Assessment of the Chernobyl Radiological Consequences
Mikhail V. MALKO
Institute of Physical and Chemical Radiation Problems of the Academy of Sciences of Belarus
Minsk, Sosny, 220109, Republic of Belarus; fax: + 375 (0172) 467317

established in the affected regions of the former
USSR [4,7,17].
One of the reasons for such controversy has been
explained by J. Gofman [18]. He managed to showthat the abovementioned discrepancies in prognosis of
medical consequences of the Chernobyl accident
arose due to the incorrect risk coefficient of ionizing
radiation employed by some specialists to forecast
additional number of solid cancers and leukemia
induced by Chernobyl radiation.
Another incorrectness that can seriously influence
the forecasting of biomedical consequences of theChernobyl accident is related to the collective dose
estimation. It is well known, that assessments ofauthors [8, 12-16] have been made on the basis ofdata of nuclides release into the environment
established soon after the accident [19, 20]. During
the last years, however, more accurate data were
established on the total discharge of radioactive
species due to the Chernobyl accident, as well as moreaccurate data on deposition of different radionuclides
in the affected areas of the former USSR [5-7].
The facts discussed above justify any independent
analysis of possible medical consequences of theChernobyl accident. This paper presents our attempt
to assess the pure radiological consequences of theaccident at the Chernobyl NPP.
The following limitations were taken into
consideration in our assessment. First, we haverestricted our analysis to stochastic effects of ionizing
radiation only, such as solid cancers and leukemia.
Second, we have also excluded from our analysis
members of the personnel of the Chernobyl NPP and
the cohort of liquidators. It means that our study wasconcentrated only on the population of areas affectedby the Chernobyl accident. Third, our assessment was
based on the use of simplified model of collective
dose estimation very similar to the models used byauthors [13-16,20]. The first step in collective dose
assessment is the calculation of the exposition dose in
air on the basis of experimental data on radionuclide
deposition on the ground. The results of ourassessment are given below.

INTRODUCTION
The Chernobyl accident has been the worst
accident in the history of peaceful use of nuclear
energy. The nuclear explosion and the following 10days graphite fire have not only completely destroyed
the fourth unit’s reactor of the Chernobyl NPP but, aswell, resulted in the release of a large amount ofradioactive species into the environment. This
accident caused radioactive contamination in a lot
countries of the Northern hemisphere, even incountries many thousand kilometers away from
Chernobyl. For example, the deposition of different
radionuclides has been found even in Japan [1-3].
The Belorussian Republic was affected by the
Chernobyl accident much more than any other country
in the world [4]. Twenty three percent of its territory
were contaminated by caesium-137 with 1 Ci/km2 andhigher. As a result of the accident at the Chernobyl
NPP, large territories in the Russian Federation and in
the Ukraine have been contaminated as well [5-7].
Experts of different countries and internationalorganizations are unanimous in the opinion that the
Chernobyl
accident
hascausedenormoussocio-economic consequences in Belarus, the RussianFederation, and the Ukraine [4, 7-9]. It is also
recognized that residents of the affected areas of theformer USSR have been subject to various
psychological burdens soon after the Chernobyl
accident [4, 7-11].
However, there exists a significant controversy
among specialists about the medical consequences(other than psychic) of the Chernobyl accident. For
example, according to the assessment of J. Gofman[12] this accident will result in additional 475,000
fatal solid cancers, 19,500 leukemia and additional
475,000 non-fatal solid cancers. The abovementioned
data were evaluated by J. Gofman [12] for all
countries of the Northern hemisphere affected by the
Chernobyl
accident.
Significant
medicalconsequences, especially additional thyroid cancers
and leukemia, have been as well predicted by E.
Ivanov [13].
The whole International Radiation Community, on
the contrary, rejected the possibility of serious
medical consequences other than psychic stresses andfeeling of anxiety suffered by the residents of theaffected areas [8-11, 14-16]. Such controversy isunbelievable in the light of the reliable data

METHOD OF THE COLLECTIVE DOSEASSESSMENT
The collective irradiation dose within some time τ,H τcoll , can be estimated as:
65

H τ

c o llwhere,NH τ= N ⋅ H τ

(1)*values: H τ , ext , Q0 and S∑. The mean individual
equivalent dose of external irradiation normalized tothe initial level of 137Cs contamination equal to 1

= number of irradiated people,= mean individual effective equivalentdose accumulated within the time τ.

*

Ci/km2, H τ , ind , can be determined on the basis ofmeasured or calculated exposition dose rates incontaminated areas. By means of exposition dose
rates integration for the period of time τ one can thencompute the exposition dose Pτ. This value can betransformed to the air-absorbed dose Dτ by:(7)
Dτ = C 1 ⋅ PτThe value of H τ is estimated as a sum of external,H τ , ext , and internal, H τ , int , doses:

H τ = H τ,

ext

+ H τ,in t(2)

On the basis of data given in the Catalogue ofdoses [21] we have estimated that averagecontributions of external and internal irradiation to theequivalent doses delivered to inhabitants of theaffected areas of Belarus in 1991-1992 were 60 and
40 percent respectively.
Assuming that the same contribution of external
and internal radiation will be sustained at any timewithin a period of time τ we can write:

H τ =
Hτ =

H τ ,ext
,
0 .6

where
C1

required equivalent irradiation dose:H τ = C ⋅ DτDOSE RATE AND DOSE IN AIR
RECONSTRUCTION
There are only sparse measurement data on
exposition dose rates in different areas of Belarus
affected by the Chernobyl accident. Thus, one needs
to assess these values by means of somecomputational methods and data on contamination of
the soil.
The most simple model which can be used forcomputation of dose rates is based on the so-called
model of infinite half-space source geometry at areference height of 1 m. According to this model the
exposition rate of external radiation at the time t isgiven by:because the procedure of assessment of H τ , ext is
much easier than that of H τ , int . The mean externalH τ , ext , can be determined by meansof the equation:
0

137

⋅

(9)

= mean external individual
equivalent dose of inhabitants
living in areas with initial
contamination level by 137Cs equal
to 1 Ci/km2,= average initial deposition level ofAs0 (137C s) 137 determined for the total area ofcontaminated territories.

H τ*, ext0

A s0 ( 1 3 7 C s ) =

137

Q0
S

n

R γ ( t ) = ∑ K i ,γ ⋅ σ i0 ⋅ exp ( − 0.693⋅ t ) ⋅ K i,L ( t ) ,
i =1
T1i2

(5)

where

Thus, the value of As (

(8)

2

(4)

H τ , ext = H τ*, ext ⋅ As ( Cs )remone can later estimate theraddetermined in

Any of these expressions can be used forassessment of the collective equivalent dose delivered
to the Belorussian population.
We shall base our investigation on the equation (3)equivalent dose,

rad
[22].
R

By means of another conversion factor C2 which is(3)

H τ , in t.
0 .4

= conversion factor equal to 0.873

where
n

K i ,γσ i0Cs) is given by:

T 1i2= number of nuclides contributing to thetotal exposition dose rate,= conversion factor of ith nuclide perunit deposition, (mR/hr)/(Ci/km2),= initial surface contamination with ith
nuclide normalized to initial surface
contamination equal to 1 Ci/km2 of 137Cs,= half-life of ith nuclide,

K i,L (t) = shielding factor of ith nuclide(6)

originated from its penetration into thesoil (function of time).

where
Q0

= total amount of 137Cs deposited on allaffected territories (source term)= total area of contaminated territories
S
As can be seen from the equation given above the taskof the collective equivalent dose assessment results in⋅

Computation of R (t) is usually carried out on thebasis of the assumption, that all nuclides have thesame shielding factor K L (t) . Then the equation (9)66can be written in the form:⋅nRγ (t) = KL (t) ⋅ ∑K i,γ ⋅ σi ⋅ exp (−
0

i =1

0693
.

T1i2

periods of time after the Chernobyl accident are given
in Table 6. They were determined from experimental
data on vertical migration of radionuclides into thesoil measured by specialists of Goshydromet of theformer USSR [5]. They measured the verticalmigration of radionuclides in the undisturbed soil fordifferent kind of soils. We used data given in [5] forthe sod-podsolic soil as more characteristic forcontaminated territories of Belarus.
Figure 1 shows the change in exposition dose rates
of external radiation in different areas of Belarus
within the first weeks after the nuclear explosion at
the Chernobyl NPP.
One can see that as a result of different
composition or radionuclides deposited on the ground,roofs and walls of houses and other buildings the
exposition dose rate in air in different contaminatedareas of Belarus can differ by factor 3 even at thesame 137Cs contamination level.
The highest exposition dose rate had to be in the
Northern sector of the so-called “nearest zone”. This
zone is a not very broad stripe that is extended in the
Northern direction up to 100 kilometers from the
Chernobyl NPP.
The lowest exposition dose rate had to be in theso-called “caesium spots”, which are characterized byrelative enrichment of radioactive deposition bycaesium isotopes.
The difference in exposition dose rates diminishedvery quickly because of a radioactive decay ofshort-lived isotopes. At the end of the first month after
the explosion at the Chernobyl NPP the expositiondose rates at different areas of Belarus were quite
similar.

⋅ t),

(10)
Integration of the equation (10) from t=0 up to t=ττgives the exposition dose of external radiation
accumulated within the period of time τ:τnPτ = ∫ KL (t ) ⋅ ∑ K i ,γ ⋅ σi0 ⋅ exp (− 0.693⋅ t )dt.
i =1
0
T1i2
(11)
Data on exposition dose rates and doses calculatedon the basis of the equations (10) and (11) for
different areas of Belarus are given in Fig. 1 and in
Tables 1, 2 and 3. In computing these dataexperimental data on deposition of radionuclides as aresult of the Chernobyl accident given in the book [5]were used (see Table 4). Table 5 consists of values ofhalf-lives of gamma-emitting nuclides considered by⋅

calculation of R γ and Pτ . The shielding factor
K L was calculated for the exponential model as it
was done by T. Imanaka, T. Seo and H. Koide [23]:K = a ⋅ exp(−l ⋅ t) + a ⋅ exp(−l ⋅ t), (12)
L

1

1

2

2

where
= fractions of fast and slow
migration of radionuclides into
the soil= constants of vertical migrations
l1 and l2
into the soil
Values of these fractions and constants for different

a1 and a2

1. Sector “North” of the near zone;
2. Averaged composition of the total release;
3. Gomel oblast;
4. “Caesium” spots;
5. Mogilev oblast.

