Abstract
Significant differences in transient response and materials of construction give high temperature gas-cooled reactor (HTGRs), the potential for alternate approaches to the key issues of selection and analysis of postulated accidents, the radionuclide source-term mechanisms, containment design, and emergency planning. For the MHTGR, the siting goal is to use the U.S. Environmental Protection Agency's protection action guidelines (PAGs) for notification, sheltering, and evacuation, rather than the NRC's doses of 300 rem to the thyroid and a 25 rem whole body. This paper discusses how the design and inherent characteristic of the MHTGR lead to a radionuclide source term of prompt and delayed components. Options for the MHTGR containment design are discussed for this source term and give support to the concept of a vented, low pressure containment in comparison to the high pressure, low leakage containments characteristic of LWRs. The source term concept has been proposed to the NRC and is currently under review.
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