Part 3 of 3 Parts (Please read Part 1 and Part 2 first)
During the retrieval of radioactive waste from the tanks, workers have to operate retrieval equipment inserted through relatively small openings in the top of the tank from a nearby control trailer. They use pressurized water to dissolve the solid or salt-cake waste and flush it to the pump that transfers the waste to a double-walled tank.
Peggy Hamilton is the retrievals manager for WRPS. She said, “It takes a particular combination of water and pressure to create a slurry, which suspends the heavier solids in a liquid that can be pumped out and sent via transfer lines to another tank. We use lessons we learned and technologies developed during the successful retrieval of waste from other tanks to help us complete this challenging work.”
Tank AX-103 is the third million-gallon tank to have its radioactive waste removed in a group of four tanks referred to collectively as the AX Tank farm. WRPS has already retrieved waste from tanks AX-102 and AX-104. Retrieval from the last tank, AX-101 is scheduled to begin next year.
Preparing a decades old tank farm for the safe retrieval of radioactive wastes takes years of planning a retrofitting. Hanford workers remove old, contaminated equipment from the tank in order to make space for the equipment needed to retrieve the waste. Then they install modern retrieval equipment, ventilation safety and leak-detection systems and transfer lines to transfer the waste to a double-walled tank.
To date, workers have completed retrieving the waste for seventeen of Hanford’s one hundred and forty-nine older single walled tanks. After tanks AX-102 and 104 go through a standard technical review for completion that can take several months, the list of retrieved tanks will grow to nineteen. Hanford’s single-walled tanks were constructed of carbon steel and reinforced concrete between 1943 and 1964 to store radioactive and chemical waste created during the production of plutonium in World Was II and the Cold War era.
For a long time at Hanford, there was little concern for the environmental damage caused by weapons production. Millions of gallons of highly toxic chemical and radioactive waste were simply poured out on the ground and allowed to sink into the soil. Some of this waste eventually wound up leaching out and contaminating the Columbia River. A great deal of work has been put into preventing this in the future.
When the waste was put into single-walled tanks, poor records were kept with respect to what was being put into each tank. Different blends of toxic chemicals and radioactive materials with different particle sizes and viscosities were stored in different tanks. The tanks were intended to last until the waste could be vitrified. Unfortunately, some of the single-walled tanks began to leak. This led to the construction of double-walled tanks which received waste from leaking tanks. Then, in time, some of the double wall tanks began to leak.
The state of Washington and the U.S. DoE have been involved in legal battle for years over the lack of progress in cleaning up Hanford. The completion of the vitrification plant is way behind schedule and way over budget. Maybe the cleanup program can now move forward more swiftly.