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:
rs to the radiological dose model are determined (see Item 5 below). The parameters are emergency zone volume, filter efficiency, filtered makeup airflow rate, unfiltered inleakage (infiltration), and filtered recirculated airflow rate. c. The ventilation system components and the system layout diagrams are examined. The review will be coordinated with the ASB in particular if there are questions pertaining to the system design. ASBThe reviewer will determine if the system 52 meets the single failure criterion as well as other safety requirements under SRP Section 9.4.1. Damper failure and fan failure are especially important. The review should confirm that the failure of isolation dampers on the upstream side Within the range of interest, the iodine protection factor is directly proportional to ** recirculation flow rate times efficiency. 6.4-11 DRAFT Rev. 3 - April 1996 of fans will not result in too much unfiltered air entering the control room. The radiation dose and toxic gas analysis results are used to determine how much unfiltered air can be tolerated. d. The following information may be used in evaluating the specific system types (see Ref. 6 for further discussion): (1) Zone isolation with filtered incoming air and positive pressure. These systems may not be sufficiently effective in protecting against iodine. The staff allows an iodine protection factor (IPF), which is defined as the time-integrated concentration of iodine outside over the time-integrated concentration within the emergency zone, of 20 to 100 for filters built, maintained, and operated according to Regulatory Guide 1.52. 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 GDC 19 with this system. (2) Zone isolation with filtered recirculated air. These systems have a greater potential