32 result from any conceivable single event but would be the consequence of cumulative effects over a long period (plus, of course, the absence of any attempt to make repairs). It is the committee's view, however, that even if this eventually were to happen, the dome would continue to perform its intended fiinctions. The collapsed dome probably still would prevent human access to the contaminated debris buried within. Any soil-cement or tremie material spilling or eroding from the dome into the lagoon would cause little change to the concentrations of transuranics there. Measurements on such material drilled from the dome showed a mean concentration of transuranics of 21.4 pCi/g with a range of 1.8 to 52.3 pCi/g. Lagoon surface sediment measurements taken within a mile of Cactus Crater show a range of transuranic concentrations of from 1.9 to 64 pCci/g (dry) with a mean of about 30 pCi/g (dry) (Atomic Energy Commission 1973). Thus, deposition of material from the dome on the lagoon floor would not necessarily increase the concentrations of transuranicsa in the superficial sediments. Even if material from within the dome were to contribute to the water column concentrations independently of the radioactivity now in the sediments, the upper limit of the radiological hazard would be the game as that estimated in the previous section for leaching. Thus, if all of the transuranics in the dome were remobilized to the water column of the lagoon, the result at most would be an increased dose of only 1 mrem (to bone marrow) through the ingestion of marine foods. 5.9 Summary : It is clear that the estimates made here and in the previous section depend directly on the validity of the dose estimates calculated by Robison and co-workers. These, in turn, depend on diet surveys made at Ujelang and on measurements made by Noshkin and co-workers (1980) of the transuranic concentrations in marine foods. It is conceivable that new observations will lead to new estimates of the bone marrow dose from transuranics in marine foods. However, two points can be made to support the view that such changes are not likely to alter the basic conclusions of this report. The assumption of the rapid remobilization of all the dome's trans- - uranics is an extreme one and is not supported by any existing tal € cD CH evidence. Por example, if the rate of remobilization from the dome to the lagoon was similar to that from the lagoon's sediments, i.e., having an effective half-life of 400 years (Noshkin 1980), and only 20 percent of the dome's contents were available for remobilization, the 30-year integral dose to bone marrow would be only 0.01 mrem (see section 5.7). Purther, the estimated dose from the ingestion of marine foods from present concentrations in the lagoon is small. It would require an increase of about 10’ in the present estimate to produce a dose level that would be of serious concern. In summary, the committee believes that it is highly unlikely that the containment structure will fail in its function of preventing human access to its contents and that no credible health hazard would result even if the containment structure! 8 transuranics were leached or eroded into the lagoon. ~ ae Foe Re