Microreactor Reference Plant Model
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Microreactor Reference Plant Model Stephen M. Bajorek, Ph.D. Senior Technical Advisor for Thermal - Hydraulic Code Development Office of Nuclear Regulatory Research United States Nuclear Regulatory Commission Ph.: (301) 415 - 2345 / [email protected] GAIN-EPRI-NEI Microreactor Program Virtual Workshop August 18 - 19, 2020 RES Implementation Action Plan for Advanced Non-LWR ; Codes and Tools
Transcript of Microreactor Reference Plant Model
Microreactor Reference Plant Model
Stephen M. Bajorek, Ph.D.Senior Technical Advisor for Thermal-Hydraulic Code Development
Office of Nuclear Regulatory ResearchUnited States Nuclear Regulatory Commission
Ph.: (301) 415-2345 / [email protected]
GAIN-EPRI-NEI Microreactor Program Virtual WorkshopAugust 18-19, 2020
RES Implementation Action Plan for Advanced Non-LWR ; Codes and Tools
Slide 2
Acknowledgement
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• This work was a cooperative effort. Major contributors to the effort were:
– Joe Kelly, Nuclear Regulatory Commission– Rui Hu and Guojun Hu, Argonne National Laboratory– Javier Ortensi, Idaho National Laboratory
Slide 3
Introduction
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• “Strategy 2” of the Implementation Action Plan (IAP) is directed at identification & development of computer codes and tools to prepare the staff for evaluation of advanced non-LWRs.
• An important step in code readiness is development of a “reference plant” model which will:– Contain many / most features expected in a design– Exercise code(s) to be used in analysis– Provide early identification of technical issues
Slide 4
TRACESystem and Core T/H
MOOSETensor Mechanics, Data Transfer
PARCSNeutronics
SCALE Cross-sections
FASTFuel Performance
BISONFuel Performance
PRONGHORNCore T/H
SAMSystem and Core T/H
Nek5000CFD
DOE CodeNRC Code
GRIFFINNeutronics
Comprehensive Reactor Analysis Bundle
SERPENT Cross-sections
Int’l Code
FLUENTCFD
Commercial
Planned Coupling
Completed Coupling Input/BC Data
Current View; Jan 2020
“BlueCRAB”
Slide 5
Identify Plant & Scenario
PIRT(Phenomena Identification & Ranking Tables)
Analysis Code
Model Acceptable ?
Model Development
Establish Assessment
Matrix
Experimental Testing & Data
Evaluation
Code AssessmentCompare Code vs. IET and SET
Application Uncertainty Methods
Deficiency
Yes
Reg Guide 1.203 Code Development
Slide 6
PIRT and Scenarios: “Micro Reactors”
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Scenarios• loss of heat sink• inadvertent reactivity insertion transients, including ATWS events• localized heat pipe failure• cascading loss of heat pipes• seismic event (causing reactivity increase)• events related to coupling the reactor to the power conversion unit• monolith temperature and stress under normal operating conditions• monolith temperature and stress under postulated accident conditions.
Phenomena• monolith thermal stress (thermal expansion)• single heat pipe failure (localized thermal conduction, gap conductance)• machining and inspection of the monolith• heat pipe performance (evaporator/condenser heat transfer, solidification)• reactivity and core criticality (neutron leakage, reactivity feedback)
Comprehensive Reactor Analysis Bundle
BlueCRAB
DOE CodeNRC Code Int’l Code Commercial
Planned Coupling
Completed Coupling Input/BC Data
Comprehensive Reactor Analysis Bundle
BlueCRAB - MicroReactor
MOOSETensor Mechanics, Data Transfers
SAMSystem and Core T/H
GRIFFINNeutronics
SERPENT Cross-sections
Slide 8
NRC’s Microreactor “Reference Model”
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• Based on the “Design A” microreactor described by Sterbentz et al [INL/EXT-17-43212, Rev. 1] , with several simplifications.
Fuel ElementReactor Core
Slide 9
SERPENT: Monte-Carlo Reference Solution
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• SERPENT Calculations-– Cross-sections– Initial power distribution
Slide 10
Coupled Code Simulations
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Reactivity Feedback Coefficients [pcm/K]
Doppler Effect -0.320
Axial Expansion -0.905Radial Expansion -1.349Combined Effect -2.540
Table 10 Reactivity feedback coefficients
• MAMMOTH: Neutronics• MOOSE: Tensor mechanics, conduction• SAM: Heat pipes, secondary side HX
Slide 11
“MultiApp Code Coupling
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Slide 12
SAM Heat Pipe Model
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Slide 13
Single Heat Pipe Failure
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Fuel temperatures increase near failed HP and surrounding elements.
Heat removal by failed HP drops quickly, but increases in surrounding HPs.
Slide 14
Loss of Heat Sink
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Heat removal by HPs stops and fuel temperatures increase. Strong negative reactivity due to core expansion results in decrease in core power.
Slide 15
Summary & Next Steps
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• BlueCRAB system of codes has been demonstrated as capable of microreactor simulation.
• Verification & Validation remain important steps. Tests such as KRUSTY, MAGNET, MARVEL, Godiva can provide data for coupled code simulations.
• Improvement of heat pipe model, secondary side HX, “exterior” cooling models.
• Development of microreactor models to assist regulatory review and investigate safety margins.
