Abstract
The High Flux Isotope Reactor (HFIR) is a high performance isotope production and research reactor which has been in operation at Oak Ridge National Laboratory (ORNL) since 1965. In late 1986 the reactor was shut down as a result of discovery of unexpected neutron embrittlement of the reactor vessel. In January of 1988 a Level 1 Probabilistic Risk Assessment (PRA) (excluding external events) was published as part of the response to the many reviews that followed the shutdown and for use by ORNL to prioritize action items intended to upgrade the safety of the reactor. A conservative estimate of the core damage frequency initiated by internal events for HFIR was 3.11 × 10-4. It was dominated by flow blockages and loss of all AC power. In June 1989 a draft external events initiated PRA was published. The dominant contributions from external events came from seismic, wind, and fires. The overall external event contribution to core damage frequency is about 50 percent of the internal event initiated contribution and is dominated by seismic events. Several design and safety analysis studies were undertaken to support the restart of the HFIR. The first study involved a fracture mechanics analysis and redesign of the reactor operating conditions and safety system settings to provide a basis for future operation. Another study involved performing a risk analysis by combining the Level 1 PRA results with offsite consequence analyses under conservative assumptions about the fission product removal within the plant. Additional studies were performed to establish a long-term decay heat removal design basis. Finally, updated and upgraded loss-of-cooling accident studies were performed and are still underway.
Original language | English |
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Pages | 352-382 |
Number of pages | 31 |
State | Published - 1990 |
Event | Proceedings - International Symposium on Research Reactor Safety, Operations and Modifications - Chalk River, Ont, Can Duration: Oct 23 1989 → Oct 27 1989 |
Conference
Conference | Proceedings - International Symposium on Research Reactor Safety, Operations and Modifications |
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City | Chalk River, Ont, Can |
Period | 10/23/89 → 10/27/89 |