Thickness and mixed sample effects on areal density measurement with NRTA for particle like debris of melted fuel

中性子共鳴透過分析法を用いた溶融燃料デブリ中の面密度測定に与える厚みと混合されたサンプルの効果

土屋 晴文 ; 原田 秀郎   ; 小泉 光生 ; 北谷 文人  ; 高峰 潤 ; 呉田 昌俊   ; 飯村 秀紀  ; 木村 敦   ; Becker, B.*; Kopecky, S.*; Kauwenberghs, K.*; Moens, A.*; Mondelaers, W.*; Schillebeeckx, P.*

Tsuchiya, Harufumi; Harada, Hideo; Koizumi, Mitsuo; Kitatani, Fumito; Takamine, Jun; Kureta, Masatoshi; Iimura, Hideki; Kimura, Atsushi; Becker, B.*; Kopecky, S.*; Kauwenberghs, K.*; Moens, A.*; Mondelaers, W.*; Schillebeeckx, P.*

Neutron resonance densitometry (NRD) is based on a combination of neutron resonance transmission analysis (NRTA) and neutron resonance capture analysis (NRCA). This technique is a non-destructive method to quantify nuclear materials in particle-like debris of melted fuel that is generated by a severe accident like the one at the Fukushima Daiichi Nuclear Power Plant. To verify the effectiveness of NRD, the Japan Atomic Energy Agency (JAEA) and the Joint Research Center, Institute for Reference Materials and Measurements (EC-JRC-IRMM) started collaboration in 2012. One of the main objectives of this collaboration is to quantitatively investigate all uncertainty components on results of NRD measurements. Clearly, systematic effects due to the characteristics of samples such as the sample inhomogeneity, presence of impurities, radioactivity and temperature have a strong impact on the accuracy. To study the uncertainty due to the sample characteristics, NRTA and NRCA experiments are in progress at the time-of-flight facility GELINA (Geel Electron LINear Accelerator) of the EC-JRC-IRMM. In this presentation, we show results considering mixed sample effect on NRTA measurements. Data are analyzed with the resonance shape analysis code REFIT to derive the elemental composition of the sample and the areal density of the main components. In addition the effect of neutron absorbing matrix material will be discussed.