Document: NUREG-0800
Document ID: e3249d77-0411-430a-9793-06aea8669075
Document Type: srp
Title: FISSION PRODUCT CONTROL SYSTEMS AND STRUCTURES
Source: NUREG-0800
Source URL: https://www.nrc.gov/docs/ML0520/ML052070474.pdf
Revision Date: 2023-06
Chapter: 6
Section ID: 6.5.3
CFR Part: 
CFR Title: 

Content:
o ascertains that the 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 and other fission product control structures are 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 treated by one or more ventilation systems. c. 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 which are part of the secondary containment, but if these regions are maintained at a negative pressure during normal operation, it is most 6.5.3-9 DRAFT Rev. 3 - April 1996 likely done with the auxiliary building ventilation system. Both theThe ability of the vacuum exhaust and auxiliary building ventilation systems 84 fall under the purview of the ASBSCSB. The systems' ability to 85 maintain a negative pressure of sufficient margin under varying wind conditions and