Neutron Resonance Transmission Analysis for Measurement of Nuclear Materials

In fields of nuclear safeguards and nuclear security, non-destructive assay (NDA) techniques are needed in order to accurately quantify special nuclear materials (SNMs) in nuclear fuels such as spent fuels, fuel debris and the next generation fuel for nuclear transmutation. Among those techniques, active NDA ones would be preferable to passive ones, because nuclear fuels themselves are high-level radioactive materials to hamper SNM measurements. One candidate of active NDA techniques is neutron resonance transmission analysis (NRTA). It relies on a neutron time-of-flight measurement and is a well-established method to apply for the evaluation of nuclear data, including total cross sections and resonance parameters. In fact, experiments done at GELINA under the collaboration of JAEA and JRC have shown that NRTA has high potential enough to quantify SNMs in complex materials. Currently, such a NRTA system requires a large electron accelerator facility to generate intense neutron sources. In other words, it is very difficult to perform NRTA measurements at various facilities that need to measure SNMs. Thus, downsizing a NRTA system would be one solution of its difficulty. In order to realize a compact NRTA system, we develop a prototype with a D-T neutron generator that has a pulse width of 10 μs. For this aim, numerical calculations to optimize the compact NRTA system were done. In addition, NRTA measurements with simulated fuel pins were made at neutron time-of-flight facilities such as GELINA. In this presentation, a brief explanation on the basics of NRTA is given. Then, we present results of the numerical calculations and the experimental results. On the basis of those results we discuss a future prospect of a compact NRTA system that would be applicable to SNM quantification. This research was implemented under the subsidiary for nuclear security promotion of MEXT.