DOE: Tests show key Hanford vit plant processes will work

By Annette Cary, Herald staff writer

A $90 million project has provided more confidence that Hanford's one-of-a-kind, $12.2 billion vitrification plant should operate as expected, according to the Department of Energy.

DOE and its contractors just completed the first phase of testing at the Pretreatment Engineering Platform, a quarter-scale model of the process that will be used at the vit plant to separate Hanford tank waste into high-level waste and low-activity waste for separate treatment. DOE's goal is to minimize the amount of costly high-level waste canisters produced.

"The facility has verified some of the key processes at the vitrification plant will work," said Bill Gay, a URS employee and assistant project director for the plant, formally called the Waste Treatment Plant.

There will be fewer unanswered questions when the plant starts up, said Suzanne Dahl of the Washington State Department of Ecology, a regulator on the project.

With the completion of the test, Bechtel can proceed with ordering equipment for the vitrification plant. Manufacturing of equipment such as filters for separating waste, pumps to feed the filter and a related heat exchanger had been on hold until DOE was confident that waste separation processes at the vitrification plant are likely to work as expected.

The first phase of testing at the Pretreatment Engineering Platform, or PEP, answered questions about whether processes that worked on cupfuls of materials in the laboratory would also work at the scale needed to turn millions of gallons of waste into a stable glass form at the vit plant for permanent disposal.

And the initial testing gathered some information that will be used to help the plant operate as efficiently as possible. More testing to help optimize operations at the plant may be conducted in Phase 2 of testing at PEP, which is not expected to be done until at least 2010.

PEP, which is about the size of a basketball court and two stories high, was designed and manufactured by URS in Carlsbad, N.M., and trucked to Richland in 16 skids. It was assembled on the Pacific Northwest National Laboratory campus in Richland and testing was done by staff from the national lab, Bechtel National, which is building the vit plant, and its subcontractor, URS.

The complicated system includes 25 tanks and 1,500 instruments and is the largest testing platform built and operated in more than 20 years for DOE's national program to clean up former weapons site.

Mock waste -- which is not radioactive -- was concentrated in ultrafiltration tubes with pores many times smaller than the width of a human hair. Hanford's radioactive tank waste left from the past production of plutonium for the nation's nuclear weapons program includes solids, which are mostly high-level radioactive waste, and liquids, which are mostly low-activity waste.

The Phase 1 test showed that the ultrafiltration tubes worked as envisioned at the scaled-up size in the PEP, said Rob Gilbert, the DOE technical lead for PEP.

The test also looked at whether a second process would remove nonradioactive aluminum from the rest of the solids to allow it to be treated with the low-activity waste rather than the high-level waste. Sodium hydroxide was added to dissolve the aluminum and keep it in solution.

"At a high level it did show the process was effective," Gilbert said.

Data collected from the Phase 1 test also will be used in models to determine how much caustic is optimal by plugging different amounts of caustic, different temperatures and different types of waste into equations, said Steve Barnes, the PEP technical director for URS.

Researchers are looking at how much sodium hydroxide must be added to make sure that too much aluminum does not end up in high-level waste glass without adding so much that the overall volume of waste is increased enough to cause the vitrification plant to operate longer.

The next phase of testing at PEP, if approved, would look at the issue of how much caustic to use, how the system would work for different types of tank waste and how often filters would need to be cleaned, which could slow operation of the vit plant.

The completion of the first phase of testing puts DOE close to resolving work on two more of the technical issues raised -- those concerning the aluminum leaching and ultrafiltration -- by an independent expert panel. That would leave just two of 28 issues left, one concerning how well mixers will perform in tanks in the vit plant and the other concerning how well an automatic sampling system will work.

All the issues could be resolved by fall, Gay said.

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Saturday, Apr. 11, 2009

DOE: Tests show key Hanford vit plant processes will work

By Annette Cary, Herald staff writer