Regulatory Guide 1.91

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

ML12298A133
Person / Time
Issue date:	01/31/1975
From:	US Atomic Energy Commission (AEC)
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RG-1.091
Download: ML12298A133 (6)

January 1975 U.S. ATOMIC ENERGY COMMISSION

7 REGULATORYDIRECTORATE OF REGULATORY STANDARDS

GUI DE

REGULATORY GUIDE 1.91 EVALUATION OF EXPLOSIONS POSTULATED TO OCCUR

ON TRANSPORTATION ROUTES NEAR NUCLEAR POWER PLANT SITES

A. INTRODUCTION

explosions is still under study. This regulatory guide describes a method for determining distances from the.

General Design Criterion 4, "Environmental and power . plant to a railway, highway, or navigable Missile Design Basis" of Appendix A, "General Design waterway beyond which any explosion that might occur Criteria for Nuclear Power Plants," to 10 CFR Part 50, on, these transportation routes is not likely to have an

"Licensing of Production and Utilization Facilities," adverse effect on plant operation or prevent a safe requires that nuclear power plant structures, systems, shutdown. Under these conditions, a detailed review of and components important to safety be appropriately the transport of explosives on these transportation protected against dynamic effects resulting from routes would not be required.

equipment failures which may occur within the nuclear In establishing the distances referred to above, it is power unit as well as events and conditions which may necessary to determine the dynamic wind pressure occur outside the nuclear pov, er unit. These latter events include the effects of explosion of hazardous materials associated with the wind speed of the design basis which may be carried on nearby transportation routes. tornado determined from Regulatory Guide 1.76 for This guide describes a method acceptable to the each of the three regions of the contiguous United Regulatory staff for determining safe distances from a States. Table 1 presents the wind speeds for the three nuclear power plant to a transportation route over which regions and the associated dynamic pressures calculated explosive material (not including gases) may be carried. from q = 0.002558V 2 (this represents the kinetic energy per unit volume of moving air), where is the dynamic

B. DISCUSSION

pressure in pounds per square foot and V is the maximum wind velocity in miles per hour (see Reference

1).

In order to meet General Design Criterion 2, "Design Basis for Protection Against Natural Phenomena," of TABLE 1 Appendix A to 10 CFR Part 50 with respect to tornadoes, the structures, systems, and components DESIGN BASIS TORNADO

important to safety of a nuclear power plant must be designed to withstand the wind pressure and sudden WIND SPEED CHARACTERISTICS

internal pressure changes due to a design basis tornado I ý 1xamumaWind 1Dynamic Wind Dynamic Wind without causing an accident, and without damage that Region Speed, mph Pressure,psi Pressure,psf would prevent a safe and orderly shutdown. Since the nuclear power plant is designed to safely withstand the I 360 2.3 331.2 design basis tornado described in Regulatory Guide 1.76, II 300 1.6 230.4

"Design Basis Tornado for Nuclear Power Plants," an III 240 1.0 144.0

explosion which produces a peak overpressure no greater than the wind pressure caused by the tornado should not aThe maximum wind speed is the sum of the rotational speed cause an accident or prevent the safe shutdown of the coniponent and the maximum translational speed component.

plant. It should be noted that -this applies only to the adequacy of the plant with respect to external dynamic The calculational method used to analyze the overpressure. The potential effect of missiles from these relationships of explosive charge to distance is first to USAEC REGULATORY GUIDES Copies of published guides may be obtained by request indicating the divisions desired 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 for methods acceptable to the AEC Regulatory staff of implementing specific parts of improvements in these guides are encouraged and should be sent to the Secretary the 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 compliance with 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 to the issuance or continuance of a permit or license by the Commission. 1. Power Reactors

6. Products

2. Research and Test Reactors

7. Transportation

3. Fuels and Materials Facilities 8. Occupational Health Published guides will be revised periodically, as appropriate, to accommodate 4. Environmental and Siting 9. Antitrust Review comments and to reflect new information or experience. 5. Materials and Plant Protection 1

0. General r

assume that the limiting peak overpressure due to an (equivalent TNT). The distance from the shipping explosion is equal to the dynamic wind pressure channel beyond which such an explosive charge will have resulting from a design basis tornado for a specific region no adverse effect on plant operations or prevent a safe and then to calculate the limiting distance beyond which shutdown is shown on Figures 2, 3, and 4.

the peak overpressure resulting from an explosion will Table 2 summarizes the results of the minimum not exceed the design dynamic wind pressure. distances shown on Figures 2, 3, and 4 for the maximum The conservative correlation for determining the peak postulated shipments by truck, railroad boxcar, multiple explosion overpressure as a function of distance and railroad boxcars, and ship.

weight of explosive (TNT) is the curve for peak reflected TABLE 2 pressure, Pr, on Figure 1. As defined in Reference 2, the peak reflected .pressure occurs when the shock wave DISTANCES (IN FEET) TO EQUIVALENT

impinges on a surface oriented so that a line which TORNADO OVERPRESSURES

describes the path of travel of the wave is normal to the 1 Tornado 43,000-1b 132,000-1b 396,000-tb 10,000,000-l1 surface. This curve is taken from Figure 4.12 of Regionj Truckload 1-Boxcar Load 3-Boxcar Loa Shipload Reference 2 with some of the symbols modified.

