Shohei Kanamura

Development of Hybrid Reprocessing Technology Based on Solvent Extraction and Pyrochemical Electrolysis

Toshiba has been proposing a new fuel cycle concept for a transition period from LWR to FR. This concept has a higher proliferation resistance for a fuel cycle than for a conventional cycle because plutonium could be recovered with minor actinides. Toshiba has been developing a new advanced hybrid process technology with solvent extraction and pyrochemical electrolysis of spent fuel reprocessing for a transition period from LWR to FR. The advanced hybrid process combines the solvent extraction of the LWR spent fuel in nitric acid to recover pure uranium and the pyrochemical electrolysis in molten salts to recover impure plutonium with minor actinides. Highly pure uranium is used for LWR fuel and impure plutonium with minor actinides for metallic FR fuel. The pyrochemical process for the FR fuel recycle system is based on the research on the electrorefining process in molten salts since 1988 in cooperation with Central Research Institute of Electric Power Industry (CRIEPI). The solvent extraction test with an electrolytic reduction test using actual LWR spent fuel and an oxalate precipitation test were carried out to confirm the feasibility of the new advanced hybrid process. The electrolytic reduction test was conducted to investigate the impurity of uranium recovery and the oxalate precipitation test to evaluate the recovery yield of plutonium with minor actinides. The results suggest that the purity of recovered uranium (U) and the recovery yield of plutonium with a minor actinide (Pu+MA) could achieve the target value in a stage (U purity: 99.97%, Pu+MA recovery yield: 99.9%).

Advanced ORIENT Cycle: Progress on Fission Product Separation and Utilization

Fission reaction of U-235 and/or plutonium generates more than 40 elements and 400 nuclides in the spent fuel. Among them, 31 elements are categorized as rare metals. In a conventional fuel cycle U and Pu are reused but others are vitrified for disposal. Adv.-ORIENT (Adv anced O ptimization by R ecycling I nstructive E lement s) Cycle strategy was drawn up for the minimization of radio-toxicity and volume of radioactive waste as well as the utilization of valuable elements/nuclides in the waste. The present paper describes the progress on Fission Products (FP) separation in this Cycle. Highly functional inorganic adsorbent (AMP-SG, silica gel loaded with ammonium molybdophosphate) and organic microcapsule (CE-ALG, alginate gel polymer enclosed with crown ether D18C6) were developed for separation of heat-generating Cs and Sr nuclides, respectively. The AMP-SG adsorbed more than 99% of Cs selectively from a simulated High-level Liquid Waste (HLLW). The ALG microcapsule adsorbed 0.0249 mmol/g of Sr and exhibited the order of its selectivity; Ba > Sr > Pd >> Ru > Rb > Ag. The electrodeposition is advantageous for both recovery and utilization of PGMs (Ru, Rh, Pd) and Tc because PGMs are recovered as metal on Pt electrode. Among PGMs, Pd was easily deposited on the Pt electrode. In the presence of Pd or Rh the reduction of Ru and Tc was accelerated more in hydrochloric acid media than in nitric acid. In the simulated HLLW, the redox reaction of Fe(III)/Fe(II) disturbed deposition of elements except for Pd. The deposits on Pt electrode showed higher catalytic reactivity on electrolytic hydrogen production than the original Pt electrode. The reactivity of deposits prepared from the simulated HLLW was higher than that from solution containing only PGM.Copyright