based on a speci al survey withaboUl 20 000respon d e n ts.

Thyroid Irradiation

The importance of thyroid dose estimation was realizedearly in May1986 .More than 100specia l dosimetricteams carrie d out directmeasurem ents of radioiodinein the thyroidglandsof theinhabit- antsofUkraine.Thus a uniquedatabase wasdevel- oped, where more than 150000 direct measure- me ntresultsare sto re d (5,6) .

Direct measurements

ThemapinFig.1sho ws the te rritorialdistribution of dire ct measurements of ¹³¹1 in the thyroid glands of the Ukrain ian populati on (7).The quality analysisof thesemeasurem ents (5,6)makesit po ssi- ble todivide these measurementsinto two grou ps:

"any" an d "h ig h quali ty". In Fig. Jthe different qualitymeasurem ents are markedby shading.

Itispossibl etodevelopthedistributionofave r- age individualthyr oiddoses(1)fo r themost affec t- ed areas ofUkraine, based onlyonreliab lyverified results(Fig. 2).

spective,currentand futuredoses:and (c)risk esti- mates forvario us territories andage and occupa- tional grou psofthepopul ation.

The storage of prima rydata (usuallythe result of directmeasurement)is providedat the first level ofthe CDR, whi ch is calle d thelocal databaselevel.

At the second level (Box2),theinform ationfrom the first level isgeneralized within the framework of the ecological-dos ime tric territorial data base of settlements.Co m b in ing the resultsof directmea- sureme nts and modeJlingcalculation make sit pos- sible to estimate more general characteristics,fo r example , the "rad ia tio n portrait " of a singlesettle - ment.At the third levelof the CDR" thenextstage of integration and organization of the data provides estimatesof the possible damag e (me d ica l,social, psychological oreconom ic) tothepeople sincethe accide nt. It is called the riskestima tion levelof the CDR.

Retrospectivedosimetry' of thethyroid gland

About 30-90% of the ch ild populati on an d 1-10% of the adult population living in the scttlements shown on the map inFig.1 were cove red bydire ct measurements of 1311activityin the thyroidglan d in May-jun e 1986 (1). Un fo r tu nate ly, in manyset- tlem en ts,neither the whole population. nor even all age grou ps have been measured. In many af- fe cted areas,direct measurements have not been made at all. That is why a specialstu dy to recon- struct thyro id dose s for the te rritori es an d thei r inhabitants covered by radioactive fallout is now being carriedout.

The retrospective pro cedures developed were basedon the followingdata:

dire ctmeasurements of 1311activity in the thy- roid glandsof 150 000 inhabitants ofUkraine;

42 Rapp.tnmes:statist.sann.mond.,49(t996)

Fig.1

Geographicdistribution of thyroiddoses of 1311 in the populationof Ukraine

Distribution geographiquedesdosesde 1311

a

^{la thyroidedans}la population d'Ukraine

..,".

Kiev'sreservoir- reservoir de Kiev

<30000 30000-100 000 100 000-300000 300 000- 1000 000

>1 000000

Scale-ecnene 1:2400000 o

rj)

Boundaries-Limites:

ofomasr-dei'oblast ......... of rayon- du rayon

Inhabitedlocalities- LocaliMshabltees ...--~'-"._;.'

c.."... rayonofthyroiddosemonitoring -

I -, rayonsoussurveillancede la dose -" , i-'

a

la thyroIde

NumberandQuality ofmeasurements- Nombreetqualitedesmesures:

<12of anyquality- deQualitequelconcue 0 212 ofany quality - dequalite quelconq ae

m

212of high quality-debonnequali!. IiI

.~..

L

in thefirstye ar afterthe accident,and continues^to playthe prim ary role in a nurnbc rofregi o ns atthe moment.

Duringthe whole post-Ch emobyl period. more than 50 000 direc t ther moluminescentdosimetry (TLD) measureme ntsof in d ivid ualexterna l do ses forvariouspopulation groups in the contam inated territori e s we re carried out. The se data covered on lyI%of theseinhabitants,and th us itisneces-

sary tore con struct and predictthe exte rnal dose s.