Rg(t
mR/h
2

1.5
1
1

0.5

2
43
5

0

0

10

20

30

Days

Fig. 1 Exposition dose rates in air at a height of 1 m during the first weeks after the
Chernobyl accident in different areas of Belarus (normalized to the contamination level of
caesium-137 equal to 1 Ci/km2).
67

Table 1. Free air gamma exposition doses at a height of 1 m accumulated in different contaminatedareas of Belarus within the period from 26.04.1986 to 26.04.2056 (normalized to the level of 137Cs
contamination of 1 Ci/km2, mR).
Year

Vetka rayonof Gomel oblast

Krasnopoljerayon of
Mogilev oblast“Caesium spot”

Sector“North” of thenear zone

Averagecomposition of
the total release

1986
1987
1988
1989
1990
1991
1992
1993
1994
1995
1996
1997
1998
1999
2000
2001
2002
2003
2004
2005
2006
2016
2026
2036
2046
2056

258.0
414.0
531.7
623.4
698.0
760.8
815.2
863.2
906.5
946.2
983.0
1017.41049.81080.51109.91138.01164.91191.11216.31240.31263.21447.81573.81660.81721.11760.4

212.7
358.8
471.9
561.4
635.0
697.2
751.4
799.3
842.6
882.2
919.1
953.4
985.8
1016.61046.01074.01101.01127.31152.41176.41199.31383.91509.91596.91657.21696.6

225.1
366.7
476.8
564.2
636.2
697.4
750.8
798.2
841.1
880.5
917.2
951.4
983.8
1014.41043.81071.81098.71125.11150.11174.11197.11381.61507.6
1594.61654.91694.3

622.5
815.1
947.9
1048.61128.81195.11251.71301.31345.71386.11423.41458.11490.21521.51551.1
1579.21606.31632.41657.41681.31704.21888.82014.72101.82162.12201.4

369.1
517.6
628.0
715.5
787.5
848.7
902.1
949.5
992.4
1031.81068.51102.71135.01165.71195.11223.11250.01276.31301.41325.41348.31532.81658.71745.71806.01845.3

Table 2. Contribution of different radionuclides to the summary free air gamma exposition dose,
accumulated within the period from 26.04.1986 to 31.08.1986 in contaminated areas of Belarus.
Di / D, %Radionuclide
239

Np
Mo
132
Te
131
I
140
Ba
141
Ce
103
Ru
95
Zr
110m
Ag
144
Ce
106
Ru
134
Cs
125
Sb
137
Cs
99

Vetka rayon of
Gomel oblast
0
0
25.3
12.6
9.1
0
10.0
0
0
0
6.8
21.1
0
15.1

Krasnopoljerayon of
Mogilev oblast
0
0
21.6
10.7
7.6
0
11.1
0
0
0
3.3
26.7
0
19.0

“Caesium spot”

Sector “North”
of the near zone

0
0
26.9
10.5
6.5
0
11.6
1.4
0
0
4.0
22.1
0
17.0

0.9
0.2
22.1
6.6
11.3
0.8
10.2
27.8
0
0.7
3.7
9.9
0
5.8

Averagecomposition of thetotal release
0.8
0.1
19.5
7.3
16.6
0.5
5.2
25.0
0
0.7
2.0
12.6
0
9.7

According to our calculation nuclides withhalf-lives shorter than 1 year played an important role
during the first months after the Chernobyl accident.
It can be seen from Table 3, where individual
contributions to the total exposition dose of externalradiation of different nuclides at different areas ofBelarus are given.
Data presented in Table 2 show that short-lived

According to [7], there are places in the 30
kilometers zone with level of contamination by 137Cs
as high as many hundred Ci/km2. It means that soonafter the explosion the exposition dose rate in air
could reach in such places many hundred millirentgen
per hour and therefore exceed many hundred thousand
times the exposition dose rate in air before theChernobyl accident.

68

Table 3. Contribution of different radionuclides to the summary free air gamma exposition dose,
accumulated within the period from 26.04.1986 to 31.04.2056 in contaminated areas of Belarus.
Di / D, %Radionuclide
Vetka rayon
Krasnopolje rayon
Sector “North” of“Caesium spot”
of Gomel oblastof Mogilev oblast
the near zone
239
Np
0
0
0
0.2
99
Mo
0
0
0
0
132
Te
2.7
1.9
2.5
5.1
131
I
1.3
0.9
1.0
1.5
140
Ba
1.0
0.7
0.6
2.6
141
Ce
0
0
0
0.2
103
Ru
1.2
1.1
1.2
2.6
95
Zr
0
0
0.2
8.3
110m
Ag
0
0
0
0
144
Ce
0
0
0
0.6
106
Ru
3.0
1.2
1.6
3.4
134
Cs
16.4
17.0
15.5
16.0
125
Sb
0
0
0
0
137
Cs
74.4
77.2
77.4
59.5
Table 4. Composition of nuclide deposition in the affected areas of Belarus (normalized to theactivity of 137-Cs) [5]
Di / D, %Radionuclide

Vetka rayon of
Gomel oblast

Krasnopolje rayonof Mogilev oblast“Caesium
spot”

239

Np
Mo
132
Te
131
I
140
Ba
141
Ce
103
Ru
95
Zr
110m
Ag
144
Ce
106
Ru
134
Cs
125
Sb
137
Cs

Sector “North”
of the near zone

14.13
14.13
1.086

9.5
9.5
0.714

12.78
10.0
0.67

1.957

1.714

1.994
0.056

33.33
3.33
33.3
20.0
3.67
3.67
5.33
3.33

1.413
0.545

0.55
0.545

0.722
0.5

2.00
2.00
0.67

1.00

1.00

1.00

1.00

99

Averagecomposition of
the total release
6.67
3.33
16.7
16.7
3.33
3.67
2.67
3.33
0.01
2.33
1.0
0.5
0.02
1.0

given in Table 3. In this table results of the exposition
doses calculated for different areas of Belarus for theperiod of time from 26.04.1986 to 26.04.2056 (70years period) are presented.
As can be seen from this table nuclides withhalf-life shorter than the half-life of isotope 134Cs,
give together only about 7% of the total expositiondose in air delivered during the 70 years after the
Chernobyl accident.
It means that caesium isotopes determine
practically the total exposition dose of externalradiation delivered during a rather long period of timeafter the Chernobyl accident.
So, in the assessment of the total collective
irradiation dose one does not have even to take into
consideration nuclides other than caesium isotopes
and concentrate the efforts on accuracy of

nuclides determined more than 50 percent of the total
exposition dose in air delivered within the firstmonths after the accident.
In case of the Northern sector of the so-called“near zone” (Bragin district is settled in this zone)
short-lived nuclides gave about 85 percent of the total
exposition dose.
It is clear that one needs to consider the total
spectrum of the deposited radionuclides in theassessment of the possibility of direct effects ofradiation on inhabitants of 30 kilometers zone, thatwere evacuated within the first months after the
Chernobyl accident.
The total contribution of short-lived nuclides to the
exposition dose of external radiation which can bedelivered within quite a long period is not very large.
Such conclusion may be drawn on the basis of data69

Table 5.

Half lives and conversion factors of radionuclides deposited in the areas affected by the
Chernobyl accident [5].
Conversion* factor, Ki,8
NuclideHalf life, T1/2, days
239
Np
2.35
2.9
99
Mo
2.73
5.1
132
3.27
45.9
Te
131
8.04
7.3
I
140
12.6
41.5
Ba
141
32.5
1.2
Ce
103
Ru
39
8.9
95
64
28.3
Zr
110m
250
50.3
Ag
144
284
0.8
Ce
106
Ru
368
3.8
134
755.6
29.1
Cs
125
985.5
7.9
Sb
137
11023
10.7
Cs
* Note: Conversion factors are given in units

Table 6.

m R /HC i/km 2

Parameters of nuclide vertical migration in soil.

Period of time, years
0 ≤ t ≤ 1 year
0.5 ≤ t ≤ 16.5 years
16.5 ≤ t ≤ 100 years

a1
—
0.61
0.44070.5345l1
year-1
1.25
0.18
0.18

computational models and accuracy of data on
contamination levels of caesium isotopes.
Only in case of the Northern sector of the “nearzone” the contribution of nuclides other than caesium
isotopes to the total exposition dose in air delivered
over the 70 after the Chernobyl accident has reachedabout 25%.
It is well known, that radioactive contamination of
the soil in the major part of the affected territories ofBelarus, the Russian Federation and the Ukraine issimilar to contamination in “caesium spots”.
This fact simplifies the assessment of collective
irradiation doses of the affected population in Belarus,
Russia and the Ukraine because it allows to use some
uniform data that transform data on the initial surface
contamination of the soil to external exposition doses.
According to the data given in Table 1, the total
exposition dose of external radiation in air at areference height of 1 m delivered over the 70 years
after the Chernobyl accident in an area with 137Cs
isotope contamination equal to 1 Ci/km2 is about
1,700 mR.
The contribution of the 137Cs isotope to the total
exposition dose is about 1,311 mR or 77.4 percent
within the 70 years period.

a2
—
0.39
0.40680.4934l2
year-1- 0.4
2.75•10-3
1.375•10-2

SETTLEMENTS ENVIRONMENT
It is clear that the data established for the areas
with undisturbed soil can not be used for assessmentof the collective irradiation doses delivered byexternal radiation because only a small fraction of
population affected by the Chernobyl accident has aregular access to such areas.
For example it was established by the Ukrainian
specialists [7] that children at the age of 7 years andunder living in contaminated areas spend only 13
percent of the day outside the houses and otherbuildings. This means automatically that such children
forming the most sensitive subpopulation toirradiation spend 87 percent of day inside thebuildings and at least 87 percent of their time insettlements.
Children and teenagers at the age of 7-18 years
according to the Ukrainian National Report [7] (seeTable 4.1.3 on pages 4.18) spend about 18 percent of
their time outside the buildings and this means about
82 percent inside the buildings.
The largest fraction of time outside the buildings
spend pensioners. It reaches 36 percent of the day.
These data show that the inhabitants ofcontaminated areas spend about 20 percent of theirtime outside the buildings and 80 percent of time
inside the buildings.

