D.4 ACCIDENT SCENARIOS INVOLVING HIGH EXPLOSIVES
To develop accident scenarios involving high explosives, all facilities designed or designated to handle high explosives were identified (Fisher, 1989; SNL, Livermore, 1991a). Then, for each facility, the at-risk quantities of high explosives were determined. Various pertinent documents (e.g., safety analysis reports, facility safety procedures, unusual occurrence reports, DOE's April 1990 Tiger Team assessment) were reviewed in this process, and the facilities were visited to examine mitigating design features like blast walls, blast vents, and the physical settings. Procedural controls, such as limits on the quantity of explosive allowed (1) in the work station, (2) in storage, and (3) in transportation were also examined in the screening process. Finally, the analysis took into consideration previous incidents involving high explosives. The principal factors in identifying potential accident scenarios were identifying the at-risk quantity of high explosives in use, the population at-risk, and the passive mitigation features/administrative controls in place.
D.4.1 Selection of Site and Operations for Accident Scenarios
Initially, all facilities containing high explosives at the LLNL Livermore site, LLNL Site 300, SNL, Livermore and all operations involving high explosives were considered. The first screening step (Table D.4-1 was to evaluate the hazard rankings for all buildings at the LLNL Livermore site. The buildings reviewed are listed in Table D.4-2 . Facilities not containing or excluded from using high explosives were eliminated from further consideration since they would, by definition, be bounded by the moderate-hazard facilities. No facilities containing high explosives at the LLNL Livermore site or LLNL Site 300 were ranked as high hazard facilities.
Next, the facilities at SNL, Livermore were compared to those at the LLNL Livermore site. Because the High Explosives Application Facility, Building 191 at the LLNL Livermore site, has a greater at-risk quantity of high explosives (10 kg) than any facility at SNL, Livermore, all buildings at SNL, Livermore were therefore removed from further consideration.
In the third step of the screening process, the consequences of an accident at or associated with Building 191 on the LLNL Livermore site were compared to the consequences of high explosives accidents at LLNL Site 300. It was determined from this comparison that larger amounts of high explosives are formulated in the chemistry area of LLNL Site 300 than at Building 191. In addition, larger charges are assembled in the LLNL Site 300 high explosives assembly buildings (Morse and Weingart, 1989) and larger charges are fired at LLNL Site 300 than are allowed in Building 191, which currently has a limit of 10 kg of TNT-equivalent high explosives. (Possible future operations may allow the use of 40 kg of TNT-equivalent high explosives in Building 191; however, this will require additions and modifications to existing hardware.) Based on this criterion, LLNL Site 300 was selected for scenario development bounding the onsite high explosives hazard to staff personnel.
In addition to the bounding high explosives accident onsite, transportation accidents involving high explosives were examined. High explosives used at LLNL and SNL, Livermore are shipped mainly by truck; however, 1000-kg shipments are transported by air to the Tracy Municipal Airport and then trucked to LLNL Site 300. An aircraft crash with this quantity of high explosives would bound the equivalent ground transportation accident considering the impact velocity and fuel loading. Based on this criterion, an airplane crash was selected for scenario development.
Transportation of 10 kg of TNT-equivalent high explosives from Building 191 to LLNL Site 300 was also considered (LLNL, 1989g). Since Building 191 is well designed to withstand blast effects, a transportation accident outside Building 191 involving 10 kg of TNT-equivalent high explosives would bound any operation inside Building 191. Because the population of staff and civilians at the LLNL Livermore site and along the approved transportation routes to LLNL Site 300 are much higher than that from Tracy Municipal Airport to LLNL Site 300, this accident could be bounding for all high explosives accidents, offsite and onsite. Based on these criteria, a truck accident scenario was selected for scenario development.
Table D.4-1 High Explosive Accident Selection Criteria
| Initial number of buildings: 653 |
|
|
Airplane crash (offsite) Truck accident (offsite) |
Source: Fisher, 1989; SNL, Livermore 1991a.
