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:
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 of beta radioactivity per cubic meter, the beta dose rate in air at the cloud center is:2 χ = ′ β ∞ β E 457 .0 D ∞′ D β = beta dose rate from an infinite cloud (rad/sec) β E = average beta energy per disintegration (MeV/dis) χ = concentration of beta or gamma emitting isotope in the cloud (curie/m3) Because of the limited range of beta particles in tissue, the surface body dose rate from beta emitters in the infinite cloud can be approximated as being one-half this amount or: χ = ′ β ∞ β E 23 .0 D 1 These diffusion factors should be used until adequate site meteorological data are obtained. In some cases, available information on such site conditions as meteorology, topography and geographical location may dictate the use of more restrictive parameters to insure a conservative estimate of potential offsite exposures. 2 Meteorology and Atomic Energy–1968, Chapter 7. RG-1.24, Page 5 For gamma emitting material the dose rate in air at the cloud center is: χ = ′ γ ∞ γ E 507 .0 D Where: ∞′ D γ = gamma dose rate from an infinite cloud (rad/sec) γ E = average gamma energy per disintegration (MeV/dis) However, because of the presence of the ground, the receptor is assumed to be exposed to only one-half of the cloud (semi-infinite) and the equation becomes: χ = ′ γ γ E 25 .0 D Thus, the total beta or gamma dose to an individual located at the center of the cloud path may be approximated as: ψ = ψ = γ β γ ∞ β E 25 .0 D E 23 .0 D or Where ψ is the concentration time integral for the cloud (curie sec/m3). b. The beta and gamma energies emitted per disintegration, as given in Table of Isotopes,3 are averaged and used according to the methods described in ICRP Publication 2. 3 C. M. Lederer, J. M. Hollander, and I. Perlman, Table of