Neutronics and Safety Studies on a Research Reactor Concept for Advanced Neutron Sources

Published

July 17, 2017

Author(s)

Zeyun NMN Wu, Robert E. Williams, J. Michael Rowe, Thomas Henderson Newton, Sean O'Kelly

Abstract

This paper presents the neutronics and thermal-hydraulics safety analysis results for an LEU-fueled research reactor concept being designed and studied at NIST. The main goal of the research reactor is to provide advanced neutron sources for scientific experiments with a particular emphasis on high intensity cold neutron sources. A tank-in-pool type reactor with an innovative horizontally split compact core was developed in order to maximize the yield of the thermal flux trap in the reflector area. The reactor was designed with 20 MW thermal power and 30 days operating cycle. For non-proliferation purposes, the LEU fuel (U₃Si₂-Al) with 19.75 wt% enrichment was used. The core performance characteristics of an equilibrium cycle with several representative burnup states - including startup (SU) and end of cycle (EOC) - were obtained using the Monte-Carlo code MCNP6. The estimated maximum thermal flux of the core is ~5×10¹⁴ n/cm²-s. The calculated brightness of the cold neutron source (CNS) demonstrates the superiority of the cold neutron performance of the design. Sufficient reactivity control worth and shutdown margins are provided by hafnium control elements. Reactivity coefficients were evaluated to ensure negative feedback. Thermal-hydraulics safety studies of the reactor were performed using the multi-channel safety analysis code PARET/ANL. Steady-state analysis showed that the peak cladding temperature (PCT) and minimum critical heat flux ratio (MCHFR) are less than design limits with sufficient margins. Detailed transient analyses for a postulated reactivity insertion accident and a loss of flow accident showed that no fuel damage or cladding failure would occur with the protection of reactor scrams.

Citation

Nuclear Technology

Volume

199

Pub Type

Journals

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Keywords

Low-Enriched Uranium, Research Reactor, Cold Neutron Source, Neutronics, Therma-hydraulics, Safety Analyses

Citation

, Z. , , R. , , J. , , T. and O'Kelly, S. (2017), Neutronics and Safety Studies on a Research Reactor Concept for Advanced Neutron Sources, Nuclear Technology, [online], https://tsapps.nist.gov/publication/get_pdf.cfm?pub_id=921641 (Accessed October 24, 2025)