.e, ot U.S. NUCLEAR REGULATORY COMMISSION STANDARD REVIEW PLAN OFFICE OF NUCLEAR REACTOR REGULATION 15.6.1 INADVERTENT OPENING OF A PWR PRESSURIZER PRESSURE RELIEF VALVE OR A BWR PRESSURE RELIEF VALVE REVIEW RESPONSIBILITIES Primary- Reactor Systems Branc

The inadvertent opening of a pressure relief valve results in a reactor coolant inventory decrease and a decrease in reactor coolant system pressure. A pressure relief valve, as defined in ANSI B95.1-1972 (Ref. 1), is a pressure relief device which is designed to reclose and prevent further fluid flow after normal condi-tions have been restored. The effect of the pressure decrease is to decrease the neutron flux (via moderator density feedback). In a pressurized water reactor (PWR), a reactor trip occurs due to low reactor coolant system (RCS) pressure. In a boiling water reactor (BWR), the pressure relief valve discharges into the suppression pool. Normally there is no reactor trip in a BWR. The pressure regulator senses the RCS pressure decrease and partially closes the turbine control valves (TCV) to stabilize the reactor at a lower pressure. The reactor power settles out at nearly the initial power level. The coolant inventory is maintained by the feedwater control system using water from the condensate storage tank via the condenser hotwell. The review of these transients should consider the sequence of events, th