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THE AIR FORCE AND THE TRANSPORTATION OF DINITROGEN TETROXIDE

The Air Force buys, stores and transports liquid dinitrogen tetroxide (N2O4) in support of the nation's space program. N2O4 is a liquid oxidizer which is combined with rocket fuel for spontaneous ignition. It is used primarily in Titan and Delta rockets and the Space Shuttle.

The Air Force contracts with the Vicksburg Chemical Company, Vicksburg MS for the manufacture of the oxidizer. Commercial carriers transport N2O4 to Air Force, National Aeronautics Space Administration and defense contractor facilities throughout the country. It is shipped in bulk quantities by tank trailer and by rail. Smaller quantities are also transported in cylinders by truck and ship.

The San Antonio Air Logistics Center Directorate of Aerospace Fuels Management at Kelly Air Force Base, Texas, manages the procurement, transportation, storage and disposal of the product for the Air Force. Shipments are made under the direction of the directorate's Transportation Office. This office initiates many safeguards to ensure shipments are made in the safest manner possible and constantly looks for ways to improve the safety of the transportation system.

The Transportation Office also publishes Emergency Response Plans which provide guidelines for responding to highway and rail accidents or incidents involving N2O4. The Department of Transportation requires such a plan for moving this product in bulk on public highways and railways. The Air Force conducts training exercises on these plans.

Product users base their shipping requirements for N2O4 on operational needs and forward their requirements to the Directorate of Aerospace Fuels Management. An inventory manager coordinates shipments with the directorate's Transportation Office, which monitors all shipments until they are received at their destination. Since N2O4 requirements fluctuate, there is no average delivery frequency. From Dec. 31, 1994 through Dec. 31,1995 there has been a total of 5 loaded tank trailers shipped and 7 loaded tank cars shipped.

Routes for the transportation of N2O4 are selected using a computerized route risk assessment program. The program computes a risk factor for each proposed route, considering such things as population, probability of an accident, and the potential effect an accidental product leak could have on the population along that particular route. The routes are reviewed periodically to meet Department of Transportation exemption and approval requirements.

The Air Force recognizes the risk in transporting N2O4 and has taken many precautions over the years to enhance the safety of product shipment. These precautions have proven effective. There has been no accident or incident resulting in the loss of liquid product on public highways in more than 30 years.

PROPERTIES OF N2O4

N2O4 is identified as an inhalation hazard. It is nonflammable, but will readily support the combustion of other materials. In rockets, the oxidizer is combined with fuel to produce the thrust which lifts them into space.

Liquid N2O4 released into the atmosphere turns into a gas. It will remain in liquid form in an enclosed environment. The Department of Transportation's Emergency Response Guidebook states that applying water, as a fog or fine mist, is one recommended method for controlling an accidental release of this product. Although the propellant is water-soluble, it also reacts with water to form either a nitrous or nitric acid vapor or liquid. These acids are neutralized by using a dilute inorganic basic solution of either lime, sodium carbonate or caustic acid.

N2O4 HIGHWAY SHIPMENTS

The Air Force makes bulk highway shipments of N2O4 to Cape Canaveral Air Station, FL.; Lockheed-Marietta Aeronautics., CO.; NASA Test Facility, White Sands Missile Range, N.M.; Vandenberg Air Force Base, CA.; Aerojet Propulsion Systems Plant, CA., and Arnold Engineering Development Center, TN.

CARGO TANK TRAILER DRIVERS

The Air Force contracts only with long-established commercial motor carriers who have excellent, industry-proven safety records. The experience, qualifications and training required of drivers exceed Code of Federal Regulations requirements for drivers of other hazardous materials. Two drivers are assigned to each tank trailer carrying the product. Two tank trailers comprise a normal shipment.

Drivers receive formal training every two years on the physical and chemical characteristics of N2O4. Training includes instruction on authorized routes of movement and safe stopping places; actions to take in the event of mechanical breakdown, accident or product loss, and other responsibilities such as required documentation and special shipping instructions.

TECHNICAL ESCORT TEAM (TET)

A trained technical escort team accompanies all shipments. The TET provides an immediate emergency response capability and communications link to local and federal emergency response resources.

The Air Force contracts with Vicksburg Chemical Company to provide a nine-member team for each shipment. The team is drawn from a predesignated pool of company personnel who possess expert knowledge on N2O4 production, distribution, storage and safety.

All team members are thoroughly trained on the physical and chemical properties as well as the hazards of the propellant, and on the characteristics of the cargo tank trailer. They also receive hands-on training for minor repairs of the trailer.

They receive training on hazardous material incident response which satisfies the Environmental Protection Agency training requirements for those who first respond to the scene of such an incident. In addition, they receive classroom training on the Emergency Response Plan.

