Evaluation of neutron flux and gamma heating for irradiation tests of JMTR

JMTR照射試験における中性子束及び加熱率の評価

長尾 美春  ; 板橋 行夫; 小森 芳廣 ; 新見 素二; 藤木 和男

Nagao, Yoshiharu; Itabashi, Yukio; Komori, Yoshihiro; Niimi, Motoji; Fujiki, Kazuo

モンテカルロコードMCNPを用いたJMTRにおける照射場評価手法の検討を行ってきた。これまでに行われた検証の結果、高速中性子束,熱中性子束のMCNP計算値は、フルエンスモニタによる測定値に対して各々10%,30%の精度であった。加熱率については、試料部の温度で比較した結果、解析値は、測定値に対して-3~+14%で評価できた。以上の結果から、JMTR照射試験においては、中性子束,料部温度において高精度な評価が可能である。

An improved analysis procedure has been introduced to evaluate irradiation field at each specimen in the irradiation capsule by using the MCNP code, which is able to model the complicated structure of the capsule directly. As the verification results, it was confirmed that the calculated fast and thermal neutron flux/fluence were agreed with measured ones within 10% and 30%, respectively, for the irradiation tests in the JMTR. Concerning gamma dose/spectrum, it was confirmed that the calculated temperature was evaluated within -3+14% using gamma heating obtained by MCNP calculations. The evaluations of neutron flux/fluence and specimens temperature with high accuracy are therefore possible in the irradiation test of the JMTR.