STOCHASTIC SIMULATION OF RADIONUCLIDE UPTAKE
805
It is now necessary to assign distributions to the variables, which
are assumed to be probabilistically independent. Thyroidal uptake of
ingested ‘*\], F, and the effective half-life of this ‘I in the thyroid, b,
are considered constant for any individual, but they differ among individuals. The term F was chosen randomly from 114 values ranging
from 0.05 to 0.35 (see Table 1). The nature of the distribution was inferred from the work of French,’ The value of b (days) was chosen
randomly from the following distribution: 1.5, 2.0, 2.0, 2.5, 2.5, 2.5,
3.0, 3.0, and 3.5. The values of D, and v, change from day to day. The
value of D, (grams) was chosen at random from thefollowing distri-
bution: 80, 90, 90, 100, 100, 100, 100, 110, 110, and 120. The value of
v, (days) was similarly selected from the following distribution: 5.0,
9.33, 5.33, 5.5, 5.5, 5.5, 5.75, 5.87, 6.0.
Table 1— FREQUENCY DISTRIBUTION ASSIGNED TO F IN THE OPERATION OF THE
PROBABILISTIC MODEL
Number
to to BOT
to F
0.19
0.20
0.21
0.22
0.23
or ee DOD ND
of cases
Value
assigned
0.24
0.25
0.26
0.27
0.28
meee
PWNHrF OO
onan
cocoon
oce ef ©
eRe OOOO D
YoOAAa YH
to F
Rie ee
—
sooo
wonton
m ww wh
of cases
Value
assigned
ocoo
Number
0.29
0.31
0.32
0.35
In the preceding discussion the successive amounts of ‘I per
gram of vegetation consumed have been expressed as functions of
X,-..Xg9- SO we must now consider the nature of the distribution of
131] ber gram on the first day. Let this distribution be represented by
values
of x.
A typical
distribution of x (based on 41 values from
Penoyer Valley, about 40 miles from ground zero) and the distribution
of X (equals log x) are portrayed in Fig. 1. Because of its shape, the
distribution of XK was aSsumed to be normal, with mean and variance
equal to the mean and variance of the sample values of X. The means
and variances of four such distributions of X are given in Table 2
(see Fig. 2 for locations of sampling areas with regard to the Nevada
Test Site).