Document: NRC Regulatory Guide
Document ID: 5cdd8024-5f0a-4a1b-8e14-1026125c5667
Document Type: regulatory_guide
Title: Assumptions Used for Evaluating the Potential Radiological Consequences of a Pressurized Water Reactor Radioactive Gas Storage Tank Failure (Rev. 0)
Source: NRC Regulatory Guide Division 1
Source URL: https://www.nrc.gov/docs/ML0833/ML083300020.pdf
Revision Date: 2023-06
Chapter: 
Section ID: RG-1.24
CFR Part: 
CFR Title: 

Content:
e horizontal standard deviation of the plume (meters) [ See Figure V-I, Page 48, Nuclear Safety, June 1961, Volume 2, Number 4, “Use of Routine Meteorological Observations for Estimating Atmospheric dispersion,” F. A. Gifford, Jr.] σz = the vertical standard deviation of the plume (meters). (See Figure V-2, Page 48, Nuclear Safety, June 1961, Volume 2, Number 4, “Use of RG-1.24, Page 4 Routine Meteorological Observations for Estimating Atmospheric Dispersion,” F. A. Gifford, Jr.] b. For ground level releases, atmospheric diffusion factors1 used in evaluating the radiological consequences of the accident addressed in this guide are based on the following assumptions: (a) windspeed of 1 meter/sec; (b) uniform wind direction; (c) Pasquill diffusion category F. c. Figure 1 is a plot of atmospheric diffusion factors (χ/Q) versus distance derived by use of the equation for a pound level release given in regulatory position 2.a. above under the meteorological conditions given in regulatory position 2.b. above. d. Atmospheric diffusion factors for ground level releases may be reduced by a factor ranging from one to a maximum of three (see Figure 2) for additional dispersion produced by the turbulent wake of the reactor building. The volumetric building wake correction as defined in Subdivision 3-3.5.2 of Meteorology and Atomic Energy–1968, is used with a shape factor of ½ and the minimum cross-sectional area of the reactor building only. 3. The following assumptions and equations may be used to obtain conservative approximations of external whole body dose from radioactive clouds: a. External whole body doses are calculated using “Infinite Cloud” assumptions, i.e., the dimensions of the cloud are assumed to be large compared to the distances that the gamma rays and beta particles travel. The dose at any distance from the reactor is calculated based on the maximum ground level concentration at that distance. For an infinite uniform cloud containing χ curies