Liquid molten salt reactors that use chloride salts as fuel are characterized by the high solubility of heavy metals and a hard energy spectrum, hence are ideal for transmuting transuranic nuclides (TRU). A small modular reactor exhibits the characteristics of a modular design and construction, which is one of the future development directions for nuclear energy.

This study aims to investigate the TRU incineration characteristics of a small modular chloride fast reactor (sm-MCFR) that can be refueled online and applied to the disposal of TRU in nuclear waste produced by pressurized-water reactors.

Firstly, a 50-MW sm-MCFR scheme was proposed, and its neutron properties, as well as the performance of TRU incineration, were explored using the Monca program TMCBurnup (TRITON MODEC Coupled Burnup Code), a combination of the SCALE 6.1 (Standardized Computer Analyses for Licensing Evaluation) and the high-precision point burn-up program MODEC (Molten Salt Reactor Specific DEpletion Code). Then, the analysis of critical parameters, burn-up evolution, and the transmutation efficiency of both TRU mixed with Depleted Uranium (DU) and TRU combined with ²³²Th were investigated, using a straightforward post-processing approach.

The findings of this study indicate that using TRU as fission fuel in the sm-MCFR requires the online addition of TRU. When the heavy metal balance is maintained, the effective multiplication factor (k_eff) is less than 1. Conversely, when the balance is not maintained, k_eff > 1, allowing continuous operation. When operating at full power for 40 years, the core's residual TRU content will be significantly higher than the initial fuel load, with 657 kg remaining for the TRU+Th mix and 725 kg for the TRU+DU mix. Notably, the sm-MCFR demonstrates efficient transmutation when TRU is added online without maintaining the heavy metal balance. Over 40 years at full power, the transmutation rates will be 41% for TRU+DU and 49% for TRU+Th, effectively reducing the production of long-lived small-actinide elements.

The sm-MCFR can effectively incinerate TRU and provide a feasible scheme for minimizing spent fuel.