Table D.4-2 Buildings Reviewed for High Explosive Accident Scenario Development LLNL Livermore Site
| Building Number | Name of Facility | Building Number | Name of Facility |
| 164 | Preparation/Lasers | 227 | Chemistry |
| 191 | High Explosives Applications Facility | 228 | Waste Retention for B226 |
| 224 | Chemistry–Analytic Sciences Lab | 229 | Storage Area |
| 225 | Chemistry–High Explosives | 341 | Physics Research |
| 226 | Environmental Analytic Sciences Lab |
* This facility has been converted or is in the process of being converted
to non–high explosives applications.
| Building Number | Name of Facility | Building Number | Name of Facility |
| 801 | Flash X-Ray (FXR) Facility | M-32 | Magazine |
| 804 | Staging Area | M-33 | Magazine |
| 805 | High Explosives Assembly/Machining | M-34 | Magazine |
| 806 | High Explosives Machining | M-35 | Magazine |
| 807 | High Explosives Machining | M-37 | Magazine |
| 809 | Radiography and High Explosives Machining | M-51 | Magazine |
| 810 | High Explosives Assembly | M-52 | Magazine |
| 817 | Pressing and Oven Complex | M-58 | Magazine |
| 818 | High Explosives Shipping and Receiving | M-70 | Magazine |
| 822 | Storage | M-71 | Magazine |
| 825 | Chemistry Processing Facility | M-72 | Magazine |
| 826 | Chemistry Processing Facility | M-80A | Magazine |
| 827 | Chemistry Processing Facility | M-80B | Magazine |
| 828 | High Explosives Machining | M-82 | Magazine |
| 829 | High Explosives Disposal Facility | M-82B | Magazine |
| 834 | Environmental Test Complex | M-83 | Magazine |
| 836 | Dynamic Test Complex | M-83A | Magazine |
| 837 | Storage | M-83B | Magazine |
| 840 | Explosives Study | M-804 | Magazine |
| 850 | Firing Facility | M-809 | Magazine |
| 851 | Firing Facility | M-810 | Magazine |
| 854 | Dynamic Test Facility | M-812-2 | Magazine |
| 855 | Disassembly Complex | M-812-2 | Magazine |
| 858 | Drop Tower Complex | M-817 | Magazine |
| M-1 | Magazine | M-817-C | Magazine |
| M-2 | Magazine | M-825-2 | Magazine |
| M-3 | Magazine | M-825-3 | Magazine |
| M-4 | Magazine | M-825-4 | Magazine |
| M-5 | Magazine | M-825-5 | Magazine |
| M-6 | Magazine | M-826-1 | Magazine |
| M-7 | Magazine | M-826-6 | Magazine |
| M-8 | Magazine | M-828-D | Magazine |
| M-9 | Magazine | M-829 | Magazine |
| M-21 | Magazine | M-834-1 | Magazine |
| M-22 | Magazine | M-834-2 | Magazine |
| M-23 | Magazine | M-840-1 | Magazine |
| M-24 | Magazine | M-850 | Magazine |
| M-30 | Magazine | M-851 | Magazine |
| M-31 | Magazine | M-858-A | Magazine |
| Building Number | Name of Facility | Building Number | Name of Facility |
| 906 | Combustion Research Facility Complex | 974 | Explosive Assembly |
| 910 | Weapons Laboratory Facility | 978 | Explosive Test Facility |
| 913 | Model Shop, Test Assembly, Laboratories | 981 | Explosives Shipping and Receiving |
| 956 | Vibration Test Facility | 982 | Explosives Packaging Storage |
| 973 | Firing and Support Labs and Offices |
D.4.2 Method of Analysis
The high explosives accident scenarios were analyzed to determine a hazard radius from an accidental detonation of high explosives. The evaluation was made by hand calculation, using the following procedure and equations: After determining the quantity of high explosives at risk for an accident scenario, the mass equivalent in TNT was determined. Table D.4-3 lists high explosives commonly used at the LLNL Livermore site, LLNL Site 300, and SNL, Livermore and their TNT equivalents.
