Document: NUREG-0800
Document ID: 8c2fce42-281a-4a50-9de7-513df024f27c
Document Type: srp
Title: CONTROL ROOM HABITABILITY SYSTEM
Source: NUREG-0800
Source URL: https://www.nrc.gov/docs/ML0523/ML052340712.pdf
Revision Date: 2023-06
Chapter: 6
Section ID: 6.4
CFR Part: 
CFR Title: 

Content:
52 (Ref. 5). An IPF of 100 requires deep bed filters. Such systems are likely to provide a sufficient reduction in iodine concentration only if the source is at some distance from the inlets. Thus, in most cases only plants with high stacks (about 100 meters) would meet GOC 19 (Ref. 3) 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 5000 cfm and a filter efficiency of 95% would be rated as follows: Infiltration (cfm) IPF* 200 25 100 49 50 96 25 191 *Within the range of interest, the iodine protection factor is directly proportional to recirculation flow rate times efficiency. Infiltration should be determined conservatively. The calcu- lated 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: (1) The leakage from the control room when pressurized to 1/8-inch water gauge is calculated on the basis of the gross 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, References 9 and 10). (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 10 cfm is used for this additional contribution. (iii) An additional factor that is used to modify the base infiltration rate is the enhancement of the infiltration 6.4-8 Rev. 2 - July 1981 occurring at the dampers or valves upstream of recircula- tion fans. When closed, these dampers typically are exposed to a pressure