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:
r bonnet seals. 6. Sealed-closed barriers may be used in place of automatic isolation valves. Sealed-closed barriers include blind flanges and sealed-closed isolation valves which may be closed manual valves, closed remote-manual valves, or closed automatic valves which remain closed after a LOCA. Sealed-closed isolation valves should be under administrative control so they cannot be opened inadvertently. Administrative control includes mechanical devices to seal or lock the valve closed or to prevent power supply to the valve operator. 7. Relief valves may be used as isolation valves provided the relief setpoint is greater than 1.5 times the containment design pressure. 8. 10 CFR 50.34(f)(2)(xiv) requires that systems penetrating the containment be classified as either essential or nonessential. Reference 26 presents guidance on the classification of systems as essential and nonessential. Essential systems, like those 6.2.4-7 Revision 3 - March 2007 described in items 2 and 3, may include remote-manual containment isolation valves, but there should be provisions for detecting leakage from the lines outside containment. 10 CFR 50.34(f)(2)(xiv) also requires that nonessential systems be isolated automatically by the containment isolation signal. 9. Isolation valves outside containment should be located as close to it as practical, as required by GDCs 55, 56, and 57. 10. To meet the requirements of GDCs 55 and 56, upon loss of actuating power, automatic isolation valves should take the position of greatest safety. The position of an isolation valve for normal and shutdown plant operating and post-accident conditions depends on the fluid system function. If a fluid system has no post-accident function, the isolation valves in the lines should be closed automatically. For engineered safety feature or engineered safety feature-related systems, isolation valves in the lines may remain open or be opened. In a power failure to the valve operator isolation valves should be