Assessment of TRU burning in a molten salt reactor moderated by zirconium hydride rods

摘要

Inventory reduction of transuranium (TRU) nuclides can effectively reduce the long-lived and high-level radioactive hazards in the spent nuclear fuel (SNF) from the current light water reactors (LWRs), which is of importance to the long-term development and deployment of nuclear energy. Considering its outstanding fea-tures such as excellent neutron spectrum, high fuel utilization and compact core structure, a molten salt reactor moderated by zirconium hydride rods (ZrH-MSR) is considered as one of the potential reactor types for TRU burning. In this work, several fuel salts and molten salt volume fractions (SVFs) are analyzed to assess the TRU burning capability in a ZrH-MSR. The fuel salt of 77.5 mol% LiF-22.5 mol% (ThF4 + TRUF3) is selected since it can meet the requirement of TRU solubility limit during 50 years operation and can achieve a high initial TRU loaded mass in the core to improve TRU burning capacity. The optimized SVF is 0.5, and the TRU burning rate and the Support factor can achieve about 28.76 kg/TW(th)h and 2.9, respectively. The TRU burning mass, TRU fuel utilization ratio and 233U production after 50 years operation are about 12.6 tons, 70.4 %, and 0.7 tons, respectively. The total TRU radiotoxicity after discharge is about 63.9 % smaller than that without burning. This optimized core is beneficial to get a high TRU burning rate to reduce the storage of TRU and to minimize the long-term radiotoxicity risk in a relatively short reactor life. The total temperature feedback coefficient can remain negative during the whole operation time, which ensures the safety of the ZrH-MSR.