A neutronic evaluation of a thorium-based molten salt breeder reactor

The global energy demand is continuously rising, requiring the search for attractive and low-emission energy generation options. Molten Salt Reactors (MSRs) have emerged as a promising solution in the Generation IV roadmap due to their inherent safety features and fuel flexibility. Operating at high temperatures, MSRs efficiently convert heat into electricity and offer potential applications beyond energy production. Nevertheless, challenges related to materials, fuel management, commercial viability, and regulatory acceptance persist. This study focuses on the Single -fluid Double-zone Thorium-based Molten Salt Reactor (SD-TMSR), an advanced nuclear design utilizing 232Th as the primary fuel source. Four initial fissile materials were examined for fuel cycle flexibility: conventional recovery uranium (RU) with 233U, enriched uranium (EU) with 235U, reprocessed plutonium (RP), and reprocessed plutonium/minor actinides (RA) matrices. Using the MCNP6 code, a comprehensive model of the SD-TMSR core was developed to study the performance of proposed fuels during a reactor cycle. The analysis encompassed neutronic parameters, reactivity, neutron flux profile, and fuel evolution. The findings indicated EU, RP, and RA fuels as viable alternatives to RU, exhibiting efficient neutron capture scenarios and reduced nuclear waste production. The study verified the reliability of the developed model by comparing main neutronic parameters with literature data, confirming their statistical equivalence. The proposed fuels, EU, RP, and RA, exhibit subcritical characteristics compared to conventional RU fuel. To improve reactor reactivity, the mole percentage of uranium tetrafluoride (UF4) and (TRU)F3 was gradually increased while reducing thorium tetrafluoride (ThF4) proportion. The burnup analysis revealed the changes in isotopes' concentration during the reactor cycle, and the breeding ratio (BR) indicated that SD-TMSR operates as a converter reactor in the first cycle. Actinides, especially thorium and protactinium, dominated the fuel's activity, while iodine activity was significant for all fuel types. The research provided valuable insights into the proposed fuels' behavior, offering relevant data for the SD-TMSR's design and operation.