The com mon me thod fo rso lvin gsuc h dosim etri c problems istodevelop thecorrect model of tempo- ral-spatial distribu tion of exter na l dose s.

Oosimelty model of external gamma-exposure

When developing amodel of externalexposureof a popul ation,it is nec e ssary to take into accoun t thefoll owin grel ationships,facto rs andcon ditio ns:

WldhIM stalist.quart.•49(1996) 43

Fig,2

Averagethyroiddosesbyagegroup among residents of 16regions

Dosemoyennea lathyroid e,par groupe d'Age, chez teshabitantsde16regions

_---======:R:n = ~ =- =-=-=- =-=-- =-- ---J,2800

²⁴⁰⁰

2000

1

1600

200

800

it

400 E

Regions- Regions Year of birth - Anneedenaissance

Regi;Jns:

1 Pripyot Town 2 Narodichi 3 Polesye 4 Chemobyl 5 lvankovo

6 Makarovsk 7 Borodyansk 8 Vyshgarod 9 Ovroch 10 Koseletsk

11 Chemiguv 12 Korosten 13 Repkinsk 14 Kievo-Svyatoshin 15 Chem igovCity 16 Olevsk

where Q; is the age-depend ent transfer factor fro m the GER in air to the effective external dose formembersof s-thgro u pofpopulation, - the func tion ofthe time v-ariation in the gam-

ma-exposurerate (GER)inair,P, ,,,(I),normal- ized on the uni t of fallou tden sityon the soil

c

(Fig. 7) (3);

- the average ("refere n ce") level of137Csfallou t den sity on the soil for a given settleme nt CID' whic h isdetermin ed as onc ofthe main para- me tersof the model;and

- age-occupa tio nal "be ha vio uralfactors"

(K;

bih)' where i = ]•..., 5 is the s-th age-occ u p ational gro upofthepopulation. If theaverageexternal dose received by the members of ~th gro up duringthe tim e-interval Tdesign atedas Dr_s.ex"

then themain expressio nof theexte rnalexpo- suremodel"illbe:

0

8 i

• ⁸

·

•

2

~ IJ · ·

. T _I ^•

^•

^•

^{~ 8}

r- -L ^.

·

s

1 • f--- ⁰

·

^!0

ⁱ i

^{I - - -}

·

^§

1 0" ·

o o -u.s

0.5'3.5 3.5·7 7·11 11-15 15-18 >18

Age group (years)- Groupes d'Age(annees) Fig, 3

Age-dependenceofmeanthyroiddosesforthe village ofRUdka, Ukraine

Relation Age/dosemoyenne

a

^{lathyroidedansievillage de}

Rudka,Ukraine 10'

>;10

'"

-"- '"

'"

0 Cl 10

44 Rapp.trimest.stalist.sanit mond.,49(t996)

Fig.4

Averagedistributionof thyroiddosesinchildrenbornin1986,ChernigovskayaRegion,Ukraine

Distributionmoyennede ladose alathyroide chezlesenfantsnes en 1986, regiondeChernigovska, Ukraine

~ Dose(cGy) Chern obyl Power Plant Centralede

~ Tchernobyl

!

Distance(km)

Fig.5

Average distributionot thyroiddosesinadults(over18years),ChernigovskayaRegion,Ukraine

Distributionmoyennedela dose

a

^{la thyroidechez lesadultes(plusde18ans),region}deChernigovska,Ukraine

.~

.,

ChernobylPowerPlant Centrale deTchernobyl

WldMhslatisl.ousn..49(1996)

, ,,

.~

.p7

,

45

I

Flg.6

Thyroid dose zonescorrespondingto cases of accidentalexposure in childhood,Ukraine

Zones dedose

a

la thyroidecorrespondant

a

des cas d'expositionaccidentelleau coursdeI'enfance, Ukraine

Zone 1 Zone2 Zone3 Zone4 Zone5 Zone6 Zone 7

Averagedose (Gy) - Dose mayenne(Gy)

