31 5.8 Hazards Associated with Breaching of the Containment Structure ‘As discussed above, radioactive material can escape from the con- “tainment structure either by leaching, in which case all the radioactivity would be waterborne, or by actual breaching of the dome structure, in which case the radioactivity would be both waterborne and airborne. If part of the dome were torn away, transport of the radio- active material, now aggregated for the most part into larger particles by the cementing process, most likely would occur during heavy storms, and the most credible result would be that the wet and heavy contents would be swept into the lagoon. ‘The whole area would be drenched and, ‘ hence, any material that had become airborne would be washed out rapidly. It is noteworthy that throughout the cleanup effort field workers wore air filters for protection against airborne plutonium. Radioactivity on all but a handful of filters was too low to be detected in totally dry conditions. Thus, even during the most adverse ‘possible conditions (i.e., during the scraping, transporting, and dumping of the contaminated soil), the amount of airborne plutonium was negligible. Zatimates of the potential future radiological dose at Enewetak due to atmospheric resuspension of transuranics have been made by Robison and co-workers (1980) based on resuspension experiments conducted at Fnewetak and Bikini. These measurements included both the contribu- tions of sea spray and suspended aerosols of terrestrial origin (the "normal or background" mass loading at both locations was approximately 55ug/m of which about 60 percent was due to sea salt); they also included high activity situations such as the cultivation of open fields.” Dose rates were calculated assuming & hours per day of high activity work. For surface soil transuranic concentrations equal to those at Enjebi (which averages approximately 20 pCi/g), the potential dose rate due to the inhalation pathway is estimated as 12 mrem/yr (Robison et al. 1980}. This would certainly overestimate the dose rate to a visitor to Runit even if large quantities of unconsolidated material were to erode from the dome. Thus, if the “off limits” ban on the island were violated, potential health effects from such resuspension appear unimportant. . With respect to the future of the containment structure, the committee believes that the structure will maintain its physical integrity for a long period of time (probably in the range of 10 to 10° years). However, it is impossible to estimate this with any degree of certainty because the principal threat comes from the longterm cumulative effects of large storms. If the key-wall eventually were to be breached, the most likely outcome would be an erosion of unconsolidated material out of the dome to the lagoon and reef, with the dome subsiding upon the consolidated material. This would not - 1 "Based on measurements made near Windscale there is some evidence that plutonium may be concentrated in the sea surface and subsequently injected into the atmosphere by sea spray and transported by the wind (Cambray and Eakins 1980). Any such concentration effect, if it does exist, would be included in the measurements reported by Robison and co-workers.