Document: NUREG-0800
Document ID: 1c401e6c-8c2d-47df-b05f-2978939cbd15
Document Type: srp
Title: CONTROL ROOM HABITABILITY SYSTEM
Source: NUREG-0800
Source URL: https://www.nrc.gov/docs/ML0705/ML070550069.pdf
Revision Date: 2023-06
Chapter: 6
Section ID: 6.4
CFR Part: 
CFR Title: 

Content:
/s (400 to 600 cfm) is provided from compressed air containers for about 1 hour to assist in preventing inleakage. It is used in systems having containments whose internal atmospheric pressure becomes negative within an hour after a DBA (subatmospheric containments). B. The input parameters to the radiological dose model are determined. 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. As noted earlier the reviewer 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 determine how much unfiltered air can be tolerated. D. The iodine protection factor (IPF) methodology of Reference 9 may not be adequately conservative for all DBAs and control room arrangements because it models a steady-state control room condition. Since many analysis parameters change over the duration of the event, the IPF methodology should only be used with caution. E. The following information may be used in evaluating the specific system types (see Ref. 9 for further discussion): i. 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 3 Within the range of interest, the iodine protection factor is directly proportional to recirculation flow rate multiplied by efficiency. 6.4-12 Revision 3 - March 2007 time-integrated concentration of iodine outside over the time-integrated concentration