DOSE RATES AND DOSES IN

70

Table 7.

Mean exposition dose rates in different areas of Bryansk oblast in autumn 1990 at a heightµR/h) [24].
of 1 m (µSettlement
Fedorovka
Glinnoe
Klintsy
Veliki Topol
Lopatni
Unoshevo
Lesnovka
Novo-zybkov
Gordeevka
ZlynkaVyshkov
MirnyiStaryi Vyshkov

Table 8.

Mean level ofcontamination,
Ci/km2
2.2
5.2
5.9
7.1
8.1
10.8
15.9
18.5
21.6
28.4
29.6
32.6
33.9

Street

Bench

Yard

Bed

Garden

House

19
27
20
28
32
35
54
53
50
106
82
58
145

18
23
19
28
30
39
51
52
65
85
85
65
132

19
27
19
27
31
39
49
49
67
90
89
78
108

20
28
21
30
34
45
61
58
79
87
100
109
112

21
28
22
32
34
48
73
62
84
100
109
113
143

14
15
14
16
17
17
26
19
25
25
47
22
32

Mean exposition dose rates outside and inside the buildings in contaminated areas ofBryansk oblast in autumn 1990 at a height of 1 m (µµR/h).
Mean level ofcontamination, Ci/km2
2.2
5.2
5.9
7.1
8.1
10.8
15.9
18.5
21.6
28.4
29.6
32.6
33.9

Settlement
Fedorovka
Glinnoe
Klintsy
Veliki Topol
Lopatni
Unoshevo
Lesnovka
Novozybkov
Gordeevka
ZlynkaVyshkov
MirnyiStaryi Vyshkov

These values show that at least 80 percent of timethe inhabitants of contaminated areas spend insettlements or areas with disturbed soil.
Therefore, use of the data calculated for areas with
undisturbed soil for the assessment of the collective
dose will cause a significant overestimation of thecollective doses.
In order to avoid this mistake one needs to correct
the equations (10) and (11) by introducing an
additional correcting factor KS , which is determined
as a ratio of the exposition dose rate in air measured
in settlements to the exposition dose rate in air overthe undisturbed soil measured at the same level ofradioactive contamination.
The equations (10) and (11) can be then rewritten
as follows:⋅

Outside the building

Inside the building

19.4
26.6
20.2
29
32.2
41.2
57.6
54.8
69
93.6
93
84.6
128

14
15
14
16
17
17
26
19
25
25
47
22
32

(13)
τ

n

Pτ* = Ks ⋅ ∫ KL (t) ⋅ ∑ K i ,γ ⋅ σi0 ⋅ exp (− 0.693
⋅ t)
i =1
0
T1i2
(14)
where:⋅= exposition dose rate at a reference

R γ* ( height of 1 m in the settlements
environment.

= exposition dose of externalPτ* radiation in air at a reference height of 1
m in the settlements environment
delivered over a period of time τ
We describe here a very simple method that allows
to consider the differences in external radiation insettlements and in areas with the undisturbed soil. It isbased on experimental data on exposition dose rates
measured by specialists of the scientific organization“Typhoon” of the Goshydromet of the former USSR

n

.
⋅ t),
Rγ*(t) = Ks ⋅ KL (t)∑ K i,γ ⋅ σi0 ⋅ exp (− 0693
i =1
T1i2

71

[24].
Specialists of this organization have carried out
extensive measurements of dose rates in autumn 1990
in different contaminated settlements of the Bryansk
oblast.
They performed measurements of exposition dose
rates in the streets, yards, on benches, over beds ofkitchen gardens, in gardens and inside the houses aswell. Dose rates measured in the course of thisinvestigation and averaged for each studied settlement
are given in Table 7.
On the basis of data given in columns 3-7 of Table
7 we can estimate the mean arithmetic dose rates

levels Aeff that can be described on the basis of thelinear function:⋅
R γ (t)out = A + B ⋅ A eff,(17)
where A and B are some constants.
They have a very easy meaning. As can be seen from⋅(17), at Aeff→0 R γ (t)out→A. It means that A isthe exposition dose rate on territory not contaminatedby the Chernobyl accident or the exposition dose rateof the background radiation. The constant B in theequation (17) is the exposition dose rate in autumn
1990 per unit of the effective contamination Aeff,(µR/h)/(Ci/km2).
On the basis of the standard LSM procedure wehave established the following values of A and B:
A=8.555 µR/hr, B = 2.381 (µR/h)/ (Ci/km2).
Substitution of quantities A and B into the equation(18) transforms it to:⋅outside the buildings, R γ (t)out, by:⋅Rγ (t)out
⋅

⋅

⋅

⋅

⋅

Rγ (t)str. + Rγ (t)bn. + Rγ (t)y + Rγ (t)b + Rγ (t)g
=
5

(15)

⋅

where:Rγ (t ) out = 8.555 + 2.381 ⋅ Aeff ,⋅= exposition dose rates measured in
the streets,

R γ (t)str.

where R γ ( t ) out is expressed in µR/h.
The solid line in Fig. 2 was drawn on the basis of theequation (18).
We have performed the same procedure with thedata on measured exposition dose rates established by[24] inside the houses of settlements of the Bryansk
oblast (see column 8 of Table 7 or column 4 of Table
8).
For the exposition dose rates inside the buildings⋅

R γ (t)bn. = exposition dose rates measured atbenches,⋅= exposition dose rates measured inyards,R γ (t)y⋅= exposition dose rates measured
over beds of kitchen gardens,R γ (t)b⋅⋅

R γ ( t ) in , we have established the following formula:= exposition dose rates measured ingardens.

R γ (t)g⋅+ 0505Rγ (t ) in = 11814.
. ⋅ Aeff(19)
The solid line in Fig. 3 was calculated by means of theequation (19). One needs to notice much larger
scattering of measured data from the solid line in Fig.
3 in comparison to Fig. 2.
This phenomenon has an easy explanation.
Conditions of irradiation outside the houses and otherbuildings in different settlements of the Bryansk
oblast do not differ very much. On the contrary conditions of irradiation inside the houses and otherbuildings can differ very significantly. It is known thatin rural settlement houses and other buildings aremostly constructed of wood that has much lower
attenuation capability than brick or concrete used as aconstruction materials in urban settlements. Therefore,
the exposition dose rates inside the urban buildings
are lesser than in rural settlements even if the
exposition dose rates outside the buildings are thesame. This is a reason of much larger scattering ofexperimental points from solid line in Fig. 3 than in
Fig. 2.

⋅

Values of R γ (t)out determined this way arepresented in the third column of Table 8. Here arealso given the values of exposition dose rates
measured by [24] inside the houses for comparison(see the fourth column of Table 8).
⋅

Values of R γ (t)out as a function of effective
contamination levels, Aeff, are also shown in Fig. 2.
Here Aeff is estimated by:Aeff =1137n⋅ ∑ Ki ,γ ⋅ Ai0 ⋅ exp( −Kγ ( Cs) i =1

(18)

⋅

0.693
t ),
T1i2
(16)

where:
137
per unit
K γ (137C s) = conversion factor of Cs
2deposition, (µR/h)/(Ci/km ),= initial surface contamination of thesoil by ith nuclide.
Figure 2 shows the existence of a strong dependence

A i0⋅

of R γ (t)out from the effective contamination

72

µR/h
140
120
100
80
60
40
2
Aeff, Ci/km

20
00Fig. 2.

10

20

30

40

50

Exposition gamma dose rates at a height of 1 m outside the buildings as a function of
Aeff
50

µR/h

40

30

20

10

2
Aeff, Ci/00

Fig. 3.

10

20

F (t)

A 0 ( 137 C s )⋅ F ( t ),K ( 137 C s )γ

F (t) =R γ*()
t = K s⋅ K L ()t⋅
The value of

(20)

i =1

K γ (137Cs)
t . (23)⋅ Aeff()A 0 (137Cs)

Rγ* (t ) in 1990 R γ*(90), can be

R γ*(90)= K s ⋅ K L (90)⋅K γ (137Cs)⋅ Aeff(90),A 0 (137Cs)(24)

where:= numeric value of shielding factor
originated from natural verticalmigration of nuclides into the soil,
A eff(90) = effective contamination of the soili

K L (90)
0.693⋅ t ).
T1i2(22)

calculated from the following formula:= initial surface contamination by the
nuclide 137Cs,= some function of time.

F ( t ) = ∑ K i ,γ ⋅ σ i0 ⋅ exp( −K γ (137C s)⋅ A eff(t).
A 0 (137C s)

Then the equation (13) can be rewritten as:

This function is given by:n50

On the basis of the equation (20) one can estimate
F (t)as:where:A 0 (137C s)

40

Exposition gamma dose rates at a height of 1 m inside buildings as a function of Aeff

One needs to remember that the equations (18) and(19) can be used only for calculation of expositiondose rates outside and inside buildings in settlements
environment in autumn 1990.
They can be transformed to such equations thatwill allow the assessment of the exposition dose rates
at any arbitrary time t.
Let us rewrite the equation (16) in the following
form:

Aeff ( t ) =

30

(21)

73

Multiplication of the left and right parts of theequation (32) by A 0 (137C s)gives:in 1990.
On the other hand the equation (18) can be written as:⋅⋅

R γ (90)out = R γ ,bgr.+ R γ (90)ch,⋅

R ( t ) ch =(25)

where:⋅

where:⋅= exposition dose rate outside theR γ (90)out building in settlements environment

R (t)chin autumn 1990,⋅= exposition dose rate of backgroundradiation; does not depend on time,R γ ,bgr.

