Adding radioactive waste treatment capabilities beyond those planned at Hanford's vitrification plant would save money, get leak-prone waste tanks emptied sooner and speed treatment, according to a draft of a new Department of Energy study.

"The report definitely told us they need that second facility," said Suzanne Dahl, tank waste disposal project manager for the Washington State Department of Ecology, the regulatory agency for the project.

Hanford DOE officials already were preparing a business case evaluation for top DOE officials in Washington, D.C., on how to treat low-activity radioactive waste when a Government Accountability Office report in June raised questions about treatment.

The GAO report to Congress said DOE should reassess whether bulk vitrification, a proposed supplemental treatment method, is needed to treat radioactive waste, given the escalating costs of studying the process. The DOE case study will help provide a response to Congress on that question.

The study looked at four ways to supplement waste treatment capabilities at the $12.2 billion vitrification plant as it currently is designed and being constructed.

The plant is designed to treat all high-level radioactive waste among the 53 million gallons of waste stored in Hanford's underground tanks. But it is planned to treat only half of the low-activity radioactive waste, which accounts for 90 percent of the waste by volume but has just 5 percent of the tank waste's total radionuclides.

The study assumed treating the high level-waste left from production of plutonium would take 27 years. Without expansion of the vit plant or a supplemental treatment method, treating the low-activity waste would take 60 years, a time span that cannot be justified, the study said.

"Supplemental treatment is needed to treat waste in a cost-effective and timely manner," said Delmar Noyes, DOE acting assistant manager of the tank farms.

Extending the treatment over 60 years at the vit plant, which would turn the waste into a stable glass form, would cost $1 billion to $3 billion more than using a supplemental treatment technology, the draft study said.

Using supplemental technology also would allow leak-prone single-shell tanks to be emptied faster. They're being emptied into 28 sturdier double-shell tanks, but space in those newer tanks is constrained by how fast the waste from them can be treated to create room for more waste.

Supplemental treatment of the low-activity waste would allow the single-shell tanks to be emptied 20 years after the vit plant starts operating in 2019, the study said.

Four types of supplemental treatment are being considered, including adding a second Low Activity Waste Facility to the one being built at the vit plant. DOE also is considering bulk vitrification, which would produce large blocks of waste in land-sea shipping containers that would be buried with the waste inside.

The other two technologies are cast stone, which would grout the waste in place, and steam reforming, which would heat the waste with steam and mix in chemical additives to form a granular mineral-like waste form.

The study found no significant cost differences among the four supplemental approaches. But it did find that expanding the vitrification plant and using bulk vitrification were more technically mature for Hanford waste and would be ready to use sooner, Noyes said.

Design for expanding the vitrification plant to add more low-activity waste capacity is the furthest along, said Ken Wade, DOE's lead author on the study. However, bulk vitrification could provide more operational flexibility because a treatment line could be added easily, the study said.

The study also looked at possible benefits to starting low-activity waste treatment before the entire vitrification plant, including the Pretreatment Facility, is ready to operate in 2019. The Low Activity Waste Facility at the vit plant should be ready to operate by 2014.

The study convinced the state that an early start to low-activity waste treatment is definitely worth considering to speed emptying the tanks and getting more waste treated sooner, Dahl said.

An early start to treatment would require some waste to be pretreated outside the plant. DOE has selected certain liquid wastes that contain fewer radionuclides for possible early vitrification.

Vitrifying the low-activity waste for disposal beginning in 2014 could allow five to 10 leak-prone tanks to be emptied before the vitrification plant is in full operation in 2019, the study found.

"Enabling additional SST (single-shell tank) retrievals over the next decade is an important factor," the study said.

The study was not intended to determine which supplemental treatment approach should be picked, Noyes said. But it will help guide DOE as it starts more detailed study of how to treat the additional low-activity waste, evaluates pretreatment of waste outside the vit plant and looks at options for dealing with secondary waste from treatment processes.

Although the study was prepared by DOE, it was reviewed by outside experts, Noyes said.