Impact assessment of alternative back-end fuel cycles on geological disposal of resultant spent fuels and high level wastes

Abstract

The aim of this study is to assess the impact of closing the nuclear fuel cycle on geological disposal of resultant spent fuels and high level wastes. Once-through and closed fuel cycles with different back-end scenarios are compared with regard to geological disposal. The comparison is carried out in terms of two significant parameters for permanent geological repository: disposal densities and long term radiotoxicity indices of wastes generated from fuel cycles. In the first part of the study, fuel cycles are identified and waste characteristics (amount, composition and thermal output) for the burnup values of 33,000, 40,000 and 50,000 MWd/t are estimated by using MONTEBURNS code. Then, areas needed for waste types under consideration are determined by thermal analysis carried out in ANSYS code for a reference repository concept. The second part of the study consists of an assessment of the radiotoxicities (namely ingestion-toxicity indices) of the wastes generated from the fuel cycles considered. According to the results of the disposal density analysis the once-through cycle is the most advantageous one at low burnups. However, at burnups higher than 40,000 MWd/t, the closed cycle with the standard reprocessing is better than the once-through cycle and the other closed fuel cycles. According to the results of the radiotoxicity analysis, the closed cycle with MOX recycling is more advantageous than the once-through cycle and the other closed cycles for the whole burnup range studied.