Radium Institute Research on Actinide Separation from High-Level Waste (Review)

Abstract

Development of efficient technologies for recovery of long-lived radionuclides from high-level wastes (HLW) is urgent for implementation of the promising management methods (transmutation and disposal), as well as for existing practice of HLW management. In Russia at “Mayak” radiochemical plant since 1996 there has been in operation the industrial facility UE-35 which provides the recovery of cesium and strontium from HLW. The next stage is aimed at development and implementation of actinide separation technology from HLW. For this purpose the following four processes are studied and tested: processes based on chlorinated cobalt dicarbollide (ChCoDiC-process), isoamyldialkyl-phosphine oxide (POR-process), diphenyldibutylcarbamoylphosphine oxide (modified TRUEX-process) and mixture of ChCoDiC, carbamoylphosphine oxide (CMPO) and polyethylene glycol (PEG) (UNEX-process). After comprehensive study of extraction, physico-chemical and operational properties of selected extraction systems, testing of processes was conducted at test facilities with the use of actual or simulated HLW. Mixer-settlers and centrifugal contactors were used as extraction equipment in these tests. The test results show that the ChCoDiC-process can afford recovery of transplutonium and rare-earth elements (TPE and REE) from HLW and separation of them into fractions. POR-process and modified TRUEX-process enable to recover from HLW uranium, neptunium, plutonium, TPE, REE and technetium with the possibility for production of individual fractions. UNEX-process permits to attain simultaneous recovery of actinides, REE, cesium and strontium from HLW. During tests the potentialities of UNEX-process for obtaining such fractions as cesium, cesium+strontium and actinides+REE at stripping stage were demonstrated as well.