TRU management and 235U consumption minimization in fuel cycle scenarios with AP1000 and VHTRs
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This paper is focused on the evaluation of different strategies for TRU reduction and 235U consumption minimization in an AP1000-VHTR fuel cycle. The first step was to quantify characteristics of AP1000 and VHTR fueled with UO2 to provide reference data for performance analysis of the VHTRs fueled with TRU. Reactor's metrics such as the core multiplication factor and lifetime, the energy spectrum and the spent fuel isotopic mass and activity at EOL were computed for both reactors and compared. Fuel cycle parameters such as the system's reprocessing speed, the VHTR daily consumption of 235U and TRU destruction rate were derived. To sustain criticality for 600 days, the AP1000 needed to be fueled with 3 wt% 235U enriched UO2 while the VHTR's enrichment needed to be raised to 15 wt%. Consequently, 4-5 times more Pu were left at EOL in the VHTR than in the AP1000 per unit initial mass of fuel. It remained 3 times more 235U and also almost 6 times more 236U in the VHTR than in the AP1000. In the second step of the study, the VHTR was fueled with 20%, 40% or 100% of TRU arising from the AP1000. A VHTR containing 40% of TRU where RGPu had been replaced by WGPu was also studied. TRU fuels were complemented by UO 2. UO2 + TRU fueled VHTRs performances were ranked and also compared to UO2-fueled VHTRs. The reactor life was extended by at least 36.7% when part of the LEU is replaced by TRU. A transuranic fuel containing 40% of TRU with WGPu appeared as the best compromise. It reduced the inventory of TRU in the VHTR by 67.7% and had the lowest 235U daily consumption (100% TRU fuel apart). Furthermore, with this configuration, a single VHTR could reprocess the TRU wastes of 1.57 AP1000s. 2012 Elsevier Ltd. All rights reserved.
