Document: NRC Regulatory Guide
Document ID: 769c53ca-7692-4fdf-9301-9fd64e37aa8f
Document Type: regulatory_guide
Title: Evaluations of Explosions Postulated To Occur on Transportation Routes Near Nuclear Power Plants (Rev. 3)
Source: NRC Regulatory Guide Division 1
Source URL: https://www.nrc.gov/docs/ML2110/ML21105A439.pdf
Revision Date: 2023-05
Chapter: 
Section ID: RG-1.91
CFR Part: 
CFR Title: 

Content:
t nearby facilities no closer than the minimum safe distance computed, or carriers that transport potentially explosive materials can approach vital structures of a nuclear facility no closer than the minimum safe distance computed, no further consideration need be given to the effects of explosions from these sources in plant design. For calculating TNT equivalents, Table 1 provides acceptable assumptions for determining the mass of TNT to use in Equation (1). Lower effective yields may be justified by analyses accounting for release scenarios, reaction kinetics, site topography, and prevailing meteorological conditions when the potentially explosive materials can be identified. For unconfined vapor explosions, for which the material class is not identifiable, 15 percent yield is an acceptable conservative value, based on the information presented in Ref. 8. Table 1 Assumption for Determining Mass of TNT Materials For Mass of TNT Solids not intended for use as explosives Use actual weight of material Explosive materials Use known TNT equivalent (yield factor) or effective charge weight determined by Equation (2) Confined Vapors (Ref. 7) Use α=100% in Equation (3) Class I Unconfined Vapors (Ref. 9) Use α=5% in Equation (3) Class II Unconfined Vapors (Ref. 9) Use α=10% in Equation (3) Class III Unconfined Vapors (Ref. 9) Use α=15% in Equation (3) Unconfined vapors of unknown class and Boiling Liquid Expanding Vapor Explosions (BLEVEs) (Ref. 9) Use α=15% in Equation (3) 2. If the facility with potentially explosive materials or the transportation routes are closer to SSCs important to safety than the distances computed using Equation (1), the applicant or licensee may show that the risk is acceptably low on the basis of low probability of explosions. A demonstration that the rate of exposure to a peak positive incident overpressure in excess of 1.0 psi (6.9 kPa) is less than 1x10-6 per year when based on conservative assumptions, or 1x10-7 per year when based on