Russian Issue 3 - Harvard University Department of Physics

-Radiation & Risk", 1993, Issue 3
assumed that since 1990,12991 the main role in
137 Cs decontamination of agricultural produce
will be played by the "slow" component.
The statistical distributions of specific activity
with respect to the mean in different kinds of
agricultural produce are presented in Fig. 5-7
and Table 13.
The presented data suggest that all distributions
of activity by products and in human body
99.9
99
95
80
50
20
5
^ r
1 f " *
^
* *
0.1
-2.5 -1.5 -0.5 0.5 L.5
InCAij/Aj)
Scientific Articles
can be approximated by lognormal dependence
with close values of fig of about 1.8.
This is of principal importance for the scope
and frequency of radiation monitoring. If there
are no additional sources of activity in a settlement,
it is enough to determine the mean value
and then use data of Figs. 4-7 and Table 13.
1
Pasture grass p
*
V
-"i
r f
^ m •
: ^
2.5 3.5
Fig. 5. Distribution of logarithm of relative concentration of 137 Cs in pasture grass samples
in the vicinity of settlement.
99.9
99
95
BO
50
30
»#»»
Pol tato 1
^^r i
0.1 1! '
-1.6 -0.8 0.4
„ lnCAjj/Aj)
J .
*—;—•— •
Fig. 6. Distribution of logarithm of relative concentration of 137 Cs in potato samples
in the vicinity of settlement.
86
1.4
3.4
'Radiation & Risk', 1993, issue 3
99,9
99
95
80
50
F.%
20
u9 J'
Milk i
1 ..-*
f
0.1 •
•
f
•3.6 -2.6 -1.6 -0.8 0.4 L4 2.4
ln(AM/Aj)
!
* *
Scientific Articles
Fig. 7. Distribution of logarithm of relative concentration of 137 Cs in milk samples in the vicinity of
settlement.
Table 13
Statistical characteristics of distribution of relative radiation parameters in the exclusion zone
N
1.
2.
3.
4.
5.
6.
7.
Radiation
parameter
Dose rate
" r Cs soil contamination density
" r Cs concentration in grass
157
Cs concentration in potato
137
Cs concentration in milk
External exposure dose
,37
Cs concentration in body
\ 6. External and internal
exposure doses
6.1. External exposure
Distribution
type
normal
normal
tognorm.
lognorm.
lognorm.
lognorm.
lognorm.
According to the results of IDM, in May-June
1989 in Lubyanka and Opachichi the mean daily
doses were practically the same - 8.3 uGy/day
at maximum individual values of 16 ^Gy/day in
Lubyanka and 13.7 u,Gy/day in Opachichi.
As is seen from Fig. 8, individual doses can
be well approximated by the lognormal dependence
with pg = 1.52.
Based on the results of IDM in the areas of
rigorous monitoring [15] it was established that
probability density fi(ln(H/)) of distribution
of ratio of individual doses H to settlement a
averaged is rather stable and practically
universal for a rural settlement:
87
Mean
1.0
1.0
1.0
1.0
1.0
1.0
1.0
Standard
deviation
0.224
0.558
0.667
0.614
0.784
0.439
0.729
A
1.81
1.76
2.00
1.52
1.92
f1(ln(H/))=0.96exp{-[ln(H/)+
90%
quantite
1.29 3
1.56
1.64
1.58
1.87
1.54
2.00
+0.088f/0.3S}. (8)
If we compare the distribution variances in
settlements of the rigorous monitoring zone and
settlements of the 30-km zone we see that they
are close. The analysis of the relation of nonuniformity
of contaminations of settlements and
distribution of individual doses shows that in the
range of 10 to 95 percentile the form of distribution
and its parameters (mode, median, variance)
with 10% error do not depend on the nature
of radioactive contamination of a settlement.
The effect of non-uniformity of radioactive
contamination becomes noticeable only for extreme
values.
For practical purposes it is convenient to use
the distribution f^H/am) of ratio of external
individual doses H to mean density of 137 Cs