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:
the dose guidelines of 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 ensure some degree of mixing of the 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 outlet headers if both have distributed openings or if one has distributed openings and the other is at the top of the containment. Partial dual containments should meet the same basic criteria as secondary containments in order to be given credit for fission product holdup and removal. The fraction of leakage source considered to be controlled by such partial fission products control structures is determined after consultation with the SCSB reviewer on a case-by-case basis. 4. Other Fission Product Control Systems. Fission product retention credit may be taken by the applicant for other systems- e.g., containment spray systems as evaluated in SRP Section 6.5.2, pressure suppression pools as evaluated in SRP Section 6.5.5, and 6.5.3-6 Revision 3 - March 2007 filtration and adsorption units as described in Regulatory Guide 1.52. Justification for fission product retention systems should include analytical bases addressing the important physical and chemical variables of