Document: NRC Regulatory Guide
Document ID: 0cfc3978-32da-4370-9f31-8a3547d82846
Document Type: regulatory_guide
Title: Assumptions Used for Evaluating the Potential Radiological Consequences of a Fuel Handling Accident in the Fuel Handling and Storage Facility for Boiling and Pressurized Water Reactors (Rev. 0)
Source: NRC Regulatory Guide Division 1
Source URL: https://www.nrc.gov/docs/ML0833/ML083300022.pdf
Revision Date: 2023-06
Chapter: 
Section ID: RG-1.25
CFR Part: 
CFR Title: 

Content:
, 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 Routine Meteorological Observations for Estimating Atmospheric Dispersion , “ F. A. Gifford, Jr.] h = effective height of release (meters) (2) For elevated releases, atmospheric diffusion factors7 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) envelope of Pasquill diffusion categories for various release heights; (d) a fumigation condition exists at the time of the accident.8 (3) Figure 3 is a plot of atmospheric diffusion factors versus distance for an elevated release assuming no fumigation, and Figure 4 is for an elevated release with fumigation. (4) Elevated releases are considered to be at a height equal to no more than the actual stack height. Certain site conditions may exist, such as surrounding elevated topography or nearby structures, which will have the effect of reducing the effective stack height. The degree of stack height reduction will be evaluated on an individual case basis. 8 For sites located more than 2 miles from large bodies of water such as oceans or one of the Great Lakes, a fumigation condition is assumed to exist at the time of the accident and continue for one-half hour. For sites located less than 2 miles from large bodies of water a fumigation condition is assumed to exist at the time of the accident and continue for the duration of the release (2 hours). RG-1.25, Page 6 3. The following assumptions and equations may be used to obtain conservative approximations of thyroid dose from the inhalation of radioiodine and external whole body dose from radioactive clouds: a. The assumptions relative to inhalation thyroid dose approximations are: (1) The receptor is located at a point on or beyond the site boundary where the maximum ground level