= contribution of Chernobyl nuclides
to the exposition dose rate.
Comparison of the equations (18) and (25) gives:

R γ (90)ch(26)
Let us transform the last equation by dividing its left
0 137
and right parts by A ( Cs ) :⋅R ( t ) ch = 3.944 ⋅ Aeff * ( t ),⋅= exposition dose rate in air per unit of theeffective contamination expressed in(µR/h)/ (Ci/km2).
The total exposition dose rate outside the buildings
expressed in µR/h can be described by the following
equation:⋅. + 3944. ⋅ Aeff * (t ).
R(t ) out = 8555

(36)
The same procedure allows to develop the equation
for calculation exposition dose rates in air inside thebuildings (expressed in µR/h):⋅R(t ) ins = 11814.
+ 0.836 ⋅ Aeff * (t )Combining the equations (24), (27) and (28) gives thefollowing equation:

A 0 ( 137 Cs )Aeff ( 90 ).
A 0 ( 137 Cs )(29)

From here:

K s ⋅ K L (90) ⋅ Kγ ( 137 Cs) = 2.381 .

(30)

⋅

R ( t ) ch = 0.836 ⋅ Aeff * ( t ).

(38)
There are some arguments allowing to state thatthe equations (35)-(38) can be used for the assessmentof the collective doses not only in settlements of the
Bryansk oblast but outside of this area. Thesearguments are discussed below.
Data on measurements of exposition dose rates in
air outside and inside were measured by specialists of
the “Typhoon” in settlements of the Bryansk oblastthat borders the Gomel oblast. That allows the
supposition that (35)-(38) are also valid forcontaminated territories in the Gomel oblast.
One also needs to consider that the major part of
the total deposition of radioactive species in the

The equation (30) can be rewritten as follows:

Ks =2 .381.
K L ( 90 ) ⋅ K γ ( 1 3 7 C s )(31)

Let us insert the correcting factor K s determined by
the equation (31) into the equation (23). After somechanges this gives the following:⋅Rγ* (t ) =2.381
1⋅ 0 137⋅ Aeff * (t ),K L (90) A ( Cs)(32)

where Aeff * ( t ) is determined by:

A eff * ( t ) = K L ( t ) ⋅ A eff ( t ).

(37)

Here the numeric constant 11.814 in the part of theequation (37) determines the average exposition dose
rate inside buildings, originatedfrom thebackground radiation. The second member of the rightpart of this equation gives the contribution of theChernobyl nuclides to the total exposition dose rate⋅
inside buildings, R (t)ch (expressed in µR/h):⋅ Aeff ( 90 )= 2 .381 ⋅(35)

where:
3.944(27)

The left part of this the equation can be denoted as⋅
R γ*(90)ch. It is the exposition dose rate of externalradiation normalized to the initial surface
contamination by 137Cs.
It is clear that:⋅⋅(28)
R γ*(90)ch.= Rγ* (90)ch .

K s ⋅ K L ( 90 ) ⋅= exposition dose rate of externalradiation at the time t at the initial
surface contamination with 137Cs
originated from the Chernobyl accident
0 137
equal to A ( C s).

by means of the equation (12). It gives K L = 0.604.
Insertion of this value into the equation (34)transforms it into:R γ ( 9 0 ) c h = 2 .3 8 1 ⋅ A e ff ( 9 0 )

K γ ( 137 Cs )(34)

The numeric value of K L (90) can be estimated⋅Rγ (90) ch
Aeff (90)= 2.381 0 137.
0 137
A ( Cs)A ( Cs)2.381⋅ A eff * ( t ),K L ( 90 )

(33)

74

SF
1.5

1

0.5

*
2
Aeff , Ci/km
0

0

10

20

30

40

50

60

70

80

Fig. 4 Shielding factors as a function of contamination levels
former USSR lies in the Belarussian-Ukrainian
Woodland with quite uniform geochemical
characteristics. Moreover, urban and rural settlementsin the affected areas of Belarus, Russia and the
Ukraine are very similar as well as are the life-styleand occupational activities of their inhabitants.
Our assumption on the similarity of irradiation of
the Bryansk oblast inhabitants and inhabitants of otheraffected areas of the former USSR is also supportedby the data on the natural radiation background in
Belarus prior to the Chernobyl accident [25].
So according to the publication [25], the average
exposure dose rate in air in 1981-1982 was 10.6 µR/h
in urban areas of Minsk, Borisov, Vitebsk, Soligorsk
and 9 µR/h in rural areas of Minsk rayon. These
values very well agree with the dose rate of
background radiation (∼ 8.6 µR/h) that we haveestimated for the settlements environment in the
Bryansk oblast.
An additional evidence of justified application of
the equations (18), (19) and (35)-(38) for assessmentof exposition dose rates and doses in the settlements
environment outside of the Bryansk oblast gives alsoa very good agreement between the shielding factorsof buildings SF, calculated on the basis of theequations (18), (19) or (36), (37) and estimated on thebasis of experimental data.
The shielding factors of buildings are expressed asa ratio of the exposition dose rates inside and outside
the buildings.
They can be calculated on the basis of theequations (18), (19) or (35)-(38).
Figure 4 shows the shielding factor estimated by
the following equation:

SF =11.814 + 0.836 ⋅ Aeff *.
8.555 + 3.944 ⋅ Aeff *with the increase of the A eff* . Its value changes
from about 1.4 at A eff * = 0 (noncontaminatedterritory) to 0.4-0.3 in the interval of A eff* from
20 to 80 Ci/km2.
Table 9 demonstrates the data on the expositiondose rates in air outside of buildings that were
calculated for different periods of time on the basis of
the equation (35). Here are shown separately
individual contributions of short-lived nuclides,
isotopes of caesium as well as the total expositiondose rates. Data of Tables 1 and 3 have been also usedby calculation of data given in Table 9.
On the basis of Table 9 we have calculated the
air-absorbed doses inferred only by 137Cs insettlements environment accumulated over different
periods of time τ after the Chernobyl accident. Resultsof this calculation are presented in Table 10. There
are also our estimates on the air-absorbed doses inareas of “caesium spots” with the undisturbed soil.
They were calculated on the basis of data presented inTable 1 and 3 of our report.
We have also included in Table 10 the data
estimated on the basis of data of Miller et al [27] anddata used by J. Gofman [12] in his assessment of theChernobyl consequences.
As it is known, J. Gofman [12] did not carry out astudy for estimation of the air-absorbed doses inferredby the isotope 137Cs. He had based his assessment on
investigations conducted by H. Beck and G. de
Planque [28] and recommendations of UNSCEAR[29].
Data in Table 10 shows that there is very good
agreement between our values of air-absorbed doses
estimated for areas with undisturbed soil and values of
air-absorbed doses delivered in forest that we
estimated on the basis of data [27]. Our doses
calculated for areas with undisturbed soil as well very(39)

As can be seen from Fig. 4 this factor decreases

75

kilometers away from the contaminated territories of
the Bryansk oblast.
Taking into consideration all arguments given
above one can conclude that our method of dose rates
estimation and doses described in this part of ourreport gives quite correct data.
One can also agree with our statement that theassessment of the collective doses delivered to the
population affected by the Chernobyl accident has tobe based on results estimated for the settlements
environment. The use of data established for
undisturbed soil for this purpose will cause an
overestimation of the collective dose at least by factor
3. Taking in account this conclusion we shall carryout our further calculation on the basis of data given
in Table 9.
The value of the mean equivalent dose of externalradiation normalized to the level of contamination by137
Cs equal to 1 Ci/km2 can be estimated by use ofdata from Table 9 on the basis of the equation:

good agree with data estimated on the basis of data
used by J. Gofman [12]. On the other hand, our results
for settlements environment fall into intervals formedby data of Miller et al [27] estimated for plowed lands
with depth plowing of 15 and 30 cm respectively.
It is also necessary to notice that our air-absorbed
doses estimated for settlements environment
practically coincide with the arithmetic mean values
calculated on the basis of data [27] estimated for
different depth of plowing.
For example, air-absorbed doses that we haveestimated by use of data of Miller et al [27] for theperiod of time τ=70 years are 0.559 rad for the plowed
land with depth plowing of 15 cm and 0.348 rad for
depth plowing of 30 cm (see Table 10).
The arithmetic mean of these values is 0.453 rad.
The last value is only about 7 percent higher than thevalue of air-absorbed dose that we have calculated forthe settlements environment (0.425).
This agreement is surprising, especially, if one
remembers that our estimations are based on
experimental data of [24] established in areas of the
Bryansk oblast affected by the Chernobyl accident
and contaminated by 137Cs to very high levels.
On the contrary, the data of K. Miller et al [27]have been established in course of experimental
investigations of 137Cs soil-penetration due to global
fallout from atmospheric nuclear weapons tests.
Moreover, these investigations have been carried out
in the USA, which means in areas many thousandH τ*,ext = C1 ⋅C 2 ⋅ F1(F2 + (1− F2 )F3 )⋅ Pτ ,(40)

where:
C1 = conversion factor from exposition dose totissue-absorbed dose (rad/R),
C2 = conversion factor from tissue-absorbed doseto equivalent dose (rem/rad),F1 = correction factor (considers different factor
that can influence the exposition dose in air,for example snow cover, etc.),

Table 9.

Exposition doses in air at a height of 1 m in “caesium spots”, accumulated during different
periods of time after the Chernobyl accident (normalized to 1 Ci/km2 of 137Cs), in mR.
All nuclides
134
137
Periods of time, years
Short lived isotopes
Cs
Cs
together
50
45.4
98.6
449
593
70
45.4
98.6
486.6
630.6
90
45.4
98.6
508.6
652.6

Table 10. Calculated doses of caesium-137 in air at a height of 1 m accumulated during different
periods of time after deposition (given in rads) normalized to 1 Ci/km2
Period of time, years
Place
Source of information
50
70
90
Infinite time
Forest
1.195
1.365
1.495
—
Kevin M. Miller et all [27]Undisturbed field
0.707
0.807
0.866
—
Kevin M. Miller et all [27]Plowed land (to 15 cm
0.481
0.559
0.625
—
Kevin M. Miller et all [27]depth)
Plowed land (to 30 cm
0.296
0.348
0.370
—
Kevin M. Miller et all [27]depth)
Undisturbed field
1.058
1.145
1.193
—
M.Malko, this paper
Settlement, outside the
0.392
0.425
0.444
—
M.Malko, this paperbuildings
Used for assessment of the
1.15*
1.25**
1.44
J.Gofman [12]Chernobyl consequences
Notice:***this value is evaluated by multiplication of the value 1.44 rad per km2 by factor 0.80;
this value is evaluated by multiplication of the value 1.15 rad per km2 by factor 0.425/0.392.

