Title: Thermal-Hydraulic and Neutronic Phenomena Important in Modeling and Simulation of Liquid-Fuel Molten Salt Reactors

Abstract

In this paper, we discuss liquid-fuel molten salt (cooled) reactors (MSRs); how they will operate under normal, transient, and accident conditions; and the results of an expert elicitation to determine the corresponding thermal-hydraulic and neutronic phenomena important to understanding their behavior. Identifying these phenomena will enable the U.S. Nuclear Regulatory Commission (NRC), U.S. Department of Energy, and industry to develop or identify modeling functionalities and tools required to carry out confirmatory and licensing analyses that examine the validity and accuracy of an applicant's calculations and help determine the margin of safety in plant design. The NRC frequently does an expert elicitation using a Phenomena Identification and Ranking Table (PIRT) to identify and evaluate the state of knowledge of important modeling phenomena. However, few details about the design of these reactors and the sequence of events during accidents are known, so the process used was considered a preliminary PIRT. A panel comprising a group of subject matter experts met to define phenomena that would need to be modeled and considered the impact/importance of each phenomenon with respect to specific figures of merit (FoMs) (e.g., salt temperature, velocity, and composition). Each FoM reflected a potential impact on radionuclide release or loss ofmore » a barrier to release. The panel considered what the path forward might be with respect to being able to model the phenomenon in a simulation code. Results are explained for both thermal and fast spectrum designs, with an emphasis on the thermal-hydraulic takeaways. It was concluded that compared to light water reactors, the lack of high-pressure operation, energetic break flow, depressurization, and quench front tracking may simplify some aspects of an MSR analysis. However, MSRs have new phenomena both for a license applicant and NRC confirmatory analysis. There is a need for enhanced understanding of physical properties for MSRs that encompass several individual thermophysical properties, including thermal conductivity, viscosity, specific heat, density, optical properties, thermodynamic properties, volatilities, solubilities, etc. Salt composition is closely linked to both these properties and the neutronics of the system. Additionally, the large number of MSR concepts and system designs means that there is wide variation in the potential modeling needs for these systems.« less

Authors:

Brown, Nicholas R.  ^[1];

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Diamond, David J. ^[2]; Bajorek, Stephen ^[3]; Denning, Richard ^[4]

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+ Show Author Affiliations

1. Univ. of Tennessee, Knoxville, TN (United States)
2. Brookhaven National Lab. (BNL), Upton, NY (United States)
3. US Nuclear Regulatory Commission (USNRC), Washington, D.C. (United States)
4. Consultant, Columbus, OH (United States)

Publication Date:

Mon Apr 22 00:00:00 EDT 2019

Research Org.:

Brookhaven National Lab. (BNL), Upton, NY (United States)

Sponsoring Org.:

USDOE; USNRC

OSTI Identifier:

1600470

Report Number(s):

BNL-213629-2020-JAAM
Journal ID: ISSN 0029-5450; TRN: US2103533

Grant/Contract Number:  

SC0012704

Resource Type:

Accepted Manuscript

Journal Name:

Nuclear Technology

Additional Journal Information:

Journal Volume: 206; Journal Issue: 2; Conference: 4.International Topical Meeting on Advances in Thermal Hydraulics 2018 (ATH 2018), Orlando, FL (United States), 11-15 Nov 2018; Journal ID: ISSN 0029-5450

Publisher:

Taylor & Francis - formerly American Nuclear Society (ANS)

Country of Publication:

United States

Language:

English

Subject:

73 NUCLEAR PHYSICS AND RADIATION PHYSICS; Phenomena Identification and Ranking Table; molten salt (cooled) reactors; flouride-salt–cooled high-temperature reactors; advanced reactors