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:
es the containment isolation system for whether valves in piping systems that penetrate the containment are designed to close reliably under accident conditions and prevent the uncontrolled release of radioactive materials. To ensure reliability of these valves, this SRP section provides guidance as to leak detection, redundancy, leakage testing, and functional testing. RGs 1.11 and 1.141 provide guidance acceptable to the staff for isolating instrument lines that penetrate the containment and for fluid systems, respectively. Nonessential lines are isolated automatically by the containment isolation signal. Compliance with GDC 54 requirements provides reasonable assurance that the containment isolation system will isolate piping systems penetrating containment reliably as required. 6. GDC 55, "Reactor Coolant Pressure Boundary Penetrating Containment," requires that each line of the reactor coolant pressure boundary penetrating the primary reactor containment meet specified criteria for 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 connection between the primary coolant and the plant environs. This assurance is provided by specific 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 must take the position of greatest safety. Other requirements (e.g., those for higher quality in design, additional inservice inspection, and protection against severe natural phenomena) may be imposed based on use and physical characteristics of the plant-site environs. Compliance with GDC 55 requirements provides reasonable assurance that lines penetrating the containment and connected to the reactor