The Japan Atomic Energy Agency is collaborating with European Commission Joint Research Centre (JRC) to develop Delayed Gamma-ray Spectroscopy (DGS) non-destructive assay to measure the fissile content of small, mixed nuclear material samples. The main goal of this project is to develop a compact instrument in order to make DGS practical for installation into an analytical laboratory. Toward this goal, the instrument must combine elements for neutron irradiation and gamma-ray measurement that address the challenges required to properly evaluate the U and Pu contributions to the fission product gamma-ray signature. For example, commercial neutron sources that allow for installation in a laboratory (e.g. neutron generators or radioactive sources) emit high-energy neutrons that require a moderator to get sufficient fission rates for the delayed gamma-ray signals. The minimum source intensity would be determined by various factors like the type of sample, the interrogation pattern, and the thickness of the detector shield. For instance, the measurement of spent fuel samples requires much higher source intensities than MOX samples since higher gamma-ray signals are necessary to penetrate the thick detector shield needed to suppress the passive background from Cs-137. Here we present lessons learned from experiments performed at JRC-Ispra (Italy) that will be used to evaluate fundamental requirements in DGS instrument designs. Specifically, we will compare and contrast results from PUNITA, which uses a deuterium-tritium neutron generator, to a preliminary DGS instrument based on Cf-252, tested at PERLA. From these results, we will then present a description for the demonstration and installation instruments we are designing.
Year
2020
Abstract