Document: NUREG-0800
Document ID: a28650b3-fa03-428d-a2bd-4a27f583710b
Document Type: srp
Title: NUREG-0800
Source: NUREG-0800
Source URL: https://www.nrc.gov/docs/ML0520/ML052070484.pdf
Revision Date: 2023-06
Chapter: 6
Section ID: 6
CFR Part: 
CFR Title: 

Content:
or BWR Containments." 1g. NUREG-0978, "Mark III LOCA-Related Hydrodynamic Load Definition." DRAFT Rev. 7 - April 1996 6.2.1.1.C-14 Appendix A to SRP Section 6.2.1.1.C (FormerlyFormally Appendix I) 107 Steam Bypass for Mark I, II, and III Containments A. Background This appendix pertains to steam bypass from the drywell to the suppression pool air volume in the Mark I, II, and III containment design. In a pressure suppression-type containment, steam released from the primary system following a postulated LOCA is collected in the containment drywell volume and directed through connecting vents to the suppression pool in the containment wetwell volume and steam is condensed as it enters into the suppression pool. Thus, no steam enters the wetwell air volume. The potential exists for steam to bypass the suppression pool by leakage through the vacuum breakers or directly from leak paths in the drywell-to-suppression chamber vent pipes, the diaphragm-wall seal around diaphragm penetrations or cracks in the concrete diaphragm. The capability for steam bypass for small primary system breaks in the Mark I, II and III containment design are as follows: the Mark I design is of the order of 18.6 cm (0.02 ft ),; the 2 2 108 capability of the Mark II containment is approximately 46.5 cm (.050.5 ft ) , and the Mark III 2 2 109 design has a capability of A/ K = 929 cm (1 ft ). 2 2 110 This steam bypass position was developed to assure that containment integrity will be maintained following the onset of small breaks in the drywell. This can be achieved by upgrading the wetwell spray to an engineered safety feature and requiring automatic actuation of the wetwell spray 10 minutes following a break (Mark II and Mark III). To provide assurance that the bypass leakage is not substantially increased over the life of a plant, this position includes requirements for leakage tests. The leakage tests include both periodic low-pressure leak tests and a preoperational high-pressure leak test