Thermodynamic study on the separation of strontium and barium from LWR spent fuel

Abstract

The separation of high heat load fission products, such as alkaline earth metals, from nuclear spent fuel can significantly reduce the burden of spent fuel disposal. This study investigates the feasibility of separating strontium and barium from light water reactor spent fuel through non-aqueous processes. Process flows were developed for treating spent nuclear fuel by heating it at high temperatures to remove volatile nuclides, followed by chlorination with a chlorinating agent. The chlorinated products were then treated with a precipitating agent in LiCl-KCl molten salt for further separation. The remaining liquid was distilled to recover strontium and barium. Thermodynamic equilibrium calculations were conducted for the process flows. Under the conditions of the process flows, the chlorinating agents MgCl2 and NH4Cl both converted SrO and BaO entirely into SrCl2 and BaCl2, respectively. The precipitating agent Li2CO3 exhibited superior separation effectiveness compared to Li3PO4. Thermodynamic calculations indicate that strontium and barium recovered by MgCl2 chlorination, Li2CO3 precipitation, and distillation will contain 0.18 %, 1.06 %, and 0.32 % impurities in terms of mass, radioactivity, and decay heat, respectively.