HTGR Knowledge Base

Conference Article: Quantitative HTGR safety and forced outage goals

Houghton, W.J.; Parme, L.L.; Silady, F.A. (GA Technologies, Inc., San Diego, CA (USA))

Abstract

Quantitative safety and forced outage goals have been adopted for the High Temperature Gas-Cooled Reactor (HTGR). These goals are comprised of both top-level regulatory criteria and user requirements. The development of these goals and their implementation within the Integrated Approach to guide the design of the HTGR is discussed. The forced outage goal addresses user requisites regarding both the average plant availability, as impacted by forced outages, as well as an aversion to single, rare, but relatively severe events that result in lengthy outages. In particular, the forced outage goal specifies a limit of an average annual equivalent unscheduled unavailability of less than 10%. Limiting the risk of longer outages to a level comparable with fossil fired plants, the goal further stipulates that only a small fraction of this average outage rate should be due to outages of six months or greater. Finally the frequency of events that could result in irreparable damage and plant loss is limited to less than 10-5 per plant year. The HTGR safety goal addresses top-level regulatory criteria assuring the licensability of the plant. The criteria represent direct statements of acceptable consequences or risks to the public or the environment. They are quantifiable and the criteria do not discriminate between current generation reactors and the HTGR. In addition, the goal includes a user requirement that releases be limited, even for very unlikely events, to support eliminating the need for offsite evacuation planning. These goals, along with other goals addressing the planned aspects of power production, are used to guide plant design using the Integrated Approach. The Integrated Approach is a project management tool in which plant level goals, such as those described above, are used to generate the numerous specific requirements for the design and operation of a nuclear power plant. Thus, the development of goals is a key aspect in this ''top-down'' approach which provides a framework for establishing and defending a well-developed nuclear plant design.

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key words: decommissioning; decontamination; economics; htgr type reactors; outages; reactor safety; risk assessment; specifications; cleaning; gas cooled reactors; graphite moderated reactors; reactors; safety
Reference:
Specialists' meeting on safety and accident analysis for gas-cooled reactors. Oak Ridge, TN (USA). 13-15 May 1985
International Atomic Energy Agency, Vienna (Austria)
IAEA-TECDOC--358, pp:121-129