1.6291 0.6613 0.3338

,,!Xi! 0.1582

'";c.}.' 0.0750

0.0300

0.0050 _{7 ...0n8}

The em piricalparam eterse.B,up(l2'At and"'"2 are:

a = 188.4pGy. c'on kBq •m·² 13⁼0.98

A,=2.95• 10.²day 10.₂=7.69. 10.⁵day

a,

^{= 28•102 pGy•}

c'

^{on kBq•m·2}

"2⁼5.4• 10.2pGy•cio n kBq•m·2

Behaviouralfactors

First of all, we em p hasize that the inhabitants of ruralareaswere subje ct to the highest accid ental externaland internal exposure.Therefore in Ta- bleIthe valuesofK_i.u/,are sh own for rural inhabit- ants only. These values are given for one whole year, alth ough the values of K;.../, for the rural in hab ita n ts in each seasonare al;oavaila ble (3, 9).

III

;n1l*'~*'"',..,..___14_<4+..\-...n__9__f._...---J~

~

¥

11

200 400 600 800 1000 1200 1400 t days after the accident-t jours apras I'accident

0.1..j.L-~---l~-~-~-~-~­

o

Flg.7

Externalgammaexposure rate for137CSactivityper unitarea, Pyla(t)

Debit de dosed'exposition externe auxrayonnements gamma du137Cs, par unitede surface,Pyla(t)

100- n - -"..-- - , . - - - ----,."..-- - - ----i NE

Analyticalfunction P, ,,,(t)

The em pirical function of time-variation of the GERin airisbasedonthe results ofdire ctmeasur e- mentsof the GER in air ,normalized on the 137Cs falloutdensityonthesoil,producingthefollowing functions:

aM3.witht&360 days after the acciden t

a, e-),lt+~e-~I.withr>360daysafterthe acciden t

(3)

Externalexposuredose

The estimates of annual external doses for the rural inhabitantsofUkrai n e during thefirst6 yea rs afte r the Cherno bylacciden ts,calcula ted acco rd- ing to the abovemodel,aregivenin Table2.Thus, both the annual doses and cumulative doses for differentage-occupa tionalruralgroups are seento diffe rby1.5 to2 times.

Itshou ldbestressed that theaverage individual external do se received by the population during May I986is the samea' the exposure during the

46 RilPP·trimest.statist.sanit.mond.,49(1996)

Table 1

Annual behaviour factor(Ki,"h)(nondimensionalvalue) for differentpopulation groups Tableau 1

Facteurcomportementalannuel(Ki,Oih)(valeursans unite)pour differentsgroupesdepopulation

I I

1 I

1

: 1

Population group-Groupedepopulation

Children uptoage 7- Enfantsagesde

° ^a

^7ans

Childrenaged8-17- Entantsagesde8a17ans Employees- Ernployes

Agriculturalworkers- Agriculteurs Pensioners- Retraites

0,13 0,18 0,26 0,38 0,26

:I

^,,

;

I

j

I

Table 2

Effective doses (SvperkBQ•m-²)due to external irrad iation for differentpopulati on groups, during the 6years after the accident (1986-1991)

Tableau2

Doseseffectives(Svpar kBQ• m-²)duesauxrayonnementsexterieurs pour ditterentsgroupesdepopulationpendant lessix am ees(1986-1991)suivant I'accident

May1986-April1987 May1987- April1991

Mai 1986-avriI1987 Mai1987-avri11991

Populationgroup-

Groupedepopulation First month - 2·12 '·12

1987 1988 1989 1990 1991 1987- 1986- Premier months- months-

mors mcrs moe 1991 1991

Childrenunderage7 2,9 5.2 8.1 1.9 1.9 1.8 1,8 1.7 9_1 17

-Enfantsdemoinsde7ans

Children7-17- 3,6 6.4 10 2.4 2,3 2,3 2,2 2.2 11 21

Enfantsde7a17ans

Employees- Employes 4.9 8.8 14 3.4 3,2 3,2 30 2.3 15 29

Agricultural workers - 7,3 13 20 5,0 4,8 4,6 4,5 4.4 24 44

Agriculteurs

Pensioners- Hetraites 5,0 8.8 13 3,3 3.2 3.1 3,0 3.0 16 29

wh e re: ^{Kdfl·\" i} is the dose[actor,normalized on the unit oflS7Cs intak e (Sve Bq-l) for the s-th agegro up;an d

qj(t) is the intakefunction, describing the time variation of the intake of 137Cs into Main relationshipsin the model

