Regulatory Guide 1.91

Evaluation of Explosions Postulated to Occur on Transportation Routes Near Nuclear Power Plant Sites.

ML12298A133
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Issue date:	01/31/1975
From:	US Atomic Energy Commission (AEC)
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RG-1.091
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January 1975U.S. ATOMIC ENERGY COMMISSION7 REGULATORY GUIDIRECTORATE OF REGULATORY STANDARDSREGULATORY GUIDE 1.91EVALUATION OF EXPLOSIONS POSTULATED TO OCCURON TRANSPORTATION ROUTES NEAR NUCLEAR POWER PLANT SITESDEA. INTRODUCTIONGeneral Design Criterion 4, "Environmental andMissile Design Basis" of Appendix A, "General DesignCriteria for Nuclear Power Plants," to 10 CFR Part 50,"Licensing of Production and Utilization Facilities,"requires that nuclear power plant structures, systems,and components important to safety be appropriatelyprotected against dynamic effects resulting fromequipment failures which may occur within the nuclearpower unit as well as events and conditions which mayoccur outside the nuclear pov, er unit. These latter eventsinclude the effects of explosion of hazardous materialswhich may be carried on nearby transportation routes.This guide describes a method acceptable to theRegulatory staff for determining safe distances from anuclear power plant to a transportation route over whichexplosive material (not including gases) may be carried.B. DISCUSSIONIn order to meet General Design Criterion 2, "DesignBasis for Protection Against Natural Phenomena," ofAppendix A to 10 CFR Part 50 with respect totornadoes, the structures, systems, and componentsimportant to safety of a nuclear power plant must bedesigned to withstand the wind pressure and suddeninternal pressure changes due to a design basis tornadowithout causing an accident, and without damage thatwould prevent a safe and orderly shutdown. Since thenuclear power plant is designed to safely withstand thedesign basis tornado described in Regulatory Guide 1.76,"Design Basis Tornado for Nuclear Power Plants," anexplosion which produces a peak overpressure no greaterthan the wind pressure caused by the tornado should notcause an accident or prevent the safe shutdown of theplant. It should be noted that -this applies only to theadequacy of the plant with respect to external dynamicoverpressure. The potential effect of missiles from theseexplosions is still under study. This regulatory guidedescribes a method for determining distances from the.power .plant to a railway, highway, or navigablewaterway beyond which any explosion that might occuron, these transportation routes is not likely to have anadverse effect on plant operation or prevent a safeshutdown. Under these conditions, a detailed review ofthe transport of explosives on these transportationroutes would not be required.In establishing the distances referred to above, it isnecessary to determine the dynamic wind pressureassociated with the wind speed of the design basistornado determined from Regulatory Guide 1.76 foreach of the three regions of the contiguous UnitedStates. Table 1 presents the wind speeds for the threeregions and the associated dynamic pressures calculatedfrom q = 0.002558V2 (this represents the kinetic energyper unit volume of moving air), where is the dynamicpressure in pounds per square foot and V is themaximum wind velocity in miles per hour (see Reference1).TABLE 1DESIGN BASIS TORNADOWIND SPEED CHARACTERISTICSI ý 1xamuma Wind 1 Dynamic Wind Dynamic WindRegion Speed, mph Pressure, psi Pressure, psfI 360 2.3 331.2II 300 1.6 230.4III 240 1.0 144.0aThe maximum wind speed is the sum of the rotational speedconiponent and the maximum translational speed component.The calculational method used to analyze therelationships of explosive charge to distance is first toUSAEC REGULATORY GUIDES Copies of published guides may be obtained by request indicating the divisionsdesired to the US. Atomic Energy Commission, Washington, D.C. 20545,Regulatory Guides are issued to describe and make available to the public Attention: Director of Regulatory Standards. Comments and suggestions formethods acceptable to the AEC Regulatory staff of implementing specific parts of improvements in these guides are encouraged and should be sent to the Secretarythe Commission's regulations, to delineate techniques .sed by the staff in of the Commission, U.S. Atomic Energy Commission, Washington, D.C. 20545,evaluating specific problems or postulated accidents, or to provide guidance to Attention: Dockeiing and Service Section.applicants. Regulatory Guides are not substitutes for regulations and compliancewith them is not required. Methods and solutions different from those set out in The guides are issued in the following ten broad divisions:the guides will be acceptable if they provide a basis for the findings requisite tothe issuance or continuance of a permit or license by the Commission. 1. Power Reactors 6. Products2. Research and Test Reactors 7. Transportation3. Fuels and Materials Facilities 8. Occupational HealthPublished guides will be revised periodically, as appropriate, to accommodate 4. Environmental and Siting 9. Antitrust Reviewcomments and to reflect new information or experience. 