ML20151V806

Reg Guide 1.91,Rev 1, Evaluations of Explosions Postulated to Occur on Transportation Routes Near Nuclear Power Plants

ML20151V806
Person / Time
Issue date:	02/28/1978
From:	NRC OFFICE OF STANDARDS DEVELOPMENT
To:
References
01.091, REGGD-01.091, REGGD-1.091, NUDOCS 8808230010
Download: ML20151V806 (6)

Text

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[** %g U.S. NUCLEAR REGULATORY COMMISSION February 1978

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@\,g$)OFFICE CF STANDARDS DE m, DEVELOl A REGULATORY GUIDE 1,91 EVALUATIONS OF EXPLOSIONS POSTULATED TO OCCUR ON TRANSPORTATION ROUTES NEAR NUCLEAR POWER RANTS Il A. INTRODUCTION systems, and components must be designed to ac-Oeneral Design Criterion 4, "Environmental and # mm date the vibratory ground motion associated Missile Design Basis," of Appendis A, "General with the Safe Shutdown Earthquake.

Design Criteria for Nuclear Power Plants," to 10 The effects of explosives that are of concern in CFR Fart 50, "Licensing of Production and Utiliza analyzing structural response to blast are incident or tion Facilities, requires that nuclear power plant b reflected pressure (overpressure), dynamic (drag) V structures, systems, ud components important t safety be appropriately protected against dynamic ef- pressure, blast induced ground motion, and blast- g fects resulting from equipment failures that may occur enerated missiles. It is the judgment of the NRC  ;

within the nuclear power plant as well as events and staff that, for explosions of the magnitude considered ' 3 conditions that may occur outside the nuclear power in this guide and the structures, systems, and compo- I' plant. These latter esents include the effects of ex. nents tFat must be protected, overpressure effects are plosion of hazardous materials that may be carried on controlling. Drag pressure effects will be much =

nearby transportation routes. This guide describes srnaller than those due to the wind loading auumed --

methods acceptable to the NRC staff for determining for the design basis tornado. The effects of blast-w hether the risk of damage due to an explosion on a [

generated missiles will be less than those associated ,

nearby transportation route is sufficiently high to with the blast oserpressure lesels considered in this warTant a detailed investigation. Acceptable methods 1 guide. If the oserpressure criteria of this guide are for evaluating structural adequacy whei an investiga-esceeded, the effects of missiles must be considered.

tion is warranted are also described. This guide is .

limited to solid explosises and hydrocarbons liquified The effects of blast induced ground motion at the ,,,,

under pressure and is not applicable to cryogenically oserpressure levels considered in this guide will be ,

liquified hydrocarbons, e.g., LNG. It considers the less than those of the sibratory ground motion as- -

effects of airblasts on highw av, rail, and w ster routes sociated with the Safe Shutdown Earthquake. '

d but culudes pipelines and fixed facilities.

This regulatory guide describes a method for de- I terminiog distances from critical plant structures to a B, DISCUSSION 1 railway, highway, or nasigable waterway beyond in order to meet General Design Criterion 2, "De- . "I ' n at mW occm on he trano putan n mutes is not Mely to hau an ahem cued E

sign Basis for Protection Against Natural Phenomena," of Appendis A to 10 CFR Part 50 with n Nant opera n m to present a sak duswn.

Under these conditions, a detailed review of the respect to tornadoes, the structures, systems, and components important to safety of a nuclear power transport of explosises on these transportation routes plant must be destgried to withstand the effects of a would not be required. 4 g

dei,ign basis tornado, including wind, pressure drop, A method for establishing the distances referred to Ili and the effects of missiles, without causing an acci- abose can be based on a lesel of peak positive inci- 8 dent and without damage that would present a safe dent overpressure (designated as P.,,in Ref.1) below q and orderly shutdown. In addition, those structures, which no significant damage would be expected. It is i USNRC REGU,.LATORY G UIDE S cam ~'.i*ws m.,w , cm .. e i. . ~ - ..

