Development of NRD, 2; Investigation on systematic effects due to sample thickness for areal density derived from NRTA

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.*

We are developing neutron resonance densitometry that combines neutron resonance transmission analysis (NRTA) and neutron resonance capture analysis. The aim is to establish a non-destructive technique that can quantify nuclear materials in particle-like debris of melted fuel resulting from severe nuclear accidents like the one at the Fukushima Daiichi Nuclear Power Plant. Systematic effects due to sample thickness and mixed sample for the areal density measurement by NRTA were investigated at a neutron time-of-facility GELINA, IRMM. The experiments were conducted utilizing natural Cu metal discs with different thickness and a BC disc. Areal densities were derived with a resonance shape analysis code REFIT. It was found that they were inconsistent with those calculated by mass and area, when using recommended resonance parameters. Hence, a neutron width of resonance parameters was newly evaluated with the NRTA data and we found that derived areal density agreed within 2% with the expected ones. We also discuss the impacts of mixed sample for the areal density derived from NRTA measurement.