government
NUCLEAR WASTE CLEANUP STIRS Contractor chosen to begin treating deadly brew of high-level radioactive chemical waste at DOE's Hanford site Jeff Johnson C&EN Washington
O
n June 30, the Department of Energy intends to announce details of a contract that DOE officials say will lay the groundwork for the largest high-level nuclear waste cleanup program in the world. The contract will be with an enterprise led by BNFL Inc., the U.S. subsidiary of British Nuclear Fuels Ltd., and includes Bechtel National, GTS Duratek, and Science Applications International Corp. It will result in construction of a privately financed plant that will vitrify up to 13% of 55 million gal of high-level radioactive and hazardous waste held in 177 underground tanks at DOE's Hanford site in Richland, Wash. Vitrification is a process that chemically bonds waste into a durable and stable glass. In Hanford's case, a brew of radioactive and hazardous waste and metals will be mixed with glass-forming chemicals and heated to 1,150 °C. Once fused, the matrix will be poured into stainless-steel canisters that are to be placed in a repository. The shiny black vitrified waste and borosilicate
glass must by regulations remain in a stable form for at least 10,00 years. In the U.S., vitrification technologies for high-level nuclear waste are being used at DOE's Savannah River site in South Carolina and West Valley Demonstration Project in New York. They also are being used for high-level radioactive wastes in Britain, Belgium, France, and Japan—but at nowhere near the U.S. volume. Many of Hanford's tanks are leaking into groundwater, and DOE is under great pressure to get the program under way. In a sense, the contract is for a huge demonstration project because initially only 6 to 13% of the waste will be treated within a five-year period. The entire 55 million gal is supposed to be treated later—by 2028—under an agreement with Washington State and the federal Environmental Protection Agency. All eyes will be on the operation because it is the largest single item in DOE's $147 billion program to clean up the mess left at some 50 federal sites by Cold War scientists and engineers in their rush to make nuclear weapons. Even the contract itself must be reviewed by Congress before DOE can issue it.
When announcing BNFL's preliminary selection on May 21, John D. Wagoner, manager of DOE's Richland Operations Office, was circumspect in answering cost questions, saying only that the vitrification program would run in the "billions" of dollars. He noted that the exact deal has not been finalized, and that it will be announced June 30. However, BNFL is now DOE's only candidate. In a demonstration of the size of the project, DOE paid $27 million to both BNFL and Lockheed Martin Advanced Environmental Systems, the unsuccessful suitor, to prepare a design and show they can treat the waste on schedule. Lockheed Martin's proposal was rejected, Wagoner said, because of an "unacceptably high technical risk." The technology it selected would require more research and development, he said, before it could be put to use to ensure an acceptable risk level. Wagoner defended DOE's decision to place all its eggs in BNFL's basket even before negotiating afinalcontract, saying its' technology was best, more proven, and is being used in other parts of the world and at other DOE sites. "DOE did it right on this one," says Lynn Stenbridge, director of the Hanford Education Action League (HEAL), a Spokane, Wash., citizens' group that has closely monitored the Hanford cleanup. Based on what she had learned, she says, Lockheed planned to rely on one of its partners, the French firm Cogema, to vitrify nuclear wastes. Cogema reprocesses and treats waste in France using a different technology. "BNFL looks best to get the job done, and heaven knows it is a job that desperately needs to be done," she says. She warns that this is only a small
Vitrification process for Hanford's radioactive waste stored in tanks Liquids
55 million gal of radioactive waste in 177 tanks
Low-level radioactive waste 90% of total volume High-level radioactive waste
Sludge
75% glass
Buried on-site
25% waste
Glass-forming chemicals 10% of total volume .
75% glass
To high-level repository
25% waste Canister Glass-forming chemicals
26 JUNE 8, 1998 C&EN
step forward, "but with a mess as big as Hanford's, you really have to savor any victory." Complicating the task at Hanford is the amount of waste to be treated and its condition. A system must be designed that will continuously and speedily process the tanks' complex mix of chemicals and hazardous and radioactive wastes without blocking the flow of glass or corroding critical melter components, says Carol Jantzen, a research scientist at the Savannah River Technology Center at DOE's Savannah River site. Jantzen is a key scientist at the center that set up Savannah River's vitrification program. After a difficult start, the DOE facility began treating waste in 1996, and its operation is second in size only to Hanford's. Savannah River Technology Center is also under contract to BNFL to help it develop the Hanford vitrification program. Two melter process lines are proposed for Hanford, mirroring the two that are in operation at Savannah River. One will vitrify high-level nuclear waste and one low-level waste. The low-level wastes are in a liquid form and are filtered and processed through ion-exchange columns and a precipitation process to remove the most radioactive elements. The remaining waste will be vitrified and placed in stainlesssteel boxes, 1.2 x 1.2 x 1.8 meters. These will be stored on-site in engineered vaults, similar to what is used for lowlevel radioactive commercial waste. This low-level waste is about 90% of Hanford's volume. High-level wastes will be vitrified in a similar manner but stored in 4.5-meterlong stainless-steel canisters, 0.61 meter in diameter. Each canister will weigh about 9,200 lb when full. Its contents will be 25% waste and the rest glass. These will be housed on-site until the long-stalled high-level waste repository is completed at Yucca Mountain, Nev. Complicating the process is sodium hydroxide, which was added to Hanford's waste to neutralize its acidic makeup. The hope was that the addition would slow corrosion of steel holding tanks. Nevertheless, the mammoth tanks—up to 1 million gal in capacity—still leaked, and the addition of sodium hydroxide and other chemicals that were dumped in the tanks over the years has increased the volume to be treated (C&EN, July 22, 1996, page 14). This mismanagement also will make it much more difficult to characterize
the waste, which is needed to set melter operating parameters. Jantzen says juggling properties of the glass/waste mix to maintain viscosity and avoid crystallization of the blend in the melter is one of the most vexing vitrification problems. So far, the Savannah River facility has processed about 375,000 gal of its 34 million gal of high-level radioactive waste and has filled 390 canisters—at a rate of one per day. Its biggest problem, critics say, has been in pretreating liquid and "saltcake" wastes, a thick material lighter than sludge. In processing liquid and saltcake wastes, flammable benzene was produced, which stopped these operations because of safety concerns. Consequently, Savannah River is only vitrifying sludge at this time. Brian Costner, director of the Energy Research Foundation of Aiken, S.C., a citizens' group near the site, worries DOE may be relying too strongly on the Savannah River model for Hanford. "Sludge processing has been okay," he says, "but more than 90% of the
waste is liquid or saltcake, and they've had to go back to the drawing board on that." He points out that Savannah River's vitrification start-up was seven years late and several billion dollars over budget. On the other hand, he says, DOE may profit from Savannah River's mistakes. In response, Savannah River scientists note sludge holds 90% of the radioactive constituents and say delays and cost overruns were attributable in large part to DOE changes in design criteria. Mike Johnson, a BNFL engineer, notes that the Savannah River facility is reevaluating its pretreatment plans now. He stresses, however, that BNFL plans to handle pretreatment differently at Hanford. The overall deal still could fall through, and several sources add: BNFL and DOE may not reach agreement, or Congress may object to the contract. Then DOE could be back to the starting line. Local groups such as HEAL remain sanguine, however. "You know, we have been 'back to square one' so many times at Hanford," Stenbridge says, "it's just 'home.' "
