Document: NUREG-0800
Document ID: a650b8f2-b0fa-4f0f-bc8f-55bb3f6ec603
Document Type: srp
Title: INADVERTENT OPENING OF A PWR PRESSURIZER PRESSURE RELIEF VALVE
Source: NUREG-0800
Source URL: https://www.nrc.gov/docs/ML0708/ML070820094.pdf
Revision Date: 2023-06
Chapter: 15
Section ID: 15.6.1
CFR Part: 
CFR Title: 

Content:
o this section because the reviewer evaluates the consequences of the inadvertent opening of a PWR pressurizer pressure relief valve or a BWR pressure relief valve (i.e., AOOs). As part of the reactor coolant pressure boundary, the pressurizer relief and safety valves must be able to reseat properly after actuation. As an AOO, the inadvertent opening of a pressurizer relief valve should not prevent the plant from returning to power a short time after shutdown. 4. GDC 26 requires that reactivity control systems at nuclear power plants include control rods that can control reactivity changes so specified acceptable fuel design limits are not exceeded under conditions of normal operation, including AOOs. This system design must have an appropriate margin to accommodate malfunctions (e.g., stuck rods). GDC 26 applies to this section because the transient analyzed by the reviewer may require the responsive movement of control rods. In such instances, rod misalignment, including stuck rods, can result in more severe thermal-hydraulic conditions. GDC 26 requires that the thermal margin be sufficient to accommodate these conditions. SRP Section 15.6.1 examines this margin for whether thermal criteria are satisfied. Compliance with GDC 26 is best demonstrated by showing that adequate thermal margin is maintained, during the event, as the result of automatic protective action (e.g., a reactor trip) actuated by the monitoring of parameters related directly to thermal margin (e.g., the OTΔT trip, the low thermal margin trip, or low DNBR trip). The review should encompass claims that automatic reactor protection is available from specified trip signals in addition to the trip signal credited in the licensing basis analysis. The review should verify whether such signals can provide adequate, timely protection. GDC 26 requirements provide assurance of appropriate margins to accommodate malfunctions of the reactivity control system, including stuck rods, minimizing the possibility