Improved technologies for cleaning up Hanford's radioactive tank wastes have the potential to reduce the cost of environmental cleanup by $16 billion, according to the Department of Energy.
It also could reduce the time needed to treat the Hanford waste by up to seven years, shaving the end date from 2047 to 2040.
The proposals still are preliminary, but Shirley Olinger, previous manager of the DOE Hanford Office of River Protection, has been put in charge of further investigation of what DOE is calling "transformational technologies" at Hanford and other DOE sites with tank waste.
Olinger is assigned to reduce the cost of emptying tanks and treating the waste sooner than current schedules allow.
Never miss a local story.
DOE weapons complex environmental cleanup is projected to cost $190 billion to $244 billion, with 43 percent of that cost related to tank waste, including Hanford tank waste left from chemically processing irradiated fuel.
"It's the dominant risk, the dominant cost and the dominant liability because of the uncertainty," Olinger said.
Among technologies under investigation are methods to perform pretreatment in or near Hanford's underground tanks that store waste awaiting treatment. The $12.3 billion vitrification plant under construction includes a Pretreatment Facility to divide waste into high-level radioactive waste streams and low-activity radioactive waste streams to be turned separately into a stable glass form.
The vitrification plant never was planned to be large enough to treat all 53 million gallons of Hanford waste stored in underground tanks in a reasonable time. One option for treating all the waste at the plant is to add a second Low Activity Waste Facility.
However, the amount of waste that could be treated at the two Low Activity Waste Facilities could be limited by how efficiently the Pretreatment Facility operates.
By pretreating certain liquid waste to remove high-level waste at the tanks, the waste could bypass the Pretreatment Facility. Technologies under investigation include an ion exchange process at the tanks to remove cesium.
In addition, a rotary microfilter is being investigated at the Savannah River, N.C., nuclear site to see if a centrifuge technology could remove solids from the liquid.
Another project is looking at steam reforming, which was earlier considered for treating Hanford's low-activity tank waste but rejected. However, technology developments in the past four years on steam reforming are promising, Olinger said.
The technology uses high-pressure steam to turn waste into a granules. Newer steam reforming technology turns waste into a ceramic form that's more robust, Olinger said.
Steam reforming will be looked at first for secondary waste streams, particularly technetium that is not captured in waste glassified at the vit plant.
But if the ceramic form proves to hold radioactive waste as well as glass, it could be considered for primary treatment of some low-activity waste in Hanford's tanks.
Longer term, as the first generation of melters at the vitrification plant wear out they could be replaced with new cold crucible melters. Those could prove to be more efficient, allowing more waste to be loaded in the glass and handling more corrosive chemicals than the melters now being built.
Some efficiencies planned to reduce the cost and schedule for tank waste would help tank farm operations.
New methods to empty the underground tanks are being investigated, including ways to dissolve the hard layer of waste at tank bottoms and a robotic arm that's larger and stronger than any technology used to date.
DOE also is looking at the possibility of consolidating some waste in single-shell tanks rather than consolidating all waste emptied from those tanks into newer double-shell tanks.
If some of the single-shell tanks could be shown to be sturdy enough to hold consolidated waste without leaking, the distance that some waste would need to be transferred between tanks would be shortened. That also would require less infrastructure to transfer waste.
Some of the other single-shell tanks or even groups of tanks might be closed sooner, Olinger said. Hanford has 149 single-shell tanks -- 67 suspected of having leaked in the past -- and 28 newer double-shell tanks.