Millstone 3 risk evaluation report. An overall review and evaluation of the Millstone Unit 3 probabilistic safety study

Technical Report · Sun Jun 01 04:00:00 EDT 1986

OSTI ID:5736989

Kelly, G; Barrett, R; Buslik, A

In 1981, the US Nuclear Regulatory Commission (NRC) requested Northeast Utilities to perform a design-specific probabilistic safety study (PSS) for Millstone Nuclear Power Station, Unit No. 3 (Millstone 3). In 1983, Northeast Utilities submitted the Millstone 3 Probabilistic Safety Study for review by the NRC staff. The NRC staff prepared the Millstone 3 Risk Evaluation Report, which discusses the findings regarding the PSS. The PSS estimates that the mean annual core damage frequency due to internal and external events is 5 x 10/sup -5/ and 2 x 10/sup -5/, respectively. The NRC staff's Risk Evaluation Report estimates that the mean annual core damage frequency is about 2 x 10/sup -4/ for internal events and lies between 1 x 10/sup -5/ and 2 x 10/sup -4/ for external events. The NRC staff estimates that station blackout dominates internal and external event core damage frequencies. The staff recommends that Northeast Utilities perform an engineering analysis on upgrading the diesel generator lube oil cooler anchorage system and on adding a manually operated, AC-independent containment spray system. The staff also recommends that Northeast Utilities prepare two emergency procedures (loss of room cooling and relay chatter due to an earthquake) to help reduce uncertainties. (Subsequent to the completion of this document, Northeast Utilities and the NRC staff have continued a dialogue regarding station blackout from events other than earthquakes. Both Northeast Utilities and the staff have performed additional evaluations, which have drawn their results closer together. Final requirements, if any, for the prevention or mitigation of station blackout from events other than earthquakes have not yet been determined.) 26 refs., 16 tabs.

• Research Organization: Nuclear Regulatory Commission, Washington, DC (USA). Office of Nuclear Reactor Regulation
• OSTI ID: 5736989
• Report Number(s): NUREG-1152; ON: TI86901520
• Country of Publication: United States
• Language: English

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CONTAINMENT
CONTAINMENT SYSTEMS
DESIGN
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EVALUATION
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