Transition to thorium fuel cycle in a small modular molten salt reactor based on a batch reprocessing mode

Abstract

There is currently a renewed interest in small modular reactor (SMR) and molten salt reactor (MSR) concepts, since the former is recognized as the most accessible form of nuclear energy with a lower cost compared to conventional reactors while the latter is considered as one of the reference reactors of the Generation IV International Forum (GIF) suited for thorium fuel cycle. The TRUs from the spent fuel of LWRs containing more than 50% of fissile fuels may be used to start up a MSR due to its outstanding features of no fuel assembly and online/ batch reprocessing. This study aims to analyze the characteristics of a small modular thorium-based molten salt reactor (sm-TMSR) using TRUs and Th as fissile and fertile fuels towards thorium fuel cycle with a batch reprocessing mode. The neutronic properties using TRUs as an igniting fuel in the core configurations with the fuel salt fraction (SF) of 18.4%/27.4% and the reprocessing periods (RPs) of 5/10 years are first analyzed and compared. To obtain a high production of U233, the configuration with SF = 27.4% and RP = 5 years is recommended. The recovered uranium production and the purity of U233 can achieve ∼69 kg/y and over 75%, respectively. Furthermore, the recovered uranium demand with thorium fuel cycle in the 27.4% core and other thermal sm-TMSRs are evaluated. In the 27.4% core, the recovered uranium demand during 40-year operation is ∼38 kg/y. For the new sm-TMSRs with the SF ranging from 2% to 18.4%, the recovered uranium demand varies from 148 to 48 kg/y. Finally, transition scenarios to thorium fuel cycle are proposed. The transition time is about 22 years in the 27.4% core while it is about 28 years in the SF = 18.4% core. The simulated results demonstrate that it is feasible to achieve the transition from TRUs to thorium fuel cycle in sm-TMSRs if a batch reprocessing mode can be adopted.