Document: NUREG-0800
Document ID: 632e6c59-03bd-4648-b0b3-e8b2efd6fa04
Document Type: srp
Title: CONTAINMENT ISOLATION SYSTEM
Source: NUREG-0800
Source URL: https://www.nrc.gov/docs/ML0703/ML070380197.pdf
Revision Date: 2023-06
Chapter: 6
Section ID: 6.2.4
CFR Part: 
CFR Title: 

Content:
C 57, "Closed System Isolation Valves," requires, for each line penetrating the primary reactor containment which is neither part of the reactor coolant pressure boundary nor connected directly to the containment atmosphere, at least one containment isolation valve that is automatic, locked-closed, or capable of remote-manual operation. Isolation valves must be located on the outside of the containment barrier as close to the containment as is practical. GDC 57 applies to this SRP section because the reviewer evaluates the containment isolation system for whether there is no direct connection between the fluids in the closed system and the plant environment. Assurance is by specific requirements for a closed system and for an isolation valve that is locked-closed, automatic, or capable of remote-manual operation. A single valve is specified because the system is closed; hence, failure of the valve to close would not, by itself, allow contact between fluids in the closed system and the plant environment. Compliance with GDC 57 requirements provides reasonable assurance that lines penetrating the containment and connected to closed systems will not be sources of excessive offsite radiation doses due to line rupture or failure of a valve to close. 9. 10 CFR 50.63 requires that all light-water-cooled nuclear power plants be able to withstand and recover from an SBO, that necessary systems be capable of cooling the core, and that appropriate containment integrity be maintained in SBO. Guidance for compliance with 10 CFR 50.63 is provided in RG 1.155. As many safety systems necessary to support safe operation and shutdown of the reactor depend on alternating current (AC) power, the consequences of an SBO could be severe, particularly if the integrity of barriers to prevent the release of fission products (e.g., fuel cladding, reactor coolant pressure boundary, containment) are not maintained throughout the event and its recovery period. The containment isolation system,