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:
ross-connect provides an alternate injection path for the train that remains in service. This configuration mitigates the effect of degraded safety injection caused by steam entrainment during a LOCA, when the only available LPSI connection (considering one is unavailable because of a single failure, another is out for maintenance, and another train feeds the broken loop) is adjacent to the broken leg. During such maintenance activities, the motor-operated valves for both cross- connects are secured open (breakers racked out) for protection against active single failures. The component cooling water system is the cooling medium for the LPSI heat exchangers (all four trains), the MPSI pump motor coolers (all four trains), and the LPSI pump motor and seal coolers for trains 2 and 3. The safety chilled water system is the cooling medium for the LPSI pump motor and seal coolers for trains 1 and 4. The essential service water system serves as the final cooling medium, rejecting the heat transferred from the component cooling water system to the ultimate heat sink. Electrical divisions 1 through 4 power the four SIS trains, respectively. Each electrical division is a separate and independent power supply housed and protected in its own shield building. Its assigned emergency diesel generator in the event of a loss of offsite power supplies each electrical division. A.4 AP1000 Passive Core Cooling System The ECCS for the AP1000 is the passive core cooling system (PCCS). The primary function of the PCCS is to provide emergency core cooling after postulated design-basis events. To accomplish this primary function, the PCCS is designed to perform the functions described in the following sections. A.4.1 Safety Injection System Figure A.4-1 shows the SIS, which provides safety injection 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