The NBSR is a 20-MW research reactor operated by the NIST Center for Neutron Research (NCNR) as a neutron source providing beams of thermal and cold neutrons for research in materials science, fundamental physics, and nuclear chemistry. The cold neutron facilities at NCNR have expanded steadily since the completion of the first guide hall in 1989, and currently about 70% of the research uses cold neutrons. The NBSR is one of five research reactors in the US using high-enriched uranium fuel (HEU) preparing to convert to low-enriched uranium (LEU) fuel, when a suitable fuel has been developed and certified for use. Fabrication of fuel plates with an alloy of uranium and molybdenum has encountered technical challenges; however, delaying fuel conversion at least a decade and perhaps to 2029 when the current operating license expires.
NCNR is exploring an alternative replacement reactor for the NBSR, designed to operate with LEU fuel and to optimize the performance of multiple cold neutron sources to illuminate 20 to 30 neutron guides. A conceptual design of a compact reactor core will be the focus point of discussions regarding the initial suite of cold neutron scattering instruments and other capabilities needed to serve the user community for the next half century. The design will include the core geometry, fuel-management scheme, cold sources, control elements, a thermal-hydraulic analysis of the primary cooling system, and a preliminary safety analysis. It is possible a 40-50 MW reactor could be built adjacent to the NBSR site so that existing office and laboratory space can be used.
Williams RE (invited), Richards WJ, et al: “LEU Conversion of the NIST Research Reactor: Maintaining Core Geometry to Avoid a Startup Core,” Proceedings of the Conference on the Physics of Reactors, PHYSOR 2010, Pittsburgh, PA, May 9-14, 2010 (Program CD, ISBN: 978-0-89448-079-9, American Nuclear Society, Inc., La Grange Park, Illinois)
Kopetka, P, Rowe JM, Williams RE: “Cold Neutrons at NIST”, Nuclear Engineering Technology (38) 5: 427, (2006) www.koreascience.org
Nuclear engineering; LEU fuel; Reactor physics analysis; Research reactor; Research reactor utilization; Cold neutron source; Core thermal-hydraulics; Reactor safety; Compact reactor core;