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:
etween 0.3 and 5 miles from the CR, and the three columns to the right list the calculated weights for three ACH values. 2. “Pasquill stability class” is a meteorological classification method for categorizing atmosphere stability and is defined by, among other things, the regional conditions of wind speed, solar radiation during the day, and cloud cover during the night. See https://www.ready.noaa.gov/READYtools.php for more information. DG-1387, Page 8 Table 1. Selected IDHL Values for Twenty-Nine Hazardous Chemicals Chemical ppm(a) mg/m3 (b) Chemical ppm mg/m3 Acetaldehyde 2,000 3,600 Fluorine 25 50 Acetone 2,500 6,000 Formaldehyde 20 24 Acrylonitrile 85 149 Halon 1211 20,000 Anhydrous ammonia 300 210 Halon 1301 50,000 Aniline 100 380 Helium asphyxiant Benzene 500 1,600 Hydrogen cyanide 50 55 Butadiene 2,000 4,400 Hydrogen sulfide 100 150 Butene asphyxiant Methyl alcohol 6,000 7,800 Carbon dioxide 40,000 7,360 Nitrogen (liquid or compressed) asphyxiant Carbon monoxide 1,200 1,320 Chlorine 10 30 Sodium oxide 2 Ethyl chlorine 3,800 9.880 Sulfur dioxide 100 520 Ethyl ether 1,900 5,700 Sulfuric acid 15 Ethylene dichloride 50 200 Vinyl chloride 1,000 2,600 Ethylene oxide 800 720 Xylene 900 3,915 (a). Parts of vapor or gas per million parts of air by volume at 25 °Celsius and 760 torr (standard temperature and pressure). (b). Approximate milligrams of chemicals per cubic meter (mg/m3) of air, at standard temperature and pressure, based on listed ppm values. To convert ppm to mg/m3, multiply the “ppm” value with the chemical’s molecular weight (i.e., gram/mole) and divide by the universal standard temperature and pressure gas constant, 24.45. Table 2. Minimum Chemical Weights That Require Consideration in CR Habitability Evaluation(a) Distance from CR in Mile (km)(b) ACH 0.015(c) ACH 0.06 ACH 1.2 0.3 (0.5) to 0.5 (0.8) 4.1(d) 1.0 0.050 0.5 (0.8) to 0.7 (1.1) 16 4.0 0.20 0.7 (1.1) to 1.0 (1.6) 55 14 0.68 1 (1.6) to 2 (3.2) 123 31 1.5 2 (3.2) to 3 (4.8) 590 150