Staff Reports
WC Monitor
12/18/2015
The Department of Energy is working aggressively to start emptying the Hanford Site’s double-shell Tank AY-102 by the state deadline of March 4, according to the technical program manager for the project. The tank, the oldest of Hanford’s 28 double-shell waste storage tanks, was discovered to be leaking waste from its inner shell into the space between its shells in 2012. Washington River Protection Solutions has 100 percent of the engineering and design work completed for emptying the tank’s waste into another double-shell tank and has purchased 90 percent of the equipment, said DOE technical program manager Reggie Eakins. It is still waiting for enhanced-reach sluicing systems that will be placed in Tank AY-102 this summer after some initial waste retrieval is done. Construction and installation is 85 percent complete and commissioning is 20 percent finished for the project, Eakins said. The Washington State Department of Ecology agrees that a March 4 start to retrieval is achievable based on work conducted so far. “It’s a hard job and lots of people are doing a good job,” said Jim Alzheimer, a tank engineer for the department.
DOE has spent $58 million on the project to date and expects to spend $25 million more to meet the March 4, 2017, deadline for completing retrieval. Contingency built into the schedule has kept work on track, even after workers had difficulty removing a mixing pump from the double-shell tank that will receive the waste, Tank AP-02, to replace it with a liquid waste pump better suited for upcoming work, Alzheimer said. Workers succeeded in removing the highly contaminated pump in two pieces after they were unsuccessful in breaking it down into three pieces as planned. Tank AY-102 has about 750,000 gallons of waste, filling about three-fourths of its capacity. The receipt tank for the waste is nearly full and a series of waste transfers will be conducted to move its waste to other double-shell tanks with space and compatible waste. Then the Tank AY-102 waste can be transferred through 1,500 feet of hose-in-hose line to Tank AP-02.
“We are not going to reinvent the wheel with this retrieval,” said Joni Grindstaff, the deputy designated federal officer to the Hanford Advisory Board, at a December board meeting.
After some liquid is decanted from the tank, WRPS plans to start retrieval of waste using two conventional sluicing systems inserted into the top of the tank. The technology, which has been used for more than a decade to empty Hanford single-shell tanks, uses a jet of recycled liquid to dissolve and move waste toward a pump within the tank. As the level of sludge drops in the tank, the sluicing systems will be removed and four enhanced-reach sluicing systems will be inserted, likely in early summer. They can reach deeper into the tank and fold out to get closer to waste in all parts of the container. They also have been used successfully in single-shell tank waste retrieval, but are a newer technology. The enhanced-reach sluicing systems are equipped with high-pressure water systems that might be needed to break up a hard heel of waste at the bottom of the tank.
The state had proposed that the liquid that sits above the sludge in Tank AY-102 be removed earlier. But DOE, bolstered by input from the Defense Nuclear Facilities Safety Board, persuaded the state that it would be prudent to leave the liquid in the tank until ready to begin sludge retrieval. The liquid helps cool the sludge, which contains cesium and generates heat. The tank loses about 20,000 gallons of volume a year to evaporation. WRPS plans to begin sluicing out the sludge immediately after the liquid is pumped out. If there is an issue that delays sludge retrieval, liquid waste can be added back into the tank, said Jeremy Johnson, a DOE deputy project director in the tank farms.
About 60 gallons of waste is estimated to have leaked from the inner shell into the annulus, or space between the tank’s shells, with about five gallons believed to have leaked over the last year, Eakins said. Monitoring of the leak is done biweekly by lowering a camera down risers that extend into the underground tanks. A pump was installed recently into the annulus in case the leak increases and waste would need to be removed. There also is concern that the waste might be interfering with the tank’s cooling system. It could be running through channels at the bottom of the tank that were designed to allow airflow to help cool the tank.
“The problems are severe and this tank needs to be emptied soon,” said Dirk Dunning, who represents the state of Oregon on the Hanford Advisory Board. The outer shell of Tank AY-102 is just a quarter of an inch thick and has been rusting for 40 years, he said. Emptying the tank will allow it to be inspected to learn more about the cause of the leak, which could provide valuable information about Hanford’s other 27 double-shell tanks, Johnson said. However, work at Tank AY-102 has come at the expense of other cleanup projects. Resources devoted to emptying Tank AY-102 has forced WRPS to move one of two shifts of workers emptying the C Tank Farm’s leak-prone single-shell tanks to work in the AY Tank Farm. Work on other higher-risk projects, such as moving cesium and strontium capsules from underwater to dry storage, may have been deferred to empty Tank AY-102, said Dick Smith, who represents the city of Kennewick on the advisory board. The DOE Inspector General’s Office said in 2014 that the Waste Encapsulation Storage Facility, where the capsules are stored, was at the highest risk of any DOE facility in the cleanup complex in the event of a beyond design-life earthquake or other natural disaster.
