Technology Development Of A Neutron Resonance Transmission Analysis Using A Laser Driven Neutron Source

Neutron Resonance Transmission Analysis (NRTA) using the pulsed neutrons has been considered as the one of useful active neutron non-destructive assay (NDA) techniques to quantify nuclear materials (NMs) in spent nuclear fuel that have high radioactivity. As the pulsed neutron source, a laser-driven neutron source (LDNS) is able to generate very short-pulsed neutron beams. This feature has the advantage of designing compact NRTA systems, which holds great promise for the future. In order to use the developing LDNS in a compact NRTA system, it is necessary to optimize the systems. For this reason, the technology development study has been carried out in three parts: the development of a neutron moderator, neutron detector, and data acquisition system. Then, these development studies have been applied to demonstrate NRTA with LDSN. The moderator is used to slow down the fast neutrons (~MeV) emitted from LDNS to the resonance energy region required by the NRTA. In order to take advantage of the short pulse of LDNS, the neutron broadening in the moderator should also be taken into account. In the present study, the characteristics of various moderator materials and geometries for the neutron intensity and the neutron pulse width after the slowing down in the moderator were investigated by using the Monte Carlo simulation code PHITS with JENDL-4.0. The compact NRTA system has a large gamma background effect and a high counting rate. The research and development work for developing a detector having a high neutron efficiency with a low gamma sensitivity, and a data acquisition system having a low measurement error at high counting rates have been carried out in collaboration with Kyoto University. In addition, experiments were carried out using the Laser for Fast Ignition Experiment (LFEX) at Osaka University to demonstrate NRTA using LDNS. In this presentation, the detail of the research achievements will be reported. The present research programs are supported by MEXT (the Ministry of Education, Culture, Sports, Science, and Technology of the Japanese government) under the subsidiary for “promotion of strengthening nuclear security and the like”.