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Tuesday, September 23, 2014         

FACTS OF THE MATTER


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Nuclear storage options all come with drawbacks

By Richard Brill

POSTED:

 / April 13, 2006The U.S. government had no backup plan for the permanent storage of spent nuclear fuel when politicians finally had to admit defeat this year and take Yucca Mountain off the table. Above, an engineer conducts an underground train at the entrance of the Nevada site, which has been controversial since its selection as the potential geologic repository more than 20 years ago.

Currently 126 temporary facilities scattered across 39 states are keeping 71,862 tons of nuclear waste in cooling ponds and in storage buildings near nuclear reactors.

Storing high-level nuclear waste above ground for a century allows observers to detect and manage problems as radioactive decay reduces the level of radioactivity and associated harmful effects to the container material.

The U.S. nuclear industry says the power-plant sites are storing waste safely, although it has long pushed for a long-term storage facility.

Meanwhile, the pile of waste is growing by 2,200 tons a year, even as some of the sites already have in storage four times the amount of spent fuel that they were designed to handle.

In 1987 Congress selected Yucca Mountain in Nevada as the only site to be investigated as the potential geologic repository for U.S. spent nuclear fuel and high-level nuclear waste. It condemned the United States to pursue a policy that had no backup if Yucca Mountain failed politically or technically.

And politically fail it did. Recent action to shelve Yucca Mountain leaves no specific site in the plans and reconvenes the need for exploring alternatives.

Even if a facility had been built there, the U.S. already has more waste than it could have handled.

A commission appointed by the U.S. Department of Energy is studying different options for dealing with spent nuclear fuel.

Beds of salt from evaporating seas more than half a mile thick lie within a mile or so of the surface across much of the U.S. Salt under pressure at that depth can flow, and fissures tend to seal themselves, so buried waste would quickly become encapsulated as salt closed in around it.

Shale is formed from fine clay particles in various eras over 550 million years. It underlies most of the United States. and can trap radioactive material in the crystal structure of the clay.

Granite is a hard, solid and stable rock that formed hundreds of millions of years ago deep in the earth's crust from cooling magma. It is brittle and fractures easily, creating fissures through which nuclear waste could migrate. It requires man-made barriers made of metals that could potentially fail while the waste was still radioactive.

Deep boreholes rely on new drilling technology that can bore an 18-inch-wide hole three miles below the surface. Canisters of spent nuclear fuel would be lowered into the bottom to fill 1.25 miles of each bore-hole, and the rest would be covered with a thick seal of clay, asphalt and concrete. Deep bore-holes are far below any freshwater aquifers, so radioactive material that seeped into the surroundings would remain trapped in dense, highly saline water at depth.

Sea-based options include burial beneath a stable abyssal plain and burial in a subduction zone that would slowly carry waste downward into the earth's mantle.

Technical and legal considerations make these less than viable prospects at pres­ent due to fears of leakage and contamination.

Like much of our technology, the means for producing nuclear power were discovered and implemented before thought was given to the end product.

Such foibles are so very human.






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