Year
2013
Abstract
The shortage of helium-3 ( 3He) has created a need to identify alternative neutron detection options for a variety of nuclear nonproliferation applications. One application that may be affected by 3He replacement technology is that of mass accountancy, which utilizes coincidence and multiplicity counters to verify special nuclear material declarations. A preliminary Monte Carlo N-Particle eXtended study was conducted to evaluate candidate alternatives whose neutron detection efficiencies and die-away times (average lifetime of a neutron in the coincidence or multiplicity counter) may be comparable to those of 3He proportional counters. Of the technologies evaluated, 6 LiF/ZnS scintillating sheets were the most promising due to a combination of efficiency and die-away time in the material. A small-scale test unit using these sheets was constructed and experimentally characterized. In parallel, test units using 6 LiF/ZnS scintillating sheets were built using two different light-guide materials, non-scintillating polymethyl methacrylate, and wavelength-shifting plastic. In this paper, we present the measured data from different light-guide materials, and an estimation of the capability of the system to detect and measure neutron signatures.