CH-TRU Waste Disposal
Currently, only contact-handled transuranic (CH-TRU) waste is allowed to be received and buried at WIPP. A specific procedure is followed when the waste arrives at the facility from the time it comes through the gates until it is stacked in the disposal room. Before it arrives, it has already been through characterization at its generator site (see the section on The Waste/Waste Characterization for more information on characterization). It is then loaded into the TRUPACT-II transportation container which is transported by truck to WIPP. Each tractor-trailer is capable of carrying 3 TRUPACT-IIs. Although DOE originally planned to receive 17 shipments per week at WIPP, in fact they are receiving about half of that. Information about each shipment is carried in several databases including an electronic database and in shipping papers that accompany each load.
Upon arrival at WIPP the tractor trailer and TRUPACT-II undergo 'surface processing' which includes a security inspection, a radiological survey, and a shipping documentation review. Radiological surveys include checks with a dose rate meter and surface swipes taken at specific points on the outside of the TRUPACT-II. Once the shipment checks are completed, the tractor-trailer is parked near the Waste Handling Building (WHB) for additional inspection and radiological survey. A 13-ton forklift is then used to transfer each TRUPACT-II from the trailer, through an air lock, and into the Waste Handling Building.
Inside the Waste Handling Building, each TRUPACT-II is placed in a TRUDOCK, which holds the shipping container in place while workers unload the waste. An overhead crane is used to remove the TRUPACT-II lids. First the outer lid is removed. (The picture at right shows the outer lid being removed with the inner lid visible underneath.) Then workers put the vent hood cover around the inner lid and hook up an exhaust system which vacuums the air and any contamination which might be inside through HEPA filters. More radiological surveys are conducted and the crane is used again to remove the inner lid.
The overhead crane then removes the waste containers from the TRUPACT-II and places them on a facility pallet. Each TRUPACT-II can hold three different waste container configurations: two seven-packs (seven 55-gallon steel drums wrapped together), two standard waste boxes, or one ten-drum overpack. (However, as noted above, the TRUPACT-IIs do not always arrive with a full load.) A forklift moves the loaded facility pallet either to the storage area in the WHB or to the conveyance loading car inside the air lock at the waste handling shaft if the waste is going to be placed underground immediately. The conveyance loading car is used to load the facility pallet onto the waste hoist (mine elevator) where it descends 2150 feet to the underground repository. (The picture at left shows waste handlers guiding a loaded facility pallette onto the waste hoist.)
An underground transporter (similar to a lightweight flatbed truck) pulls the loaded facility pallet off the hoist and onto the bed of the transporter. It then moves the waste to a disposal room where a forklift removes the waste containers from the facility pallet and stacks the waste in the room. Bags of magnesium oxide (MgO) are placed on top of the containers to serve as backfill. The magnesium oxide is the only engineered barrier at WIPP and, among other things, attempts to control the solubility of the radionuclides in the waste.
Waste is stacked 3 layers high and 6 columns wide in the disposal rooms. This leaves no aisle space so it is impossible to access areas where waste has been stacked to fight fires or to perform maintenance on the roof support systems used in the rooms of Panel 1. Because the ceilings, floors and walls are closing into the rooms there may soon come a time when DOE will be able to stack the containers only 2 layers high. They have received permission to do this but have not needed to yet. If the containers are stacked only 2 high there could be a difference in the size of the space between the MgO and the ceiling from the figure that was used in the original performance assessment calculations for the repository. If the distance is greater than in the original calculations, the effects of a roof-fall on the waste containers could be greater than expected, possibly causing contamination problems in the rest of the facility.
In the underground repository there are, currently, 2 excavated panels. Each panel is made up of 7 disposal rooms. DOE is only emplacing waste in Panel 1 right now even though it is structurally in poor condition (see The Facility/Panel 1). They want to reserve Panel 2 for remote-handled transuranic (RH-TRU) waste. Since RH-TRU waste is buried in the walls of the disposal rooms before the CH-TRU waste is stacked on the floor, it must be emplaced first, before any CH-TRU is brought to the room. However, although DOE wants to get the Hazardous Waste Facility permit changed to allow the receipt of RH waste at WIPP, they are not actually ready to characterize, treat, transport and bury RH waste at WIPP
RH-TRU Waste Disposal
If RH-TRU waste is ever allowed at WIPP the procedure for receiving and disposing of this waste would be somewhat different from that for CH-TRU waste. Because of the large dose of radioactivity on the outside of the RH-TRU waste canister (up to 1000 rem per hour as compared to only 200 millirem per hour on the surface of a CH-TRU waste container) it must be constantly shielded. During transport the waste canister which is 2 feet in diameter and 10 feet long (seen at right) would be placed inside the RH 72-B transportation container which is lined with 2 inches of lead. The 72-B only holds one canister. When the shipment arrived at WIPP, the 72-B would be unloaded into a special room in the Waste Handling Building where the RH canister would be removed and lifted into the shielded Hot Cell. In the Hot Cell the waste container would be inspected and then placed in a shielded facility cask for transport to the underground disposal room where the facility cask would be placed in the Horizontal Emplacement and Retrieval Equipment (HERE) machine (seen at left). This machine uses a hydraulic ram to push the canister out of the facility cask and into a predrilled hole in the disposal room wall. After the waste was pushed into the wall, the hole would be plugged. The facility cask can be reused. Only after the RH waste had been emplaced in the walls of a disposal room could the CH waste be stacked on the floor since the CH waste fills the room from wall to wall.