Spent fuel pools lack the hardened steel and concrete containment structures designed to limit the impact of a nuclear reactor meltdown. That means that fuel in a pool that catches fire, explodes, or even resumes chain reactions is more likely to widely disperse its radioactive material. The risk of such spent fuel accidents may be particularly acute in the United States. Unlike France and Japan, the U.S. government rejected recycling of spent fuel in centralized reprocessing facilities. It subsequently failed to implement its plan B: shipping spent fuel to a national repository at Nevada’s Yucca Mountain. The result is that spent fuel pools designed to cool fuel bundles for five years are instead packed with decades’ worth of fuel bundles.
Charles Forsberg, an MIT research scientist and executive director of a nuclear fuel cycle report issued last fall by MIT’s Energy Initiative, predicts that Fukushima Daiichi will accelerate the movement of U.S. spent fuel from pools to dry casks. The casks are cylindrical steel, lead, and concrete containers designed to hold 10 to 15 metric tons of spent fuel. Cooling is passive, relying on natural air circulation. “Dry cask storage is a big dumb can with thick walls. There isn’t much that can go wrong with it,” says Forsberg.
Dry casks are already used at several dozen U.S. reactors to accept fuel that no longer fits in the pools. Putting even more spent fuel in dry casks, says Forsberg, would make the fuel that’s left in the pool less vulnerable to the loss of cooling that is thought to have partially melted down some of Fukushima Daiichi’s spent fuel. “You’ve got less decay heat, and more water to boil off, if bad things happen,” says Forsberg.
A 2006 report by the U.S. National Research Council affirmed the advantages of dry cask storage, suggesting that it would be “prudent” to accelerate the shift to dry casks. The year before President Obama nominated him as the chairman of the Nuclear Regulatory Commission, Gregory Jaczko called a mandated move to dry cask storage the “most clear-cut” opportunity to expand the U.S. nuclear power industry’s margin of safety.
Whether that happens now may come down to who is willing to foot the bill. The cost of moving most fuel to dry casks is on the order of $43 million to $109 million, according to estimates prepared for the Massachusetts attorney general in 2006 (the figures supported a petition to mandate dry cask storage at New England’s Pilgrim and Vermont Yankee nuclear plants).
Forsberg says that investment would represent an “insignificant” increase in the price of nuclear power. But nuclear utilities in the U.S. are reluctant to absorb any costs associated with spent fuel waste management, citing nearly $18 billion in fees they have collected from ratepayers for a federal trust fund that was supposed to cover the cost of Yucca Mountain. “It remains the U.S. government’s responsibility and contractual obligation to remove used fuel from reactor sites,” says a spokeswoman for Southern Company, which operates six reactors in the southeastern United States.
David Lochbaum, a nuclear safety expert with the Union of Concerned Scientists, says he hopes reactor operators will come around, and make the move to protect their power plants. “The owners … have billion-dollar assets to protect. One of the cheapest ways to protect that asset is to get the spent fuel into a less vulnerable position. I would hope that the NRC wouldn’t have to make this happen,” he says.