Document: NUREG-0800
Document ID: 55688d47-80f6-498a-af38-5bfb9d7420aa
Document Type: srp
Title: Revision 3 - March 2007
Source: NUREG-0800
Source URL: https://www.nrc.gov/docs/ML0707/ML070740004.pdf
Revision Date: 2023-06
Chapter: 6
Section ID: 6
CFR Part: 
CFR Title: 

Content:
determine the time periods during which these threshold conditions exist. Determination of the duration of periods of positive pressure within the secondary containment should be based on analyses of the secondary containment pressure response to postulated LOCAs within the primary containment and the effectiveness of the depressurization systems. The evaluation of bypass leakage identifies bypass leakage paths and determines leakage rates. Potential bypass leakage paths are formed by penetrations which pass through both the primary and secondary containment boundaries and which may include a number of barriers to leakage (e.g., isolation valves, seals, gaskets, and welded joints). While these barriers reduce 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 that of the containment leakage tests required by 10 CFR Part 50, Appendix J. B. BRANCH TECHNICAL POSITION 1. A secondary containment structure should enclose the primary containment structure completely with the exception of such parts imbedded in the soil as the base mat of the containment structure. For partial dual containment concepts, leak rates less than the design leak rate of the primary containment should not be used in the calculation of the radiological consequences of a LOCA unless the magnitude of unprocessed leakage can be adequately demonstrated. Quantitative credit for leakage collection in a partial-dual containment will be reviewed case by case. 2. Direct leakage from the primary containment to the environment, equivalent to the design leak rate of the primary containment, should be assumed to occur following a BTP 6-3-3 Revision 3 - March 2007 postulated LOCA whenever the secondary containment volume is at a "positive" pressure (i.e., greater than -0.063 kPa (-0.25 inches water gauge)). Positive pressure periods should be