5. Materials and Plant Protection 10. Generalr, assume that the limiting peak overpressure due to anexplosion is equal to the dynamic wind pressureresulting from a design basis tornado for a specific regionand then to calculate the limiting distance beyond whichthe peak overpressure resulting from an explosion willnot exceed the design dynamic wind pressure.The conservative correlation for determining the peakexplosion overpressure as a function of distance andweight of explosive (TNT) is the curve for peak reflectedpressure, Pr, on Figure 1. As defined in Reference 2, thepeak reflected .pressure occurs when the shock waveimpinges on a surface oriented so that a line whichdescribes the path of travel of the wave is normal to thesurface. This curve is taken from Figure 4.12 ofReference 2 with some of the symbols modified.Table 1 gives 2.3 psi as the external dynamic windpressure due to a design basis tornado in Region I. FromFigure 1, the scaled distance, ZG, corresponding to apeak reflected pressure of 2.3 psi is found to be 41. Thefollowing function of distance and explosive charge isthen determined for Region I:RG = 41Wl/3Similarly, the correlations for the remaining regions are:Regionl RG =55Wl/3Region III RG = 80Wl/3Iwhere RG is the distance in feet from an explodingcharge of W pounds of TNT. Reference 3 provides theTNT equivalents of other types of explosives. Forhazardous materials not listed in Reference 3, theapplicant should substantiate the derivation of the TNTequivalent used.The maximum probable hazardous cargo for a singlehighway truck is approximately 43,000 pounds (equiv-alent TNT). The distance beyond which an explodingtruck will not have an adverse effect on plant operationsor will not prevent a safe shutdown is indicated inFigures 2, 3, and 4 for Regions I, II, and III,respectively.Similarly, the maximum explosive cargo in a railroadbox car is approximately 132,000 pounds (equivalentTNT). The distance beyond which an exploding railroadbox car will not have an adverse effect on plantoperations or will not prevent a safe shutdown is shownin Figures 2, 3, and 4. In this case, it is also necessary toconsider the possible effects of a simultaneous explosionof connected box cars. For illustrative purposes anevaluation for three box cars is provided. The distancebeyond which three box cars exploding simultaneouslywill not have an adverse effect on plant operations orwill not prevent a safe shutdown is shown on Figures 2,3, and 4. If there is a significant probability that morethan three box cars of explosives will pass by the nuclearpower plant in one shipment, further evaluation by theapplicant will be necessary.The largest probable quantity of explosive materialtransported by ship is approximately 10,000,000 pounds(equivalent TNT). The distance from the shippingchannel beyond which such an explosive charge will haveno adverse effect on plant operations or prevent a safeshutdown is shown on Figures 2, 3, and 4.Table 2 summarizes the results of the minimumdistances shown on Figures 2, 3, and 4 for the maximumpostulated shipments by truck, railroad boxcar, multiplerailroad boxcars, and ship.TABLE 2DISTANCES (IN FEET) TO EQUIVALENTTORNADO OVERPRESSURESTornado 43,000-1b 1 132,000-1b 396,000-tb 10,000,000-l1Regionj Truckload 1-Boxcar Load 3-Boxcar Loa ShiploadI 1500 2100 3000 9000II 1900 2800 4000 11500III 2800 j 4000 5800 17000C. REGULATORY POSITIONIn the design of nuclear power plants, the ability towithstand the possible effects of explosions occurring onnearby transportation routes should be consideredrelative to the effects of the design basis tornado.When carriers that transport explosives can approachvital structures of a nuclear facility no closer than thedistances indicated in Figures 2, 3, and 4, no furtherconsideration need be given to the effects of externaldynamic overpressure in plant design. If transportationroutes are closer to structures and systems important tosafety than the distances indicated in Figures 2, 3, and 4,the applicant should show that the risk to the public isacceptably low on the basis of, for example, lowprobability of explosions or structural capability forsafety-related structures to withstand explosions.D. IMPLEMENTATIONThe purpose of this section is to provide guidance toapplicants and licensees regarding the Regulatory staff'splans for utilizing this regulatory guide.Except in those cases in which the applicant proposesan alternative method for complying with specifiedportions of the Commission's regulations, the methoddescribed herein will be used' in the evaluation ofconstruction permit applications docketed on or afterMarch 14, 1975.REFERENCES1. "Wind Forces on Structures" Paper No. 3269, ASCETransactions, Vol. 126, Part II, 1961.2. Department of the Army Technical Manual TM5-1300, "Structures to Resist the Effects of AccidentalExplosions." June 1969.3. Annals of the New York Academy of Science,Volume 152, Article 1, "Prevention of and ProtectionAgainst Explosion of Munitions, Fuels and otherHazardous Mixtures." Part 4, October 28, 1968.1.91-2 1000if If IEW1IIIiI3]EFtIIIFEFE~IL I LLa.I-a.E0z%10010Pr-0.1I10100SCALED GROUND DISTANCE ZG = RG /W1/3P = Peak Positive Normal Reflected Pressure, psiW = Charge Weight, lbRG = Radial Distance from Charge, ftZG = Scaled Ground Distance, ft/lb1/3Figure 1Peak Positive Normal Reflected Pressure forHemispherical TNT Surface Explosion at Sea Level1.91-3 100,000i-LL,-z0rh00-JLLU-LUzI-co)a10,0001,000o~.103105 106AMOUNT OF EXPLOSIVE IN POUNDSFIGURE 2 APPLICABLE TO TORNADO REGION I 100,000I-j I.Luz 10,000 __ _ _ _ _ _ _-z00u-0.0oi 0 -uLu Luo~ > U00II -T 1 1.-1 11o3 104 ios.16 107 108AMOUNT OF EXPLOSIVE IN POUNDSFIGURE 3 APPLICABLE TO TORNADO REGION Ut I.-LuLuU-z20a-6CLx0ILALuz"0ON105 106AMOUNT OF EXPLOSIVE IN POUNDSFIGURE 4 APPLICABLE TO TORNADO REGION 1T1