A safety assessment of the use of graphite in nuclear reactors licensed by the US NRC
This report reviews existing literature and knowledge on graphite burning and on stored energy accumulation and releases in order to assess what role, if any, a stored energy release can have in initiating or contributing to hypothetical graphite burning scenarios in research reactors. It also addresses the question of graphite ignition and self-sustained combustion in the event of a loss-of-coolant accident (LOCA). The conditions necessary to initiate and maintain graphite burning are summarized and discussed. From analyses of existing information it is concluded that only stored energy accumulations and releases below the burning temperature (650/sup 0/C) are pertinent. After reviewing the existing knowledge on stored energy it is possible to show that stored energy releases do not occur spontaneously, and that the maximum stored energy that can be released from any reactor containing graphite is a very small fraction of the energy produced during the first few minutes of a burning incident. The conclusions from these analyses are that the potential to initiate or maintain a graphite burning incident is essentially independent of the stored energy in the graphite, and depends on other factors that are unique for these reactors, research reactors, and for Fort St. Vrain. In order to have self-sustained rapid graphite oxidation in any of these reactors, certain necessary conditions of geometry, temperature, oxygen supply, reaction product removal, and a favorable heat balance must be maintained. There is no new evidence associated with either the Windscale Accident or the Chernobyl Accident that indicates a credible potential for a graphite burning accident in any of the reactors considered in this review.
- Research Organization:
- Brookhaven National Lab. (BNL), Upton, NY (United States); US Nuclear Regulatory Commission (NRC), Washington, DC (USA). Office of Nuclear Reactor Regulation
- DOE Contract Number:
- AC02-76CH00016
- OSTI ID:
- 6102304
- Report Number(s):
- NUREG/CR-4981; BNL-NUREG-52092; ON: DE88000046; TRN: 87-035151
- Country of Publication:
- United States
- Language:
- English
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