Document: NUREG-0800
Document ID: c23d52ec-d83f-4468-b35e-e8c97fdf2f09
Document Type: srp
Title: CONTAINMENT ISOLATION SYSTEM
Source: NUREG-0800
Source URL: https://www.nrc.gov/docs/ML0520/ML052070461.pdf
Revision Date: 2023-06
Chapter: 6
Section ID: 6.2.4
CFR Part: 
CFR Title: 

Content:
the use and positioning of isolation valves. GDC 56 applies to this SRP because the reviewer evaluates the containment isolation system to ensure (a) that there is no direct communication between the containment atmosphere and the plant environs or (b) if there is direct communication (such as that which occurs during containment purging or venting), that the line in question can be reliably isolated. This assurance is provided by specifying requirements for isolation valves (i.e., locked-closed, automatic, or a combination of locked-closed and automatic) on both sides of the containment barrier. Isolation valves outside the containment should be located as close to the containment as is practical. Upon loss of actuating power, automatic valves are to take the position that provides greater safety. BTP CSB 6-4 contains specific requirements for containment purge and vent valves, providing a high degree of assurance that these valves will isolate reliably under accident conditions. Meeting the requirements of GDC 56 provides assurance that lines penetrating the containment and connected to the containment atmosphere will not be a source of excessive offsite radiation doses due to either line rupture or failure of a valve to close.70 8. Compliance with GDC 57, "Closed System Isolation Valves," requires that each line penetrating the primary reactor containment which is neither part of the reactor coolant pressure boundary nor connected directly to the containment atmosphere must have 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 to ensure that there is no direct communication between the fluids in the closed system and the plant environment. This assurance is provided by specifying