報告書番号

L05005

タイトル（和文）

乾式貯蔵時における使用済燃料被覆管中の水素移動量評価

タイトル（英文）

Calculation of Axial Hydrogen Redistribution on the Spent Fuels during Interim Dry Storage

概要 （図表や脚注は「報告書全文」に掲載しております）

本研究では20年間乾式保管した使用済PWR-UO2燃料被覆管（燃焼度31および58MWd/kgHM)を用いて被覆管軸方向の水素移動に関係したデータの取得を行った。この試験で取得した20年保管燃料被覆管の水素の輸送熱は10.6-17.7kcal/molとなり、未照射被覆管に比べ顕著に大きくなる結果となった。また、拡散係数や固溶限のデータも取得し、未照射被覆管との差異は少ない結果となった。40年間乾式貯蔵した場合の水素再分布を1次元拡散計算で求めた。この計算では照射被覆管で得られた輸送熱、拡散係数および固溶限の最大値、使用済燃料の種々の温度分布の実測データ（文献値）を用いた。その結果、40年乾式貯蔵の水素移動量は少なく、未照射被覆管の輸送熱。拡散係数および輸送熱の最大値を用いた計算によって保守側の評価を与えることがわかった。

概要 （英文）

In this study, hydrogen redistribution experiments were carried out to obtain the data related to hydrogen axial migration by using real twenty years dry (air) stored spent PWR-UO2 fuel rods which burn-ups were 31 and 58 MWd/kgHM. From the hydrogen redistribution experiments, the heat of transport of hydrogen of zircaloy-4 cladding from twenty years dry stored spent PWR-UO2 fuel rods were from 10.6 to 17.7 kcal/mol and they were significantly larger than that of unirradiated zircaloy-4 cladding. This means that hydrogen in irradiated cladding can move easier than that in unirradiated cladding. In the hydrogen redistribution experiments, hydrogen diffusion coefficients and solubility limit were also obtained. There are few differences in the diffusion coefficients and solubility limits between the irradiated cladding and unirradiated cladding. The hydrogen redistribution in the cladding after dry storage for forty years was evaluated by one-dimensional diffusion calculation using the measured values. The maximum values as the heat of transports, diffusion coefficients and solubility limits of the irradiated cladding and various spent fuel temperature profiles reported were used in the calculation. The axial hydrogen migration was not significant after dry storage for forty years in helium atmosphere and the maximum values as the heat of transports, diffusion coefficients and solubility limits of the unirradiated cladding gave conservative evaluation for hydrogen redistribution.

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