Technical findings and regulatory analysis related to generic issue 70

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

OSTI ID:5229424

Kirkwood, R

Examining Generic Issue 70 (GI-70), Power-Operated Relief Valve and Block Valve Reliability,'' involves the evaluation of the reliability of power-operated relief valves (PORVs) and block valves and their safety significance in pressurized water reactor (PWR) nuclear power plants. Traditionally, the PORV and its block valve are provided for plant operational flexibility and for limiting the number of challenges to the pressurizer safety valves. The block valve is installed upstream of the PORV because of the potential for the PORV to leak or stick open. For overpressure protection of the reactor coolant pressure boundary (RCPB) at normal operating temperature and pressure, the operation of PORVs has not been explicitly considered as a safety-related function. Also, an inadvertent opening of a PORV or safety valve has been analyzed in the final safety analysis reports as an anticipated operational occurrence with acceptable consequences. For these reasons, most PWRs, particularly those licensed prior to 1979, do not have safety-related PORVs. The valve operators and their electrical control systems are normally designed to non-safety-related standards. However, the pressure-retaining elements of PORVs and block valves are within the RCPB and are constructed to the same codes and standards as those required for similar safety-related RCPB components. 20 refs., 3 figs., 8 tabs.

• Research Organization: Nuclear Regulatory Commission, Washington, DC (USA). Div. of Safety Issue Resolution
• Sponsoring Organization: NRC
• OSTI ID: 5229424
• Report Number(s): NUREG-1316; ON: TI90005364
• Country of Publication: United States
• Language: English

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220900 -- Nuclear Reactor Technology-- Reactor Safety
ACCIDENTS
CONTROL EQUIPMENT
CONTROL SYSTEMS
COOLING SYSTEMS
COST
DESIGN
ENERGY SYSTEMS
ENERGY TRANSFER
ENGINEERED SAFETY SYSTEMS
EQUIPMENT
FAILURES
FLOW REGULATORS
FLUID FLOW
FLUID MECHANICS
HEAT TRANSFER
HYDRAULICS
LOSS OF COOLANT
MAINTENANCE
MANAGEMENT
MECHANICS
MELTDOWN
PERFORMANCE TESTING
PRESSURE EFFECTS
PROGRAM MANAGEMENT
PWR TYPE REACTORS
QUALITY ASSURANCE
REACTOR ACCIDENTS
REACTOR COMPONENTS
REACTOR CONTROL SYSTEMS
REACTOR COOLING SYSTEMS
REACTOR CORES
REACTOR MAINTENANCE
REACTOR SAFETY
REACTOR SHUTDOWN
REACTORS
RELIABILITY
RELIEF VALVES
RISK ASSESSMENT
RUPTURES
SAFETY
SCRAM
SHUTDOWNS
TECHNOLOGY ASSESSMENT
TEMPERATURE EFFECTS
TESTING
TRANSIENTS
VALVES
WATER COOLED REACTORS
WATER MODERATED REACTORS