Measurement and analysis of reactivity worth of Np sample in cores of TCA and FCA

臨界実験装置TCAとFCAにおけるNpサンプル反応度価値の測定と解析

桜井 健; 森 貴正; 岡嶋 成晃  ; 谷 和洋*; 須崎 武則*; 齊藤 正樹*

Sakurai, Takeshi; Mori, Takamasa; Okajima, Shigeaki; Tani, Kazuhiro*; Suzaki, Takenori*; Saito, Masaki*

Measurements and analyses were performed for the reactivity worth of Np oxide sample of 22.87 g in seven uranium cores at Tank Type Critical Assembly(TCA) and two uranium cores at Fast Critical Assembly(FCA) in Japan Atomic Energy Agency. The cores at TCA provided neutron spectra from thermal to resonance energy regions. Two cores of FCA, XXI and XXV, provided a hard spectrum of fast reactor and a soft spectrum in the resonance energy region, respectively. The analyses were made with the JENDL-3.3 nuclear data by a Monte Carlo method for the TCA cores and by a deterministic method for the FCA cores. A sensitivity analysis was also made to estimate the error of reactivity worth due to those of JENDL-3.3 nuclear data. The error of calculation to experiment ratio(C/E) of reactivity worth was estimated from the error of measurement, the statistical error in the Monte Carlo calculation and the error due to those of the nuclear data, among which the contribution from the error of Np capture cross section was dominant in the cores except FCA XXV. The calculation underestimates the measurement by 3 to 9 %. This underestimation, however, is within the error of C/E at three level.