Over the weekend, a giant tank of radioactive sludge in Hanford, Washington, sprung a new leak. It wasn’t the first time, and it likely won’t be the last. Hanford is home to 177 of these decades-old tanks, and workers have been scrambling to shuffle nuclear waste from tank to tank as they become leaky with age. This, ladies and gentlemen, is the current plan for dealing with the US’s dangerous high-level radioactive waste.
This was not Plan A, of course. Plan A was a geological repository at Yucca Mountain in Nevada, where radioactive waste could be entombed for at least 10,000 years. Yucca Mountain was supposed to open---take a deep breath---in 1998. But politics have dragged the Yucca Mountain plans through five presidents, and the Obama administration effectively mothballed it in 2010. So the radioactive sludge continues to sit in Hanford’s aging underground tanks.
Hanford started accumulating radioactive waste during the Manhattan Project, when the site cranked out plutonium for nuclear bombs. By the time the Cold War ended and Hanford stopped its plutonium production, 53 million gallons of high-level waste had piled up. The once top-secret atomic city morphed into the site of the biggest environmental cleanup project in the world.
At the same time Yucca Mountain has stalled, the cleanup at Hanford has blown through deadline after deadline, despite $19 billion over 25 years from the Department of Energy. “It’s kind of like watching glaciers move,” says Cheryl Whalen, cleanup section manager at the Washington State Department of Ecology. The radioactive waste in the tanks was supposed to have been “vitrified” into glass logs for permanent storage in 1998. The vitrification facility at Hanford is still under construction, and vitrification has been pushed back to 2032. With no Yucca Mountain, that vitrified waste still has no permanent place to go. But maybe everything will be sorted out by 2032? You can always hope?
Meanwhile, engineers at Hanford have to deal with underground tank trouble. Hanford has 149 single shell tanks as well as 28 newer double shell tanks. “When the single shell tanks were built,” says Whalen, “they didn’t necessarily think about what to do with the liquid.” Fearing leaks, the Department of Energy eventually moved the liquid waste from single shell tanks into million-gallon double shell tanks, which were built in the 1970s to have an extra layer of protection.
That did not do the trick. The radioactive waste in single shell tanks was a sludge-like mix of metals and water; when the liquid waste went into double shell tanks, the remaining sludge just became thicker sludge. Over time, more liquid settled out and leaked. One single shell tank, the T-111, is still actively leaking low-level waste into the ground at Hanford.
But potentially more dangerous is the high-level radioactive waste in some double shell tanks at Hanford. The waste gives off so much radiation, it's actually hot to the touch. In this most recent incident, high-level waste---a stew of plutonium, uranium and many other metals---leaked from the inner shell of the double shell tank AY-102. Back in 2012, a Hanford worker had discovered small leaks in AY-102, and workers were in the middle of pumping the waste into another intact double shell tank when they discovered the latest leak. The pumping may have disturbed solids that plugged up the old leaks, causing thousands of gallons to flood into the space between the inner and outer shells. Thankfully, the waste does not appear to have seeped into the ground around the tank.
But with limited tank capacity and at least sixteen years to go before the tanks can retire, this is still bad news. “It could hurt a great deal to lose a double shell tank capacity,” says Ken Niles, the nuclear safety division administrator for the Oregon Department of Energy. Worse still, this leaking tank could be a sign of problems to come with other double shell tanks.
Pumping radioactive sludge between tanks is complicated operation. “One of the most challenging areas is retrieving waste from the tanks,” says Niles. The work has to be done remotely because the tanks are seven to ten feet underground and accessible only through a foot-wide hole. Workers have to thread down equipment that can mix the radioactive solids and liquids to a pumpable consistency. (Without liquid to cool it, the remaining radioactive solids would also get too hot to handle.) Sometimes, they may need to pump in extra liquid from yet other tanks. Because of the way the tanks are connected, says Niles, moving waste between two tanks might mean a series of maneuvers involving six or seven tanks total.
As those tanks age, playing musical chairs with the waste is clearly not sustainable. Eventually, the US will need a permanent nuclear waste storage solution. Just don’t hold your breath---at least not until 2032.