Analysis of Curium in MOX Fuel Irradiated in Fast Reactor

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逢坂 正彦  ; 逢坂 正彦  ; 小山 真一  ; 三頭 聡明

Osaka, Masahiko; Osaka, Masahiko; Koyama, Shinichi; Mitsugashira, Toshiaki

高速実験炉「常陽」にて照射されたMOX燃料中のCm同位体を放射化学的分析手法により分析した。Cmを陰イオン交換クロマトグラフィーにより分離し、質量分析法及びスペクトロメトリーによりCm同位体を定量したところ、Cm含有率は軽水炉のものより大幅に小さいことが分かった。分析値を用いてCm同位体の高速炉内における核変換特性を様々な観点から評価し、Cmの変換速度は既存の値よりも大きいこと等を明らかにした。本分析・評価により、高速炉がCmの消滅に適していることを実験的に示すことができた。

Cm isotopes formed in irradiated MOX fuel in the experimental fast reactor JOYO were analyzed by applying a sophisticated radiochemical technique. Cm was isolated from the irradiated fuel by anion ion-exchange chromatography using a mixed medium of nitric acid and methanol. The isotopic ratio of Cm and its content were determined by thermal ionization mass spectroscopy and alpha-spectrometry, respectively. U, Pu, Am and Nd were also isolated and analyzed for the determination of the Cm content and burnup. The Cm content was less than 0.004 at.%, which is much smaller than that of PWR-MOX at 60 GWd/t. On the basis of the present analytical results, the transmutation behavior of Cm isotopes in a fast reactor was discussed from various viewpoints. Transmutation speeds of Cm isotopes were estimated; the speed for 246Cm, which is known to be a key nuclide in the transmutation of Cm, was smaller than the previously reported value. Transmutation behavior of each Cm isotope was also eval