Development of Active Neutron NDA System for Radioactive Nuclear Materials

Nuclear material accountancy plays a key role in nuclear safeguards and security. However, to the best of our knowledge, there is no established technique that enables us to accurately quantify the amount of Special Nuclear Materials (SNM) and Minor Actinides (MA) in highly radioactive nuclear materials, such as spent fuel and MA transmutation fuel. The collaboration between the Japan Atomic Energy Agency (JAEA) and the Joint Research Centre (JRC) of the European Commission aims to develop an active neutron NDA system for nuclear non-proliferation and nuclear security. Active neutron NDA techniques, Differential Die-Away Analysis (DDA), Prompt Gamma-ray Analysis (PGA), Neutron Resonance Capture Analysis (NRCA), Neutron Resonance Transmission Analysis (NRTA) and Delayed Gamma-ray Analysis (DGA) have been studied and improved in the collaboration. The different analytical methods can provide complementary information. In the first phase of the project, we developed a combined NDA system, which enables the simultaneous measurements of DDA and PGA, at NUclear fuel Cycle safety Engineering research Facility (NUCEF) in the JAEA. The DDA detects fission neutrons, and it can determine very small amounts of the fissile mass, such as U-235 and Pu-239. PGA is well acknowledged to be especially valuable for the measurement of light elements such as H, B, N, S, and Cl, as well as Cd, Gd, Sm, and Hg which have large neutron capture cross sections. Therefore, PGA is utilized for the quantification of neutron absorber and particularly useful for the detection of explosives because the most typical high explosive materials contain nitrogen. The second phase of the project was launched in 2018. The second phase focuses on the development of the active neutron NDA system for highly radioactive materials. In the second phase, we will continue to conduct additional research to improve the methodology and develop a new integrated NDA system which can use for NRTA as well as DDA and PGA. In this presentation, we will provide an overview of the project and report the recent results, especially the design of new integrated NDA system. We would like to acknowledge the Japanese government (MEXT; Ministry of Education, Culture, Sports & Technology).