Document: NRC Regulatory Guide
Document ID: bd0ffb9e-22f8-46a4-ab36-f5cffd435ed7
Document Type: regulatory_guide
Title: Assumptions Used for Evaluating the Potential Radiological Consequences of a Loss of Coolant Accident for Boiling Water Reactors (Rev. 2)
Source: NRC Regulatory Guide Division 1
Source URL: https://www.nrc.gov/docs/ML0037/ML003739601.pdf
Revision Date: 2023-06
Chapter: 
Section ID: RG-1.3
CFR Part: 
CFR Title: 

Content:
beta particles to the receptor" (Meteorology and Atomic Energy, Section 7.4.1.1-editorial additions made so that gamma and beta emitting material could be considered). Under these conditions the rate of energy absorption per unit volume is equal to the rate of energy released per unit volume. For an infinite uniform cloud containing X curies of beta radioactivity per cubic meter the beta dose in air at the cloud center is: SD4g = 0.457 EX The surface body dose rate from beta emitters in the infinite cloud can be approximated as being one-half this amount (i.e., 0D± = 0.23 ETX). For gamma emitting material the dose rate in air at the cloud center is: D 0.507 .EX From a semi-infinite cloud, the gamma dose rate in air is: S= 0.25 E~x Where = beta dose rate from an infinite cloud (rad/sec) gamma dose rate from an infinite cloud (rad/sec) Eg = average beta energy per disintegration (Mev/dis) EB = average gamma energy per disintegration "(Mev/dis) X = concentration of beta or gamma emitting isotope in the cloud (curie/m 3) f. The following specific assumptions are acceptable with respect to the radioactive cloud dose calculations: (1) The dose at any distance fronthe reactor should be calculated based on the maximum concentration in the plume at that distance taking into account specific meteorological, topographical, and other characteristics which may affect the maximum plume concentration. These site related characteristics 1.3-2 must be evaluated on an individual case basis. In the case of beta radiation, the receptor is assumed to be exposed to an infinite cloud at the maximum ground level concentration at that distance from the reactor. In the case of gamma radiation, the receptor is assumed to be exposed to only one-half the cloud owing to the presence of the ground. The maximum cloud concentration always should be assumed to be at ground level. (2) The appropriate average beta and gamma energies emitted per disintegration, as given in the Table of Isotopes,