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l the judgment of the NRC staff that, for the structures. Determination of the masimum ptobable quantity sptems, and components of concem, this lesel can of hazardous cargo is dependent on both the transpor-be conservatisely chosen at I psi (approximately 7 tation mode and the schicles utilized. The masimum kPa). Ibed on esperimental data on hemispherical probable hazardous solid cargo for a single highway charges of TNT cited in Refererce 1, a safe distance truck is 50,000 pounds (23,000 kg). Similarl), the r can then be consenatnely defined by the relationship masimum esplosise cargo in a single railroad bos car is appros mately 132,000 pounds (60,000 kg). T he R a N, (1) largest probable quantity of esplosise material tranu where R is the distance in feet from an esploding ported by ship is approximately 10,000,000 pounds (4.500,000 kg). For illustralise purposes, the safe charge of W pounds of TNT. When R is in feet and distances, as defined by inequality (I), are shown in W in pounds, L = 45. When R is in meters and W in Figure i for these quantities of TNT. When ship-kilograms, L = 18.

ments are made in connected schicles such as rail-The concept of TNT equhalence, i.e., finding the road can or barge trains, an insestigation of the pou man of substance in question that will produce the sibility of explosion of the contents of more than one same blast effect as a unit man of TNT, has long schicle is neccuary .

been used in establishing safe separation distances for solid esploshes. A test program is required to estab. In cases where the distinees from the transporta-lish that equisalence (Ref. 21. For solid substances tion route to the structures, sptems, and components more efficient in producing blast effects than TNT, that must be protected are not sufficiently great to equisalents are known by the manufacturers. For allow a conclusion tbased on conservative auump-solid substances not intended for use as exploshes tions) that the peak posithe incident overpreuure

$ut subject to accidental detonation, it is consen atise would be leu than I psi (.pproumately 7 kPa), an o use a TNT equivalence of one in estaNishing safe anahsis of the frequene) of haiardous cargo ship-

.tandoff distances, i.e., use the cargo man in Equa- ment may show that the uttendant risk is sufficiently ion (1). Iow. It is the judgment of the NRC staff that, if the esposure rate, r, defined in Equation (2) can be Application of the TNT equhalence concept to show n to be leu than 104 per year, the risk of dam-somble detonations of sapor clouds formed af ter an age due to esplosions k sufficiently low.

iccidental release of hydrocarbons is not as well '

Joeumer,ted. Howes er, ins estigations of accidents r = nfs (2) hat resulted in blast damage hase used this concept where r = esposure rate, n attempts to cuimate, based on blast damage, the n = esplosion rate for the substance and

ffecthe >icid of the esplosion (Ref. 31. Most a* transportation mode in question in scuments of this type hase led to estimates that esplosions per mile, less than one percent of the calorifie energy of the f,g gg gg substance was released in blast effects. Since the stance in question in shipments per ratios of heat of combustion of hydrocarbons to that year, and of TNT are 13pically about 10, this corresponds to an "" "*"#' ## ..E' equh alence on a mau basis of 10 percent. Iloweser, h((3 there hase been accidents in which estimates of the If the substance in qt.estion is shipped on more than l calorific energy released were as high as 10 percent.

one transportanon mode near the plant, esposure The blast energy realized depends, in great measure, rates calculated for the modes should be summed, on phenomena that are accident specific, i.e., the rate if an adequate data base for estimating the nplo-of release of the substance and the way in which the sion rate for a substance is lacking, an estimate can cloud is ignited. A reasonable upper bound to the be made by utiliiing nationwide statistia for the par-blast energy potentially available based on esperi' ticular transportation mode, i.e.,

- mental detonations of confined sapor clouds is a n = nina (3) mau equisalence of 240 percent (Ref. 4). A detailed analph of pouible accident scenarios for particular where ni = accidents per mile for the transporta-tion mode, and utes, including consideration of the actual cargo, site

- topography , and pres ailing meteorological conditions n, = cargo esplpions per accident for the transportanon mode.

ma) junify a lower effecthe yield. But, when estab-lishing safe stand off distances inJependent of site Hecause of the low frequency of occurrence of the conditions, use of an upper bound is prudent. esents under consideration, estimates based on aser-l l

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age frequency may hase wide confidence bands, and further consideration need be risen to the effects of conserutise estimates may be pretmu h estimates blast in plant design in calculating TNT equisalents, of esplosion rate. frequency of shipment, and espo. auumptions of 100 percent TNT (mam equiulence I sure distance are made on a realistic or best esumate for solid energetic materials and 240 percent TNT hasis, an espmure rate ten than 10 ' per year is suf- (mau) equiulence for substances subject to upor fielently low. If co ncrutise estinistes are used, an phase esplosions are acceptable upper bounds when espmure rate few than 10' per year is sufficiently effectise yields generated from test data do not exist.

