Hanford officials expect the pipes and tanks that make up the Pretreatment Engineering Platform to be assembled into a web of machinery the size of a basketball court by the end of the month.
The platform is an approximately quarter scale model of the equipment for some of the least thoroughly tested processes that are planned to be used at the one-of-a-kind vitrification plant being built at Hanford.
The nuclear reservation has 53 million gallons of radioactive waste held in underground tanks from the past production of plutonium for the nation's nuclear weapons program, much of which will be turned into a stable glass form for disposal at the vitrification plant, known as the Waste Treatment Plant.
Processes to separate the waste into high-level radioactive waste and low-activity radioactive waste have worked in the laboratory using samples of Hanford waste. But independent experts assembled by the Department of Energy to take a look at the vit plant recommended major separations processes needed to be verified on a larger scale.
"Anything that's wrong with it we don't want to learn during the Waste Treatment Plant commissioning," said Rob Gilbert, the DOE technical lead for the Pretreatment Engineering Platform.
Instead, DOE hopes to discover any problems and correct them early by testing the process on a 1 to 4.5 scale with nonradioactive mock waste.
Vit plant contractor Bechtel National awarded a subcontract to URS Corp. in Carlsbad, N.M., in January 2007 to design and build the test equipment and to ship it to Pacific Northwest National Laboratory in north Richland. That portion of the project cost $30 million.
Now the equipment, which arrived in 16 skids, is being installed and will be tested and operated by PNNL. Although more tests could be added later, initial tests planned will bring the cost of the project to $75 million.
When waste is piped into the vitrification plant after operations begin in about 2019, it will first go to the Pretreatment Facility. There it will be concentrated, separated and blended and then piped to either the High Level Waste Facility or the Low Activity Waste Facility to be turned into a stable glass form.
Solids in the tank waste contain much of the high-level radioactive waste, but the Pretreatment Facility will need to remove nonradioactive aluminum and chromium from the solids to reduce the quantity of waste treated as high level.
That will be done with technology being tested at the Pretreatment Engineering Platform, which is about
18 feet tall and includes 25 tanks and 1,500 instruments.
Waste will be concentrated in ultrafiltration tubes, sintered metal tubes with
0.1 micron pores that filter out liquids. A human hair is about 40 microns in diameter. The test facility will have about
72 square feet of filter surface area, compared with
1,445 square feet in the vit plant's Pretreatment Facility.
Then sodium hydroxide will be added to the concentrate to dissolve the aluminum and keep it in solution. The mixture will be heated to up to 212 degrees and held for up to 12 hours.
At the Pretreatment Facility, the liquid waste then would be sent to an ion exchange process to remove radioactive cesium.
The solids would be washed to make sure all sodium hydroxide has been removed and sodium permanganate would be added to oxidize the chromium into a liquid. Solid waste then makes another loop through the ultrafilters to wash the chromium out.
Finally, the solid waste is washed and blended with the cesium to be ready for vitrification.
DOE expects to test the equipment using water beginning in June. By the end of October or early November, tests with the mock waste should begin.
Print
E-Mail
