Document: NRC Regulatory Guide
Document ID: de79d411-4fc9-456e-a5a0-f4a910ca4c9a
Document Type: regulatory_guide
Title: Assumptions Used for Evaluating a Control Rod Ejection Accident for Pressurized Water Reactors (Rev. 2)
Source: NRC Regulatory Guide Division 1
Source URL: https://www.nrc.gov/docs/ML2111/ML21119A157.pdf
Revision Date: 2023-05
Chapter: 
Section ID: RG-1.77
CFR Part: 
CFR Title: 

Content:
tal plume travel distance between the CR and the chemicals; and (9) local meteorological data. For determining the air quality in the CR for habitability evaluation, the NRC recommends the following 7 considerations: (1) the design height of air intake windows; (2) the volume size of CR; (3) the air-exchange rate of CR; (4) the flow rate as cubic feet per minute of the CR; (5) the unfiltered DG-1387, Page 10 makeup or inleakage air for the CR; (6) the filtered makeup and recirculated air under normal and emergency operations; and (7) the use of a filtered nuclear air-cleaning system or personal breathing-air supplying device during an emergency. 3.1 IDHL Concentrations Table 1 presents the IDHL values as maximum toxic concentrations for the selected 29 chemicals. An unprotected operator should not stay in a CR with chemical concentrations exceeding the Table 1 for longer than 2 minutes. 3.2 Accident Types and Release Characteristics Two types of industrial accidents should be considered for each source of hazardous chemicals: maximum concentration chemical accidents (MCAs) and average concentration-duration chemical accidents (ACAs). MCAs result in a short-term puff or instantaneous release of a large quantity of hazardous chemicals. An example of this type of accident would be the failure of a manhole cover on the chemical container or the outright failure of the container itself. Such a failure could occur during transport of a container from a handling mishap or from naturally or accidentally produced environments such as earthquakes, flooding, fire, explosive overpressure, or missiles. A significant inventory could be released right away, with the balance releasing over an extended period. Under MCAs, the analysis should consider: (1) the largest storage container within the guidelines of Table 2 located at a nearby stationary facility; (2) the largest shipping container within the guidelines of Table 2 that is frequently transported near the site; or (3) the