The dosesofthe internalexposure,caused bythe consu m p tio n during the time T of foods co n tam i- nated byISi Csbythemembersofthe i-thgrou p of the popula tion JiL T/I'can bedet ermined (8)as:

The modeldescribed belowof internal expo- su re from the ingestion of 137Cs with food, inte- gra tes both the internati on al ex perie n ce ofsuc h kinds ofecologica l transp ortmodels,an d themost impo rtant resul ts of large-scale. rad io-eco logical an d dosimcu-ic monitoring provid edin the condi- tions of a real, large, radiation accident such as Chernobyl.

su bseq ue n t 11 months.Thefirstyea r (12 mon ths) provided pra cti callyhalfthe dose of the followin g 6years.

137CS internal exposure

Intern al exposure from 134Cs.and 137Cs,ingested with radioactivel y co ntam inatedfoodsisoneofthe main pathways (to gether wit h exte r na l gam ma- expo su re from radio active deposits) of mass exposure of the populati on.

Incon trastto externalexposu re,itispossibleto take well-regulated cou n te r me asu res for intern al expo su re .Itwo u ld bepossible¹⁰prcvent exp osure from the co ns u m p tio n ofcon ta m inated foods (in this case 134Cs and 13iCs) by com plete exclus io n an d replacem ent of that pari of the diet wh ich co n sistsoflocallyproducedfo ods.However,pract i- calsuccess and efficiencyof this kind ofcou n ter- measu res are closely co n nected to a number of socia lan d eco nom icaspe ct sof the life ofthe pe o- ple who found themselves in the co n ta m inate d terri to ry.

DJ". ~Rh,,,.f..q(t)dt

I,ml I I I (4)

Wldhlthstatist.quart"49(19961 47

thebodies ofpe ople alo ngwith theirdaily diet (Rq.nay-' ).

The two intak e functi ons,namedin the mode l as "refere nce"- ifl(t) - an d "real"- Qi,l7!all)- were developedbyLikh ta rev et al.(8).

Referenceintake function, qO/t). This fu nctio n de- scri bes the intak e of 1~7Cs with diet. in the case whe ntheinhab ita ntsofa speci fic re gionwouldnot change theirbeh aviour.living con d itio nsor die t.

In the developed model, the fu nc tio n q1(1) is presented asfoll ows:

(5) where : (,mll) (Bq •I-1 perkBq • m-2) isa fu nc tio n describingthe time-vari a tion of!:l7Csco n- cen tratio n in milk,no rmali zed on (To:an d wQ',m(1) isthe so-called "m ilkequivalen tof diet" (I • day" ), which is the am o u n t of milk co ns u med (in litre s) , wh ic h co uld provid e a daily intake of IS7Cs in a com- ple te die t.

In the model, the math emat ical form of the fu nctio n cm(l)forthe territories with vario uslevels of tran sfe r facto r of 137Csfrom soil to milk (8, 9) was esta blished by ap p ro ximating the results of dire ct mass spen ro me te r me asu rements of J37Cs conce ntra tio n in milk, provide d durin g the total po st-acciden tperi od.Thus,the hal f-life ofecologi - caleliminati on of 137Cs fro m milk was fou n d tobe 34 years.

The "mil k eq uiva le nt of diet", wQ',m(I), estim- ated usin g the da ta on the ratio of conce n tra tio ns ill different componen ts of the diet, daily con - su m ptio n of vario us die t compone nts an d the proportionoflo callyproducedfoodsin thediet is 1.61. dart.

Real intake function.The functi on qi

,ml l)

^describes

the levelof137Csintake in the diet'existing in the speci fic region an d forthespe cifi c i-th groupof the populati on.

