Table 6.
Fractions of 739Pu in Bone, Liver, or Kidney
Ingestion/Inhalation
1
10
100
200
400
1,000
Fraction Due
Fraction Due
0.9005
0.0053
0.0506
0.0964
0.1758
0.3478
0.9995
0.9947
0.9494
0.9036
0.8242
0.6522
to Ingestion
to Inhalation
Plutonium reaches man by ingestion of contaminated food and water or inhalation
of contaminated air.
Part of this plutonium is distributed throughout the
body where it may remain for some time. While it remains within the body,
those organs that retain the plutonium will receive a radiation dose which
depends on the weight of the organ, the amount of plutonium retained, and the
time that the plutonium is retained.
There are several models which we have
used to estimate piutonium distribution in man and these are discussed in this
section.
Dose and Dose Commitment
In all of the dose estimation models, the formula for estimating the radiation
dose to a critical organ of man, i.e., one of those organs which tend to
receive the highest radiation doses, is
aD/dt = BE y/m
Estimated burdens based on ICRP Publications 2 and 19.
(303
-
| O et
where
“<
(a)
DOSE ESTIMATION MODELS
Due to Chronic Inges rage and Inhalation for
a Period of 50 Years
is time, days
is the dose to the reference organ ( rems),
= 51.2159 €, is a dose rate factor (g rem/{yCi day)),
is the effective energy absorbed in the reference
organ per disintegration of radionuclide (MeV/dis),
is the plutonium burden in the organ (uci),
m is either the mass of the organ if the organ is not
part of the gastrointestinal tract or twice the
mass of the contents if the organ is part of the
gastrointestinal tract (2).
The values of the parameter in Equation (30) for 239pu and other transuranium
elements are given in Table 7.
Most of these values were reported by the ICRP
(1959, 1964).
The masses of deep lung and other portions of the respiratory
tract are the values used by Snyder (1967) and Kotrappa (1968, 1969).
The
mass of thoracic lymph nodes was assumed to be the value (15g) reported by
Pochin (1966). The mass of abdominal lymph nodes was assumed to be less than
the thoracic lymph nodes and was arbitrarily set at 10g.
The dose accumulated
in the organ from the beginning of the exposure period (t=0) to some later
time (t#T)) is given by
1
D
D = (E/m) |0 y dt.
;
(31)
If ingestion and inhalation of plutonium were halted at time T_, and the
individual were to live to some later time The each organ would accumulate an
659