14mm径球形NE213スペクトロメータの製作と応用

Development of a spherical NE213 spectrometer with 14 mm diameter

大山 幸夫; 田中 俊一; 津田 孝一; 池田 裕二郎; 前川 洋

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核融合炉中性子工学実験での応用を目的とし、14mm球形のNE213スペクトロメータを開発した。このスペクトロメータは14MeV中性子場での速中性子スペクトルを体系内で測定するために用いる。中性子スペクトルをアンフォールディングによって得るために必要な応答関数行列モンテカルロ法に基づいて計算し、その一部について測定値と比較検討したところ良く一致することが分った。本スペクトロメータをD-T中性子場においた酸化リチウム体系でのスペクトル測定に応用し、輸送計算との比較検討した結果、本スペクトロータは核融合炉中性子工学実験で非常に有用であることが実証された。

A 14 mm diameter spherical NE213 spectrometer has been developed for applying to fusion neutronics experiments. It is used to measure the fast neutron spectra in assemblies of various materials irradiated with 14 MeV neutrons. The characteristics of neutron gamma-ray discrimination was investigated, and it was found that the wall-escape of recoil protons produced in the detector should be treated carefully in the case of a small size detector such as this one. Response matrix for spectrum unfolding has been calculated by a Monte Carlo code. Calculated response for 14 MeV neutrons agreed well with measured one. The present spectrometer was applied to in-system neutrons spectrum measurements in a lithium-oxide assembly bombarded by D-T neutrons. The spectra obtained by unfolding were compared with the results calculated by the neutron transport code DOT3.5, and with reaction rates measured by fission counters and activation detectors. Consequently it has been demonstrated that the spectrometer is very useful for fusion neutronics experiments.