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:
ccident LOCA. Sealed-closed isolation valves should be 40 under administrative control to ensure that they cannot be inadvertently opened. Administrative control includes mechanical devices to seal or lock the valve closed, or to prevent power from being supplied to the valve operator. 6.2.4-7 DRAFT Rev. 3 - April 1996 g. Relief valves may be used as isolation valves provided the relief setpoint is greater than 1.5 times the containment design pressure. h. Item II.E.4.2 of NUREG-0737 and NUREG-071810 CFR 50.34(f)(2)(xiv) requires that 41 systems penetrating the containment be classified as either essential or nonessential. Regulatory Guide 1.141 will containReference 23 contains guidance on the 42 classification of essential and nonessential systems. Essential systems, such as those described in items b and c above, may include remote-manual containment isolation valves, but provisions should be made to detect possible leakage from the lines outside containment. Item II.E.4.2 of NUREG-0737 and NUREG-071810 CFR 50.34(f)(2)(xiv) also requires that nonessential systems be 43 automatically isolated by the containment isolation signal. i. Isolation valves outside containment should be located as close to the containment as practical, as required by General Design Criteria 55, 56, and 57. j. In meeting the requirements of General Design Criteria 55 and 56, upon loss of actuating power, automatic isolation valves should take the position that provides greater safety. The position of an isolation valve for normal and shutdown plant operating conditions and postaccident conditions depends on the fluid system function. If a fluid system does not have a postaccident function, the isolation valves in the lines should be automatically closed. For engineered safety features or engineered safety feature-related systems, isolation valves in the lines may remain open or be opened. The position of an isolation valve in the event of power failure to the valve operator should be the