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:
detonation of the explosive material using the following equation from UFC 3-340-02: ܹா= ுಶ೉ು ೏ ு೅ಿ೅ ೏ ܹா௑௉ (2) where, WE = effective charge weight (equivalent TNT charge mass for use in Equation (1)) WEXP = weight of the explosive in question HdEXP = heat of detonation of explosive in question (values available in Table 2-1 of UFC 3-340- 02) HdTNT = heat of detonation of TNT (values available in Table 2-1 of UFC 3-340-02) When establishing safe standoff distances for solid substances not intended for use as explosives but subject to accidental detonations, the minimum yield factor used should be 1 (i.e., use the mass of potentially explosive material as the mass of TNT in Equation (1)). The TNT equivalence concept also may be applied to detonations of either confined or unconfined vapor clouds formed as a result of the presence of potentially explosive materials. The blast energy realized depends, in great measure, on phenomena that are accident-specific (e.g., the amount of vapor formation because of substances stored or released and the way in which the vapor cloud is ignited). However, investigations of accidents and experimental data have yielded basic equations for use in estimating TNT equivalence for vapor clouds. One common method for assessing the blast wave effects of vapor cloud explosions is based on the blast wave energy (i.e., TNT equivalence) given by NUREG-1805, “Fire Dynamics Tools (FDTs) Quantitative Fire Hazard Analysis Methods for the U.S. Nuclear Regulatory Commission Fire Protection Inspection Program,” issued December 2004 (Ref. 7), and the Society of Fire Protection Engineers’ (SFPE’s) “Handbook of Fire Protection Engineering” (Ref. 8): ܧ= ߙΔܪ௖݉ி (3) DG-1388, Page 6 where, E = blast wave energy (British thermal units (BTU) or kilojoules (kJ)) α = yield (i.e., the fraction of available combustion energy participating in blast wave generation) ΔHc = theoretical net heat of combustion