Document: NRC Regulatory Guide
Document ID: c256f223-ee35-43e0-82e7-aa7b14469259
Document Type: regulatory_guide
Title: Preoperational Testing of Emergency Core Cooling Systems for Pressurized Water Reactors + HISTORY - HISTORY DG-1253 , Proposed Revision 2 (Rev. 2)
Source: NRC Regulatory Guide Division 1
Source URL: https://www.nrc.gov/docs/ML1101/ML110110480.pdf
Revision Date: 2023-06
Chapter: 
Section ID: RG-1.79
CFR Part: 
CFR Title: 

Content:
ection to the RCS to provide adequate core cooling for the complete range of LOCAs, up to and including the double-ended rupture of the largest primary loop RCS piping. Appendix A to DG-1253, Page A-4 Figure A.4-1. AP1000 Passive Safety Injection System of the PCCS A.4.2 Emergency Core Decay Heat Removal System Figure A.4-2 shows the system that provides core decay heat removal during transients, accidents, or whenever normal heat removal paths are lost. This heat removal function is available for RCS conditions, including shutdowns. During refueling operations, when the IRWST is drained into the refueling cavity, other passive means of core decay heat removal are used. A.4.3 Reactor Coolant System Emergency Makeup and Boration This function provides RCS makeup and boration during transients or accidents, when the normal RCS makeup supply from the chemical and volume control system is unavailable or is insufficient. Appendix A to DG-1253, Page A-5 Figure A.4-2. AP1000 Passive Decay Heat Removal System of the PCCS A.4.4 Containment pH Control This function provides chemical addition during post accident conditions to establish chemistry control of the water covering the core. This ensures that highly radioactive compounds do not evolve from the fuel cladding and prevents corrosion of containment equipment during long-term post accident conditions. The PCCS is designed to operate without the use of active equipment such as pumps and alternating current power sources. The PCCS depends on reliable passive components and processes, such as gravity injection and the expansion of compressed gases. The PCCS does require a one-time alignment of valves on actuation of the specific components.