A Conceptual NRD system and its performance evaluation

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

Neutron Resonance Densitometry (NRD) is a non-destructive method using a pulsed neutron beam in order 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. It is a combination of neutron resonance transmission analysis (NRTA) and neutron resonance captures analysis (NRCA) or Prompt Gamma-ray Analysis (PGA). NRCA/PGA in NRD, using a newly designed -ray detector, plays a role of measuring impurities in debris that would have high radioactivity derived from Cs. Especially, the -ray detector was specially designed to measure 478-keV rays radiated by B under the presence of Cs. Then utilizing information on the amount of impurities obtained by NRCA/PGA, NRTA quantifies special nuclear materials in debris. To verify the effectiveness of NRD for quantifying nuclear materials, NRTA and NRCA/PGA experiments were conducted at GELINA, IRMM, by an international collaboration of JAEA and EC/JRC/IRMM. In addition, achievable accuracy concerning NRD was studied by Monte Carlo simulations. In this contribution, these achievements on NRD as well as its concept are reviewed.