The concept of TNT equivalence has long been used in establishing safe separation distances for solid explosives, with the scaled ground distance normally being used as a constant of proportionality. This relates a given weight of an explosive to a "safe distance," that is, the maximum distance from a detonation for which a given peak overpressure will be exerted. Scaled ground distances are tabulated graphically by the U.S. Army in Structures to Resist the Effects of Accidental Explosions (U.S. Army, 1969) and are determined as follows:
ZG = RG /W1/3
where ZG is the scaled ground distance, RG is the distance, and W is the TNT mass equivalence.
To solve for the desired safe distance for a given mass of explosives, this equation is transformed:
RG = ZGW1/3 or R = kW1/3
where R is the distance from explosive to structure, k is a constant value of 34 ft/(lb-mass)1/3 and 13.5 m/(kg)1/3 for 1 psi, and W is the TNT mass equivalence of the explosive.
For the high explosives scenarios analyzed, the safe-distance equation was used to calculate a 1-psi blast-zone radius (i.e., the straight-line distance between the explosive and any object) with no credit taken for intervening structures. The hazard radius corresponding to a 1-psi peak positive overpressure was chosen as the outer radius of concern because this pressure would damage a standard dwelling to the extent that it would be uninhabitable. Table D.4-4 summarizes k constants, overpressures, and potential for injury and property damage (Kinney and Graham, 1985).
Table D.4-3 Overpressure Ratios of Various Explosives Relative to TNT Normalized by Mass
| Explosive | Mass of TNT Required to yield an Equivalent Overpressure* |
| LX-17 | 1.0 |
| Comp B | 1.1 |
| LX-04 | 1.23 |
| Octol | 1.32 |
| LX-14 | 1.32 |
| LX-10 | 1.32 |
* This is not an exact ratio and is dependent upon the overpressure range.
The values cited are for 1 to 10 psi.
Source: Green, 1991.
Table D.4-4 High Explosives Overpressure Constants and Consequences
|
Scaled Distance Z (ft-kg1/3) |
Overpressure (psi) |
Consequences |
| 3000–890 | 0.01–0.04 | Minimum damage to glass panels |
| 420–200 | 0.1–0.2 | Typical window glass breakage |
| 200–100 | 0.2–0.4 | Minimum overpressure for debris and missile damage |
| 82–41 | 0.5–1.1 | Windows shattered, plaster cracked, minor damage to some buildings |
| 44–32 | 1.0–1.5 | Personnel knocked down |
| 44–28 | 1.0–1.8 | Panels of sheet metal buckled |
| 44–24 | 1.0–2.2 | Failure of wooden siding for conventional homes |
| 28–20 | 1.8–2.9 | Failure of walls constructed of concrete blocks or cinder blocks |
| 20–16 | 2.9–4.4 | Self-framing paneled buildings collapse |
| 20–16 | 2.9–4.4 | Oil storage tanks ruptured |
| 16–12 | 4.4–7.3 | Utility poles broken off |
| 16–12 | 4.4–7.3 | Serious damage to buildings with structural steel framework |
| 11–10 | 10.2–11.6 | Probable total destruction of most buildings |
| 15–9.0 | 5.1–14.5 | Eardrum rupture |
| 14–11 | 5.8–8.7 | Reinforced concrete structures severely damaged |
| 14–11 | 5.8–8.7 | Railroad cars overturned |
| 6.7–4.5 | 29.0–72.5 | Lung damage |
| 3.8–2.7 | 102–218 | Lethality |
| 2.4–1.9 | 290–435 | Crater formation in average soil |
Source: Kinney and Graham, 1985.
D.4.3 Description of Accident Scenarios
Three scenarios were developed and analyzed in the bounding high explosives accidents: an incident involving the misfire of a 1000 lb charge of Octol on a LLNL Site 300 firing table, an aircraft accident involving a shipment of 1000 kg of LX-10, and a truck accident involving 10 kg of TNT-equivalent high explosive.