The mathema tical fo rm an d the par ame te rs of thefunctionq._i.rea,(1)can hedeterminedby approx- imating the results of dire ct WBC (wh o le-body co un ter) measu remen tsofthe137Cs co ncen tration in the human body.made among the inhab ita nts ofcontam inate d territori e s,with various values of 137CStransfer factor from so il tomilk.Asthe analy- sis of the re sul ts of mass \\'Be-monitoring has sh m vn,the fu nc tio n q._I,re.af'It) ,usedin the mod el , on the basisof6 post-accident years,is fairly rel iable , asis the milk functi o n (m(tJ,in the mo n o-e xpon en- tial form (8).

DiVidingtheterritoryintozones according to the transfer factor

k 1.1

Ba se d on the obs e rved re sults an d experie nce of post-a cciden t radio-e col og ical an d do sim e tri c 48

mo n itorin g ,it has been po ssibl etoclassify(d ivide) the whole radioactivelyconta m ina te d terri tory of Ukraine into 4 zones,accord ing to the valueofthe transfe rfactork~~(estimate d fo r 1991 ) :

t.he first zone, for which k~~ ~ 1 Bq • 1.¹ per kBq.m-²;

thesecondzcnewherek~~is1 to 5Bq.1-¹per kBq

•m-²;

thethirdzone,wherek~~is 5to 10Bq-I-Ipe r kBq

•m-2;an d

the fourth ^Wile, where kY~ > 10 Bq • l·t per kBq.m-².

The im porta n t resu lt is tha t the cha rac ter of inte rnal exposu redoses from 137Cs form a tio n for the first an d su bse q ue nt post-a ccid entperiod s are prac ticall yiden tic alforallsuc h zones,

Dosesofinternalexposure

The diffe rence s in the values of internal doses IJT "_1,1n estimated using the function s tfJ,·II) an d q. let), depen ding on the po st-accident period

"'''''

cons idere d, can varyby2 to 6 times (4). Th e main reason for such diffe re nc es is the cou n termea- sures: repla ceme nt ofl ocally producedfood s,cen- trali zed, gove r n men ta l re stri cti ons an d self-in itia t- ed restrictio n of the cons u m p tio n of thes e foods, tempora rydeparture sforholidays,ere.

IfJ)~

, .

I,is usedtodesignatethevaluesof intern al dose sre ceivedbythe members ofthes-thgro up for the time pe riod

7 ;

th e n,using exp ress io n (4) with q ,(I) as the "real"intake fu nction,it ispos sibl e

'.rea

to estima te "do se effective ness of co u n te n nea- sures"asD7!I)/D;(I).In Table3thevalues of cu m ula- tiveindividualdose sup to 1,4 an n6 yearsafterthe accid ent forad u lts in the north ern part of Rovn o distr ict are presented.In this table thedose.... effec- tiven e ss of cou n te rmeasu res is shown aswell.

Exposure of the liquidators

All efforts in the do sim e tri c stu dyof"liq uidators"

we reaimed at the crea tio n ofaccu rate te chniqu es for do se re construction.Among these te chnique s itis necessary todistinguish two grou ps,instrumen- tal an d modelling .

To d ay, as was em p hasize d in the Final Com- muniqueof theFirstSymposium on Retrosp e ctive Dosim etry in Bad Honnef(10),the most promis- ing te chn iqu es are the use of electro n-spin reso- nan ce meas ureme ntsof tooth en a m el an d FISH- analysis (chromoso me pain tin g using Fluorescen t In Situ Hybridization ) ofre ciprocal tra n slocat ions (11, 12).

Goodcon fir matio nof the efficiency ofthe elec- tro n sp in resonancete chnique (ESR) wasdemon- strate das a resu ltof inte rcalib ratio n ,carried out in

USCRM (Kiev, Ukraine) (Fig.8).Resul t. wereve ry

well clustered in thecon fidence inte rval(le ss than 10%) for theexpo sn reinterval from tensto thou- sandsof mGy.

