Document: NRC Regulatory Guide
Document ID: 8291b9eb-e4a7-4806-8b5b-1deca2ff1fe2
Document Type: regulatory_guide
Title: Control Room Habitability at Light-Water Nuclear Power Reactors
Source: NRC Regulatory Guide Division 1
Source URL: https://www.nrc.gov/docs/ML0207/ML020790125.pdf
Revision Date: 2023-06
Chapter: 
Section ID: RG-1.196
CFR Part: 
CFR Title: 

Content:
EILLANCE FREQUENCY SR 3.7.10.1 Operate each CREFS train for [ 10 continuous hours with the heaters operating or (for systems without heaters)  15 minutes]. 31 days SR 3.7.10.2 Perform required CREFS filter testing in accordance with the [Ventilation Filter Testing Program (VFTP)]. In accordance with [VFTP] SR 3.7.10.3 Verify each CREFS train actuates on an actual or simulated actuation signal. [18] months SURVEILLANCE REQUIREMENTS (continued) CREFS 3.7.10 SURVEILLANCE FREQUENCY WOG STS Rev. 2, 04/30/01 A-5 SR 3.7.10.4 Verify one CREFS train can maintain a positive pressure of  [0.125] inches water gauge, relative to the adjacent [turbine building] during the pressurization mode of operation at a makeup flow rate of  [3000] cfm. that unfiltered inleakage into the control room envelope while in the limiting radiological mode of operation is ______ cfm. [24] months [18] months on a STAGGERED TEST BASIS [Reviewers Note: Based on actual industry-integrated and plant-specific experience from the initial and first 24 months follow- on testing, the NRC staff will work with industry to develop an appropriate performance based frequency] B 3.7 PLANT SYSTEMS B 3.7.10 Control Room Emergency Filtration System (CREFS) CREFS 3.7.10 A-6 BASES BACKGROUND The CREFS provides a protected environment from which operators can control the unit following an uncontrolled release of radioactivity[, chemicals, or toxic gas]. The CREFS consists of two independent, redundant trains that recirculate and filter the control room air. Each train consists of a prefilter or demister, a high efficiency particulate air (HEPA) filter, an activated charcoal adsorber section for removal of gaseous activity (principally iodines), and a fan. Ductwork, valves or dampers, and instrumentation also form part of the system, as well as demisters to remove water droplets from the air stream. A second bank of HEPA filters follows the adsorber section to collect carbon fines and provide backup in case of