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:
es, a detailed review of potential explosions or fire at the fixed facility or on these transportation routes would not be required. An acceptable method for establishing the distances beyond which no adverse effect would occur is based on a level of peak positive incident overpressure (designated as Pso in Department of Defense Unified Facilities Criteria (UFC) 3-340-02, “Structures to Resist the Effects of Accidental Explosions,” December 5, 2008 (Ref. 6)) below which no significant damage would be expected. The NRC staff determined that, for the SSCs of concern, this level is conservatively 1.0 pound per square inch (psi) (approximately 6.9 kilopascals (kPa)). Based on the experimental data on hemispherical charges of TNT DG-1388, Page 5 cited in UFC 3-340-02, the minimum safe distance from an explosion that results in Pso equal to 1.0 psi (6.9 kPa) can be calculated as: ܴ௠௜௡= ܼ∗ܹ భ య (1) where Rmin = distance from explosion where Pso will equal 1.0 psi (6.9 kPa) (feet or meters) W = mass of TNT (pounds or kilograms (kg)) Z = scaled distance equal to 45 (ft/lb1/3) when R is in feet and W is in pounds Z = scaled distance equal to 18 (m/kg1/3) when R is in meters and W is in kilograms A safe distance from a source of potential explosion to critical plant structures would be equal to or greater than Rmin. The concept of TNT equivalence (i.e., finding the mass of the substance in question that will produce the same blast effect as a unit of mass of TNT) has long been used in establishing safe separation distances for explosives. Manufacturers of substances intended to be used as explosives report the TNT equivalence (yield factor) of these substances. For use in Equation (1), the equivalent TNT weight can be determined based on the weight and heat of detonation of the explosive material using the following equation from UFC 3-340-02: ܹா= ுಶ೉ು ೏ ு೅ಿ೅ ೏ ܹா௑௉ (2) where, WE = effective charge weight (equivalent TNT charge