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A large-volume (ϕ 12.0 cm × 12.7 cm) LaBr 3 scintillation detector equipped with a specially-designed radiation shield was evaluated for neutron resonance capture analysis at the neutron time-of-flight (TOF) facility GELINA. By using the LaBr 3 detector with and without the shield, measurements were carried out at a 13-m TOF station with three metallic samples, namely, Ni, Cr, and Fe. In addition, Monte Carlo simulations with Geant4 were performed, and the results were compared with the measurements to analyze the observed energy spectra and TOF spectra. Energy spectra obtained with the shield showed that prompt γ -ray peaks emitted from each sample can be used to identify the isotopes. Moreover, the signal-to-noise ratios of resonance peaks in a TOF spectrum with the shield were enhanced 1.5–2.5 times in comparison with those without the shield. Furthermore, simultaneous measurements conducted using the three samples demonstrated that the shield employed herein was indispensable for identifying impurities in a composite sample such as particle-like fuel debris. [ABSTRACT FROM AUTHOR]

A fast neutron detector system that can figure out neutron source direction is developed. The system consists of two rod-shaped fast neutron detectors and one polyethylene moderator. Pulse shape discrimination plastic scintillators are applied for reduced gamma-ray background and improved system sensitivity for fast neutron detection. The neutron detectors are placed on the back and front sides of the moderator facing a neutron source. Experiments are conducted for a single rod-shaped detector and the system changing the PuBe neutron source direction. Simulation-based studies are also performed using the Monte Carlo simulation code, PHITS (Particle and Heavy ion Transport code System). Taking the ratio of counts of the front and back system detectors, linear change with an increased detector angle is observed, except for near 0° and 90°. This enables us to deduce neutron source direction from several measurements. The method is probably useful for a quick and efficient survey of neutron sources or special nuclear materials. [ABSTRACT FROM AUTHOR]

We propose neutron resonance fission neutron analysis (NRFNA), an active nondestructive assay (NDA) technique, to improve the capability to identify and quantify a small amount of fissile material in a sample. NRFNA uses pulsed neutrons to induce fission reactions in the sample. Fission neutrons are detected by a neutron-gamma pulse shape discrimination (PSD) scintillation detector with time-of-flight (TOF) technique. The obtained nuclide-specific resonance peaks in the neutron energy spectrum provide information to identify and quantify a fissile material in the sample. The possibility of using PSD for NRFNA was confirmed through a test experiment using a natural uranium sample. We successfully observed the resonance peaks from 235 U(n,f) reaction and showed that NRFNA would be useful for measuring a small amount of fissile material in a sample. • Neutron resonance analysis method to identify and quantify a fissile material. • Fission neutron detection with a neutron-gamma pulse shape discrimination technique. • Resonance peaks of fission reaction by 235U in natural uranium was observed. • Applicable to nuclear nonproliferation, safeguard etc. [ABSTRACT FROM AUTHOR]