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:
ted time. In this arrangement a flow rate of 400 to 600 cfm is provided from compressed air containers for about one hour to prevent inleakage. It is used in systems having containments whose internal atmospheric pres- sure becomes negative within an hour after a DBA (subatmospheric containments). b. The input parameters to the radiological dose model are determined (see Item 5 below). The parameters are emergency zone volume, filter efficiency filtered makeup air flow rate, unfiltered inleakage (infiltration), and filtered recirculated air flow 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. ASB will determine if the system 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 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 deter- mine how much unfiltered air can be tolerated. 6.4-7 Rev. 2 - July 1981 d. The following information may be used in evaluating the specific system types (see Reference 6 for further discussion): (1) Zone isolation with filtered incoming air and positive pres- sure. These systems may not be sufficiently effective in pro- tecting 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 (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