Model design of a deuterium-deuterium neutron generator moderator and evaluation for delayed gamma-ray nondestructive assay for safeguards verification

• Published in: Journal of nuclear science and technology Vol. 58; no. 3; pp. 302 - 314
• Main Authors: Rossi, Fabiana, Koizumi, Mitsuo, Rodriguez, Douglas Chase
• Format: Journal Article
• Language: English
• Published: Tokyo Taylor & Francis 04.03.2021; Taylor & Francis Ltd
• Subjects: Delayed gamma-ray spectroscopy; Deuterium; deuterium-deuterium neutron generators; Gamma spectroscopy; Interrogation; MCNP; Neutron emission; Neutron flux; neutron moderator; Neutrons; nondestructive assay; Nondestructive testing; Nuclear energy; Nuclear engineering; Nuclear fuel cycle; Q factors; Questioning; Radioactivity; Reprocessing; safeguards; Spectrum analysis; Spent nuclear fuels; Thermal neutrons; Verification
• ISSN: 0022-3131; 1881-1248
• DOI: 10.1080/00223131.2020.1825236

The Japan Atomic Energy Agency is evaluating delayed gamma-ray spectroscopy as an active interrogation nondestructive assay technique to quantify the fissile composition of nuclear materials for improved safeguards verification in nuclear fuel cycle facilities. In this paper, we optimize a moderator to thermalize the 2.5 MeV neutrons emitted from a deuterium-deuterium (D-D) neutron generator. The moderator is optimized to maximize the thermal neutron flux, maintain a high moderator quality factor, and be compact for easy installation in the analytical laboratories of reprocessing facilities. With the objective of applying our system to high-radioactivity nuclear materials (e.g. spent fuel solution), we applied this moderator's flux to an interrogation using delayed gamma-ray spectroscopy for various sample sizes and timing patterns. The results indicate that our 78-cm 3 system is sufficiently able to use commercially available D-D neutron generators with neutron emission rates less than 109 n/s for 25- and 100-ml solutions under specific interrogations.