D.4.3.1 Misfire of High Explosives at LLNL Site 300
The accidents initially considered and eliminated were detonations in a storage magazine and in the chemistry area of LLNL Site 300, where high explosives are formulated. A detonation in a storage magazine is unlikely because of the controls required by LLNL procedures and because the high explosives are resistant to impact. Also, if a detonation were to occur, the magazines are designed to mitigate the consequences. All storage magazines at the LLNL Livermore site, LLNL Site 300, and SNL, Livermore were built in accordance with guidance provided by the U.S. Army in Structures to Resist the Effects of Accidental Explosions (U.S. Army, 1969). For example, the magazines have blast vents to direct the blast upward and prevent the structure from blowing apart. The principal time a detonation in a magazine would have significant consequences is during loading or unloading, when the doors are open and personnel are in the area.
Development of ScenarioA device containing the explosive Octol was assumed to be triggered on a firing table at LLNL Site 300. A delayed or unintentional ignition or misfire occurs. It was assumed that the device being fired contained 1000 lb of Octol rated at 1.32 times the strength of TNT. The device therefore contained 1320 lb of TNT-equivalent high explosives. Charges approaching this size have been fired at LLNL Site 300, though since 1982 most of the charges fired at LLNL Site 300 have been under 100 lb. A 1000 lb quantity was chosen to provide a bounding accident. The explosion would result in serious injury or death to unprotected personnel.
Effects of the ExplosionA blast-force radius of 24 ft was selected to determine the effects in the immediate vicinity of the firing table. At a distance of 24 ft, the peak positive overpressure created by 1320 lb of TNT would be approximately 200 psi, 20 times the force needed to raze a standard dwelling to the ground. This force would probably kill any unshielded personnel.
At a distance of 90 ft from the firing point, the peak positive overpressure would be 10 psi— enough to raze a standard dwelling to the ground. A peak positive overpressure 10 times lower (i.e., 1 psi, damaging to most standard homes to the point of their being uninhabitable) would extend to a radius distance of about 370 ft.
There are no dwellings within 3300 ft of the firing tables; therefore, the offsite consequences of the combustion byproducts and the blast force would have no consequences for the general population.
Preventative MeasuresThe terrain of LLNL Site 300 minimizes offsite consequences, although noise and window rattling may occur in surrounding areas. More significantly, personnel training and the use of procedures governing conduct during the execution of hazardous tests virtually preclude worker exposure to accidental detonations (LLNL, 1987).
D.4.3.2 Aircraft Accident with a Detonation of High Explosives
The high explosives used at LLNL and SNL, Livermore are shipped mainly by truck. However, air-shipment logs show that twice in a year single shipments of high explosives in quantities of approximately 1000 kg have been made. Since essentially the same amounts of explosives are carried by truck and aircraft, the most severe accident scenario would be one where the damage caused by an aircraft crash is combined with the detonation of the explosives. This event would bound the consequences of a high explosives transportation accident associated with the LLNL Site 300 testing area.
Before selecting the aircraft crash as the bounding transportation accident scenario, two types of truck accidents were considered: (1) an accident on public roads during the shipment of high explosives between the LLNL Livermore site and LLNL Site 300, and (2) an accident during the transfer of explosives at LLNL Site 300. It is not likely that the LLNL Livermore site high explosives would detonate during an accident on public roads, because the explosives must be transported in special containers approved by the U.S. Department of Transportation. However, this accident was analyzed separately as the potential bounding accident.
Truck accidents at LLNL Site 300 were eliminated for the same reasons. In addition, they are less likely to occur than offsite shipment on public roads for two reasons: at LLNL Site 300, speed limits for vehicles carrying high explosives are lower than those for public roads, and there is little traffic at the site.
By agreement, LLNL does not ship Class A or Class B explosives (as defined by 49 C.F.R. sections 173.53, 173.88) into Livermore Municipal Airport. This bounding transportation accident was therefore assumed to take place enroute at another airport. Only a turboprop aircraft was considered in the scenario.
Development of an Estimate of Probability of OccurrenceSince this accident is bounding, the probability of occurrence was analyzed. The aircraft accident rate per departure for large commercial jets is 3.1×10-6 and the associated probability that a crash caused fire exceeds one hour duration is 1×10-2 (VanSant, 1990). The probability of a detonation with respect to burn time was not determined, but is estimated not to exceed that of a fire with one hour duration. Although, the transporting aircraft in this scenario is a turboprop, the increased risk associated with the lighter aircraft is estimated to be no more than 10 times higher. Finally, two shipments per year double the risk of a single departure. The overall probability of occurrence is therefore (3.1×10-6)×(1×10-2) ×10×2 = 6.2×10-7 per year.
