Document: NRC Regulatory Guide
Document ID: 4b34bbdf-f837-4227-9a0d-3f0ad3778b30
Document Type: regulatory_guide
Title: Protection of Nuclear Power Plant Control Room Operators Against an Accidental Chlorine Release (Rev. 1)
Source: NRC Regulatory Guide Division 1
Source URL: https://www.nrc.gov/docs/ML1229/ML12298A134.pdf
Revision Date: 2023-06
Chapter: 
Section ID: RG-1.95
CFR Part: 
CFR Title: 

Content:
leakage dampers or valves installed on the upstream side of recirculation fans or other loca- tions where negative systems pressure exists and where inleakage from chlorine-contaminated outside air is possible. b. Type II control rooms should include the protective features of paragraph a except that the isolation time should be 4 seconds or less rather than 10 seconds or less. c. Type III control rooms should include the protective features of paragraph a except that the normal fresh air makeup rate should be limited to 0.3 air change per hour or less. d. Type IV control rooms should include the protective features of paragraph a except that the isolation time and the normal air exchange rate should be equal to or less than 4 seconds and 0.3 air change per hour, respectively. In addition, the con- trol room isolated air exchange rate should be reduced to 0.015 air change per hour or less (see description of required leak rate verification test in Regulatory Position 5). e. Type V control rooms should include theprotec- tive features of paragraph a with the addition of remote chlorine -detectors located at the chlorine storage and unloading location. These additional detectors should be placed and the detector trip points adjusted so as to ensure detection of either a leak or a container rupture. A detector trip signal should accomplish automatic isolation of the control This is the time interval between the time the chlorine concentration exceeds 5 ppm at the isolation dampers and the time the dampers are completely closed. Note that if the chlorine detectors are upstream from the isolation dampers, credit will be allowed for the travel time between the detectors and the dampers. room before chlorine arrives at the isolation dampers. The detector trip signal should also set off an alarm and provide a readout in the control room. An alternative to the installation of remote detectors would be to provide an isolation system using local detectors but having an