Engineered Components for Radioactive Waste Disposal Systems - Are They Technically Justified

摘要

The technical justification for the development and use of sophisticated engineered components in radioactive waste disposal systems was evaluated. The evaluation applied information from many studies in the nuclear waste disposal literature and focused their combined results on determining the relative contribution of a number of subsystem functions to overall system performance. A wide range of spent fuel, commercial high-level, and Savannah River defense high-level waste disposal systems in dome salt, bedded salt, basalt, and granite geologic media were investigated. The results showed that the site portion of the disposal system so dominated overall system performance that even relatively poor sites were more than adequate to isolate the waste without the use of any engineered components. The performance-dominating nuclides were so long-lived that even extremely sophisticated waste containers could not increase overall system performance above that required for adequacy. Even relatively poor sites are effective in controlling the release of nucides with short half-lives, like exp 90 Sr, and even exceptional waste containers are ineffective in controlling the release of nuclides with long half-lives, like exp 237 Np. Based on the results of this study and other studies in the nuclear waste disposal literature, the use of long-lived waste containers and very low transport rate man-made subsystems seems unjustified from a technical standpoint and a geologic disposal point of view. The design objective for the waste container lifetime should not be greater than that desired for retrievability (0 to 100 years), and the design objective for the man-made subsystem transport rate should not be less than the 10 exp -2 to 10 exp -4 per year range. (ERA citation 08:035321)