Boron-Coated Straws Imaging Panel Capability for Passive and Active Neutron Measurements of Radioactive Waste Drums

Abstract

The evaluation of fissile mass inside radioactive waste drums is essential for radioactive waste management, nuclear safety, and criticality issues. However, passive and active neutron measurements can be strongly impacted by the uncertainty on the neutron source position within the drum and by matrix attenuation effects. Therefore, an imaging panel proposed by Proportional Technologies Inc., composed of seven Boron-coated straw (BCS) detectors has been tested to localize neutron interactions, in view to reduce uncertainties associated with plutonium or uranium position inside radioactive waste drums. A numerical model of the imaging panel has been developed and validated from a comparison with experimental profiles obtained with a 252Cf source. A passive measurement system equipped with 12 such imaging panels has been designed by numerical simulation, in view to provide information on neutron source location in a 118-L radioactive waste drum filled with organic, metallic, or mixed organic–metallic matrices. Additionally, an experimental setup dedicated to active measurements with a D-T neutron generator has been implemented to test the imaging panel. Prompt fission neutron signals have been recorded, which is induced by thermal interrogating neutrons in fissile material samples. This article presents 2-D images indicating the position of fissile materials. Consequently, BCS imaging panels open interesting prospects to reduce the uncertainty associated with plutonium or uranium localization both in passive and active neutron measurements.