Document: NUREG-0800
Document ID: 7e0d3b3e-62c3-4492-ba89-6cebb4e82234
Document Type: srp
Title: SECONDARY CONTAINMENT FUNCTIONAL DESIGN
Source: NUREG-0800
Source URL: https://www.nrc.gov/docs/ML0523/ML052340701.pdf
Revision Date: 2023-06
Chapter: 6
Section ID: 6.2.3
CFR Part: 
CFR Title: 

Content:
.g. (water gauge), to account for wind loads and the uncertainty in the pressure measurements. Whenever the pressure in the secondary containment volume exceeds -0.25 in. w.g., the leakage- prevention function of the secondary containment is assumed to be negated. Since leakage from the secondary containment during positive pressure periods cannot-be determined, the conservative assumption is made that, all primary containment leakage is released directly to the environment during these time periods. Therefore, it becomes necessary to determine the time periods during which these threshold conditions exist. The existence and duration of periods of positive pressure within the secondary containment should be based on analyses of the secondary containment pressure response to postulated loss-of-coolant accidents within the primary containment and the effectiveness of the depressurization systems. 6..2.3-9 Rev. Z - July 1981 The evaluation of bypass leakage involves both the identification of bypass leakage paths and the determination of leakage rates. Potential bypass leakage paths are formed by penetrations which pass through both the primary and secondary containment boundaries. Penetrations that pass through both the primary and secondary containment may include a number of barriers to leakage (e.g., isolation valves, seals, gaskets, and welded joints). While each of these barriers aid in the reduction of leakage, they do not necessarily eliminate leakage. Therefore, in identifying potential leakage paths, each of these penetrations should be considered, together with the capability to test them for leakage in a manner similar to the containment leakage tests required by Appendix J to 10 CFR Part 50. B. BRANCH TECHNICAL POSITION 1. A secondary containment structure should completely enclose the primary containment structure, with the exception of those parts of the primary containment that are imbedded in the soil, such as the base mat of the containment structure.