76

F2

= occupancy factor (fraction of time spentoutside the buildings, dimensionless),
F3 = shielding factor of buildings (dimensionless).
Pτ = exposition dose in air (R).
*By carrying out the calculations of H τ ,extwe used
the following numeric values of these factors:
C1=0.93 rad/R; C2=0.72 rem/rad; F1=1; F2=0.2 [20],F3=0.211.
We estimated the value of factor F3 by use of theequations (35) and (38). Therefore: F3 is determinedby the equation:

F3 =0.836 ⋅ Aeff * 0.836== 0,2123.944 ⋅ Aeff * 3.944

The total release of nuclides to the environment(source term) is an important parameter in any
radiological accident because it determines the scaleof this accident. Soon after the Chernobyl accident theSoviet specialists had suggested their data on theamounts of radionuclides that escaped from thedestroyed Chernobyl reactor [19]. In this paper thesedata are presented in Table 11.
According to the estimations of the Soviet
specialists about 100 MCi of different nuclides
including 50 MCi of radioactive inert gases came into
the environment over the 10 days after the first
explosion at the reactor of the fourth unit of theChernobyl NPP.
Later it was recognized that the data published in[19] were underestimated. For example, the
UNSCEAR had shown in its report published in 1988
[20], that the total release of 137Cs into theenvironment as a result of the Chernobyl accident
had been in reality 2 times higher than claimed by theSoviet specialists.
According to the Ukrainian specialists [7] the total
release of all radioactive isotopes during the accident
at the Chernobyl NPP reached 10,813 PBq (about 296
MCi). This value is about factor 3 higher than theestimations of the specialists of the former USSR in1986. The data of the Ukrainian specialists on the
total release of nuclides from the Chernobyl reactor
are presented in this paper in Table 12.

(41)

As can be seen from the equation (41), the shielding
factor of buildings F3 does not depend on the effective
contamination level A eff* . It means that F3 is an
uniform factor for all contaminated areas. The
differences in shielding factors of buildings (39) and(41) arises from the fact, that the equation (39)determines the shielding effect of buildings fromcombined action of background radiation and
Chernobyl nuclides. On the contrary, the equation(41) describes only the shielding effect against
radiation caused by nuclides deposited on the groundas a result of the Chernobyl accident. As the task ofour study is the assessment of the consequences of theChernobyl accident we need to separate the influenceof background radiation and radiation caused by theaccident.
Insertion of the numeric values of the factors C1,
C2, F1, F2 and F3 into the equation (40) results in thefollowing formula:

CAESIUM DEPOSITION IN BELARUS,
RUSSIA AND THE UKRAINE.
Over the years that passed since the Chernobyl
accident extensive measurements of contaminationlevels by 137Cs have been undertaken in Belarus,
Russia and the Ukraine. Results of thesemeasurements allowed to establish the meancontamination levels by 137Cs in many thousand
settlements in these countries.
The total area of contaminated territories withinitial levels of contamination by 137Cs that change
0
from some minimal value As,min to some maximalH τ*,ext = 0.247 ⋅ Pτ .

(42)
The next step is estimation of the total mean*equivalent dose H τ ,ext normalized to the initial
surface contamination by 137Cs equal to 1 Ci/km2.
On analogy to the equation (3) one can write:

H =
*
τ

H τ*,ext
0.6

(43)

.

value

0
As,maxhas also been determined.

As a rule 6 different intervals for characterizing ofareas of contamination were established:
0.27-0.54 Ci/km2 (10-20 kBq/m2);
0.54-1.0 Ci/km2 (20-37 kBq/m2);
1-5 Ci/km2 (37-185 kBq/m2);
5-15 Ci/km2 (185-555 kBq/m2);
15-40 Ci/km2 (555-1480 kBq/m2);
and higher than 40 Ci/km2 (> 1480 kBq/m2).

Combination of the two last equations gives:H τ* = 0 .4 1 2 ⋅ Pτ .

(44)
Application of the equation (44) to a 70 years periodof time yields the following value of the normalized
mean equivalent dose: H τ = 0.26 rem / 1 Ci/km2.
*

The last value was calculated by use of the value, ⋅ R given in Table 9.
Pτ = 0631

SOURCE TERM

77

Table 11. Radionuclide composition of discharge from damaged unit of Chernobyl nuclear power
plant* [19]Nuclide***

*)
**)
***)

Activity of discharge, MCi
Fraction of activity discharge
25.04.86
06.05.86**
from reactor on 6 May 1986, %
133
Xe
5
45
Possibly up to 100
85m
Kr
0.15
—
-“85
Kr
—
0.5
-“131
I
4.5
7.3
20
132
Te
4
1.3
15
134
Cs
0.15
0.5
10
137
Cs
0.3
1
13
99
Mo
0.45
3
2.3
95
Zr
0.45
3.8
3.2
103
Ru
0.6
3.2
2.9
106
Ru
0.2
1.6
2.9
140
Ba
0.5
4.3
5.6
141
Ce
0.4
2.8
2.3
144
Ce
0.45
2.4
2.8
89
Sr
0.25
2.2
4.0
90
Sr
0.015
0.22
4.0
239
Np
2.7
1.2
3.2
238
Pu
3%
0.1•10-3
0.8•10-3
239
Pu-“0.1•10-3
0.7•10-3
240
-3
-3
Pu
“0.2•10
1•10
241
Pu
0.02
0.14
-“242
Pu
-“0.3•10-6
2•10-6242-3
Cm-“3•102.1•10-2
Error of estimate ± 50%
Total discharge up to 6 May 1986
The data presented relate to the activity of the main radionuclides measured on radiometricanalyses

Table 12. Radionuclide composition in the active core before the accident and in the total discharge
recalculated on 26.04.1986 [7].
Inventory of the active core before the accident
Total discharge recalculated on (26.04.1986)(26.04.1986)
NuclideHalf life
Activity
Released fraction of
Activity (PBq)(PBq)
inventory, %
133
Xe
5.3 d
6 500
100
6500
131
I
8.0 d
2 300
50-60
-1760
134
Cs
2.0 a
180
20-40
-54
137
Cs
30.0 a
280
20-40
-85
132
Te
78.0 h
2 700
25-60
-1150
89
Sr
52.0 d
2 300
4-6
-115
90
Sr
28.0 a
200
4-6
-10
140
Ba
12.8 d
4 800
4-6
-240
95
Zr
1.4 h
5 600
3.5
196
99
Mo
67.0 h
4 800
> 3.5
> 168
103
Ru
39.6 d
4 800
> 3.5
> 168
106
Ru
1.0 a
2 100
> 3.5
> 73
141
Ce
33.0 d
5 600
3.5
196
144
Ce
285.0 d
3 300
3.5
-116
239
Np
2.4 d
27 000
3.5
-95
238
Pu
86.0 a
1
3.5
0.035
239
Pu
24 400.0 a
0.85
3.5
0.03
240
Pu
6 580.0 a
1.2
3.5
0.042
241
Pu
13.2 a
170
3.5
-6
242
Cm
163.0 d
26
3.5
-0.9
Total
73559.05-10933.007
Notice: The discharge activity recalculated on 6 May 1986 is about 2000 PBq

78square kilometers) gives the following minimal
average contamination of the total territory of Belarus
by 137Cs:

The data on the total area of contaminatedterritories of Belarus, Russia and the Ukraine
characterized by these intervals of contaminationlevels by 137Cs are presented in Tables 13-16.
The data given there allow to estimate the minimal
amounts of 137Cs deposited in Belarus, Russia and the
Ukraine by means of the following equation:(45)
Q mi i n = A s0, ,mi i n ⋅ S i ,As,min ≈ 125. Ci / km 2 or 46.3 kBq / m 2 .
It is interesting to notice that the UNSCEAR
performed its assessment of the collective irradiation
doses originated from the Chernobyl accident by theaverage contamination of Belarus equal to 39 kBq/m2[20]. This value is about 20 percent lower than thevalue 46.3 kBq/m2 which was calculated on the basisof the equation (45).
It is clear that the real average contamination ofBelarus by 137Cs has to be higher than 1.25 Ci/km2.
We have developed a simple method for estimation of
more correct data on the total contamination ofBelarus by 137Cs.
The corrected amount of the deposited 137Cs, Qtot,
as a result of the Chernobyl accident can be calculatedby the following equation:

where:Q mi inSi= the minimal amounts of 137Cs depositedon the area with the initial contamination
0,iby 137Cs equal to As,m in (Ci);= the area of territories contaminated by
0,i

137

Cs at the level As,m in (km2).

The results of our calculation on the basis of theequation (45) are given in Table 17. In case of Belarusithis method gives Qmin
= 260,000 Ci .
Division of this minimal deposition value of 137Cs,
Q mi in by the total area of Belarus (207.6 thousandN

Q 0 = ∑ A s0,i ⋅ ∆ S i

(46)

i= 1

Table 13. Contaminated areas in Belarus with the level of caesium-137 equal to 1 Ci/km2 or higher(square kilometers) [31].
OblastBrest
Vitebsk
Gomel
GrodnoMinsk
Mogilev
Total

1-5
3800
35
16870
1690
2030
5490
29915

Level of contamination, Ci/km2
5-15
15-40
470
6740
12
48
2900
10170

> 40

2760

1625

1450
4210

525
2150

Table 14. Contaminated areas in the Russian Federation with the level of caesium-137 equal to 1
Ci/km2 or higher (square kilometers) [31].
OblastBelgorod
Bryansk
Voronezh
KalugaKursk
Lipetsk
Leningrad
Nizhni Novgorod
Orel
Penza
RyazanSaratov
Smolensk
Tambov
Tula
Uljanovsk
Total

1-5
1620
6750
1320
3500
1220
1690
850
15
8840
4130
5210
150
100
510
10320
1060
48915

Level of contamination, Ci/km2
5-15
15-40
2628

> 40

2130

310

2130

310

1419

132

1271
5450

79

where:N∆S i ≈S,N

A s0,iN

Q0 ≈ S ⋅∑= number of all contaminated settlements;0= the average level of initial surface
As,icontamination by 137Cs in ith settlement,(Ci/km2);that belonged to ith∆S i = area of the territory
settlement (km2).
The equation (46) can be simplified in order to makethe estimation of the value Q easier.
It is known that there is no significant difference inthe population density in the affected regions ofBelarus. The same conclusion can be made in relation
to Russia as the Ukraine. It is also known that the
majority of settlements in the affected regions havequite similar number of inhabitants.
Considering the abovementioned facts we canestimate the value of ∆S i by:

i= 1

N

= S ⋅ A s0 ,(48)

where:= contamination level by 137Cs averaged
over the total contaminated area (Ci/km2).
As can be seen from the equation (48) the value of

As0

As0 is determined by the equation:
N

A s0 =∑

A s0,i

N
i= 1

.