RiJpp.tnmeet.stalisl.sanft.mona...49(1996)

I _i

^Table3

Cumulative average individual doseswithout anycountermeasures(lJO_ir), "real"doses with countermeasuresprovided(0'iT),

and dose effectiveness of countermeasures(IJOt/D'i,r),Ukraine ' ,

Tableau3

Dosesindividuellesmoyennescumuleesenl'absence de toutecontre-mesure(lJO_ir),dose s-reelles»comptetenudes contre-mesuresprises(O'i.T)'etefficacitedes contre-mesures(lJOj D;.r),Ukraine '

I31CSscil-to-rnuk-transtertactor(/(91m)- Yearsaftertheacccent- Pacteurdetranstertset-tandu37CS(/(91m) Annees acres race.dent

(Ba,.r•perkBqem"Z) 4 6

fJ'Ji.r 1-5 21 74 103

(SvIkBq.m²) 5-10 120 355 444

>10 152 490 643

O"i,T 1-5 9 21 24

(SvIkBq.m2) 5-10 17 44 52

>10 45 120 142

fJ'Ji.TlD'i,r ^{1-5 2.4 3.6 4.2}

5-10 7.2 8.1 8.5

>10 3.4 4.1 4.5

49 -0.0

-1.0 -0.0 ,

-4.0 -3.0 -2.0 -1.0 Ig(dose, Sv)

-4.0 -3.0 -2.0

Ig(dose,Sv) A.Residentsof Pripjat-HabitantsdePripjat

B.Residentsofotherlocalities-Habitantsd'autreslocaliles 5

15-,---- - - -- - - ---,

10 -

g 15,--- - -- - - -- - -- - - -- ---,

§o c.o c.

~

~ 10- Fig.9

Relativefrequencydistribution of thelogarithmof theradiation dosereceived bytheevacuatedpopulation

Frequencerelativedeladistributiondulogarithmedeladose derayonnementrecue parla populationevacuee

;fi

,

<:

~o

~_o ⁵

c.

'"

""

^'0

eft. O+- -'4 .nJ.llJ""''t'-W.W.llfJ..l.l.llJ.llJ'j-L''--_ --t -50

Wldhlthstatist.quart.,49(1996)

-200+-, --,-,-- ,- ,---,--,c-,---,--,----.----I -100 0 1002003004 00 5006 00 700 800 9001 0001100

Nominaldosevalue,mGy- Valeurnominaledeladose,mGy

1100-,- - ---."

Fig.8

Results of electronspin resonance (ESR) intercalibration' Resultatsde l'inter-etsto nnaqe parresonancepararnacnett que electronique'

Otherdirectio nsofstudyfordosesrecon struc- tio n [or liquid ators deal with the analysis of the available route-lists and also the collection and sto rageofdata on the externa lexposurerate inair [ordifferen tlocat ions neartheChe rn o bylNuclear PowerPlanL for civilian and militarypersonn el.

(£1000 ^<:0

E _~

I _~ 900 '5

>~ c.

"'E"~~ 800 ⁰c.

~=c 700 ^~

~~

'"

.o~ 'C

~" 600 ;fi

E'"

:u~ 500 ^r

.s.S: <:

.~ ~ 0

~~ ⁴⁰⁰ ~₀

0 > 300 c.

~~

~

ee

~ 200 0c.

'"

~~

~~ ~

""

~~ 100

~E • ^'0

::;~

0 :li _;fi

~0

~

0 -100

aThe solidcurve representsthe standard;thebarscorrespond10 thetechnique used bythe laboratoryofExternalDosimelry. -Lacourbe en trait plein representet'etaton.les'ntervanesd'erreurcorrespondent alatechniQueutfisee pat re Laboratoirede dosimetrieexteme

,

i i

I

I

J

Exposure of the evacuated inhabitants of Ukraine

Recon structionofdose s for thein habitantsevacu- ate dill 1986 from Prip'jat andsettle men ts in the 3D-kmzone, isoneofthe important. pro blems be- inginve stigatedbythe IPI IECApilo tproj ec tanda nu m be r of nati on al Chernobyl-relate d pro-

g-rammes.

Resu lts of re trospe ctive dose estima tes for the inhabi tan tsofthe 30-kmzone and Pripjat,car- ried out by the experts of the do simetry depart- mentofUSCR~iincollabo rat io nwith the expert.~

from (;S F(G er many) (13,14) have sh ownthatthe average externaldose recei ved bythe inhabitants ofPrip'ja tduring the time perio dbefore evac ua- tio nwas 18mS", an d maximumdose s for individu- als cou l d reach 50 mSv(Fig.9).

