Staff Reports
WC Monitor
10/23/2015
The 242-A Evaporator at the Hanford Site has completed a planned series of four operating campaigns over the last year after improvements were made to the facility. The evaporator plant is central to work to empty waste from Hanford’s single-shell tanks into newer double-shell tanks for storage until the Waste Treatment Plant begins treating the waste for disposal. It reduces the liquid volume of the waste, allowing the limited capacity of the double-shell tanks to be used more efficiently. The Department of Energy has told the federal court judge who will set new milestones in the consent decree between DOE and the states of Oregon and Washington that the evaporator will allow it to meet deadlines for emptying the 19 tanks covered by the decree. The state of Washington questions whether the evaporator can operate consistently to reduce the volume of waste in double-shell tanks enough to allow DOE to keep emptying single-shell tanks. It has asked the judge to require DOE to build the equivalent of 4 million-gallon-capacity tanks by 2022, with possibly more after that, to ensure the department has space to empty leak-prone single-shell tanks. DOE opposes building new tanks, saying the money would be better spent on work to treat the waste.
DOE started up the evaporator last fall after a four-year shutdown to make improvements. The initial operating campaign in fall 2014 freed up tank space for almost 800,000 gallons of waste. The campaign included two waste feed passes to achieve the large volume of water removed. A second campaign completed in June processed about 900,000 gallons of tank waste to remove 400,000 gallons of excess water and a third campaign completed in July processed about 878,000 gallons of tank waste to remove 384,000 gallons of excess water. The fourth campaign operated nonstop from Sept. 14 to Sept. 23 to remove 375,000 gallons of water. Together the four operating campaigns removed almost as much waste as two double-shell tanks could hold. Hanford has 28 double -shell tanks, but Tank AY-102 is being taken out of service after developing a leak contained within its shells.
The evaporator plant in central Hanford receives liquid waste that is pumped through underground pipes from the double-shell tanks. It heats the waste under vacuum until it boils, creating water vapor. The vapor is captured, condensed, filtered, and sent to the Effluent Treatment Facility for treatment and disposal. The concentrated waste is returned to the double-shell tank system.
From 2000 to 2004, Washington River Protection Solutions worked on upgrades to the evaporator facility, including revamping the control room, acquiring spare parts, and making changes to equipment and operating procedures. It addressed recommendations by the Defense Nuclear Facilities Safety Board to help the plant better withstand a severe earthquake. WRPS also conducted a review of how the facility meets nuclear safety requirements. “The 242-A Evaporator facility is mechanically sound,” said Tom Fletcher, DOE assistant manager of the Hanford tank farms, in information prepared for the court. “Continued integrity assessments and equipment upgrades, along with a proactive maintenance strategy, should keep the evaporator operating for another 30 years. Many of the upgrades that have kept the facility operational beyond its original design life involved the replacement of equipment prior to its failure.”
DOE plans to operate the evaporator facility for 23 campaigns through fall 2022 to reduce waste volume by almost 8.8 million gallons. Three of the campaigns would support removal of waste from Tank AY-102. The 23 campaigns are an increase in the number of campaigns per year, but are well within the facility’s capability, Fletcher said. Its current permit allows it to operate only six months per year, which effectively creates six months of annual contingency, he said. As the number of campaigns increases, operations “should become more routine, should avoid the gearing up and gearing down that has occurred with past campaigns, and should minimize operational delays caused by short-term startups and shutdowns,” Fletcher said. “DOE anticipates that these more routine operations will allow for better maintenance of the facility, more efficient operations and improved planning of campaigns,” he said.
The state has “serious doubts” about whether the pace of evaporation campaigns proposed by DOE can be sustained, said Jeff Lyon, the Washington State Department of Ecology tank waste storage project manager, in a court document. Despite major upgrades to the evaporator in 1987, from 1989 to 1994, and more recently, it has been plagued with operational issues, shutdowns, worker safety issues, and delays, he said. At least two of the recent operating campaigns were delayed past their planned starts, he said. One was stopped early because samples of the waste slurry indicated excessive solids were being transferred, he said. In 2004, three waste transfers were completed without proper leak detection. Operators conducted one campaign using a transfer line that had a tap improperly installed, causing waste to leak, Lyon said.
U.S. District Judge Rosanna Malouf Peterson, who is deciding modifications to Hanford’s court-enforced consent decree, has named an expert panel she has said can help her understand matters such as the likelihood of evaporation campaigns creating enough space in double-shell tanks. In August she said DOE would be required to build new storage tanks if it does not meet certain new milestones, which are yet to be determined.The amount of tank space DOE must free up through evaporation campaigns and the schedule that will trigger the requirement for new tanks will be set after the state and DOE submit more information to the court, she said.