(49)

The last equation was used for the calculation of theaveraged levels for areas with the level of0
contamination A s≥ 1 C i/km 2. Results of thecalculation performed on the basis of the experimental
0
data on A si
, presented in the publication [32] are(47)

given in Table 18. There are also the averaged levelsof contamination by 137Cs at levels of contamination
A s0 ≤ 1 C i/km 2. In this case the following
equation was used:

where:S= the total area of all contaminated territories.
Combination of the equations (46) and (47) gives:

Table 15. Contaminated areas in the Ukraine with the level of caesium-137 contamination equal to 1
Ci/km2 (square kilometers) [31].
OblastLevel of contamination, Ci/km2
1-5
5-15
15-40
> 40
Vinnitsy
1944
38
Volyn
582
Dnepropetrovsk
38
Donetsk
410
Zhitomir
9192
1780
336
154
Ivano-Frankovsk
606
Kiev
7695
957
546
417
Kirovograd
219
Nikolaev
24
Odessa
27
Rovno
9332
181
Sumy
491
Ternopol357
Cherkasy3233
72
Chernigov
2221
135
Chernovtsy
500
14
Kharkov
31.4
16
Chmelnitsk
319
Total
37205
3177
882
571
Table 16. Caesium-137 contaminated areas in Belarus, the Russian federation and the Ukraine withlevel 10-37 kBq/m2 [6].
Countries
Area ( in 1000 km2) contaminated above specified levels
10-20
20-37
Belarus60
30
Russia300
100
Ukraine1506580

Table 17. Minimal deposition of caesium-137 on territories of Belarus, the Russia Federation andthe Ukraine
Range of contamination,
Ci/km2
0.27-0.54 (10-20 kBq/m2)
0.54-1 (20-37 kBq/m2)
1-5
5-15
15-40
> 40
Total deposition
Rounded total deposition, Ci

Table 18.

Q, Ci
Russia
81000
54000
48915
27250
31950
12400
255515255000Belarus
16200
16200
29915
50850
63150
86000
262315260000

Ukraine
40500
35100
37205
15885
13230
22840
164760165000Calculated average contamination levels in different affected areas of Belarus.

Range of contamination levels, Ci/km2
0.27-0.54 (10-20 kBq/m2)
0.54-1.0 (20-37 kBq/m2)
1-5
5-15
15-40
> 40

Average contamination level, Ci/km2
0.405
0.77
2.98
8.58
24.30
52.7

Table 19. Total deposition of caesium-137 on territories of Belarus, the Russian Federation and the
Ukraine.
Range of contaminationlevels, Ci/km2
0.27-0.54 (10-20 kBq/m2)
0.54-1 (20-37 kBq/m2)
1-5
5-15
15-40
> 40
Total deposition, Ci
Rounded total deposition, Ci

A s0 =

A s0, m i n + A s0, m a x
2

.

Q, Ci
Russia12162277027
145767
46761
51759
16337
459273460000Belarus
24300
23100
89147
87259
102305113305439414440000

Ukraine
60810
50066
110871
27259
21433
30092
300531300000given in Table 19 as well as the data on the depositionof this isotope outside of the former USSR (1.2 MCi[20]) one can assess the approximate amounts of 137Cs
that was discharged from the destroyed Chernobyl
reactor. It reaches 2.87 MCi. Summing up this number
with the amounts of 137Cs deposited in the Baltic
States and Countries of the CIS other than Russia,
Belarus and the Ukraine one can assess the total
discharge of 137Cs to the environment as a result of theChernobyl accident equal to about 3 MCi of the core
inventory of this nuclide before the accident. The last
figure coincides with upper limit of the estimations
given in publication [7].

(50)

By use of the data given in Tables 13-16 and 18 dataon the initial contamination of the affected areas in
Belarus, Russia and the Ukraine were calculated.
Table 19 shows the results of this calculation. The
data given in Tables 17 and 19 show that thedescribed method of calculation has given increased
amounts of deposited 137Cs in Belarus, Russia andthe Ukraine by factor 1.7 (Belarus) -1.8 (Russia,
Ukraine) estimations made on the basis of theequation (45).
One needs to notice that the amount of 137Cs
deposited in the Ukraine which is shown in Table 19
does not include big amounts of this isotope in the 30
kilometer zone. According to the Ukrainian National
Report [7] there is about 470 thousand Ci of 137Cs in
temporary storages of radioactive materials, in thesoil, in hydrosystems, etc.
By taking into account this value and the data on thedeposition of 137Cs in Belarus, Russia and the Ukraine

COLLECTIVE DOSE ASSESSMENT
As it was shown earlier, the collective irradiationdose can be calculated by means of the equation (1). It
is possible to use for this purpose the equation:

H τcoll = N ⋅ H τ* ⋅ A s0

81

(51)

Russia and the Ukraine.

Insertion of the value A s given by (6) into theequation (51) gives the following:

0
coll
* Q
H τ = N ⋅H τ ⋅S

ASSESSMENT OF COLLECTIVE THYROIDDOSESThe assessment of collective thyroid dosesdelivered to the population of Belarus, Russia and the
Ukraine can be performed on the basis of the data
established in the course of extensive studies by V.
Stepanenko, A. Tsyb, Yu. Gavrilin et al. [34].
By use of the experimental data on [31]accumulation in thyroid measured within the first days
after the nuclear explosion at the Chernobyl accident
these Russian specialists estimated the collective
thyroid dose of 3,674,000 residents of contaminatedterritories of 7 oblasts of Russia (Bryansk, Tula,
Kaluga, Orel, Riasan, Kursk, Leningrad) as 234,000
person·Gy. [34]. This value can be used for theestimation of the factor qth that determines thecollective thyroid dose commitment per unit
deposition of 131I.
In order to fulfill this task one needs to determine
the total deposition of 131I in “7 oblasts” of theRussian Federation. It can be done by means of theequation:(55)
Q 0 (131I ) = ψ ⋅ Q 0 ,(52)

The total number of the inhabitants of the affectedareas N can be estimated by the following:N = ρ ⋅S,

(53)

where:

ρ= the average population density incontaminated areas (man/km2).
The combination of equations (52) and (53) gives:

H τcoll = ρ ⋅ H τ* ⋅ Q 0(54)
Results of the collective equivalent doses calculationthat can be delivered to affected population ofBelarus, Russia and the Ukraine within the period of
70 years after the Chernobyl accident are obtained on
the basis of the equation (54) and are given in Table
20. This table also contains data on the total
deposition of the isotope 137Cs in Belarus, Russia andthe Ukraine, the total areas of contaminated territoriesof these states as well as the data on the meancontamination levels, mean population density andmean dose delivered over 70 years on a territory withthe contamination level by 137Cs equal to 1 Ci/km2.
The data on population density presented in Table
20 were calculated for 1986 on the basis of data of thestatistical handbook of the USSR [33]. Analysis ofdata given in Table 20 shows that the highest
equivalent irradiation dose has to be delivered to the4
Ukrainian population. It can be estimated as 6.6 ⋅ 10
man·Sv over 70 years. The collective equivalent
irradiation doses of inhabitants of the affected areas ofBelarus and Russia according to our estimation are55. ⋅ 10 4 and 4.4 ⋅ 10 4 man·Sv respectively. At thesame time the highest mean individual equivalentdose can be delivered to inhabitants of thecontaminated territories of Belarus. It is practically 3
times higher than the respective values estimated for77

where:= total deposition of 131I in 7 oblastsof Russia,
0=
total deposition of 137Cs in 7 oblasts
Q7of Russia,= correlation factor averaged over theψtotal area of contaminated territoriesof “7 oblasts” expressed as a ratio of
surface contamination level by 131I tosurface contamination by 137Cs
Experimental values of the factor ψ at 23.05.1986
measured in different settlements of Belarus andRussia [35] are given in Table 21 of this report.
Table 22 shows the values of the factor ψrecalculated to 26.04.1986. On the basis of thesevalues we have estimated the mean values of factor ψ

Q 70 (131I)

Table 20. Collective equivalent irradiation doses of populations of Belarus, the Russian Federationand the Ukraine.
Parameter
Total deposition of caesium-137, Ci
Total area of contaminated territories with level of
caesium-137 ≥ 0.27 Ci/km2 (10 KBq/m2), in k m2
Mean contamination level, Ci/ km2
Mean dose equivalent commitment during 70 years
after the accident (normalized to 1 Ci/ km2), rem
Mean population density, person/km2
Total number of people living in contaminated areas
Collective dose, manrem
Collective dose in man Sv, rounded
Mean individual dose, rem

82

Belarus440000Russia460000

Ukraine3000001364453.2253489151.318

256835
1.168

0.26
48.2
65766495514520
5.5•104
0.84

0.26
36.6
12770289
4376123
4.4•104
0.26

0.26
84.5
21702558
6590633
6.6•1040.30

Table 21. Ratios of nuclide activities to Cs-137 activity in soil of different contaminated areas ofBelarus and the Russian Federation by 23.05.1986 [35].
Settlement

