Document: NUREG-0800
Document ID: 91a12934-f0d9-4573-ad3b-553ab75dabc0
Document Type: srp
Title: FISSION PRODUCT CONTROL SYSTEMS AND STRUCTURES
Source: NUREG-0800
Source URL: https://www.nrc.gov/docs/ML0636/ML063600408.pdf
Revision Date: 2023-06
Chapter: 6
Section ID: 6.5.3
CFR Part: 
CFR Title: 

Content:
h subatmospheric pressure at some time less than 30 days after the accident, the same organization should verify the time necessary to reach subatmospheric pressure. 2. Secondary Containment Design A. The design of the secondary containment is reviewed to determine how it should be modeled for the dose calculations. The reviewer also ascertains that the 6.5.3-8 Revision 3 - March 2007 applicant has considered the question of potential exfiltration from regions of the secondary containment under varying wind conditions, especially if the structure has a leakage rate greater than 100% per day. The anticipated leakage rate from each region is noted (see example of worksheet, Table 6.5.3-2), and special attention is paid to the accuracy of the proposed leakage testing if the leakage rates are less than 10% per day. (No facility reviewed to date has a proposed secondary containment leakage rate of less than 10% per day. Experience indicates that 10% per day may be difficult to achieve in actual practice.) B. The boundary of the secondary containment is determined. Usually, the secondary containment boundary is composed of more than one region e.g., a shield building (concrete) or enclosure building (metal siding) around the primary containment and all or parts (emergency core cooling pump rooms, etc.) of the auxiliary building. These regions may be serviced by one or more ventilation systems. 3. Other Fission Product Control Systems A. For PWR containments and BWR MARK III containments, the annular region between the shield building or enclosure building and the primary containment may be held at a negative pressure relative to adjacent areas by a vacuum exhaust system during normal operation. Since this system is used during normal operation, it may appear in the SAR under auxiliary systems. The exhaust system may also treat the auxiliary building regions that are part of the secondary containment, but if these regions are maintained at a negative pressure during normal