low . Lower effectise yielJs may be justified by analyses if it cannot be shown that the distance to the trane munung or reae on , e topography , and preu ng mekomlogical e nditions when the Portation route is great enough or that the espmure hazardous cargos can be identified.

rate is low enough to render sufficiently low the risk of danuge to a structure housing a >> stem or compo- 2. If transportation routes are closer to structures nent that must be protected ; analysis of the blast and systems important to safety than the distances load ef fects may be made. The loaJmp combination computed using Figure 1, the applicant may show to N conudered i.uy be limited to: that toe risk is acceptably low on the basis of low pro a ty of espMont A demonstration that the C = D + L + To + Rn + B 141 rate of esposure to a peak positise incident overprew where C = combined load effect. sure in esceu of 1 psi (7 kPa) is len than 10-* per D = dead load effect, sear, when based on conserutise awumptions, or L = Ine load effect (not including wind 'go-' per year, when based on realistic auumptions, is or snow loaJs), acceptable. Due considention should be gisen to the T, = thermal load effect during normal comparability of conditionWr7the route to those of operating or shutdown conditions, the accident data base./

R., = pipe reaction effect during normal 3. If transportation routes are closer to structures operating or shutdown conditions. anJ systems important to safet) than the distances and computed using Figure 1, the applicant may show B = blast load ef fect, with the esplmion that the risk to the public is acceptably low on the source positioned to masimite the basis of capabihty of the safety related structures to load combination for the structural withstand blast and missile effects awociated with de-element under consideration. Onl) tonation of the hatardous cargo. In anessing the l the incident (or, if appropriate, re- capacit; of structures to resist blast loads, a flec ted ) prenure loading need be simphfied quasi vatic analpis of blast effects using conddered the load combination of Equation (4) is acceptable.

Either a static analysis using twice the appropriate Effectise yields based on analyses accounting for preuure loading or an clavie analysis using dynamic reaction kinetics, site topography, and presailing load factors tref. 9 is acceptable for computing blast rneteorological conditions can be used w heyustified load effects. The blast prenure should be considered to act both inward and outwcrd in order to account for dynamie stren resersal. Oserturning and sliding D, IMPLEMENTATION stabihty as well as the ability of supporting structures The purpose af this section is to proside guidance to carry loads transmitted from the directly loaded es-to applicants and licensees regarding the NRC staff's terior surfaces must be aweued.

plans for utilizing this reFulatory guide.

C. REQULATORY POSITION Escept in those cases in which the applicant pro-In the design of nuclear power plants, the ability to pmes an alternatise method for complying with spec-withstand the pmsible ef fects of esplosions occurring ified portions of the Commission's regulations, the on nearby transportation routes should be considered. method described herein will be used in the es alua-The following methods are acceptable to the NRC tion of construction permit appbeations docketed on staff for ensuring that the risk of damage due to an or after February 24, 1978.

esplosion on a nearby trangortation route is suffi- .

ciently low. If an apph.eant wishes to use this regulatory guide in deseloping submittals for applications docketed on

1. When carriers that transport esplosises can or before February 24, 1978, the pert nent portions of approach sital structures of a tiuclear facility no the application will be evaluated on the basis of this closer than the distances computed using Figure I, no guide.

D 1.91 3

REFERENCES 1 Strehlow, R A., and W. E. Ilaker, "The Charac-terization and Esaluation of Accidental Esplo-

1. Department of the Army Technical $1anual TS1 uons, ' N AS A CR 134779, June 1975.

51.ho, ' Structures to Resist the Effects of Acci.

Jental Esplosions," June 1969. 4 Ehhler. T. V., and 11 S. Napadensky, " Acciden-tal Vapor Phase lisplosions on Transportation outes near Nuclear Power flants," Hnal Reprt l

2. Napadensks ,11. S., and 1. Jablansky , "TNT

- J 6405, llT Rewarth Institute, (,hicago Illinois, Equisakncy insestigations,, Proceedings of the April 1977' L 16th Annual Esplosnes Safety Seminar, Depart-ment of Defense Esploshes Safety lloard, Wash- 3. Iliggs, J. St., Introduction to Structural ington, D C., September 1974. Dy namics , NicGraw liill, New York,1964.

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