(Inside Science) — Nearly 30 years ago, the state of Washington and two federal agencies agreed to clean up the Hanford Nuclear Reservation, a 586-square-mile chunk of sagebrush desert where the U.S. produced plutonium for nuclear weapons starting 75 years ago. In the process, half a trillion gallons of chemically toxic and radioactive waste was dumped on the ground or injected into groundwater. Some of it has reached the Columbia River. Another 56 million gallons of concentrated, radioactive sludge and crystallized salts sit corroding within 177 steel-and-concrete underground tanks.
Although the tank waste is only a fraction of the total, its safe disposal is one of the site’s most urgent priorities, especially to the policymakers and residents of Washington and Oregon. Eighteen years ago, workers began constructing a plant for “immobilizing” the remaining waste by vitrifying it — a process whereby it is mixed with molten glass, cooled and encased in stainless steel canisters for long-term storage underground in an as yet undesignated location.
Today the task remains unfinished. Prominent among the reasons for this is that designing, building and operating the infrastructure to treat the waste may be the most complicated project of its kind ever attempted. And that’s because the waste itself is, well, complicated. Although plutonium is no longer being created at Hanford this most peculiar element continues to loom ghostlike over the government’s efforts to mitigate the damage its creation caused and prevent any further environmental and human risk for centuries to come.
How Did This Happen?
Construction of the world’s first plutonium production reactor began at the site in 1943. During World War II and throughout the Cold War, the U.S. made some 67 metric tons of plutonium at Hanford. Its reactors bombarded uranium-238 with neutrons to produce plutonium-239, the isotope best suited to producing big controlled explosions like the Fat Man bomb that burst over Nagasaki in 1945. Hanford had nine plutonium production reactors, numerous other buildings, and waste pits and dumps that in total became four Superfund sites.
