Document: NRC Regulatory Guide
Document ID: c992c9f8-7405-4a7c-afdc-b3d2a6922aad
Document Type: regulatory_guide
Title: Assumptions Used for Evaluating the Potential Radiological Consequences of a Steam Line Break Accident for Boiling Water Reactors
Source: NRC Regulatory Guide Division 1
Source URL: https://www.nrc.gov/docs/ML0037/ML003739923.pdf
Revision Date: 2023-06
Chapter: 
Section ID: RG-1.5
CFR Part: 
CFR Title: 

Content:
must be evaluated ICRP, Committee 11-1959.) on an individual case basis. In (c) The iodine dose conversion factors the case of beta radiation, the are given in ICRP Publication 2, receptor is assumed to be ex Report of Committee II, "Permis- posed to an infinite cloud at sible Dose for Internal Radiation," the maximum ground level 1959. concentration at that distance (d) External whole body doses are from the reactor. In the case calculated using "Infinite Cloud" of gamma radiation, the re assumptions, i.e., the dimensions ceptor is assumed to be ex of the cloud are assumed to be posed to only one-half the large compared to the distance that cloud owing to the presence of the gamma rays and beta particles the ground. The maximum travel. "Such a cloud would be con- cloud concentration is always sidered an infinite cloud for a re- assumed to be at ground level. ceptor at the center because any (2) The appropriate average beta additional [gamma and] beta emit- and gamma energies emitted ting material beyond the cloud di- per disintegration, as given in mensions would not alter the flux the Table of Isotopes; Sixth of [gamma rays and] beta parti- Edition; by C. M. Lederer, J. cles to the receptor" (Meteorology M. Hollander, I. Perlman; and Atomic Energy, Section 7.4.1.1 University of California, -editorial additions made so that Berkeley; Lawrence Radiation gamma and beta emitting material Laboratory should be used. could be considered). Under these (e) (1) The equation used to deter conditions the rate of energy ab- mine the atmospheric dif sorption per unit volume is equal fusion from an elevated re to the rate of energy released per lease at 30 meters, uniform unit volume.4 wind direction with a fumiga The following specific assumptions tion condition existing is: are used: 0.0133 (1) The dose at any distance from /Y the reactor is calculated based Where: on the maximum concentra- x = the short term aver tion in the plume at that dis- age centerline value tance