Table
I.
Pulmonary deposition of plutonium (
239+240
Pu) for worst- and best-case
conditions on Bikini Atoll.
Inhalation
Condition
Dust
Soil Pu
Personal
Enhancement
_
Pulmonary
rate
aerosol
activity
dosimeter
Respirable
| deposition
(m?/h)
(g/m?)
(aCi/g)
factor
factor
fraction
(aCi/h)
Bare field,
during tilling
1.04
136
15.3
3.1
0.92
0.24
1476
1.04
21
15.3
0.83
2.64
0.19
139
0.83
21
15.3
0.83
1.86
0.19
78
0.83
21
8
0.41
1.1
0.19
12
0.023
28
4.1
2.5
i>
0.24
Stabilized field,
heavy work
In and around houses,
light wosk
light work
seenta Se GaPh4
Coconut grove,
At roadside,
one vehicle/h®
1.58 + BGS
a Exposure to one !0-s, median, vehicular dust pulse not including background (BG).
b Assumed value.
© Radionuclides inhaled via background mass loading.
normal and high-activity conditions at Bikini Atoll indicate that the pulmonary deposition
239+240,, n 241,
and
would be less than 0.3 (Table |). The gut transfer factors used for
are 10° 4 and 5 x 107 respectively, as recently suggested by the ICRP. 23 Both plutonium
and americium are considered to be class-W particles.
The dose contribution from the inhalation pathway is a major source of exposure to
the transuranic radionuclides, but both the inhalation pathway and the transuranics will
contribute a minor portion of the total doses predicted over the next several decades.
The transuranic radionuclides that must be considered in evaluating the inhalation
pathway are 23942405, 24 ay and 241 a as well as the 241 ay that in the future will
result from the radiological decay of 24l Pu currently present. Because of the low-energy
beta radiation (0.02! MeV maximum) and a much shorter half-life (14 y), the doses from
atl ny are less than one tenth those from 23942405,
The concentrations of 2*!am in the soil (pCi/g) at most of the atolls are
approximately 70 to 75% of the 23942405, concentrations.
However, more 24) am will
result from the decay of 241 oy, The parent-daughter relationship for 241 py to 241 am is
shown in Fig. 2. The maximum 24 am activity that will result from an initial
14
241
Pu