DOE to Replace Ventilation System at WESF as Part of Shutdown
WC Monitor
1/9/2015
The Department of Energy is making plans to replace the hot cell ventilation system at Hanford’s Waste Encapsulation and Storage Facility, a necessary step to shut down the building. Earlier this year, DOE’s Office of Inspector General said that 1,936 capsules of cesium and strontium stored at the facility should be moved to dry storage as soon as possible, in part because of the potential risk posed by a severe earthquake. Now the capsules are stored under 13 feet of water at WESF, which was built for them at the west end of B Plant between 1971 and 1973. But the ventilation system that has been used for the hot cells is no longer up to the task of ensuring air is clean and safe when the capsules are processed to be moved to dry storage, according to DOE documents. The current filters have operated longer than planned and are deteriorating, and the work done with radioactive materials has contaminated the ventilation system.
The hot cells and ventilation system contain about 200,000 curies of radiation, some of it embedded in concrete or fixed on surfaces, and most of it not easily dispersible. Replacing just the existing filters would involve unneeded exposure for workers, according to DOE. The replacement system will be better designed with filters that are easier to change, making the work safer for personnel. DOE also is proposing replacing it with a smaller system. That would be accomplished by reducing the space in the building by filling all but one of the seven hot cells served by the ventilation system with grout, in addition to grouting the ventilation system. The plan would be protective of workers and the environment, said Julie Reddick, of DOE, at a public meeting on the proposal this week .A separate ventilation system is used for the pools where the capsules are stored. The seventh hot cell now is on standby in case one of the underwater capsules develops a leak or other issue that would require it to be pulled from the water for work. The hot cell also is tentatively planned to be used to process the capsules when DOE is ready to move them to dry storage.
DOE Wants to Leave Waste in Some Hot Cells
Most of the hot cells measure about 8-feet long and 8-feet wide and up to 13.5 feet tall, but the hot cell that would be left for operations is about twice that size. Starting in 1974 the hot cells were used to convert cesium and strontium from a liquid to solid form and package it in stainless steel canisters about 21 inches long. The material had been separated from other waste in Hanford’s underground tanks to reduce the heat in the tanks, and for a time the capsules were loaned out for industrial use. Six of the hot cells were cleaned out and prepared for closure previously. However, some waste was left stored in them. They still have two containers of floor sweepings contaminated with some strontium, which was collected during the last steps of shutdown of operations in the hot cells. The containers are about the size of flower pots, said Mandy Jones a permit coordinator for the Washington State Department of Ecology. Some debris also was swept into piping that has been closed at each end and mounted on the walls, said Suzanne Dahl, manager of the Department of Ecology’s tank waste treatment section.
Because the manipulator arms were removed from the six hot cells and electricity service was cut earlier, DOE is requesting that the state allow the waste to be left in the hot cells as they are filled with grout. Normally the waste would be required to be removed and treated for disposal separately.
Schedule Uncertain For Removing Capsules
After the cesium and strontium capsules are removed from WESF, DOE could cut the grouted cells into blocks to be disposed of or the building could be treated as part of the processing plant it’s connected to, B Plant. At processing plants, walls may be collapsed and then an earthen barrier built over the demolished building to keep out water that could spread contamination. “Ecology supports the idea that ventilation needs to be grouted and understands the need to take interim steps in the hot cells,” Dahl said.
The Department of Ecology also supports the need to put cesium and strontium into dry storage. DOE does not yet have a date for that work or money budgeted for it. Bids had been requested in 2003 to start repackaging and then putting the capsules in dry storage in Hanford’s T Plant in late 2005. However, the work was canceled as DOE decided it had more pressing cleanup concerns. Now moving the capsules to dry storage is crucial because a national repository will not be available for them for decades, the Office of Inspector General said in an April memo. The capsules hold about a third of the total cesium and strontium radioactivity at Hanford and their waste had been planned to be sent to the proposed repository at Yucca Mountain, Nev., for disposal.
The memo called WESF the DOE facility at greatest risk in the case of a natural disaster that exceeds design standards. The concrete in the cells of its underwater pools has begun to deteriorate from radiation exposure, and a severe earthquake could result in the loss of water used to cool the capsules and provide radiation shielding. The memo acknowledged that an earthquake more severe than WESF was designed to withstand is not likely and that money will not be immediately available to move the capsules to dry storage. But it urged DOE to make plans for dry storage as soon as possible, both for safety and to reduce the annual $7.2 million cost of storing the capsules underwater. Hanford officials are not discussing costs for the new ventilation system while parts of the project are being bid. Public comments may be sent through Feb. 20 to [email protected].
