JAEA-JRC Collaborative Development of Delayed Gamma-ray Spectroscopy for Nuclear Material Evaluation 2: DGS Technique, Requirements, and Interrogation Time Patterns

摘要

Delayed Gamma-ray Spectroscopy (DGS) is a non-destructive assay technique that can be used to determine the fissile U and Pu nuclides of a mixed nuclear material sample. A DGS interrogation uses neutrons from an external source to induce fission in the sample during an irradiation period followed by a measurement period wherein the gamma rays emitted by the decaying fission products are observed. Due to the various half-lives of the fission products, though, the interrogation pattern (irradiation and measurement times) significantly affects the ability to evaluate the U and Pu nuclides' contributions to the observed gamma-ray spectrum. These are further constrained by the instrumentation that can introduce delays between the irradiation and measurement periods that can affect the observed spectrum. As part of a series, this presentation describes the details and constraints of a DGS interrogation and how this affects the ability to quantify the nuclear material composition. The technique and interrogation constraints will be highlighted by examples from recent experiments performed in Ispra, Italy under the collaboration between the Japan Atomic Energy Agency and the European Commission Joint Research Centre.