30 plutonium in the containment structure simply is not sufficient to sustain any significant increase in the level of activity in the waters of the lagoon. To take an extreme example, if as much as 1 Ci/yr of plutonium were being remobilized to the lagoon now, the average concentration in the lagoon would increase only by 33 percent and the effective half-life of the plutonium in the structure would be about 8 years. Since the levels of plutonium in the waters of the lagoon would have to be increased by several orders of magnitude to exceed international standards for drinking water, leaching from the dome is not likely to create a hazard. An upper limit for the radiation dose caused by leaching from the dome can be estimated by simply assuming that all of the transuranics are rapidly remobilized to the waters of the lagoon (i.e., in a time less than 30 years so that all effects would occur within one genera- tion). As already noted, about 3 Ci of plutonium need to be remobi- 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 (section 5.5). If the concentrations of transuranics in marine organisms are proportional to the concentrations in the water column (which is the assumption behind the use of the usual “concentration factor"), then the total additional dose from the remobilization of 12.6 Ci to the lagoon's water column should be approximately 4.2 times (12.6 divided by 3) the estimated annual dose due to the present concentration, or 1.1 mrem. In other words, the dome at.most could sustain the present levels for about 4.2 years. This upper limit of 1.1 mrem for the total dose due to remobilization of the dome's transuranics to the waters of the lagoon is independent of the exact mechanisms by which it might occur. A dose of 1.1 mrem to bone marrow also is small compared to doses that can be expected from other causes at Enewetak. Por example, cosmic rays in 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 transuranics contained in the dome to the waters of the lagoon would not be ‘expected to create a significant new radiological hazard. A simple model can be constructed to estimate the increased 30-year dose to bone marrow through the marine food chain if leaching from the 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 leaching and eventually went into solution in the lagoon (certainly an overly conservative assumption), the estimated increased dose as a function of the effective half-life in the dome would be: Effective half-life in dome (years) 10 20 50 100 ~~ 200 > F 7 cs} . 400 1000 , Extra 30-year dose to bone marrow (mrem) " , 0.95 0.72 0.37 0.20 0.12 0.05 0.02