Analysis on Enrichment and Mass of Uranium Materials With Time-Correlated Measurement
Abstract Effective determination for enrichment of the uranium materials in heavy shielding is technically difficult to solve. Various technical methods so far have been proposed to deal with this problem. With the time-correlated coincidence measurement method, 14 MeV neutrons and fission spectrum neutrons are chosen to interrogate the uranium samples with different masses and enrichments. The fission spectrum neutrons are obtained by slowing down the 14 MeV neutrons. Results have shown that a good linear relationship exists between masses of the uranium materials (⩽10% enriched 235U) that possess the same enrichment. A linear relationship also exists between enrichments of the uranium materials that possess the same mass.
Neutron response characterization for an EJ299-33 plastic scintillation detector
Abstract Organic scintillation detectors have shown promise as neutron detectors for characterizing special nuclear materials in various arms-control and homeland-security applications. Recent advances have yielded a new plastic scintillator – EJ299-33 – with pulse-shape-discrimination (PSD) capability. Plastic scintillators would have a much-expanded range of deployment relative to liquids and crystals. Here, we present a full characterization of pulse-height response to fission-energy neutrons for an EJ299-33 detector with 7.62-by-7.62-cm cylindrical active volume, and compare with an EJ309 liquid scintillator in the same assembly. Scintillation light-output relations, energy resolutions, and response matrices are presented for both detectors. A continuous-spectrum neutron source, obtained via the bombardment of 27 Al with 7.44-MeV deuterons at the Edwards Accelerator Facility at Ohio University, was used for the measurement. A new procedure for evaluating and comparing PSD performance is presented which accounts for the effect of the light-output relation on the ability to detect low-energy neutrons. The EJ299-33 is shown to have considerable deficit in matrix condition, and in PSD figure of merit when compared to EJ309, especially when neutron energy is taken into account. Nevertheless the EJ299 is likely to bring a modest PSD capability into a array of field applications that are not accessible to liquids or crystals.
A measurement of the light output function of the deuterated liquid scintillator NE-230 to recoil deuterons with energies between 0.62 and 14.5 MeV
Abstract The light output function for deuterons in NE-230 deuterated liquid scintillator has been determined over the deuteron energy range 0.62 to 14.5 MeV. This was achieved by analysing the pulse-heigh distributions produced by recoil deuterons stopping in a scintillator 100 mm in diameter and 50 mm thick. The recoil deuterons were generated by bombarding the scintillator with monoenergetic neutrons produced using the T(p, n), D(d, n), 9 Be(α, n 0 ), 9 Be(α, n 1 ) and T(d, n) reactions at the Harwell 5 MV Van de Graaff accelerator facility. The light output scale was defined using Compton electron spectra, and pulse shape discrimination was use to distinguish between neutron and gamma-ray events. The light output function for deuterons was determined by measuring the upper half-height positions of the peaks in their pulse-height distributions as funtion of neutron energy, and applying a calculated correction for the finite system resolution.