Document: NRC Regulatory Guide
Document ID: ceaeb6d7-d85a-46d3-a1b6-70059a498965
Document Type: regulatory_guide
Title: 12/2001 (Rev. 1)
Source: NRC Regulatory Guide Division 1
Source URL: https://www.nrc.gov/docs/ML0131/ML013100014.pdf
Revision Date: 2023-06
Chapter: 
Section ID: RG-1.78
CFR Part: 
CFR Title: 

Content:
g chlorine, that should be considered in the control room habitability evaluation. Combining the two guides eliminates certain duplication of efforts for licensees in submitting their applications and streamlines the NRC staff review process. C. REGULATORY POSITION The following guidance is provided for evaluating the habitability of a nuclear power plant control room during a postulated hazardous chemical release. 1. HAZARD SCREENING Whether a chemical source (stationary or mobile) constitutes a hazard that requires a control room habitability evaluation depends on the quantity of chemical released, the distance from the plant, prevailing meteorological conditions, the inleakage characteristics of the control room, and the applicable toxicity limits. Licensees are encouraged to conduct periodic surveys of stationary and mobile sources of hazardous chemicals in the vicinity of their plant sites to keep the site-specific inventories up to date. The following screening criteria identify the release events that need not be considered further for control room habitability evaluation. 1.1 Screening Criteria for Stationary Sources Chemicals stored or situated at distances greater than 5 miles from the plant need not be considered because, if a release occurs at such a distance, atmospheric dispersion will dilute and disperse the incoming plume to such a degree that either toxic limits will never be reached or there would be sufficient time for the control room operators to take appropriate action. In addition, the probability of a plume remaining within a given sector for a long period of time is quite small. 1 For explosive hazards, a lower number of shipments would be considered frequent since the effects of an explosion would be independent of wind direction. 1.78-4 If sources of hazardous chemicals such as those listed in Table 1 are known or projected to be present within a 5-mile radius of the plant, and in quantities less than those shown in the table of examples