Year
2016
Abstract
In Summer 2015, the Consortium for Nonproliferation Enabling Capabilities (CNEC) and the Consortium for Verification Technology (CVT), with the support of Los Alamos National Laboratory (LANL), conducted the first university-directed subcritical experiments with Category I special nuclear material (Cat I SNM) at the Nevada National Security Site (NNSS) Device Assembly Facility (DAF). Faculty, students, and post-doctoral researchers from North Carolina State University (NCSU), University of Illinois at Urbana-Champaign (UIUC), Purdue University, and University of Michigan (UM) deployed the following radiation measurement systems to DAF: gamma spectroscopy, fast neutron time-correlation, gamma scatter and pinhole aperture imaging, dual neutron-gamma scatter imaging, and neutron coded aperture imaging. The participants conducted passive and active neutron and gamma measurements of three SNM sources: the BeRP ball, a 4.5 kg sphere of weapons-grade plutonium (WGPU) metal; the Rocky Flats (RF) shells, a series of nesting spherical shells of highly enriched uranium (HEU) metal with an approximate total uranium mass of 12.8 kg; and the center section of the Thor core, a disk-shaped spherical section of WGPu metal approximately 10.6 cm in diameter by 3.2 cm thick, with an approximate plutonium mass of 4.1 kg. These SNM sources were measured bare and reflected/shielded by polyethylene, iron, lead, and/or tungsten. Measurements of the RF shells used an americium- beryllium (AmBe) neutron source to initiate fission chain-reactions in the HEU; all measurements of the BeRP ball and Thor core were passive – fission chain-reactions were initiated in the WGPu by the intrinsic plutonium-240 spontaneous fission neutron source. This paper summarizes the experiments conducted by CNEC and CVT, highlights some of the initial experimental observations, and describes how the experiments are being used to support the research and education objectives of both consortia.