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:
ized and released over an extended period of time. As a result of the cloud formed by the release from such an acci- dent, the chlorine concentration inside the control room might increase rapidly. In the absence of special design measures to limit the buildup within the con- trol room, the operators might be incapacitated before they are able to don breathing apparatus. Adequate protection of the control room operators against the types of accidental chlorine release discus- sed above will be achieved if features are included in the plant design to (1) automatically isolate the con- trol room if there is a release, (2) make the control room sufficiently leak tight, and (3) provide equip- ment and procedures for ensuring the use of breathing apparatus by the control room operators. Protection provisions adequate for the large instan- taneous release will also provide protection against the low-leakage-rate release. Staff analysis of control room designs and the degree of protection afforded by each design has resulted in criteria for acceptance, as will be discussed in the next section. These criteria are based on the limitation (given in Regulatory Guide 1.78) that the chlorine concentration within the control room should not exceed 15 ppm by volume (45 mg/m 3) within two minutes after the operators are made aware of the presence of chlorine.' This concentration, the toxicity limit, is the maximum concentration that can be tolerated for two minutes without physical incapacitation of an average human (i.e., severe coughing, eye burn, or severe skin irritation). Table 1 gives the maximum allowable weight of a single container of chlorine as a function of distance from the control room for various control room types. It is based on an instantaneous release of 25% of the 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