Evaluation of energy responses for neutron dose-equivalent meters made in Japan

国産中性子サーベイメータのエネルギーレスポンス評価

三枝 純; 吉澤 道夫  ; 谷村 嘉彦   ; 吉田 真; 山野 俊也*; 中岡 弘*

Saegusa, Jun; Yoshizawa, Michio; Tanimura, Yoshihiko; Yoshida, Makoto; Yamano, Toshiya*; Nakaoka, Hiroshi*

国産レムカウンタ3機種のエネルギーレスポンスを、熱中性子,15.2MeVまでの単色中性子,Cf等のRI中性子線源について、モンテカルロ計算と実測により評価した。レスポンスの方向依存性及び線量当量レスポンスについても評価を行った。計算では、レムカウンタを構成する比例計数管,減速材,吸収材を詳細に模擬することにより、実測によるレスポンスとよく一致する結果が得られた。また、比例計数計数管内のHe充填気圧とエネルギーレスポンスとの関係について考察を行った。広いエネルギー範囲について得られたレスポンスの計算結果を用い、さまざまな中性子作業場においてこれらのレムカウンタを使用した際の、指示値と真の線量当量との差異についても検討を加えた。

Energy responses of three types of Japanese rem counters were evaluated by Monte Carlo simulations and measurements. The energy responses for thermal neutrons, monoenergetic neutrons with energies up to 15.2 MeV were evaluated as well as for neutrons from such radionuclide sources as Cf. The calculated results were corroborated with the measured ones. Angular dependence of the response and dose equivalent response was also evaluated. As a result, the reliable energy responses were obtained by careful simulations of the proportional counter, moderator and absorber of the rem counters. Furthermore, discussions were made about the relationship between pressure of counting gas and sensitivity of the rem counter. By using the obtained responses, relations of predicted readings of the rem counters and true dose equivalent were studied for various workplace spectra.