Development of ScenarioThe aircraft in this scenario was assumed to be carrying at least 300 lb of fuel in its tanks. The high explosive on board was assumed to be 1000 kg (2200 lb) of LX-10 with a TNT equivalent of 1.32, which is equal to 1320 kg (2910 lb) of TNT. The scenario assumed that an aircraft carrying a shipment of LX-10 explosive for LLNL Site 300 crashes enroute near final approach to the Tracy Municipal Airport. The onboard fuel ignites and the combustion causes the LX-10 on board to explode from the heat.
Effects of ExplosionThe explosive force of the LX-10 alone would create a blast force of 1 psi or more out to a radius of 490 ft. As already stated, such a force would damage a standard house enough to render it uninhabitable. A blast force of 10 psi or more would extend out to a radius of about 120 ft; 10-psi peak positive overpressure would be sufficient to raze a house to the ground.
Based on a fatal radius of 31 feet for 200 psi overpressure, the area of lethality would be 0.0003 km2. Assuming a rural population density of 6 people/km2 (the glide path into Tracy Municipal Airport is currently over farmland), only the onboard crew of 3 would likely be subjected to a blast of lethal force. Emergency response personnel would potentially be at risk, but the actual number would depended on the timing of their activities and the number of response personnel within the 0.0003 km2 area at the time of detonation. No number is assigned as it is too speculative.
Preventative MeasuresHigh explosives are transported by approved carriers in cargo aircraft. The aircraft is flown by a qualified pilot, who must file an approved flight plan. High explosives are packaged for transport in accordance with the requirements of the Department of Transportation. Finally, air transportation is less accident prone than ground transportation (Nuclear Regulatory Commission, 1977a).
D.4.3.3 Truck Accident with a Detonation of High Explosives
As discussed above, high explosives used at LLNL and SNL, Livermore are shipped mainly by truck. An accidental explosion of 10 kg (TNT equivalent) of high explosives during truck transportation from Building 191 to Site 300 would be bounding for LLNL and SNL, Livermore for onsite effects. Building 191 is designed to totally contain any explosion up to 10 kg (TNT equivalent), accidental or otherwise. Offsite impacts are relative to population density along the transportation route. Although an airplane crash of fuel and explosives would cause a larger radius of destruction, an accidental explosion of a smaller amount of explosives could cause more loss of life if the accident occurred in a congested corridor such as Interstate 580 east of the LLNL Livermore site. Currently, two approved routes exist between the LLNL Livermore site and LLNL Site 300. The first route is by way of Corral Hollow Road (west), Tesla Road, and Greenville Road. The other route is by way of Corral Hollow Road (east), Interstate 580, and Greenville Road. Both routes are approved for transportation of high explosives by the California Highway Patrol (LLNL, 1988b).
Development of ScenarioThe vehicle in this scenario was assumed to be carrying 10 kg (22 lb) of LX-10. LX-10 has a TNT equivalent of 1.32, which is equal to 13.2 kg (29.1 lb) of TNT. The fuel carried by the truck was assumed to burn (not detonate). The combustion causes the LX-10 on board to explode from the heat.
Effects of ExplosionThe explosion creates a blast force of 1 psi or more out to a radius of 95 ft. As already mentioned, such a force would cause enough damage to a standard house to render it uninhabitable. A blast force of 10 psi or more would extend out to a radius of about 23 ft; 10-psi peak positive overpressure would be sufficient to raze a house to the ground. The range of lethality is short; 200-psi peak positive overpressure extends 6 ft from impact.
Preventative MeasuresTo reiterate, it is not likely that the LLNL high explosives would detonate during an accident on public roads because the explosives are resistant to impact and must be transported in special containers approved by the U.S. Department of Transportation. In addition, Health & Safety Manual 24.05 (LLNL, 1988b) lists detailed procedures to be followed by drivers of vehicles carrying high explosives in the event of vehicle breakdowns and emergencies involving fires or accidents.
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