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Hanford Nuclear Cleanup May Be Too Dangerous, Future Of Storage Plant Uncertain
By Valerie Brown, Scientific American:
The most toxic and voluminous nuclear waste in the U.S.—208 million liters —sits in decaying underground tanks at the Hanford Site (a nuclear reservation) in southeastern Washington State. It accumulated there from the middle of World War II, when the Manhattan Project invented the first nuclear weapon, to 1987, when the last reactor shut down. The federal government’s current attempt at a permanent solution for safely storing that waste for centuries—the Waste Treatment and Immobilization Plant here—has hit a major snag in the form of potential chain reactions, hydrogen explosions and leaks from metal corrosion. And the revelation last February that six more of the storage tanks are currently leaking has further ramped up the pressure for resolution.
After decades of research, experimentation and political inertia, the U.S. Department of Energy (DoE) started building the “Vit Plant” at Hanford in 2000. It’s intended to sequester the waste in stainless steel–encased glass logs, a process known as vitrification (hence “Vit”), so it cannot escape into the environment, barring natural disasters like earthquakes or catastrophic fires. But progress on the plant slowed to a crawl last August, when numerous interested parties acknowledged that the plant’s design might present serious safety risks. In response, then-Energy Secretary Steven Chu appointed an expert panel to find a way forward. Because 60 of the 177 underground tanks have already leaked and all are at increasing risk to do so, solving the problem is urgent.
snip
And then there’s the extreme radioactivity of the waste, which is far too high for direct human exposure. Enter the Vit Plant’s notorious “black cells.” These are 18 massive concrete enclosures populated by smaller stainless steel vessels. The idea is to guide the waste through the vessels without any human intervention over the 40 years officials believe it will take to process all the waste. The only way to do this is to ensure that the black cells have no moving parts. But because the waste has to be constantly stirred to prevent settling of the noxious and radioactive solids, the plan calls for pulse jet mixers—described as “turkey basters”—to keep the solids suspended.
The pulse jet mixers suck waste into their vertical tubes and then eject it forcefully back into the tanks. Unfortunately, they have not yet been shown to provide sufficient mixing at the scale necessary for the Vit Plant. They do, however, apply enough force to the slurry for the solids to grind away at the stainless steel of tanks and pipes, weakening them enough to risk leakage. Besides this erosion, there’s also potential for chemical corrosion. The Defense Nuclear Safety Board, which advises the White House, has called these problems “a show-stopper.”
http://www.huffingtonpost.com/2013/05/09/hanford-nuclear-cleanup-too-dangerous_n_3246263.html?utm_hp_ref=green
The most toxic and voluminous nuclear waste in the U.S.—208 million liters —sits in decaying underground tanks at the Hanford Site (a nuclear reservation) in southeastern Washington State. It accumulated there from the middle of World War II, when the Manhattan Project invented the first nuclear weapon, to 1987, when the last reactor shut down. The federal government’s current attempt at a permanent solution for safely storing that waste for centuries—the Waste Treatment and Immobilization Plant here—has hit a major snag in the form of potential chain reactions, hydrogen explosions and leaks from metal corrosion. And the revelation last February that six more of the storage tanks are currently leaking has further ramped up the pressure for resolution.
After decades of research, experimentation and political inertia, the U.S. Department of Energy (DoE) started building the “Vit Plant” at Hanford in 2000. It’s intended to sequester the waste in stainless steel–encased glass logs, a process known as vitrification (hence “Vit”), so it cannot escape into the environment, barring natural disasters like earthquakes or catastrophic fires. But progress on the plant slowed to a crawl last August, when numerous interested parties acknowledged that the plant’s design might present serious safety risks. In response, then-Energy Secretary Steven Chu appointed an expert panel to find a way forward. Because 60 of the 177 underground tanks have already leaked and all are at increasing risk to do so, solving the problem is urgent.
snip
And then there’s the extreme radioactivity of the waste, which is far too high for direct human exposure. Enter the Vit Plant’s notorious “black cells.” These are 18 massive concrete enclosures populated by smaller stainless steel vessels. The idea is to guide the waste through the vessels without any human intervention over the 40 years officials believe it will take to process all the waste. The only way to do this is to ensure that the black cells have no moving parts. But because the waste has to be constantly stirred to prevent settling of the noxious and radioactive solids, the plan calls for pulse jet mixers—described as “turkey basters”—to keep the solids suspended.
The pulse jet mixers suck waste into their vertical tubes and then eject it forcefully back into the tanks. Unfortunately, they have not yet been shown to provide sufficient mixing at the scale necessary for the Vit Plant. They do, however, apply enough force to the slurry for the solids to grind away at the stainless steel of tanks and pipes, weakening them enough to risk leakage. Besides this erosion, there’s also potential for chemical corrosion. The Defense Nuclear Safety Board, which advises the White House, has called these problems “a show-stopper.”
http://www.huffingtonpost.com/2013/05/09/hanford-nuclear-cleanup-too-dangerous_n_3246263.html?utm_hp_ref=green
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