Investigation of development condition with new nuclear emulsion for neutron measurement under high gamma-ray background

高線バックグラウンド下での中性子測定のための先進的原子核乾板の現像条件に関する調査

石原 康平*; 河原林 順*; 富田 英生*; 中 竜大*; 浅田 貴志*; 森島 邦博*; 中村 光廣*; 前田 茂貴   ; 井口 哲夫*

Ishihara, Kohei*; Kawarabayashi, Jun*; Tomita, Hideki*; Naka, Tatsuhiro*; Asada, Takashi*; Morishima, Kunihiro*; Nakamura, Mitsuhiro*; Maeda, Shigetaka; Iguchi, Tetsuo*

本研究では、原子炉の使用済燃料周辺等における高線環境下での中性子測定に向けて、新型の原子核乾板NGITA(Neutron-Gamma Image TrAcker)の開発を行っている。原子核乾板の現像確率は一般に、現像液の温度に依存することが知られているので、今回は現像液温度によりS/N比の向上をはかり、NGITA乾板の高線下での中性子測定に向けた最適な現像液温度を評価した。

Spent fuel emits not only neutrons but also lots of -rays by its included fission products (for example, neutron/ ratio is in the order of 10). For its safety handling, it is important to investigate the neutron characteristics such as an emission rate, emission profile and energy spectrum. But it is difficult to measure the neutron characteristics with high precision because of lots of -rays. So the neutron characteristics are estimated by an evaluation based on its burning history. It is necessary to measure them for estimate of adequacy of the simulated result. Also, a direct measurement of the neutron characteristics is essential in the case that each spent fuel has different burning history and is mixed (for example the accident of the Fukushima Dai-ichi Nuclear Power Plant). Therefore, we develop a new nuclear emulsion in order to measure neutrons under high -rays field in our study.