Developing Delayed Gamma-ray Spectroscopy for Reprocessing Plant Nuclear Safeguards: Neutron Detection System Development

The Integrated Support Center for Nuclear Nonproliferation and Nuclear Security of the Japan Atomic Energy Agency is developing Delayed Gamma-ray Spectroscopy (DGS). The DGS instrument irradiates a sample with neutrons to induce fission and then observes gamma rays emitted during the radioactive decay of the fission products. Since DGS uses neutron sources, it is important to monitor these to both confirm the source consistency and normalize delayed gamma-ray spectra. In addition, prompt-fission and delayed neutron signatures can be used to verify the DGS analysis. To do this,
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He and
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He neutron detectors have been investigated. Since the DGS instrument must be compact, the neutron detectors will be close to the neutron sources and fissionable sample within the instrument. Consequently, several characterization studies were performed for short source-detector distances. This paper will describe experimental results with associated simulations, in light of how the neutron detection systems will be integrated into the DGS instrument.