NIST Neutron Source Pre-Conceptual Design

Published

February 10, 2025

Author(s)

David Diamond, Abdullah Weiss, Osman Celikten, Jeremy Cook, Dagistan Sahin, Hubert King, Anil Gurgen, Joy Shen

Abstract

A pre-conceptual design has been completed for a NIST Neutron Source (NNS). It would replace the existing facility at the NIST Center for Neutron Research (NCNR) to enable significantly more thermal and cold neutrons to be used in many more experiments than possible currently. The scientific community through several organizations has made recommendations to improve access to neutrons and Congress has requested that a strategic plan for the future of the NCNR be written. This report is in support of that plan. At the heart of the NNS is a 20 MW compact reactor core cooled and moderated by light water. The fuel assemblies use uranium-molybdenum plates and reactivity is controlled with hafnium blades. The core is surrounded by a reflector tank containing heavy water and cold neutron sources (CNSs) which use liquid deuterium. Cold neutron guides extend out from the reflector tank to experimental stations as do thermal neutron beams. The reactor has a 40-day fuel cycle and is cooled with three out of the four pumps that are part of the design. The design has acceptable reactivity feedback from increases in temperature or voiding and is within thermal limits for both normal operation and transients or accidents where the instrumentation and control system protects the reactor. The cold neutrons (wavelengths greater than 4 Å) that this design will deliver have an integral neutron brightness 3.5 times that at the present NCNR facility. For the two CNSs at least 15 kW of cooling would be necessary. Neutron currents at instruments will depend on future guide tube design. However, calculations of neutron currents entering guides from one CNS show that there will be a factor of 10 increase relative to the current NCNR cold source. The number of cold neutron guides from each CNS will increase to 16 whereas the single large CNS at the NCNR currently has 12. A proposed set of instruments for both cold and thermal neutron beams is presented as part of the design.

Citation

Special Publication (NIST SP) - 1327

Report Number

1327

NIST Pub Series

Special Publication (NIST SP)

Pub Type

NIST Pubs

Download Paper

https://doi.org/10.6028/NIST.SP.1327

Local Download

Keywords

Neutron Science, Research, Reactor, Neutronics, Thermal Hydraulics, Guides, Instruments, Safety, Beam

Citation

Diamond, D. , Weiss, A. , Celikten, O. , Cook, J. , Sahin, D. , King, H. , Gurgen, A. and Shen, J. (2025), NIST Neutron Source Pre-Conceptual Design, Special Publication (NIST SP), National Institute of Standards and Technology, Gaithersburg, MD, [online], https://doi.org/10.6028/NIST.SP.1327, https://tsapps.nist.gov/publication/get_pdf.cfm?pub_id=959439 (Accessed October 1, 2025)