131

Gomel
Mozyr
Pinsk
Zhitkovichi
Khoiniki
Jurovichi

3.48
1.16
5.68
1.78
1.62
1.47

Barsuki
Makarichi
Novozybkov
Nikolaevka
Berezovka
Svjatsk
Bartolomeevka

0.64
0.74
0.88
0.82
2.05
1.17
0.68

Zhisdra
Mileevo
Kolodjassy

0.91
0.95
0.95

Belev
PlavskDubovka
Uzlovaja

1.03
0.55
0.63
1.26

I

103

95
Cs
Zr + 95Nb
Belarus
1.74
0.42
4.54
1.0
0.39
1.06
1.98
0.58
2.28
3.89
0.53
2.22
3.49
0.56
11.2
2.50
0.43
6.47
Russia, Bryansk oblast
0.86
0.54
0.13
0.93
0.4
0.08
0.85
0.46
0.07
0.83
0.55
0.09
1.58
0.55
0.14
1.11
0.56
0.13
1.0
0.63
0.14
Russia,Kaluga oblast
1.0
0.52
0.03
0.85
0.53
0.1
1.01
0.56
0.07
RussiaTula oblast
1.34
0.54
0.06
0.69
0.53
0.06
1.02
0.54
0.14
2.55
0.45
0.05

Ru

134

140

La + 140Ba

90

Sr

1.97
1.06
1.0
1.67
4.6
2.21

0.17
0.13
—
—
0.07
0.06

0.30
0.39
0.38
0.36
0.34
0.31
0.06

0.11
—
—
0.008
0.008
0.03
0.04

0.25
0.37
0.31

—
—
—

0.23
0.45
0.14
0.26

—
—
—
—

Table 22. Calculated values of I-131/Cs-137 activity ratio in contaminated areas of Belarus andthe Russian Federation by 26.04.1986.
Settlement

Gomel
Mozyr
Pinsk
Zhitkovichi
Khoiniki
Jurovichi
Barsuki
Makarichi
Novozybkov
Nikolaevka
Berezovka
Svjatsk
Bartolomeevka
Zhisdra
Mileevo
Kolodjassy
Belev
PlavskDubovka
Uzlovaja

I-131
Cs-137(23.05.86)
Belarus
3.48
1.16
5.68
1.78
1.62
1.47
Russia, Bryansk oblast
0.64
0.74
0.88
0.82
2.05
1.17
0.68
Russia, Kaluga oblast
0.91
0.95
0.95
Russia, Tula oblast
1.03
0.55
0.63
1.26
131

for Russia and Belarus as 10 and 20 respectively.
By use of factor ψ=10 and the data given in Tables
14 and 18 we have calculated the total deposition of

I-131
Cs-137(26.04.86)
38.9
12.96
63.45
19.9
18.1
16.4
7.15
8.27
9.83
9.16
22.9
13.1
7.60
10.2
10.6
10.6
11.7
6.14
7.04
14.1

I in “7 oblasts” of Russia as 2.24 MCi. By
estimation of this value we did not take into
consideration the contaminated territories in “783Table 23. Collective thyroid dose of the affected populations in Belarus, the Russian Federationand the Ukraine.
Parameter
Total deposition, Ci
Total area of contaminated territories, km2
Mean population density, person/km2
Collective thyroid dose equivalent commitment
per unit release, man.Sv/Bq
Thyroid collective dose, man.Sv
Collective effective dose equivalent resulted
from thyroid irradiation, man.Sv
Mean individual dose of thyroid irradiation, rem

Belarus
8800000
136445
48.2

Russia4600000
456805
36.6

Ukraine6000000
25683584.5

3.90·10-1212.7·105

2.95·10-12
5.0·1056.80·10-12
15.0·105

6.35·10419.3

2.5·104
3.0

7.5·104
6.9

Table 24. Contributions of different nuclides to collective effective equivalent doses of irradiation
during the period of 70 years after the Chernobyl accident.
NuclideShort lived isotopes other than 131I, man.Sv
134
Cs, man.Sv
137
Cs, man.Sv
131
I, man.Sv
Total collective effective equivalent dose,man.Sv

Belarus0.4·1040.86·104
4.24·104
6.35·104

Russia0.38·104
0.68·104
3.34·1042.5·104

Ukraine0.48·104
1.03·1045.09·1047.5·104

11.85·104

6.9·10414.1·104*) Notice: these values were estimated by multiplication of collective thyroid doses by organ weighting factor 0.05 [36].

Table 25. Collective effective dose equivalent commitments per unit release of caesium and iodine
nuclides.
Country,organization
Belarus
RussiaUkraineUNSCEAR, 1988

Period of time,
years
50
70
50
70
50
70
50

134

Cs

1.06·10-12
1.06·10-12
8.04·10-13
8.04·10-13
1.86·10-12
1.86·10-12
3·10-12137

Cs
man.Sv
2.42·10-12
2.61·10-12
1.82·10-12
1.96·10-12
4.23·10-12
4.59·10-12
6·10-12131I

1.95·10-13
1.95·10-13
1.47·10-13
1.47·10-13
3.38·10-13
3.38·10-13
1·10-13UNSCEAR [20] and by V. Stepanenko, A. Tsyb, Yu.
Gavrilin et al in estimation of collective thyroid doses
resulted from the Chernobyl accident. It also statesthat the numeric value of qth,7= 2.82 ⋅ 10 −12
man·Sv/Bq can be used as the reference value of thisfactor. It is necessary to notice that the factor qth,7 is afunction of population density. Therefore, one needs
to correct the numeric value of qth,7 in case of
population density ρ that differs from the average
population density in “7 oblasts” of the RussianFederation. It can be made by means of the following
equation:oblasts” of Russia with the contamination levels by
137
Cs less than 1 Ci/km2.
Division of the collective thyroid dose established
by V. Stepanenko, A. Tsyb, Yu. Gavrilin et al [34] forthe residents of “7 oblasts” by the assessed depositionof 131I one can obtain the value of qth factor equal toorapproximately282. ⋅ 10−12 ⋅ Gy / Bq
−12
.
282
. ⋅ 10 ⋅ Sv / Bq
In order to emphasize the fact that the numericalvalues of qth given above have been estimated on thebasis of the data established by [34] for residents of “7oblasts” we shall describe it as qth,7.
Multiplication of qth,7 by the thyroid weighting
factor 0.05 [36] converts it to the collective effective
dose equivalent commitment per unit release of 131I
equal to 141. ⋅ 10 −13 man·Sv/Bq. The last value only
insignificantly differs from the collective effective
dose equivalent commitment per unit release of 131I
estimated in 1988 by UNSCEAR in its assessment of
the Chernobyl accident consequences. This surprisingagreement is a very important evidence of soundscientific backgrounds of the methods used by

q th = q th ,7 ⋅

ρ
,
ρ7

(56)

where:
qth= the collective thyroid dose commitment perunit of 131I deposition (man·Sv/Bq) byarbitrary population density,
qth,7 = the collective thyroid dose commitment perunit of 131I deposition (man·Sv/Bq)established on the basis of “7 oblasts” data,84ρ[38] had obtained his value on the basis of the Vital
Tables of the USA population. However, the life
expectancy of the American population is 10-15 years
higher than the life expectancy in Belarus, Russia andthe Ukraine [33, 39].
So, even in case the UNSCEAR will in future
increase its estimations of the risk coefficient ofradiation-induced solid cancers one needs toremember that estimations of the UNSCEAR arebased on the data established for the atomic bomb
survivors that have been living in a country with avery high life expectancy in comparison to the life
expectancy of the people in Belarus, Russia and the
Ukraine. One also needs to remember that in contrast
to the USA, Japan and other developed countries
characterized by a permanent increase of life
expectancy, Belarus, Russia and the Ukraine have apermanent decrease of life expectancy.

= population density in contaminated area
(persons per km2),= population density in contaminated areas of
ρ7“7 oblasts” of the Russian Federation.
Table 23 presents the data on the collective thyroid
doses estimated for population of Belarus, Russia andthe Ukraine by means of factor qth calculated on thebasis of the equation (56).
These data can be possibly considered as upper
limits of collective thyroid doses delivered to the
populations of Belarus, Russia and Ukraine.
The total amounts of 131I deposited in thesecountries were calculated by means of the data on
137
Cs deposition presented in Table 19 as well as thefollowing numeric values of factor ψ: 10 for Russia
and 20 for Belarus and the Ukraine.
As can be concluded from the above-discussed
facts, the correctness of the collective thyroid dose
estimations is fully determined by the correctness of131
I depositions. This means that each improvement in
the estimation of the total amounts of 131I deposited inareas affected by the Chernobyl accident will improve
estimation of the collective thyroid doses.
The results of our estimations given in Table 23
show that the highest collective thyroid dose wasdelivered to the Ukrainian population and the lowest
to the population of Russia. On the contrary, as can beseen from Table 23, the highest mean individual
thyroid dose was estimated for the residents of thecontaminated territories of Belarus. It is higher byfactor 6.4 than the mean individual thyroid dose in
Russia and by factor 2.8 than the mean individual
thyroid dose in the Ukraine.
Table 23 as well contains the data on the collective
effective dose equivalents resulted from irradiation ofpeople by 131I in Belarus, Russia and the Ukraine.
Table 24 shows the individual contributions ofdifferent isotopes to the total collective effective
equivalent doses calculated on the basis of data givenin the tables 20 and 23. The collective effective dose
equivalent commitments per unit release of caesium
and iodine nuclides are shown in Table 25.

