Development and demonstration of a Pu NDA system using ZnS/BO ceramic scintillator detectors

Nakamura, Hironobu ; Ozu, Akira  ; Kobayashi, Nozomi*; Mukai, Yasunobu ; Sakasai, Kaoru  ; Nakamura, Tatsuya  ; Soyama, Kazuhiko  ; Kureta, Masatoshi   ; Kurita, Tsutomu ; Seya, Michio

To establish an alternative technique of He-3 neutron detector that is used for nuclear material accountancy and safeguards, we have started an R&D project to develop a new type of neutron detector (Pu NDA system) using ZnS/BO ceramic scintillator with support of Japanese government. The design of the alternative system (ASAS: Alternative Sample Assay System) is basically referenced from INVS (INVentory Sample assay system) which is passive neutron assay system of plutonium and has total 18 He-3 tubes (about 42% of counting efficiency), and the small amount of Pu in the MOX powder or Pu nitrate solution in a vial can be measured. In order to establish the technology and performance after the fabrication of the new detector progresses, we are planning to conduct demonstration activity in the early 2015 experimentally. The demonstration activity implements the confirmation of reproducibility about sample positioning, optimization of detector parameters, counting statistical uncertainty, stability (temperature and -ray change) check and figure of merit (FOM) using check source and actual MOX powder. In addition to that, performance comparison between current INVS and the ASAS are also conducted. In this paper, we present some analytical study results using a Monte-Carlo simulation code (MCNP), entire ASAS design and demonstration plan to prove technology and performance.