Dissolution of uranium nitrides in LiCl-KCl eutectic melt

Abstract

A combination of the nitride fuel and pyrochemical reprocessing has been chosen as a candidate for the fuel cycle of the minor actinides (MA) burner systems. One important issue is the feasibility of the recycled use of 15N-enriched nitrogen in the nitride pyrochemical process. Dissolution of spent nitride fuel with an oxidation agent has been considered to be a promising method for recovering 15N-enriched nitrogen. The behavior of the dissolution of uranium nitrides (UN, U2N3) and UNCI with CdCl2 in LiCl-KCl eutectic melt is investigated to show feasibility of the method for uranium containing nitride fuel. Most of nitrogen is recovered as N2 gas resulting from the reaction of uranium nitrides and CdCl2 above 550 °C, which is higher than that reported for lanthanide nitrides, surrogates of transplutonium nitrides, with similar conditions. Formation of intermediate compounds is observed with the temperature below 500°C. ZrN, a candidate of dilution material for MA burner fuel, is hard to be dissolved with CdCl2 in LiCl-KCl eutectic salt even at high temperature such as 800 °C. © 2002 Atomic Energy Society of Japan.