PROGNOSIS OF STOCHASTIC
EFFECTSThe estimations of the possible stochastic effects
in the effected areas of Belarus, Russia and the
Ukraine are given in Table 27. The data on morbidity
and mortality from radiation-induced thyroid cancers
were calculated by use of the data on the collective
thyroid doses presented in Table 23 and the risk
coefficients 160·10-4Sv-1 and 16·10-4Sv-1, respectively.
The latter coefficients were estimated by thefollowing method. According to the data given in the
Table B-17 of ICRP Publication 60 [36] (see p.132 of
Publication 60) the risk coefficient of fatal thyroid
cancer for low dose, low dose rate and Low LET
radiation (DDREF is equal 2) is 8·10-4Sv-1. For thecase of an acute or quasi-acute irradiation (Chernobyl
case) one needs to use as a risk coefficient of fatal
thyroid cancer a value 2 fold higher or 16·10-4Sv-1(DDREF=1). From here one can receive the lifetime
morbidity risk coefficient 160·10-4Sv-1 as used for
calculation of data shown in Table 27.
The data on mortality from solid cancers otherthan thyroid cancer were used on the basis of the risk
coefficient from solid cancers estimated in 1994 by
the UNSCEAR and “corrected” for fatal thyroid
cancers. The “correction” was in reality a subtractionof the value 16·10-4Sv-1 from the value 1,090·10-4Sv-1
estimated by the UNSCEAR. One can receive on thissimplified way the value 1,074·10-4Sv-1 as a risk
coefficient for fatal solid cancers other than thyroid
cancers. Such "corrected" risk coefficient was used inassessment of fatal cancers in Belarus, Russia and the
Ukraine resulted from the Chernobyl accident.
By the calculation of leukaemia mortality we usedthe value 110·10-4Sv-1 determined by the UNSCEAR
in 1994 [37].

LIFETIME MORTALITY RISK FROMSOLID CANCERS AND LEUKEMIA
The latest estimations of the risk coefficient ofradiation induced solid cancers and leukemia areshown in the Table 26. In our prognosis of delayed
radiological effects we have used the data of the
UNSCEAR 94 [37] that are 2-fold less than the data
estimated in 1994 by J. Gofman [38].
We preferred the UNSCEAR 1994 risk coefficientof radiation-induced solid cancers due to thefollowing reason. It is well known that the risk
coefficient of solid cancers induced by radiation is
proportional to the frequency of spontaneous cancers
which is a function of the life expectancy. J. Gofman
85

Belarus, Russia and the Ukraine, as a result of theChernobyl accident as about 44,000 with 16,030 cases
in Belarus, 8,960 in Russia and 19,050 in the Ukraine.
As it was said above we have carried out ourassessment only for populations living in thecontaminated areas of these countries. We haveestimated the total deposition of 137Cs in these areas as
1.2 MCi (total deposition of 134Cs about 0.6 MCi).
The same amount of 137Cs deposited in the countries
outside the former USSR. If we assume that the
number of radiation-induced cancers and leukaemia
outside the former USSR caused by the Chernobyl
accident will be the same as the total number of solidcancers and leukaemia in Belarus, Russia and the
Ukraine because of similar deposition of 137Cs, wewill also obtain about 44,000 additional cancers andleukaemia for the countries outside the former USSR
and about 90,000 fatal cancers for all the countries of
the world including the former USSR. This
assumption means that the Chernobyl accident will

According to our estimations the Chernobyl
accident will cause about 20,000 additional thyroid
cancers among children and adults of the affectedareas of Belarus. About 10 per cent of this number
can be fatal (2,000 fatal thyroid cancers). We haveestimated the number of radiation-induced thyroid
cancers in Russia as 8,000 (800 fatal thyroid cancers).
For the Ukraine we predicted 24,000 additional
thyroid cancers (2,400 fatal thyroid cancers).
Considering our method of collective thyroid doses
assessment one can believe that these data on thenumber of additional thyroid cancers are upper limitsof possible thyroid cancers.
As can be seen from this Table, the numbers ofadditional fatal thyroid cancers in each state is similar
to the numbers of additional leukaemia and about 10
times less than the numbers of additional fatal solidcancers other than thyroid cancer.
We have assessed the total number ofradiation-induced fatal cancers and leukaemia in

Table 26. Lifetime solid cancers and leukemia mortality risk following acute whole body exposure
to 1 Sv.
Projection method

Lifetime risk, %Solid cancers
10.9
9.2
7.5
9.7
37.31
26.64*
25.56**
23.37*
22.35**
Leukemia
1.1
1.0

Constant relative risk
Decline to risk for age at exposure 50 years
Decline to zero risk at age 90 years
Constant relative risk (UNSCEAR 1988)
Whole body Cancer Dose (J. Gofman - 1981)
Whole body Cancer Dose (J. Gofman - 1990)
Whole Body Cancer Dose (J. Gofman - 1994)

Linear-quadratic dose response model
Constant relative risk (UNSCEAR 1988)
Notice: *)**)Data source
[37]
[37]
[37]
[20]
[12]
[18]
[18]
[38]
[38]
[37]
[20]

values determined by using T65DR dosimetric data of the RERF
values determined by using DS86 dosimetric data of the RERF

Table 27. Forecast of stochastic effects in Belarus, the Russian Federation, and the Ukraine as aresult of the Chernobyl accident (DDREF = 1).
EffectThyroid cancer (morbidity)
Thyroid cancer (mortality)
Leukemia (mortality)
Solid cancers other than thyroid
cancer (mortality)
All cancers and leukemia (mortality)

Belarus
20300
2030
1300

Russia
8000
800
760

Ukraine
24000
2400
1550

12700

7400

15100

16030

8960

19050

Table 28. Forecast of stochastic effects in Belarus, the Russian Federation, and the Ukraine as aresult of the Chernobyl accident (DDREF = 2).
EffectThyroid cancer (morbidity)
Thyroid cancer (mortality)
Leukemia (mortality)
Solid cancers other than thyroid
cancer (mortality)
All cancers and leukemia (mortality)

Belarus
10150
1010
650

Russia
4000
400
380

Ukraine
12000
1200
775

6350

3700

7550

8010

4480

9525

86

data.
The difference in the change of the morbidity on
thyroid cancer can be explained very easy on the basisof the data shown in Table 23. As it was said earlier,the highest mean individual thyroid doses weredelivered by the Chernobyl accident to the residentsof the affected areas of Belarus and the lowest to theRussian population. It is known that the latent periodsof stochastic effects induced by the radiation depend
from the irradiation doses. The lower the irradiationdose is, the longer is the latent period. This is an
explanation why marked increase in the thyroid
cancer incidence was registered first in Belarus andthen in the Ukraine and later in Russia.
Our data can also answer the question why there
are no reliable data on additional leukaemia among
the residents of the affected areas of Belarus, Russia
and the Ukraine up to present time [45-47]. This
contrasts the data established among the Hiroshima
and Nagasaki inhabitants that survived the atomic
bombardment. Additional cases of leukaemia among
them were registered firstly, and only then theradiation-induced solid cancer.
We suggest the following explanation for thesedifferences in the manifestation of stochastic effects
among the irradiated populations of Belarus, Russia,
the Ukraine and the residents of Hiroshima andNagasaki.
The survivors of the atomic bombardment of these
Japanese cities received practically the same doses onbone marrow (the whole body dose) and on thyroid.
The more earlier manifestation of leukaemia thanthyroid cancers by inhabitants of Hiroshima andNagasaki indicates that the latent period of leukaemia
is shorter than the latent period of thyroid cancers
when doses on bone marrow and thyroid are equal.
Another situation arises in the case when thyroid
doses are much higher than doses on bone marrow.
Such situation has place by the people affected by the
Chernobyl accident. Tables 20 and 23 demonstrate
clearly that thyroid doses among the affected
populations of Belarus, Russia and the Ukraine arepractically one order in magnitude higher than doseson the whole body. This is according to our pointview the reason of earlier manifestation of solidcancer (thyroid cancer) than leukaemia in Belarus,
Russia and the Ukraine.

cause in the affected countries the number of fatal
cancers and leukaemia which is similar to the death
numbers resulted from atomic bombardment ofHiroshima or Nagasaki.
One may also assume that the total number ofpotential victims in case of such accident in a country
with very high life expectancy and high population
density, for example in Japan, will be much higher asin the case of the Chernobyl accident.
The data discussed above have been estimated byuse of the factor DDREF=1, which is recommended
by the ICRP for the case of acute irradiation by highdoses and dose rates [36]. For chronic irradiation of
the population by low doses the ICRP recommends
the value of the reduction factor DDREFF equal to 2.
In the light of new data [37, 40, 41] it seems thateven in cases of low doses and dose rates this factor isvery close to 1 for solid cancers. But for leukaemia
the DDREF factor is about 2.5 or even higher [37,41]. For comparison only we have also carried out theestimations of additional stochastic effects assumingthat DDREF=2. The results of such estimation arepresented in Table 28.
We understand that the results of our assessment
have rather qualitative than quantitative characterbecause of many limitations in our study. For example
we did not consider the possible interaction ofradiation and chemical contamination in the affectedareas of Belarus, Russia, and the Ukraine. This can bea reason for the very significant difference inpredicted and manifested stochastic effects among thepeople affected by the Chernobyl accident. However,at present, there is no such quantitative informationthat could be used in assessment of radiologicalconsequences of this accident in the areas having avery strong chemical contamination. Because of alack of necessary information we also did not consider
deterministic effects that could be even more
important as radiological consequences in comparison
with stochastic effects as well as genetic affects andeffects of a very strong increase in the incidence ofgeneral somatic diseases in the affected areas
established by Belorussian, Russian and the Ukrainian
specialists soon after the accident. At the same time
we believe that our data are quite accurate for solvingof some problems that arose due to the Chernobyl
accident. It is well known, that the reliable data on theincrease of the morbidity on thyroid cancer amongchildren of the affected areas of Belarus were
established already at the end of the 80’s [42,43].
Now, practically all specialists in the field of radiation
biology and medicine recognise that this increase is
the result of the Chernobyl accident [44]. However, atthe end of 80’s no such increase in the morbidity on
thyroid cancer was established in Russia or in the
Ukraine. This fact was considered by specialists ofmany countries as an evidence of incorrectly assessed

SUMMARY
An assessment of radiological consequences(stochastic effects) caused by the Chernobyl accident
in Belarus, Russia and the Ukraine on the basis ofexperimental data on 131I and 137Cs in these countries
has been carried out.
Results of this assessment show that the Chernobyl
accident can be considered a real disaster. It can cause
about 44,000 additional fatal cancers and leukaemia
87

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Acknowledgement
Fruitful discussion of this work with T. Imanaka
and H. Koide as well as financial support from the
Toyota Foundation are gratefully acknowledged.
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