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:
ineered 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 "safe" position. Normally this position would be the postaccident valve position. For lines equipped with motor-operated valves, a loss of actuating power will leave the affected valve in the "as is" position, which may be the open position; however, redundant isolation barriers ensure that the isolation function for the line is satisfied. All power-operated isolation valves should have position indication in the main control room. k. To improve the reliability of the isolation function, which is addressed in General Design Criterion GDC 54, Item II.E.4.2 of NUREG-0737 and 44 NUREG-071810 CFR 50.34(f)(2)(xiv) requires that the containment setpoint pressure 45 that initiates containment isolation for nonessential penetrations be reduced to the minimum value compatible with normal operating conditions. l. There should be diversity in the parameters sensed for the initiation of containment isolation to satisfy the requirement of General Design Criterion GDC 54 for reliable isolation capability. m. To improve the reliability of the isolation function, which is addressed in General Design Criterion 5456 (GDC 56), system lines which provide an open path from the 46 containment to the environs (e.g., purge and vent lines which are addressed in Item II.E.4.2 of NUREG-0737 and NUREG-071810 CFR 50.34(f)(2)(xiv) ) should be 47 equipped with radiation monitors that are capable of isolating these lines upon a high radiation signal. A high radiation signal should not be considered one of the diverse containment isolation parameters. DRAFT Rev. 3 - April 1996 6.2.4-8 n. In meeting the requirements of General Design Criterion GDC 54, the performance capability of the isolation function should reflect the importance to safety of isolating system lines. Consequently, containment