Development and testing of a Delayed Gamma-ray Spectroscopy instrument utilizing Cf-252 neutrons evaluated for nuclear safeguards applications

The Japan Atomic Energy Agency (JAEA) is collaborating with the European Commission Joint Research Centre (EC/JRC) to develop delayed gamma-ray spectroscopy (DGS). Toward this, the JAEA Integrated Support Center for Nuclear Nonproliferation and Nuclear Security (ISCN) designed the Delayed Gamma-ray Test Spectrometer (DGTS) that uses a 252Cf source (DGTS-C). This instrument is used to refine the design for a compact, induced-fission safeguards technique to supplement current nuclear material accountancy in reprocessing facilities. Experiments were performed at PERLA laboratory of the EC/JRC Ispra, Italy site to evaluate the neutron-irradiation and associated instrumentation capabilities to obtain delayed gamma-ray spectral signatures of assayed nuclear material. Neutron count-rate measurements were performed using a 3He detector and confirmed with MCNP6 models that showed a fluence of ∼87.1×10−4 n cm−2 nsrc−1. Short time-pattern interrogations of various 235U and 239Pu samples resulted in quantifiable delayed gamma-ray peaks from fission products. The peak intensities and spectral signatures resulted in fissile nuclide distinction and linear mass-correlation results. Consequently, we confirm the practicality of this JAEA/ISCN instrument design for DGS interrogation safeguards capabilities.