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:
to assureensure site boundary exposures 51 less than those calculated for the design basis accidents even if exfiltration occurs. Acceptance of other fission product control structures for collection and control of postaccident releases will be determined following consultation with the CSBSCSB and the SEBECGB, on a case-by-case basis. The leakage and 52 53 filtration rates of such structures are acceptable provided that the offsite doses calculated by PERB under SRP Section 15.6.5 will meet the dose guidelines of 54 10 CFR Part 100 and provided that the preoperational testing and appropriate technical specifications are acceptable. Other criteria include specifications for intake and return headers on recirculation systems. These should be placed as far away from each other as practical. The return header should provide a wide distribution over the secondary containment. The purpose of this placement is to assureensure some degree of mixing of the 55 return flow in the secondary containment volume before it is again drawn into the system intake. With judicious placement, up to 50% mixing may be assumed. A claim for greater than 50% mixing must be supported by the applicant to the satisfaction of the staff. Spacing between intake and return headers is reviewed on a case-by-case basis. Adjustments in the mixing fraction to less than 50% may be indicated by some designs. Past practice has been to allow mixing in 50% of the volume between — and within 3 or 6 meters (10 or 20 feet) of — the inlet and 56 outlet headers if both have distributed openings or if one has distributed openings and the other is at the top of the containment. 3. Partial Dual Containment Partial dual containments must meet the same basic requirements as those for secondary containments in order to be given credit for fission product holdup and removal. The fraction of leakage source considered to be treated by such partial fission products control structures is determined after consultation