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:
contents of the chlorine container and an al- lowable chlorine concentration in the control room of 45 mg/m 3, the toxicity limit, for two minutes. The initial cloud dimensions assume expansion of the chlorine gas into a spherical cloud having. a Gaussian concentration gradient. Dispersion of the cloud was calculated using the instantaneous release diffusion model appearing in Appendix B of Regulatory Guide 1.78. For those cases where the control room was located a short distance from the release point and the amount of chlorine release was small, the model was adjusted to allow for additional dispersion in the vertical direction by assuming uniform mixing between the ground and the elevation of the fresh air Two minutes is considered sufficient time for a trained operator to put a self-contained breathing apparatus into operation, if these are to be used. inlet (a 15-meter elevation from ground level was used). The maximum allowable chlorine weights were determined by using worst case conditions for calculating the control room concentrations (signifi- cant parameters being wind speed, cloud dimensions, normal air exchange rate, time to isolate, and isolated air exchange rate). For certain control room characteristics and high wind speed, the maximum operator exposure occurs before isolation. For other cases with other control room characteristics and low wind speed, the maximum operator exposure occurs two minutes after isolation and is primarily due to in- filtration. The six control room types listed in the table span the expected range of protections required for most plants. Other combinations of the signifi- cant parameters are possible, but those listed in the table should provide sufficient guidance for most cases. This guide does not address the protection of in- dividuals either outside the control room or within the control room but not directly involved in reactor operations. Breathing apparatus should be provided and be readily accessible throughout