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論文

Structural characterization by X-ray analytical techniques of calcium aluminate cement modified with sodium polyphosphate containing cesium chloride

高畠 容子; 渡部 創; 入澤 啓太; 塩飽 秀啓; 渡部 雅之

Journal of Nuclear Materials, 556, p.153170_1 - 153170_7, 2021/12

The long-time experimental activities on pyroprocessing have generated waste eutectic salts contaminated with nuclear materials. After reprocessing tests, waste salts should be appropriately treated, with a focus on Cl disposal considering its corrosive nature. It is important to construct Cl confinement for the waste salts. Chlorapatite (Ca$$_{10}$$(PO$$_{4}$$)$$_{6}$$Cl$$_{2}$$) has great potential for Cl confinement due to Ca and P. The chemical reactivity of Cl will be drastically reduced if chlorapatite can be synthesized in calcium aluminate cement modified with sodium polyphosphate (CAP) containing CsCl. This study confirms the chemical state of Cl and metal elements in the cement by XRD, XPS, and XANES in the CAP containing CsCl. The analyses results suggest the existence of the Ca-Cl-Cs and Al-Cl-Cs bonds in CAP containing CsCl. The formation of the chemical bonds of Cl with metal elements might be one of important factors for the chlorapatite formation from the CAP containing CsCl.

論文

Fabrication of americium-based nitrides by carbothermic reduction method

伊藤 昭憲; 赤堀 光雄; 高野 公秀; 小川 徹; 沼田 正美; 糸永 文雄

Journal of Nuclear Science and Technology, 39(Suppl.3), p.737 - 740, 2002/11

(Am, Y)N及び(Am, Zr)Nのアメリシウム系混合窒化物をAmO$$_{2}$$,Y$$_{2}$$O$$_{3}$$及びZrO$$_{2}$$を出発原料として炭素熱還元法により調製した。Am-Y系窒化物では、化学量論組成以上の過剰炭素条件下,1300$$^{circ}C$$及び1500$$^{circ}C$$の2段加熱法を適用することにより、10~30mol%AmNの範囲で、酸化物が無く、固溶酸素量も低い混合窒化物固溶体を得ることができた。

論文

Dissolution and formation of nuclear materials in molten media

小川 徹; 湊 和生

Pure and Applied Chemistry, 73(5), p.799 - 806, 2001/05

 被引用回数:15 パーセンタイル:55.14(Chemistry, Multidisciplinary)

照射済燃料からアクチノイドを回収する新技術として乾式法が提案されている。原研では、消滅用のTRUを含有する窒化物に対して溶融塩プロセスを応用する手法を検討している。研究の過程で、M-N-Cl系の高温化学、酸素不純物の効果、ランタノイド・アクチノイドの通常の三価のほかの二価の存在の影響について、実験及び解析を進めてきた。溶融塩中の核燃料物質の溶解と析出の過程について、熱力学的解析と電気化学測定の結果を比較した。

口頭

Electrochemical behavior of lanthanides and actinides on a liquid Ga electrode in molten chlorides melts

村上 毅*; 坂村 義治*; 飯塚 政利*; 野平 俊之*; 北脇 慎一; 小藤 博英

no journal, , 

A novel pyroprocess is proposed for recovering actinides from spent nuclear fuels in which electrochemical reactions on a liquid Ga in molten chlorides are used. The proposed pyroprocess utilizes the large difference of alloy formation potential between actinides-liquid Ga and lanthanides-liquid Ga to achieve a higher separation efficiency of actinides from lanthanides than a conventional pyroprocess using a liquid Cd as a reaction medium. The present study investigated basic electrochemical behaviors of lanthanides, Ce and Nd, and actinides, U and Pu, on a liquid Ga electrode in LiCl-KCl melts. Alloying potentials, current efficiencies and activity coefficients in liquid Ga are presented which are the inevitable properties to evaluate the feasibility of the proposed process.

口頭

Pyroprocessing technology development for flexible introduction of fast reactor fuel cycle

飯塚 政利*; 野平 俊之*; 多田 康平; 村上 毅*; 小藤 博英

no journal, , 

By adopting the pyroprocessing together with fast reactor which is partially/fully loaded with metal fuels, a fuel cycle system concept with enhanced MA recovery and transmutation capability can be designed. This fuel cycle system flexibly accommodates various possible scenarios for the fast reactor introduction and Pu/MAs management with the largest reduction effects on nuclear waste toxicity, making the most of current R&D infrastructure and planned industrial resources using oxide fuels. As a part of above mentioned R&D, the adaptation of liquid Ga cathode to the electrorefining process of pyro-process has been examined to improve decontamination factor of rare-earth FP element.

口頭

Selective actinides recovery over lanthanides using liquid gallium cathode

多田 康平; 小藤 博英; 村上 毅*

no journal, , 

Pyroprocessing is a promising technology for a fast reactor cycle with a highly concentrated minor actinides (MA: Np, Am and Cm)-bearing metallic fuel. Separation of actinides (An) from fission products such as lanthanide elements (Ln) is one of the difficult challenges to establish practical pyroprocessing. Liquid Cd cathode (LCC) with LiCl-KCl bath has been generally used for An recovery in our process, however, An/Ln separation performance using LCC was not high enough to fabricate highly concentrated MA-bearing fuel from materials having a high ratio of Ln/An. Our recent studies showed that a combination of liquid Ga cathode with LiCl-KCl bath had potential to give higher An/Ln separation performance, and currently we are developing an innovative pyroprocessing using the liquid Ga electrode. Solubility of U and Pu in liquid Ga is smaller than in liquid Cd. Therefore, the solid precipitates (An-Ga alloy) formation could have a significant influence on designing the process compared to the case of using LCC. However, the influence of the solid precipitates formation on An/Ln separation performance is unclear. In this study, galvanostatic electrolysis test on the recovery of U, Pu and Am in liquid Ga was carried out to investigate the influence. Precipitation of Pu-Ga alloy was observed by SEM/EDX on the cross section of Ga electrode after the electrolysis, and separation factors (SFs) for each metallic elements (M) based on Ce, which is defined as (M/Ce concentration ratio in liquid Ga)/(M/Ce concentration ratio in the salt phase), were calculated to evaluate An/Ln separation performance.

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