What We Are Doing
Emptying Old Tanks
Since the beginning of waste removal from Hanford’s single-shell tanks a total of seven tanks have been emptied. Six meet the criteria of the Tri-Party Agreement that governs cleanup and the seventh is under review. In addition, waste has been removed to the limits of technology in four additional tanks and reviews are under way now to determine the best course of action to remove the remaining waste.
Most recently waste was removed from single-shell tank C-110 using modified sluicing technology. Modified sluicing uses high pressure water or liquid waste to mobilize the sludge and other solid material so it can be pumped to safer double-shell tank storage. C-110 is located in C Farm in Hanford’s 200 East Area near the center of the Hanford Site. The 530,000 gallon tank was built in 1946 and was used to store waste through much of the Cold War era.
At the time retrieval began in September 2008 tank C-110 held approximately 126,000 gallons of sludge and other radioactive and chemical materials. Waste retrieval activities were halted later that month to allow modifications to the nearby double-shell tank that was receiving the waste. Through innovation and hard work WRPS developed a new approach that allowed retrieval to resume ahead of schedule and at less cost than anticipated.
When the limits of modified sluicing technology had been reached, more than 90 per cent of the waste had been removed from C-110. Additional technologies are now being considered to remove the remainder of the waste to meet the terms of the Tri-Party Agreement.
Next in Line
The next single-shell tank to be emptied will be tank C-104, followed by C-111. Like their sister tank C-110, the two are 530,000 gallon tanks built in 1946. C-104 holds approximately 260,000 gallons of waste. C-111 holds approximately 57,000 gallons of waste. Modified sluicing will be used to remove waste from both tanks. Installation of all the complex systems required to support the safe retrieval of the waste from C-104 is now taking place while design work on the systems to support retrieval from C-111 is now taking place.
New Generation of Robotic Arm in Tank Cleanout Future
Testing is under way on an innovative robotic arm that offers the potential to increase the efficiency of waste removal from Hanford’s single-shell tanks. The arm, referred to as the Mobile Arm Retrieval System (MARS), will be capable of a wide range of motion and include telescoping capabilities to enable it to reach the tank extremities. Tools using high pressure liquid of the arm will be used to break up the waste and move it to a pump so it can be removed from the tank.
The use of robotic arms for waste retrieval has been studied at Hanford since the beginning of the cleanup program, but the state of the technology and deployment strategies limited their usefulness. Incorporating lessons learned from other DOE sites and the corporate parents of WRPS with new technology innovations have increased the options for effective tank waste retrieval. Part of the design challenge will be to make a large portion of the system transportable so it can be moved from one tank to another and make use of existing tank farm utilities, such as electrical and water systems, thus saving time and money. Installation of the first arm is expected in late 2010.
Development of new and innovative technologies to speed the retrieval of tank waste and make retrieval operations more efficient and cost-effective is a goal of Washington River Protection Solutions.
