Document: NUREG-0800
Document ID: 919b8fa0-8b11-41bd-9694-2c62120b843b
Document Type: srp
Title: Revision 7 - March 2007
Source: NUREG-0800
Source URL: https://www.nrc.gov/docs/ML0636/ML063600403.pdf
Revision Date: 2023-06
Chapter: 6
Section ID: 6
CFR Part: 
CFR Title: 

Content:
iaphragm-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 cm2 (0.02 ft2), the capability of the Mark II containment is approximately 46.5 cm2 (.05 ft2), and the Mark III design has a capability of A//K = 929 cm2 (1 ft2). 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 (Mark II and Mark III containments). In addition, Mark I containments have been operating with a positive pressure differential between the drywell and wetwell which provides a mechanism for continuously monitoring the amount of bypass leakage. B. Position The system used to quench steam bypassing the suppression pool should be designed such that the steam bypass capability for small breaks satisfies the criteria described below. Any proposed alternative criteria must be suitably justified by the applicant and reviewed by the NRC staff. 1. Bypass Capability (Mark II and Mark III) The containment should have a steam bypass capability for small breaks of the order of: 46.5 cm2 (.05 ft2) (A//K) for Mark II plants and 929 cm2 (1 ft2) (A//K) for Mark III plants. a. Containment Wetwell Sprays The wetwell spray system, including the electrical instrumentation and controls, should meet the standards appropriate to engineered safety features; i.e., quality, redundancy,