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:
rance that the containment isolation system will reliably isolate piping systems penetrating containment, as required.68 6. Compliance with General Design Criterion (GDC 55), "Reactor Coolant Pressure Boundary Penetrating Containment," requires that each line belonging to the reactor coolant pressure boundary and penetrating the primary reactor containment meet specified criteria relative to the use and positioning of isolation valves. GDC 55 applies to this SRP section because the reviewer evaluates the containment isolation system to ensure that there is no direct communication between the primary coolant and the plant environs. 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 6.2.4-13 DRAFT Rev. 3 - April 1996 actuating power, automatic valves are to take the position that provides greater safety. Other requirements (e.g., those related to higher quality in design, additional inservice inspection, and protection against severe natural phenomena) may be imposed based on the use and physical characteristics of the plant-site environs. Meeting the requirements of GDC 55 provides assurance that lines penetrating the containment and connected to the reactor coolant system will not be a source of excessive offsite radiation doses due to either line rupture or failure of a valve to close.69 7. Compliance with GDC 56, "Primary Containment Isolation," requires that each line that connects directly to the containment atmosphere and penetrates the primary reactor containment must meet specified criteria relative to 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