報告書番号

T96055

タイトル（和文）

長半減期核種の乾式分離技術の開発－溶融塩電解法による超ウラン元素と希土類元素の分離（２）－

タイトル（英文）

DEVELOPMENT OF PYROMETALLURGICAL PARTITIONING TECHNOLOGY OF LONG-LIVED NUCLIDES-SEPARATION OF TRANSURANIC ELEMENTS FROM RARE EARTH ELEMENTS USING ELECTROREFINING(2)-

概要 （図表や脚注は「報告書全文」に掲載しております）

溶融塩化物と液体金属を溶媒とする乾式法で高レベル廃液から超ウラン元素（ＴＲＵ）を分離回収する技術として，還元抽出技術と電解精製技術についての研究を進めている。このうち電解精製技術についてミズーリ大学原子炉でＴＲＵを用いた実験を実施した。ＵはＣｄ陽極からは高純度，高回収率で回収できる。塩浴中のＵ，Ｎｐは高い回収率で析出物を得ることができたが，Ｎｐの１０ｗｔ．％程度のＲＥが随伴する。一方，Ｐｕ，Ａｍに関しては，これらの析出反応より貴な電位でＮｄの３価から２価への還元反応が起こるために，電解回収は難しい。陰極電位がＰｕの析出電位より卑になる条件ではＲＥの析出も多く，また析出形状が不安定なために回収効率が低く塩化物の混入量も多い。これらの結果から，電解ではＵのみを回収し，ＴＲＵの分離は多段還元抽出法で行うのが良いと考えられる。

概要 （英文）

BOTH ELECTROREFINING AND REDUCTIVE EXTRACTION HAVE BEEN STUDIED BY CRIEPI FOR PYROMETALLURGICAL SEPARATION OF TRANSURANIC ELEMENTS(TRUS)FROM HIGH-LEVEL LIQUID WASTE.ELECTROREFINING OF TRUS AND RES IN A LIC1-KC1/CD SYSTEM WAS CARRIED OUT TO ESTIMATE THE SEPARATION EFFICIENCY AND RECOVERY RATIO.U WAS EFFICIENTLY RECOVERED ON THESOLID CATHODE USING CD ANODE.U AND NP IN THE SALT PHASE WERE RECOVEREDWHEN THE NP/RES RATIO WAS 10/1.DEPOSITION OF PU WAS NOT OBSERVED IN THIS TEST,ALTHOUGH IT IS EXPECTED AFTER NP IS DEPOSITED.HAWEVER PU DEPOSITION WAS FOUND WITH NO ND IN THE SALT PHASE,SUGGESTING THAT PU DEPOSITION IS INTERFERED REDUCTION OF TRIVALENT ND TO DIVALENT ND ON THE SOLID CATHODE.PU AND AM COULD BE DEPOSITED ON THE SOLID CATHODE AT HIGH CATHODE CURRENT DENSITY AND NO STIRRING OF THE CATHODE SURFACE.HOWEVER,EFFICIENT RECOVERY WAS DIFFICULT,BECAUSE THE DEPOSIT DROPPED OFF AND A SIGNIFICANT AMOUNT OF SALT WAS MIXED WITH THE DEPOSIT.SINCE THE CURRENT EFFICIENCY OF THE DEPOSIT REACTION OF TRUS IS VERY SMALL AND THE SEPARATIONRATIO OF TRUS AGAINST RES IS NOT HIGH,A COMBINATION PROCESS,IN WHICH ONLY U IS RECOVERED IN THE ELECTROREFINING PROCESS,AND RECOVERY OF TRUS AND SEPARATION FROM RES IS CARRIED OUT IN A MULTISTAGE EXTRACTION PROCESS,IS CONSIDERED MOST EFFICIENT.

報告者

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