Document: NRC Regulatory Guide
Document ID: 14983af3-17d8-4f7b-866e-8d603a0f811c
Document Type: regulatory_guide
Title: Assumptions Used for Evaluating the Potential Radiological Consequences of a Loss of Coolant Accident for Pressurized Water Reactors (Rev. 2)
Source: NRC Regulatory Guide Division 1
Source URL: https://www.nrc.gov/docs/ML0037/ML003739614.pdf
Revision Date: 2023-06
Chapter: 
Section ID: RG-1.4
CFR Part: 
CFR Title: 

Content:
ant Protection 10. General the accident., Peak accident pressure is the maximum pressure defined in the technical specifications for containment leak testing. 2. Acceptable assumptions for atmospheric diffusion and dose conversion are: a. The 0-8 hour ground level release concentrations may be reduced by a factor ranging from one to a maximum of three (see Figure 1) for additional dispersion produced by the turbulent wake of the reactor building in calculating potential exposures. The volumetric building wake correction, as defined in section 3-3.5.2 of Meteorology and Atomic Energy 1968, should be used only in the 0-8 hour period; it is used with a shape factor of 1/2 and the minimum cross-sectional area of the reactor building only. b. No correction should be made for depletion of the effluent plume of radioactive iodine due to deposition on the ground, or for the radiological decay of iodine in transit. c. For the first 8 hours, the breathing rate of persons offsite should be assumed to be 3.47 x 10"4 cubic meters per second. From 8 to 24 hours following the accident, the breathing rate should be assumed to be 1.75 x 104 cubic meters per second. After that until the end of the accident, the rate should be assumed to be 1.75 x 10-4 cubic meters per second. After that until the end of the accident, the rate should be assumed to be 2.32 x 104 cubic meters per second. (These values were developed from the average daily breathing rate [2 x 107 cm3/day] assumed in the report of ICRP, Committee 11-1959.) d. The iodine dose conversion factors are given in ICRP Publication 2, Report of Committee II, "Permissible Dose for Internal Radiation," 1959. e. External whole body doses should be calculated using "Infinite Cloud" assumptions, i.e., the dimensions of the cloud are assumed to be large compared to the distance that the gamma rays and beta particles travel. "Such a cloud would be considered an infinite cloud for a receptor at the center because any additional [gamma