Demonstration Result of Sample Assay System Equipped Alternative He-3 Detectors

JAEA conducted an R&D project (for past 4 years) to develop a new type of neutron detector using ZnS/10B2O3 ceramic scintillator as an alternative neutron detector to 3He with support of Japanese government. The design of the JAEA’s alternative system (ASAS: Alternative Sample Assay System) refers basically to the INVS used for small amount of Pu in MOX powder or Pu nitrate solution in a vial for nuclear material accountancy and safeguards verification. In order to prove the feasibility and performance of alternative technology instead of 3He detector, and to establish Pu measurement capability, JAEA developed and fabricated ASAS equipped with 24 alternative ceramic scintillator tubes and demonstrated. The demonstration activity implemented the confirmation of reproducibility about sample positioning, optimization of detector parameters, counting statistical uncertainty, stability check and “figure of merit” using Cf check source and actual MOX powder in Plutonium Conversion Development Facility. In addition, performance comparison between the current INVS and the ASAS was also implemented. In this paper, we present demonstration results with design information by MCNP. It is thought that these results bring us beneficial alternative technology with Pu measurement capability and help to hedge risks of 3He shortage in the future.