Wash. State Supports New LAW Pretreatment System
WC Monitor
12/5/2014
The state of Washington supports the concept of a proposed new facility that would allow Hanford’s Waste Treatment Plant to start treating some waste sooner, but has concerns about how the Department of Energy will pay for the facility. The proposed Low-Activity Waste Pretreatment System, LAWPS, would prepare some low-activity waste to be treated without first being sent to the plant’s Pretreatment Facility, where construction has stopped while technical issues are resolved. “We are all about getting waste into glass as soon as possible,” said Suzanne Dahl, the manager of the state Department of Ecology’s tank waste treatment section, at a recent committee meeting of the Hanford Advisory Board.
DOE may not have the full vitrification plant operating until 2031, but by building LAWPS, it could start treating low-activity waste as soon as 2022. But the state also has some concerns about where money for the project will come from and at what expense to other Hanford projects, Dahl said. The conceptual design of the LAWPS plant has been completed and is being reviewed by DOE, with the next phase, preliminary design, yet to begin. That means only rough estimates of the cost have been made, which will be refined as the design advances. Now the estimated cost is between $243 million and $375 million, which includes money for contingencies, said Steve Pfaff, DOE project director.
However, there also would be additional costs both at the tank farms and at the vitrification plant. The estimate does not include the costs for building roads and extending water and utility service to LAWPS, some improvements needed to double-shell tanks that hold waste and transporting the glassified low-activity waste to Hanford’s Integrated Disposal Facility. At the vitrification plant some changes to the support facilities might be needed, and the Low Activity Waste Facility would need to be prepared to begin treating waste. In addition, a way to treat secondary waste produced during treatment would be needed. That would require both improvements at Hanford’s Effluent Treatment Facility and construction of a new vit plant support facility, the Effluent Management Facility.
DOE Looking at Past Projects to Accelerate New Facility
DOE is relying on two past projects to speed up planning for the new LAWPS. A 2008 analysis concluded that the same technologies used at the vit plant’s Pretreatment Facility could be used on a smaller scale at a facility outside the plant. DOE also looked at conceptual designs for a plant in 2011, but not one that would allow the Low Activity Waste Facility to operate at full capacity. “In some respects we picked up where we left off,” Pfaff said.
The current plan calls for a facility that would allow the vit plant’s Low Activity Waste Facility to produce five canisters of glassified waste per day that stand about 7.5 feet tall and are 4.5 feet wide, or a total of 30 metric tons of glass a day. LAWPS would use crossflow filtration to get the suspended solids out of the tank liquids and then an ion exchange process to get dissolved cesium out of the liquids, similar to the two-step process planned at the vit plant’s Pretreatment Facility. Experience in using the methods at LAWPS will be helpful when operation of the vit plant’s Pretreatment Facility begins, Pfaff said.
Sections of New Facility Would be Built Underground
A site has been selected for LAWPS between the AP Tank Farm and the vitrification plant. Key parts of it would be built below ground to help with radiation shielding. Rather than use hoses contained within larger hoses strung along the ground to move the waste, as is common in the tank farms, permanent piping is proposed. Double, shielded underground pipes would be used to transfer waste from the AP Tank Farm to LAWPS and then to the vitrification plant. The permanent piping system is needed both because of the distances the waste will be transferred and also because LAWPS could be used for decades. Even after the Pretreatment Facility is operating, it could be used to allow continued waste treatment during maintenance or other outages at that Pretreatment Facility.
Some technical issues still need to be worked out for LAWPS, but they do not appear to be insurmountable, Dahl said. The Pretreatment Facility was expected to play a role in handling secondary waste from the Low Activity Waste Facility. Without it operating, an Effluent Management Facility is planned to be built near other vitrification plant support facilities. Liquid waste from the Low Activity Waste Facility’s off-gas treatment systems would be sent to the Effluent Management Facility to be evaporated, allowing most of the water to be sent to the existing Effluent Treatment Facility for further treatment. Some of the waste after evaporation would still contain enough contaminants that it would either have to be returned to the tank farms or sent back to the Low Activity Waste Facility for vitrification.
The Effluent Treatment Facility, in operation since the mid-’90s, already receives wastewater from another Hanford evaporator, the 242A Evaporator, and from groundwater treatment projects. It would need to be upgraded to extend its operating life and to handle different wastewater streams that would come from the vitrification plant. The state is ready to start work toward issuing permits for the proposed LAWPS and hopes timely progress is made on it, Dahl said. Getting some waste treated for disposal will free up more space in Hanford’s double-shell tanks to hold waste emptied from Hanford’s older and leak-prone single-shell tanks, she said.
