Putting this story into context: The Idaho Chemical Processing Plant has started its high-level liquid waste evaporation process, a pretreatment for calcining the liquid waste now stored in underground tanks at the INEL. Start of the evaporator puts the INEL ahead of the schedule in the Settlement Agreement between the state of Idaho and the Department of Energy for converting the liquid waste into a more stable form and storing it above ground.

The evaporation process to pretreat high-level liquid waste for calcining at the Idaho National Engineering Laboratory has started ahead of schedule.

The evaporation process is the first step in moving liquid radioactive waste out of underground storage tanks for conversion into a more stable solid form (calcine) and storage in aboveground bins, an action the Department of Energy and state of Idaho consider a priority in INEL waste management activities.

The June 1 evaporator startup at the Idaho Chemical Processing Plant beat by five months the Oct. 31, 1996 deadline established in the Settlement Agreement between the state of Idaho and the Department of Energy. It also puts the INEL ahead of the schedule established in the Site Treatment Plan agreed to by the state and DOE in 1995.

The evaporator, designed specifically for this application, is a new installation at the New Waste Calcining Facility. The system consists of four hastelloy (a high-grade stainless steel resistant to acid corrosion) and stainless steel vessels and associated piping for transferring high-level liquid waste between the underground storage tanks and the evaporator vessels. Installation was started in June 1994 and completed in the spring of 1996.

Following evaporator pretreatment that continues through the remainder of 1996, the liquid will be calcined beginning in early 1997 and continue through June 1998. The evaporation and calcining campaign will process nearly 500,000 gallons of liquid waste, exceeding the 300,000 gallons stipulated in the Settlement Agreement.

The evaporator pretreatment process concentrates liquid wastes that are stored at the ICPP in underground stainless steel tanks inside concrete vaults. The evaporator significantly reduces the volume of waste (by about 40 percent) that requires calcining. The concentrated liquid will be returned to the tanks and held until calcining starts.

The calcining, done at the New Waste Calcining Facility, turns the liquid waste into a granular material that resembles detergent powder and makes it more stable and easier to contain. The calcine is stored in aboveground stainless steel bins in concrete vaults. Converting the liquid waste into a granular form significantly reduces risk of waste storage and further reduces the volume of waste by about 4 to 1. About 135,000 cubic feet of calcine are now stored at the CPP from previous calcining campaigns.

The current campaign will process all the nonsodium high-level liquid waste at the ICPP. The remaining 1.5 million gallons of sodium-bearing liquid waste must be calcined by December 2012, according to the Settlement Agreement.

The liquid waste is the byproduct of reprocessing of spent nuclear fuel previously done at the Chemical Processing Plant to recover enriched uranium. Reprocessing was phased out beginning in 1992.