Radioactive Tracer Tests of Two Improved TRPO Processes for High-Level Liquid Waste Using Annular Centrifugal Contactors

Abstract

High-level liquid waste (HLLW) produced from the reprocessing of the spent nuclear fuel still contains moderate amounts of uranium, transuranium (TRU) actinides, and fission products, and thus constitutes a permanent hazard to the environment. The partitioning and transmutation (P&T) strategy has increasingly attracted interest for the safe treatment and disposal of HLLW, in which the partitioning of HLLW is one of the critical technical issues. Two improved trialkylphosphine oxide (TRPO) processes for the removal of actinides have been developed to treat Chinese HLLW, based on the original TRPO process. In one improved process N,N-diethylhydroxylamine as a reducing agent was used for reducing Np(V) and Np(VI) to Np(IV) in order to improve the extraction efficiency of Np. In the other improved process, ammonium vanadate as an oxidizing agent was used for oxidizing Np(V) and Np(IV) to Np(VI) in order to improve the extraction efficiency of Np. Radioactive tracer tests of two improved TRPO processes were carried out using 30-stage 10-mm-diam annular centrifugal contactors and simulated HLLW containing U, Np, Pu, and Am. The test results showed that the decontamination factor of total α activity was >1 × 105. During the test, 30-stage 10-mm-diam annular centrifugal contactors worked in a stable manner continuously, with no stage failing or any interruption of the operation.