HTGR Knowledge Base

Conference Article: Advanced High-Temperature Reactor (AHTR) Loss-Of-Forced-Circulation Accidents

Abstract

The Advanced High-Temperature Reactor (AHTR) is a new reactor concept that makes novel use of several existing technologies, combined to enable higher thermal-power outputs, higher efficiency, and a higher temperature heat source for process heat applications and electricity. The reactor core utilizes prismatic block designs similar to those of the Gas-Turbine Modular Helium Reactor (GT-MHR), and the TRISO coated-particle ceramic fuel universally used for helium-cooled reactors. The ultimate heat sink for safety-grade afterheat removal is a passive system similar to those in both the Modular High-Temperature Gas-cooled Reactor (MHTGR) and the liquid-metal-cooled fast reactor designs. The Brayton cycle is used for electricity production. Initial studies have shown the potential for a considerably greater thermal power output within the confines of a 600-MW(t) GT-MHR-size vessel while still retaining “passive safety” characteristics. A 3-D thermal-hydraulic (T/H) core simulation model developed at Oak Ridge National Laboratory (ORNL) for studying gas-cooled reactor accidents was modified to accommodate AHTR core T/H characteristics. The limitations of the model approximations used for molten salt vs a gas coolant were evaluated, and preliminary results indicate that there is a negligible effect for long-term transients. Initial studies of AHTR loss-of-forced-circulation (LOFC) accident scenarios show that passive cooling mechanisms are sufficient for preventing core heatups that exceed prescribed temperature limitations for fuel failure, coolant boiling, and vessel damage for a 2400 MW(t) reactor.

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Reference:

Proceedings of the Conference on High Temperature Reactors, Beijing, China, September, 22-24, 2004

International Atomic Energy Agency, Vienna (Austria)

HTR-2004, pp:1-9