PUBLICATION: INTERNATIONAL JOURNAL OF ENERGY RESEARCH

AUTHORS: Zhang, YP; Wu, JH; Chen, JG; Cai, XZ

 

Ex-core transition to thorium fuel cycle is an effective way to address the issue of the lacking of the U-233 in nature. It consists to extract online the thorium bred Pa-233 from the core and store it outside. The obtained Pa-233 stockpile will decay into the U-233 (T-1/2 = 27 days), and when enough U-233 is cumulated, a new U-233-based reactor can be loaded. However, this approach will inevitably provoke the heavy nuclides (HN) concentration in the core during the extraction operation, which would affect the chemical stability of fuel salt and subsequently endanger the safety of the core operation. In this study, an improved ex-core transition with unchanged HN concentration is proposed for a 500-MWth small modular heavy-water moderated molten salt reactor (SM-HWMSR). To achieve this, two operating stages are needed. In the first stage, transuranic (TRU) from the spent fuel of LWRs is used to feed the low enrichment uranium (LEU, 19.75 wt% U-235/U) started core with 300 operating days to ensure negative temperature reactivity coefficient (TRC). In the second stage, the thorium bred U-233 from the first stage is mixed with TRU to refuel the core. The proposed ex-core transition scheme aims to burn TRU, meanwhile breed U-233 to start new MSRs. The fuel cycle performance over 60-years' operation is analyzed. The results demonstrate that it is possible to realize ex-core transition with unchanged concentration of HN in the fuel salt. As the fraction of U-233 in the mixed fuel is set to be 15 mol%, it only takes 3 years to start a new reactor with the stored U-233. The radiotoxicity of TRU-based fuel is decreased after 60 years' burning in the SM-HWMSR core. Novelty Statement Ex-core transition to thorium cycle in an SM-HWMSR with unchanged concentration of heavy metal nuclides in the fuel salt was investigated by Yapeng Zhang, Jianhui Wu, Jingen Chen, and Xiangzhou Cai. The results demonstrate that it is possible to realize ex-core transition with unchanged concentration of HN in the fuel salt. As the fraction of U-233 in the mixed fuel is set to be 15 mol%, it only takes 3 years to start a new reactor by the stored U-233.

 

LINKS: http://dx.doi.org/10.1002/er.6574