As10 theinhabi tan ts evacuated fromthe 3D-km zo ne, the average do se for this suhpopulation is

~2roSyand doses can go as high as 200-300 IIlSV

(Fig.10).

ILshould be noted that these values of doses co nc er n only the so-calle d "local"part of expo- sure. Higher exposure dose s co uld be received people whose behaviour was out ofthe ordina ry, [o r example. tho se person s who spe n tsome time outside of Prip'ja tor in the village s (esp ecia lly on the highl ycontamin ated spo ts near the Cher- nobyl Nuclear Power Plant).Thenumberof such person swith unusualtypcsof beh aviourmigh the as high as ]5%of the wholeevacuated population.

Fig.10

Collective dose accumulation ratetor theevacuated population oftheentire3D-kmzone

Debitde dosecurnulee collective pour la population evacuee detoutela zonede 30km

11,

~Jj 500 -e>x

"'

x

'''

§

§ g 400

~Q)

", c.

-

_,S:3~c.-

'"

₃₀₀

"' ~

~E., ~

"'0

.g

~ ²⁰⁰

" 0

.==:'C

U_.,-0'"

'5"" 100/

~

"'~Cl

O -t-- - ,..-- - ? -- ...-- - ,...-J

o

5 10 15 20

TImeaftertheaccident(days) - Temps ecouie depulsI'accidentQours)

50

Summary

The problem of post-Chernobyldosimetry is uniqu ein Its complexity in the history ofradiation medicine and radiation protection.This isbecausethe earlyexperi- enceofmass exposureof people(bo mbi ng of Hiroshi- ma and Nagasaki, Windscale and South-Ural acc i- dents,exposureof inhabitantsof Nevadainthe United States01Am erica , the Sernipalatinskarea in the forme r USSR,theMarshall island s,andtheGoiania accident in Brazil.and others) differed both in the muc h simpler structure of the irradiationsource andinthe number and characteristicsof exposed persons.Itisobvious that post-Cherno byl dosimetry, both as an Inde pen den t proble m, and as a too l for epide mio log ical stud ies. requires significantexpertiseand economic andtech ni- cal expenditu res, Extensive and deep research has been carried out in Ukraine for the pasl 10years.This article reviews the main resultsof thesestudies.

R esume

Appui dosimetrique au projet pi/ote du Programme international sur les effets de f'accident de Tchernobyl sur la sante (fPHECA): principaux resuftats etproblemes

Pour ce quiest de la cornple xitele proble ms de la dosimet rie post-Tc hernobyl est unique en son genre danstoute I'histoirede larnedeclne radiolog iqueetde laradio protect ion.Cela vient du faitqueles experiences precedentes d'exposltion massivedepersonn es (bo rn- bardementsd'Hiroshima etde Nagasaki,accidentsde wmcscale etde l'Ouralmeridional,expos itiondes habi- tants du Nevada aux Etats-Unis d'Arnerique,dans la region deSemipalatinsk enex-URSSet autres) etaient ditterente sdu fait. d'une part,d'unschema beau coup plus simple des voiesd'exposition et,d'autre part,du nombre etdes caracteristiques despersonn es expo- sees.11est evident que ladosimetrie post-Tchernobyl,a la fois en tant que probterne ind ependant el en tant qu'instrumentutiliseal'appuides etudesepidernio loqi- ques,exige desconnaissances considerableset des ressources

a

^lafoiseconomiques et techniques. De nombreuses recherchesapprofond ies ont ete menses en Ukraine ces 10 dernie res annees.Le presentartic le passeen revue les princ ipa uxresultatsdeces etudes.

References/References

I. Likhtarev, lA. et al. Main probl em s in post-Chemobyl dosimetry. Assessment of the healthand muironmentalimpact fromradiationdoses duetoreleas edradionudides.J~oceedin/,.rsQJtht<

isuemationatioomshopatChiba•januarylH-20:27·51 (1994).

