Tuesday, March 31, 2015

Nuclear Spent Fuel Expert Describes Vermont Yankee Dry Cask Safety; Guy Page Guest Post

NRC illustration
Generic Dry Cask
By 2020, the spent fuel left over from all 42 years of Vermont Yankee’s operation is scheduled to be stored in huge steel “dry casks” on pads at the plant site in Vernon.

Just how strong and reliable are Vermont Yankee’s “dry cask” spent nuclear fuel containers? Consider the following dry cask testing conducted at Sandia National Lab:

  • A tractor-trailer carrying a container ran into a 700-ton concrete wall at 80 MPH.
  • A container was broadsided by a 120-ton train locomotive traveling 80 MPH.
  • A container was dropped 2,000 feet onto soil as hard as concrete, traveling 235 MPH at impact.
  • A container was subjected to a device 30 times more powerful than a typical anti-tank weapon.
  • A container was subjected to a simulated crash of a jet airliner and the armament of an F-16.

In each case, post-incident assessments demonstrated that the containers would not have released their contents. All of the information shared above was reported Jay Tarzia, Principal of Radiation Safety and Control Services Inc. and chair of the New Hampshire State Radiation Advisory Committee, on March 26 to the Vermont Nuclear Decommissioning Citizen’s Advisory Panel at Brattleboro Union High School.

Dry casks are designed to resist floods, earthquakes, tornadoes, projectiles, and temperature extremes. Tipped over, they will stay intact. And of course, heavy shielding prevents radiation leakage. They also remained intact after being submerged in water for eight hours and exposed to a 1,475 degree fire for 30 minutes. There have been no known or suspected sabotage attempts or releases of radiation since the first dry cask system was licensed in 1986.

At Fukushima, 400 dry casks were exposed to earthquake and tsunami. Although knocked over and tossed around, none were breached.

The U.S. Nuclear Regultory Commission (NRC) licensing allows fuel to be stored for up to 100 years and the NRC is developing an extended storage program for up to 300 years.

After 100 years, the fuel’s radioactivity will have shrunk to about one percent of its beginning total radioactivity. Stress on the canister will be greatly reduced. But Mr. Tarzia did not minimize the long- term nature of dry cask management. After about 4,000 years, the fuel’s radioactivity will return to the level of the original uranium ore. “The fuel will be radioactive for a long time. We need to manage it,” he said. “The security doesn’t go away when the plant goes away, when there’s a long-term storage site.”

The industry is running computer models now showing the outer limits of how long the canisters will last. Ultimately, a long-term storage process or facility will make dry cask storage unnecessary, he predicted.

In closing, Mr. Tarzia predicted that within decades, waste-free nuclear fusion will produce limitless electricity.

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Guy Page of Vermont Energy Partnership (VTEP) is a frequent guest blogger at this blog.  This post has also appeared on the VTEP blog and on Atomic Insights blog. As usual, the Atomic Insights blog post has great comments.

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