Mixed Convection in the VHTR in the Event of a LOFA

Technical Report · Tue May 01 00:00:00 EDT 2012

DOI:https://doi.org/10.2172/1048409· OSTI ID:1048409

Johnson, Richard W. ^[1]

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1. Idaho National Laboratory (INL), Idaho Falls, ID (United States). Thermal Science and Safety Analysis

The US Department of Energy, Office of Nuclear Energy (DOE-NE) is supporting the development of a very high temperature reactor (VHTR) concept as the primary focus of it next generation nuclear power plant (NGNP) program. The VHTR is cooled by forcing helium downwards through the core into the lower plenum and out the hot duct. In the event that the coolant circulators are lost, the driving pressure drop across the core will reduce to zero and there will be the opportunity for natural circulation to occur. During the time that the circulators are powering down, the heat transfer in the core from the graphite blocks to the helium coolant will transform from turbulent forced convection to mixed convection, where buoyancy effects become important, to free or natural convection, where buoyancy is dominant. Analysis of the nature of the forced, mixed and free convection is best done using computational fluid dynamic (CFD) software that can provide fine details of the flow and heat transfer. However, CFD analysis involves approximations in the results because of the finite nature of the spatial and temporal discretizations required, the inexact nature of the turbulence models that are used and the finite precision of the computers employed. Therefore, it is necessary to validate the CFD computations. Validation is accomplished by comparing results from specific CFD computations to experimental data that have been taken specifically for the purpose of validation and that are related to the physical phenomena in question. The present report examines the flow and heat transfer parameters (dimensionless numbers) that characterize the flow and reports ranges for their values based on specific CFD studies performed for the VHTR.

• Research Organization: Idaho National Laboratory (INL), Idaho Falls, ID (United States)
• Sponsoring Organization: USDOE Office of Nuclear Energy (NE)
• DOE Contract Number: AC07-05ID14517
• OSTI ID: 1048409
• Report Number(s): INL/EXT--12-26039
• Country of Publication: United States
• Language: English

Related Subjects

21 SPECIFIC NUCLEAR REACTORS AND ASSOCIATED PLANTS
22 GENERAL STUDIES OF NUCLEAR REACTORS
APPROXIMATIONS
CFD
COMPUTER CODES
COMPUTERIZED SIMULATION
COMPUTERS
CONVECTION
COOLANTS
FLUID MECHANICS
FORCED CONVECTION
GRAPHITE
HEAT TRANSFER
HELIUM
LOFA
NATURAL CONVECTION
NUCLEAR ENERGY
NUCLEAR POWER PLANTS
PRESSURE DROP
TURBULENCE
VALIDATION
natural circulation