Year
1997
Abstract
A system for detecting neutrons composed of an array of boron-loaded plastic scintillators optically coupled to bismuth germanate inorganic scintillators has been developed to measure special nuclear materials in a variety of chemical and physical forms. The greatest advantage of the boron-loaded plastic/bismuth germanate detector is its intrinsic capability for both high detection efficiency and short neutron die-away time. Results from simulation efforts indicate that the neutron capture probabilities equal or exceed those of current state of the art thermal neutron multiplicity detectors while teh corresponding neutron die-away times are an order of magnitude lower. Experiments have been performed to characterize the response of these detectors and validate computer simulations. Application to the quantitative assay of high-( ) plutonium-bearing materials (typically scrap and waste from plutonium reprocessing) is explored. In addition, a novel use of the instrument, in which the detection system is purposely made nonquantative, is described for verification activities involving dismantlement of nuclear weapons.