Preliminary study of neutron intensity and spectrum of various fuel debris

各種燃料デブリの中性子強度とスペクトルの予備的研究

松村 太伊知 ; 奥村 啓介 ; 坂本 雅洋 ; 寺島 顕一  ; Riyana E. S.   ; 近藤 千博*

Matsumura, Taichi; Okumura, Keisuke; Sakamoto, Masahiro; Terashima, Kenichi; Riyana, E. S.; Kondo, Kazuhiro*

Retrieving objects with a small amount, such as a few grams, will begin soon at the Fukushima Daiichi Nuclear Power Station as the start of decommissioning process. The retrieved objects will be sorted as fuel debris and others for reducing the amount of long-time storage. Since the fuel debris emits neutrons, the knowledge of emitted neutron features is necessary for the design of neutron detectors. For this purpose, we estimated the number and energy spectra of (, ) and the spontaneous fission neutrons emitted from 1 g of fuel debris by calculation using the SOURCES 4C code. The calculations were performed for five types of fuel debris, according to the elapsed time from the accident, burnup, and fuel type. The results showed that the average neutron energy is 2 MeV regardless of the fuel debris type, however, the intensity changed four orders of magnitude according to the fuel debris type.