166
Health Physics
DePuel'’’CsOZn), Bravo,
Rongelap] = 140 kBg m°is the
“theoretical” deposition density of
'7Cs at Rongelap
August 2010, Volume 99, Number 2
and that the relationship between '*’Cs deposition and
“initial” intake rates was the same at Rongelapandatall
other atolls.
The values of K(Z, Bravo, 7) that were used in eqn
(8) are shown in Table 4. They reflect the fractionation
that would have occurred if only the
test Bravo had con-
effects that have been estimated for the Bravo test.
inventory in 1957.
Co, and ©Zn, relative to °’Cs or “Sr, were much
greater on atolls close to the detonation site (Rongelap,
tributed to the Zn
Hence, a(°Zn) = 290 Bq d' of Zn per kBq m7
of '°’Cs. It is important to note that the value of a(°Zn)
depends only on the radionuclide that is considered and
that it is independent of the nuclear test and of the fallout
location.
Similar calculations were carried out to relate the
initial dietary intake rates and the theoretical '’’Cs
deposition densities for the five considered radionuclides
at Rongelap and Utrik. Results are presented in Table 4.
Values of the dietary intakes at any time after the test
Bravo could then be calculated using eqn (6).
Estimation of the chronic intakes resulting from
the Bravo test by adults of all other atolls. Whole-body
counting and or bioassay data similar to those available
for the Rongelap and Utrik evacueesare not available for
residents of any of the other 20 inhabited atolls. In this
case, there is no need to calculate a modified '’Cs
deposition density because the populations were exposed
to fallout from all tests at the same location. The general
formulation that was used to derive the initial intake rate
at atoll j from the '*’Cs deposition density at that atoll for
the Bravotest is given in eqn (8):
q(Z, Bravo, j, 0) = a(Z) X K(Z, Bravo, j)
xX Dep('*’Cs, Bravo, j).
(8)
Values of the dietary intakes at each atoll and at any
time after the Bravo test were calculated using eqn (6).
Weassumedthat the variation of the dietary intake rates
with time estimated for Rongelap held for all other atolls
Isotopes of Fe, Co, and Zn are highly fractionated in
comparison to *’Sr, and even more so in comparison to
'’Cs. Consequently, the deposition densities of ~Fe,
Utrik, Ailuk, Likiep, and Mejit), than on more distant
atolls where an R/V ratio of 0.5 was systematically used.
Estimation of the chronic intakes by adults re-
sulting from tests other than Bravo. Two of the
radionuclides considered (Sr and '°’Cs) are fission
products, the other three (Fe, ®’Co, and Zn) being
activation products. The ND factors for *Fe and “Co
werederived and reported by Hicks (1984) for only three
of six Castle series tests; they show a wide variability
from test to test as the activities produced depend on the
specific materials used in the construction of each nuclear device. The ND factors for the other activation
product, Zn, were not reported for any of the tests. In
the absence of relevant ND factors, two essential simplifications were made: (1) the variation of the dietary
intake rates with time was assumedto be the sameforall
tests and all atolls as described by eqn (6); and (2) the
“initial” intake rates of the long-lived radionuclides were
assumed to be proportional to the ground deposition
densities of '*’Cs as estimated in Beck et al. (2010) for
each test and at each inhabited atoll, and were calculated
by meansof eqn (8) in which K(Z,i,j) is taken to be equal
to unity. In that case, we assumed that there was no
fractionation of fallout radionuclides for any test other
than Bravo at anyatoll.
Estimation of the chronic intakes by children.
Based on a limited number of whole-body counting
measurements on Rongelap evacuees, the ratios of the
Table 4. Parameter values used to relate the '*’Cs deposition density to the initial dietary intake rates after the Bravo
test.
Radionuclide,
Z
a(Z)’,
(Bq d' per kBqm™*)
a(Zy
(Bq d™! per kBq m’”)
Fe
"Co
Zn
Sr
8.1
3.2
290
0.013
26
3.0
560
0.013
"Cs
3.0
7.7
* Applies to fallout from Bravoat all atolls, except for Utrik.
> Applies only to fallout from Bravo at Utrik.
k(Z, Bravo, j)
Rongelap
Utrik
Ailuk
Likiep
Mejit
Otheratolls
4.07
4.07
4.07
1.45
1.0
2.2
2.2
2.2
1.1
1.0
2.2
2.2
2.2
1.2
1.0
1.44
1.44
1.44
1.0
1.0
1.89
1.89
1.89
1.05
1.0
1.0
1.0
1.0
1.0
1.0