2. Likhtare v, lA .et al.Radi ationaccide nt:dosimeuymodels, effectiven ess of the protectio n acrions. At:d dm t on the (;!l.erno!J')'l l\·PP. lnf mnuuion bulletin USCRAl and Ukraine AcademyojScie11CC.2:4~J-83(1992).

3. Likhtarev, loA. et al. Effective rim es due ro exte rn al irradiation from the Che rnobyl acc ident for different popu lationgm upsof Ukraine.Jlealth physics..70(1):87-9R (ly!'lli).

4. L.ikhlllrt"\·.I .A. et.1.lnlt'nlOlIexposure fromtheingestionof hlfUI'\ l:unl:lIl1ina(NI

h r

^{137Csafterthe}Chernobylaccid ent.

Report 1. Oencral model.Ingestion dosesand counter- Rapp. tritnest.stafist.sanit.mond.,49(1996)

nu-asun-etlectivcncss fo r ihc adultsof RO\110 Oblast of Ukraine./lmlthJ,h'\'.\;n,72(IY9ti) (in print).

5. Ljkhta r e v, LA. tol at. Ukrainian lh}TOid doses afu-r tfu- C1wrnuhyl ar-ridr-ur,I/",drh!JhJ.f,jo,.6,1(fi):;)9 4-;,9 9(1 99:~ ).

fi. Likhtarev, I.A. et al. Th~TOid rlmt' a....scsxm c n t for IllI' C1wrniKcl\' r~gi( lI1 (L kraincj: csrun arton ha.snl (Ill [:ltl ilwroldrncasurr- mc nts an d e-xtrapolationof the rcs ulrs10

disuirts without rnoniroring. !lat!i u IIMI (1IIr1 enuiran mcntal llioJlh)'l'in.33:1--t-9-16()(!9~"·l),

I. So b olev, B.G.etal.Radiation risk asse sslilt 'IIIofthethyr o id

(";IIIl"t'1"in Ukrainianchildren exposed due 10Chcruobvl. Submim-d to fhalrh ph)'sin (1995) ,

8. Likhtar c v,lA.etal. ThyroidC:UH:n illrbeUkraiuc.-"a/ lire.

375(I) :(1995).

9. JST'5.I)/lfhwtl)'m/(l~}'.\ismilldo-"/'distributions.Contract COSU·

CT9:l-5:~ .Fiual Report.Reportfo r pcriOtl199·1lo 199;), 10. Likhta rev , LA.etal. Simulatiun-stochasrict:xposlln~lIlod d

an d estimation ofthe fina l retrusp ccnvc and progn o se s

Wld hlthstatiS/.aasn; 49(1996)

n-snlt umcrrainrir-s. Abstract. \\"nrkshop (HI close re- construct ion.HartHonnr-fl'\m'(,lllhf'r~(l-~n. 19!J.'l.

11.Shu lom, S.\'.et al.011Iht,radiation -cuslnvencssof the roorh-cuauret;!.ccorrli ll,ll;10thel-Rlvrcsult s. (Abstra c t)Th e ("111"1'('111 pr o blems of rllt' rr-rr ospccu vc. current and prognose-s dosimeuv of Cln-mo byl accideru. Sciemific conference.Kiev.2i-2~)0('\0 11,,1',199:~ .

12. Chu m ak,

v.

clal.Semi-routine ESR--<It,sillletry techniq ue

l'U1Tl'm lyuse-dill Ukraine.-hh lu tern.uionalSvmposi mu011

E..~R nosilll~lryand Appli<:atiuJls.Kiev.).tayIS-IU,HI95, 13, Likhtarev, I.A. et a!' Retrospective n-cu nsuuc tiou of

individual and collective exte rn al g<lllll1l<l do ses of populatio n evacuatedalterthe Che rnobylaccident.Hmi'/'

P"J~iCJ.66 (6) :(j·l3-ti':):!(199'1).

1-t. Likhtarev, l.A. et OIL Analysis of lht: effe ctive ness of crncrgencvcou ntenncasun-sill tilt'30-1..111zoru-duri ngthe early phase of [he Chcrn obyl accident. Hmtth jllt}\in. 67:(1994),

51

,.,'