Table 1 gives 2.3 psi as the external dynamic wind I 1500 2100 3000 9000

pressure due to a design basis tornado in Region I. From II 1900 2800 4000 11500

Figure 1, the scaled distance, ZG, corresponding to a III 2800 j 4000 5800 17000

peak reflected pressure of 2.3 psi is found to be 41. The

C. REGULATORY POSITION

following function of distance and explosive charge is then determined for Region I:

In the design of nuclear power plants, the ability to withstand the possible effects of explosions occurring on RG = 41Wl/3 nearby transportation routes should be considered Similarly, the correlations for the remaining regions are: relative to the effects of the design basis tornado.

When carriers that transport explosives can approach Regionl RG =55Wl/3 vital structures of a nuclear facility no closer than the distances indicated in Figures 2, 3, and 4, no further Region III RG = 80Wl/3 I

consideration need be given to the effects of external dynamic overpressure in plant design. If transportation where RG is the distance in feet from an exploding routes are closer to structures and systems important to charge of W pounds of TNT. Reference 3 provides the safety than the distances indicated in Figures 2, 3, and 4, TNT equivalents of other types of explosives. For the applicant should show that the risk to the public is hazardous materials not listed in Reference 3, the acceptably low on the basis of, for example, low applicant should substantiate the derivation of the TNT probability of explosions or structural capability for equivalent used. safety-related structures to withstand explosions.

The maximum probable hazardous cargo for a single highway truck is approximately 43,000 pounds (equiv-

D. IMPLEMENTATION

alent TNT). The distance beyond which an exploding truck will not have an adverse effect on plant operations The purpose of this section is to provide guidance to or will not prevent a safe shutdown is indicated in applicants and licensees regarding the Regulatory staff's Figures 2, 3, and 4 for Regions I, II, and III, plans for utilizing this regulatory guide.

respectively. Except in those cases in which the applicant proposes Similarly, the maximum explosive cargo in a railroad an alternative method for complying with specified box car is approximately 132,000 pounds (equivalent portions of the Commission's regulations, the method TNT). The distance beyond which an exploding railroad described herein will be used' in the evaluation of box car will not have an adverse effect on plant construction permit applications docketed on or after operations or will not prevent a safe shutdown is shown March 14, 1975.

in Figures 2, 3, and 4. In this case, it is also necessary to consider the possible effects of a simultaneous explosion REFERENCES

of connected box cars. For illustrative purposes an evaluation for three box cars is provided. The distance 1. "Wind Forces on Structures" Paper No. 3269, ASCE

beyond which three box cars exploding simultaneously Transactions, Vol. 126, Part II, 1961.

will not have an adverse effect on plant operations or

2. Department of the Army Technical Manual TM

will not prevent a safe shutdown is shown on Figures 2,

3, and 4. If there is a significant probability that more 5-1300, "Structures to Resist the Effects of Accidental than three box cars of explosives will pass by the nuclear Explosions." June 1969.

power plant in one shipment, further evaluation by the 3. Annals of the New York Academy of Science, applicant will be necessary. Volume 152, Article 1, "Prevention of and Protection The largest probable quantity of explosive material Against Explosion of Munitions, Fuels and other transported by ship is approximately 10,000,000 pounds Hazardous Mixtures." Part 4, October 28, 1968.

1.91-2

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SCALED GROUND DISTANCE ZG = RG /W1/3 P = Peak Positive Normal Reflected Pressure, psi W = Charge Weight, lb RG = Radial Distance from Charge, ft

1 ZG = Scaled Ground Distance, ft/lb /3 Figure 1 Peak Positive Normal Reflected Pressure for Hemispherical TNT Surface Explosion at Sea Level

1.91-3

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103 105 106 AMOUNT OF EXPLOSIVE IN POUNDS

FIGURE 2 APPLICABLE TO TORNADO REGION I

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FIGURE 3 APPLICABLE TO TORNADO REGION Ut

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FIGURE 4 APPLICABLE TO TORNADO REGION 1T1