WIPP - Transportation Containers
A Glossary of Terms related to WIPP Transport.
Several transportation containers for carrying different kinds of transuranic waste (TRU waste) to WIPP have been designed, but all of these containers are in various stages of development, testing or certification.
By law, shipping containers for TRU waste must be certified by the Nuclear Regulatory Commission (NRC) as Type B shipping packages - the most secure level of packaging for radioactive shipments. However, the Type B Certification - the most stringent available in this country - is not designed to protect the public from the worst possible type of accident.
Even though this is the very accident the public fears the most and from which the public wants to be protected, NRC concentrates on setting standards for the more likely, but less dangerous accident.
The DOE and the nuclear industry are planning a massive increase in all types of radioactive shipping - but they can't afford to do this if they have to account for the 'worst case scenario.'
However, highway accidents with effects more serious than those the Type B package is designed to withstand do take place...
Contact - Handled Containers
The TRUPACT-II is the only WIPP shipping container to date that has been certified as a Type B Package. It is a container within a container and holds two standard waste boxes or 14 55-gallon drums of contact-handled waste. TRUPACT-II's inner and outer containment vessels have lids which seal with O-rings much like a pressure cooker. The outer vessel is covered by about 10" of foam insulation and a stainless steel shell. Up to three TRUPACTs can be carried in each shipment.
The HALFPACK is also designed to carry contact-handled (CH-TRU) waste and is a smaller version of the TRUPACT-II. It can carry heavier and larger drums, or one standard waste box. In addition to shipping TRU waste to WIPP, the HALFPACK may also be used for shipping within and between DOE sites. Testing of a HALFPACK prototype and application to the NRC for certification as a Type B Package are planned for 1998.
The PIPE OVERPACK consists of a pipe made of stainless steel with a filter (to let out potential explosive gases) and a lid that seals with an O-ring. DOE says the pipe provides "…criticality control…shielding, and …containment of fine particulate waste material." This pipe is centered inside a 55-gallon filtered drum with fiberboard and plywood packing, and has been designed to store and transport a special kind of CH-TRU waste called RESIDUES. These residues would be coming mainly from Rocky Flats, although they will also be shipped from other DOE facilities including Los Alamos. Residues consist of soot, ash, salts, slags, graphites and other powdered materials contaminated with highly concentrated amounts of plutonium. Although some residues would be solidified with cement or glass (vitrified), an unknown quantity would be transported in a loose, powdered form. (Plutonium is most dangerous when it is inhaled as a powder,) Some time ago DOE changed the Waste Acceptance Criteria for WIPP to allow transportation of drums containing 100% "powdered" plutonium. Previously, only 2 or 3% of a drum's contents could be in a powdered form.) The pipe overpack is the container for these 100% powder loads.
Because these residues are so highly concentrated, they must have extra shielding (provided by the pipe) to make sure that the gamma and neutron radiation coming through the drum stays within legal limits.
Also, extra precaution must be taken to ensure that enough fissile material doesn't come together to cause a criticality event or nuclear reaction. When analyzing the criticality potential of the Pipe Overpack, DOE assume that the pipes would never be broken open in an accident and therefore there would be no possibility of a criticality event. (Other containers, like drums, have to be analyzed for the "worst case scenario" - where the containers are broken open and all the fissile material in the load comes together, making a nuclear reaction more likely.) Because of this assumption a TRUPACT-II fully loaded with 14 Pipe Overpacks can carry more than 8 times the fissile material allowed in a normal TRUPACT. In fact, there could be enough fissile material in a 3-TRUPACT load of residues to make a nuclear weapon. Suck a load could be a target for theft by terrorists who might want to extract the plutonium. The Pipe Overpack is not required to meet Type B standards since it will be shipped inside the TRUPACT-II. It has been minimally tested and accepted as a transportation container for WIPP wastes by the NRC.
Remote - Handled Containers
The RH-TRU 72B CASK is a cylindrical container within a container that is designed to carry remote-handled (RH-TRU) waste. Both the inner vessel and the outer cask are made of stainless steel and have lids which seal with O-rings. A two-inch lead liner between the inner and outer containment vessels provides shielding against gamma radiation. An outer thermal shield provides protection against damage by fire. Each end of the outer cask is protected from impact damage by a polyurethane foam-filled impact limiter. Only one 72-B cask will be carried in each shipment. A 5/8 scale model of the 72-B has already been tested and certification by the NRC as a Type B package is currently pending.
The 72-B is designed to hold a single CANISTER of RH-TRU waste. This Canister is made of carbon steel and has all-welded construction including a welded-on lid. The Canister is filtered to release flammable gases into thee 72-B vessel. The Canister is not required to meet Type B standards since it will ship inside the 72-B shipping cask. Each Canister can hold three 55-gallon drums of waste or the equivalent and would be removed from the 72-B and emplaced underground at WIPP robotically since it would be highly radioactive. By law, 100 rem of penetrating radiation can be coming through the Canister walls (measured at its surface). Five percent of the canisters can emit 1000 rem per hour. If the 72-B were broken open, a person in contact with an undamaged 1000-rem Canister could experience radiation sickness in 5-8 minutes and death in 35-60 minutes.