Development of High Efficiency Neutron Detectors

We have designed a novel neutron detector system using conventional 3He detector tubes and composites of polyethylene and graphite. At this time the design consists entirely of MCNP simulations of different detector configurations and materials.1 These detectors are applicable to low-level passive and active neutron assay systems such as the passive add-a-source and the 2'2Cf shuffler 2,3,4 M0nte Carlo simulations of these neutron detector designs achieved efficiencies of over 35% for assay chambers that can accommodate 55-gal. drums. Only slight increases in the number of detector tubes and helium pressure are required. The detectors also have reduced die-away times. Potential applications are coincident and multiplicity neutron counting for waste disposal and safeguards. We will present the general design philosophy, underlying physics, calculation mechanics, and results.