30
Plutonium in the containment structure simply is net sufficient to
sustain any significant increase in the level of activity in the
of the lagoon.
To take an extreme example, if as much as 1 Ci/yr
Plutonium were being remobilized to the lagoon now, the average
centration in the lagoon would increase only by 33 percent and the
effective half-life of the plutonium in the structure would be
years.
Since the levels of plutonium in the waters of the lagoon
have to be increased by several orders of magnitude to exceed inte
national standards for drinking water, leaching from the dome is
likely to create a hazard.
An upper limit for the radiation dose caused by leaching from
dome can be estimated by simply assuming that all of the transuran
are rapidly remobilized to the waters of the lagoon (i.e., in at
less than 30 years so that all effects would occur within one gene
tion).
As already noted, about 3 Ci of plutonium need to be remob
lized annually to maintain the present concentration in the water
column, and the estimated dose rate to bone marrow (for all transuranics) from the ingestion of marine foods is 0.26 mrem/yr (secti
5.5).
If the concentrations of transuranics in marine organisms
proportional to the concentrations in the water column (which is
assumption behind the use of the usual “concentration factor"),
the total additional dose from the remobilization of 12.6 Ci to th
lagoon's water column should be approximately 4.2 times (12.6 divi
by 3) the estimated annual dose due to the present concentration,
1.1 mrem.
In other words, the dome at most could sustain the pre
levels for about 4.2 years.
This upper limit of 1.1 mrem for the total dose due to remobili
tion of the dome's transuranics to the waters of the lagoon is ind
pendent of the exact mechanisms by which it might cccur.
A dose o
mrem to bone marrow also is small compared to doses that can be
expected from other causes at Enewetak.
For example, cosmic rays
the Marshall's produce a dose to bone marrow of 1.1 mrem every two
weeks.
Thus, even a relatively rapid remobilization of all the tr
uranics contained in the dome to the waters of the Lagoon would no
expected to create a significant new radiological hazard.
A simple model can be constructed to estimate the increased 30dose to bone marrow through the marine food chain if leaching from
dome to the lagoon took place with an effective half-life of T (see
appendix A).
If all 12.6 Ci in the dome were available for leachi
and eventually went into solution in the lagoon (certainly an overl
conservative assumption), the estimated increased dose as a functi
of the effective half-life in the dome would be:
Effective half-life
Extra 30-year dose
in dome
to bone marrow (mrem)
10
20
50
100
200
400
1000
(years)
0.95
0.71
0.37
0.20
0.12
0.05
0.02