Transition to thorium fuel cycle for TMSR

Molten Salt Reactor (MSR) has been recognized as one of the reference reactors of the Generation IV International Forum (GIF) with the unique potential (inherent safety, no fuel fabrication, online fuel reprocessing, etc). A thermal MSR based on 232Th/233U fuel cycle can be designed to be a breeder with low fissile inventory and leads to a short doubling time and low transuranic (TRU) inventory. However, the fissile fuel supply is one of the unresolved problems since there is no available 233U. It is therefore needed to use existing fissile materials such as 235U or Plutonium to produce 233U. In this paper, two ways for the thorium fuel cycle transition are proposed. One is that the TMSR is started with existing fissile material as starting fuel and thorium as fertile fuel. The bred 233U from thorium is reinjected into the core for critical operation to achieve the transition to thorium fuel cycle gradually in the core (in-core transition). The other also adopts the same starting fuel as the in-core transition but stores the bred 233U out of the core for starting a new TMSR which is then operated with 232Th/233U fuel cycle (ex-core transition). The transition performances for the two ways are analyzed based on a thermal TMSR configuration with negative coefficient and BR greater than 1.0. The results show that the transition capacity with Pu or TRU fuel is attractive. For the in-core transition mode, the thorium fuel cycle is quickly evoked and the characteristics of the TMSR turn out to be equivalent to the 233U started TMSR after about 15-year operation. For the ex-core transition mode, the 233U production is appreciable which needs less than 5 years to restart a new TMSR. Besides, the temperature feedback coefficients for the two ways are all negative during the entire operation. Finally, the preliminary characteristics of the thorium fuel cycle deployment are illustrated, which reveals that a thorium nuclear energy park containing various TMSRs as a TMSR fleet can provide sustainable nuclear energy with low production of long-life nuclear wastes.