Date of Award
Doctor of Philosophy
Daniel R. Bullen
Performance assessment (PA) analyses have been completed for high level nuclear waste forms derived from once through Light Water Reactor (LWR) spent fuel (SF), defense high level waste (DHLW), the closed advanced liquid metal reactor (ALMR) pyroprocess fuel cycle, and the front end processing of LWR spent fuel for possible recycling of the actinides in the closed ALMR fuel cycle. The IMARC (Integrated Multiple Assumptions and Release Calculations) and RIP (Repository Integration Program) PA tools were utilized to predict the performance of these wasteforms for emplacement in the proposed Yucca Mountain Repository;A model was developed to predict the time dependent failure distribution of the engineered barrier system. This model utilized the Weibull distribution as the tool to estimate the failure properties of each barrier of the multi-barrier waste containers. The sequential failure of each barrier was included in the model. The results were used in the subsequent PA analyses;The overall conclusion drawn from the use of two PA tools is that the total actinide release to the accessible environment is substantially lower for the closed ALMR fuel cycle and LWR actinide recycle wasteforms relative to directly disposed LWR SF. The release of fission products is similar. This is due to the significantly lower actinide inventory within these wasteforms;The maximum releases were found to occur for fracture dominated flow for all wasteforms considered. Under matrix dominated flow, sorption of the actinides is greatly enhanced. The dominant actinide under fracture flow conditions is 239Pu while under matrix flow conditions 237Np dominates as the Pu is effectively sorbed onto the tuff. The release of fission products is independent of the flow mode since they do not strongly sorb to tuff and will dominate the total release in a matrix flow situation;The benefits of incorporating LWR actinides into the closed ALMR fuel cycle are apparent at Yucca Mountain regardless of the flow mode. If fracture flow dominates, the reduction in the plutonium inventory through recycling leads to reductions in the total actinide release relative to that from LWR SF. If matrix flow dominates, the reduction in the neptunium and plutonium inventory (particularly 241Pu) through recycling again leads to reductions in the total actinide release relative to that from LWR SF. The degree of reduction is largest when matrix flow dominates.
Digital Repository @ Iowa State University, http://lib.dr.iastate.edu/
William Mark Nutt
Nutt, William Mark, "Performance assessment modeling of alternative high level nuclear wasteforms " (1995). Retrospective Theses and Dissertations. 10969.