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

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

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.