The TET operates out of a motor home and a truck. The motor home is used by off-duty escorts while en route, and serves as a command post in the event of an accident or incident. It is equipped with a citizens band radio, cellular telephone, facsimile machine, satellite communications system, and plume plotting capability.

The truck carries the emergency response equipment and tools which may be used, if needed, by the TET to mitigate minor product leaks or spills. This includes personal protective gear, tools and equipment, decontamination equipment and supplies, and first-aid equipment and supplies. Even though the Air Force has an excellent safety record for transporting N2O4, it remains sensitive to public concern regarding highway shipments of the product and continuously seeks to further enhance the safety of these shipments. Although federal law does not require escorts for each shipment, an escort team accompanies each N2O4 tank trailer shipment.

N2O4 TANK TRAILERS

Special MC 338 tank trailers are used for the bulk highway shipment of N2O4. The trailers are equipped with state-of-the-art safety features that far exceed industry standards and current federal packaging specifications for equipment used to transport products with similar hazards. The cargo tank trailers have the capacity to haul 2,500 gallons of product.

The trailers and equipment are constructed from rugged stainless steel. The tank consists of an inner tank and an outer jacket. The annular space contains a gaseous nitrogen blanket to maintain an inert corrosion-free environment. A honey-combed material similar to aluminum at the front of the trailer absorbs energy if the trailer is involved in a head-on collision, greatly reducing the possibility of a spill. The inner surface of the outer jacket is painted with a fire retarding epoxy to insulate the inner tank from extreme heat or fire.

Valves and piping are located on the top rear portion of the trailer and are enclosed in a retractable steel cover and roll bars for protection. The roll bars can withstand the full weight of the trailer and its contents in a rollover without damage to piping or valves. Also, the cover will not close if any of the valves are not completely shut off. An additional safety feature is that each trailer has an emergency valve leak kit of color-coded canisters specifically fitted for each valve. When installed, the canisters seal off any leaking valve until more permanent repairs can be made.

Government inspectors inspect the trailers each month at the carrier's terminal to ensure they comply with the maintenance and road-worthiness provisions of the contract. The same type of inspection is performed prior to the trailer's departure from the terminal to pick up a load of product, at the pick up point both before and after loading, and again at the delivery point before and after unloading. Upon return to the terminal, a government inspector inspects the trailer once more. At that time, repairs or maintenance are completed as required or identified. The trailers are also pneumatically tested every five years at one and one-quarter times the tank's designed pressure to ensure the integrity of the inner tank and its welds.

The cargo tank trailers used for moving N2O4 are owned and maintained for the Air Force under an exclusive-use contract by two motor carriers: Jack B. Kelley, Inc., Amarillo, TX, and Superior Carriers, Inc., Marion, VA. No other hazardous materials are ever shipped in these cargo tank trailers. Air Force contracts require motor carriers have the highest standard of trailer maintenance and inspection.

N2O4 RAIL SHIPMENTS

Air Force shipments of bulk N2O4 by rail are made to Cape Canaveral Air Station, FL and Aerojet Propulsion Systems Plant, CA. There are eight tank cars in the N2O4 rail fleet.

EMERGENCY RESPONSE TEAM

The Air Force contracts with the Vicksburg Chemical Company to provide emergency response teams that will respond to incidents/accidents involving N2O4 rail tank cars owned by the Air Force. The teams are situated at various locations along the routes of movement and can respond to an accident scene within hours.

All of the team members are thoroughly trained on the physical and chemical properties as well as the hazards of the propellant, and on the characteristics of the rail tank cars. Their assistance and expertise on the propellant and the equipment is invaluable to rail carriers and local responders.

N2O4 RAIL TANK CARS

The rail tank cars are built to class DOT 105J500W specifications. The tank cars are insulated stainless steel pressure cars, with a manway nozzle designed for top loading and unloading. Bottom outlets or washouts are prohibited. The tank cars are fabricated from SA-240, Type 304L stainless steel. The tank car is equipped with thermal protection, full head puncture resistance shields and double shelf couplers. The tank cars have the capacity to haul 10,000 gallons of N2O4.

The "tank" portion of the rail car is separable from the "undercarriage" portion of the car. In an accident scenario the anchor bolts and anchor members are designed as shear connections. The design feature is incorporated to minimize the likelihood of tearing open the liquid containing pressure vessel.

All valves and piping on these cars are located on the top, within a lockable dome, near the center of the car. A valve leak kit of color-coded canisters was designed to specifically fit each valve. When installed, the canisters seal off any leaking valve until more permanent repairs can be made.

Government inspectors, railroad personnel and the N2O4 contractor perform periodic inspections of the tank cars. In addition, checklists have been developed for maintenance inspections prior to loading and after unloading by the shipper and receiving activities.

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