Document: NUREG-0800
Document ID: 9f13abda-ee55-4fa1-8276-db55ac2094ef
Document Type: srp
Title: CONTROL ROOM HABITABILITY SYSTEM
Source: NUREG-0800
Source URL: https://www.nrc.gov/docs/ML0520/ML052070449.pdf
Revision Date: 2023-06
Chapter: 6
Section ID: 6.4
CFR Part: 
CFR Title: 

Content:
nlets. Thus, in most cases only plants with high stacks (about 100 meters) would meet GDC 19 with this system. (2) Zone isolation with filtered recirculated air. These systems have a greater potential for controlling iodine than those having once-through filters. IPFs ranging from 20 to over 150 can be achieved. These are the usual designs for plants having vents located at containment roof level. A system having a recirculation rate of 2400 L/s (5000 cfm) and a filter 53 efficiency of 95% would be rated as follows: Infiltration L/s (cfm) IPF 54 ** 100 (200) 25 55 50 (100) 49 56 24 (50) 96 57 12 (25) 191 58 Infiltration should be determined conservatively. The calculated or measured gross leakage is used to determine the infiltration rate that will be applied in the evaluation of the radiological consequences of postulated accidents. This rate is determined as follows: (i) the leakage from the control room when pressurized to 3.2-mm (1/8-in) water gauge is calculated on the basis of the gross 59 leakage data. One-half of this value is used to represent the base infiltration rate. Component leak rates may be used to calculate gross leakage (see, for example, Refs. 10 and 11). Normally 5 L/s (10 cfm) infiltration is assumed for conservatism. This flow could be *** reduced or eliminated if the applicant provides assurance that backflow (primarily as a result of ingress and egress) will not occur. This may mean installing two-door vestibules or equivalent. DRAFT Rev. 3 - April 1996 6.4-12 (ii) The base infiltration rate is augmented by adding to it the estimated contribution from opening and closing of doors associated with such activities as required by the plant emergency plans and procedures. Normally, 5 L/s (10 cfm) is used for this 60 additional contribution. (iii) An additional factor that is used to modify the base infiltration rate is the enhancement of the infiltration occurring at the dampers or valves upstream of recirculation fans. When closed, these dampers