Regulatory analysis for the resolution of Generic Issue 94, Additional low-temperature overpressure protection for light-water reactors''

Technical Report · Fri Dec 01 04:00:00 EST 1989

DOI:https://doi.org/10.2172/5193266· OSTI ID:5193266

Throm, E D

Low-temperature overpressure protection (LTOP) is required in pressurized water reactors (PWRs) to provide protection against brittle reactor pressure vessel failure following an anticipated event. Typically these events are a result of either mass imbalance (excess charging in comparison to available letdown flow or inadvertent safety injection) or energy input transients (restarting an idle reactor coolant pump causing an increase in the reactor coolant system pressure as a result of mixing cold water from the inactive loop with the remainder of the hot fluid and as a result of direct energy addition from a warmer secondary side heat sink). The significance of these events is heightened during water-solid operations. Low-temperature overpressure protection is required in the shutdown modes of operation, Mode 4 -- Hot Shutdown, Mode 5 -- Cold Shutdown, and Mode 6 -- Refueling with the reactor vessel head bolted down. While operating in Modes 5 and 6 and with the reactor coolant temperature below 200{degree}F, there are no technical specifications for containment integrity. The consequences of an unmitigated low-temperature overpressure event can be significant as a result of either containment bypass or failure of containment to isolate following reactor pressure vessel failure. This report presents the regulatory analysis for Generic Issue 94, Additional Low-Temperature Overpressure Protection for Light-Water Reactors.'' It includes (1) a summary of the issue, (2) the proposed technical resolution, (3) alternative resolutions considered by the Nuclear Regulatory Commission (NRC), (4) an assessment of the benefits and cost of the alternatives considered with additional emphasis on the recommended resolution, (5) the decision rationale, and (6) the impacts and relationships between GI-94 and other NRC programs and requirements. 35 refs., 60 tabs.

• Research Organization: Nuclear Regulatory Commission, Washington, DC (USA). Div. of Safety Issue Resolution
• Sponsoring Organization: NRC
• OSTI ID: 5193266
• Report Number(s): NUREG-1326; ON: TI90004828
• Country of Publication: United States
• Language: English

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ACCIDENTS
AGING
COMPILED DATA
COMPLIANCE
CONTAINERS
CONTROL SYSTEMS
COOLING SYSTEMS
DATA
ENERGY SYSTEMS
INFORMATION
IRRADIATION
JOINTS
NUMERICAL DATA
PRESSURE EFFECTS
PRESSURE VESSELS
PROBABILISTIC ESTIMATION
PWR TYPE REACTORS
REACTOR ACCIDENTS
REACTOR COMPONENTS
REACTOR CONTROL SYSTEMS
REACTOR COOLING SYSTEMS
REACTOR INSTRUMENTATION
REACTOR SAFETY
REACTOR TECHNOLOGY
REACTORS
REGULATIONS
RISK ASSESSMENT
SAFETY
SERVICE LIFE
TEMPERATURE EFFECTS
WATER COOLED REACTORS
WATER MODERATED REACTORS
WELDED JOINTS