Document: NUREG-0800
Document ID: 6c5a07e2-91cf-49ae-a450-62551ed6bcef
Document Type: srp
Title: CONTAINMENT ISOLATION SYSTEM
Source: NUREG-0800
Source URL: https://www.nrc.gov/docs/ML0523/ML052340703.pdf
Revision Date: 2023-06
Chapter: 6
Section ID: 6.2.4
CFR Part: 
CFR Title: 

Content:
coolant system, the secondary coolant system, and the containment, which generate containment isolation sig- nals. Since plant designs differ in this regard and many different combinations of signals from the plant protection system are used to initiate containment isolation, the CSB considers the arrangement proposed on an individual basis in determining the overall acceptability of the containment isolation signals. The CSB will use the guidance presented in Item II.E.4.2 of NUREG-0737 for its review of the containment setpoint pressure that initiates containment isolation for nonessential penetrations. This pressure setpoint should be the minimum value that is compatible with normal operating conditions. The CSB reviews isolation valve closure times. In general, valve closure times should be less than one minute, regardless of valve size. (See the acceptance criteria for valve closure times in subsection II of this SRP section.) Valves in lines that provide a direct path to the environs, e.g., the containment purge and ventilation system lines and main steam lines for direct cycle plants, may have to close in times much shorter than one minute. Closure times for these valves may be dictated by radiological dose analyses or ECCS performance con- siderations. The CSB will request the AEB or RSB to review analyses justifying valve closure times for these valves as necessary. The CSB determines the acceptability. of the use of closed systems inside contain- ment as isolation barriers by comparing the system designs to the acceptance criteria specified in subsection II. of this SRP section. The MEB and SEB have review responhibility for the structural design of the containment internal structures and piping systems, including restraints, to assure that the containment isolation provisions are adequately protected 6.2.4-9 Rev. 2 - July 1981 against missiles, pipe whip, and earthquakes. The CSB determines that for all containment isolation provisions, missile