Partitioning of actinides and fission products in highly-active raffinate from purex process by mixer-settlers

Batch, and counter-current flowsheet tests using mixer-settlers have been carried out in the chemical processing facility (CPF). Tokai-works, PNC. Counter-current experiments aim to provide the data for prediction of the Truex process applicability in actinides partitioning in high level liquid waste (HLLW) from the Purex process. Real highly-active (HA) raffinate from FBR spent fuel reprocessing experiments were used in these runs without adjusting the acidity. A mixed solvent composed of 0.2M CMPO in the purex solvent was employed as a Truex solvent. Some noteworthy behaviors for ruthenium were recognized; The rare earths and some fraction of ruthenium were coextracted to the actinides stream. Although they were stripped out by dilute nitric acid as expected, plutonium and some of ruthenium also remained in the organic phase during the stripping of americium. A peculiar extraction behavior of ruthenium of changing its D values stage by stage suggests a mixture of various kinds of complexes in the HA raffinate. A series of counter-current tests resulted in giving sufficiently low alpha contaminated waste giving DF's of over 103 for major actinides separation, which will endorse the Truex process. In successive counter-current runs after 1992, an effort for the selective(Am/Np/Pu/U) stripping will be continued including the solvent cleanup step as one of the separation steps. 9 refs., 10 figs., 2 tabs