Analysis of electroneutrality of fission products in molten salt reactors

Abstract

Liquid-fuel molten salt reactors are a type of Generation IV reactors that has attracted attention for their enhanced safety and thermal efficiency. However, the liquid state of the fuel introduces complexity to the reactor system, particularly in relation to the behavior of fission products and the challenge of maintaining electroneutrality. The interaction of the liquid fuel and the container material, along with the release of noble gas fission products, complicates the analysis of electroneutrality. This study examines the electroneutrality of fission products from key fissile isotopes that could be utilized in molten salt reactors. The calculations take into account variables such as the type of salt (chlorides or fluorides), fissile isotope (Th, U, or Pu), and neutron energy (thermal or fast). Three scenarios involving noble gas release are compared to assess its impact on electroneutrality. Fission of Th-232, U-233, and U-235 can mitigate oxidizing conditions post-fission, by controlling the initial valence state of the fissile isotopes. In contrast, the fission of U-238 and Pu isotopes consistently results in an oxidizing environment. These findings indicate that molten salt reactors relying solely on U-238 and Pu may experience oxidizing conditions due to the fission reaction, suggesting that additional measures may be necessary to prevent excessive oxidation of the reactor system.