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:
tor will take protective measures within 2 minutes (adequate 1.78-7 time to don a respirator and protective clothing) after the detection and, therefore, will not be subjected to prolonged exposure at the IDLH concentration levels. If toxicity limits of released chemicals are not available and no detection instruments are available in the control room for the hazardous chemicals under consideration, the human detection threshold, such as the odor threshold, may be used. 3.2 Accident Types and Release Characteristics Two types of industrial accidents should be considered for each source of hazardous chemicals: maximum concentration accidents and maximum concentration-duration accidents. A maximum concentration accident is one that results in a short-term puff or instantaneous release of a large quantity of hazardous chemicals. An example of this type accident would be the failure of a manhole cover on the chemical container or the outright failure of the container itself. Such failure could occur during the transportation of a container as a result of a handling mishap, or it could be caused by naturally or accidently produced environments such as earthquakes, flooding, fire, explosive overpressure, or missiles. A significant inventory could be released in this mode while the balance would be released over an extended period of time. For a maximum concentration accident involving hazardous chemicals, the instantaneous release of the total contents of one of the following should be considered in the analysis: (1) the largest storage container within the guidelines that is located at a nearby stationary facility, (2) the largest shipping container within the guidelines that is frequently transported near the site (for multiple containers of equal size, the failure of only one container unless the failure of that container could lead to successive failures), or (3) the largest container stored onsite (normally the total release from this container unless the containers