Gaseous and metallic fission product release characteristics of a modular pebble bed HTGR during loss of core cooling accidents
A quantitative safety criteria for the high-temperature gas-cooled reactor (HTGR) is to limit the radiological consequences for a wide spectrum of accidents to a level not requiring public sheltering. This leads to reliance on passive safety characteristics for improbable loss of core cooling accidents. Models have been developed to predict the transport of metallic and gaseous fission products (FPs) through the multilayered fuel particle coatings and the graphite matrix of the core under accident conditions. Using these models, FP transport and releases were calculated for a loss of core convective cooling accident in a 250-MW(t) 3.8-W/cc pebble bed HTGR. Fission-product transport through the particle kernel and coatings, the graphite pebbles/reflectors, the reactor vessel, and the confinement were assessed. The results of this study show that the most effective barrier to fission products is the coated fuel particle. The reactor vessel and the confinement provide additional attenuation for the small amount released from the core. The small release to the environment occurs over a period of days and is so low that the safety criterion of 5 rem thyroid dose (to avoid offsite sheltering) is satisfied with a margin of more than an order of magnitude. 6 figs.
- Research Organization:
- GA Technologies, Inc., San Diego, CA (USA)
- DOE Contract Number:
- AT03-84SF11963
- OSTI ID:
- 5843124
- Report Number(s):
- DOE/HTGR-85-025; CONF-850570-3; ON: DE85011822
- Resource Relation:
- Conference: IAEA specialists' meeting on gas cooled reactors, Oak Ridge, TN, USA, 13 May 1985
- Country of Publication:
- United States
- Language:
- English
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