A spent-fuel pool fire at the Fukushima Daiichi nuclear power plant made headlines after March’s earthquake and tsunami – but the threat may be worse in America.

Spent nuclear fuel stored in water-filled pools at many nuclear reactor sites in the US far surpasses in volume and radioactivity the threat posed by such material at Fukushima, according to a new study.. The huge hazard could be largely eliminated by moving older materials from the pools into dry cask storage, it said.

“Unprotected and crowded spent nuclear fuel pools pose an unacceptable threat to the public,” said Robert Alvarez, a senior scholar for nuclear policy at the nonpartisan Institute for Policy Studies (IPS), as well as a former Department of Energy official in the Clinton Administration, in a statement.

“Dry cask storage is a much safer alternative to pools. Some people say they are too expensive, but considering the extreme risks, the cost of doing nothing is incalculable,” he added.

A new report from the IPS, "Spent Nuclear Fuel Pools in the US: Reducing the Deadly Risks of Storage", written by Dr. Alvarez, details for the first time how much radioactivity is contained in spent nuclear fuel at all individual reactor sites in the United States – and the threat they pose.

Today, some 65,000 metric tons of spent fuel is stored at reactor sites around the country, 75 percent of it in US spent-fuel pools, according to data from the Nuclear Energy Institute cited in the report. The other 25 percent is in dry cask storage. Each pool contains spent-fuel rods that give off about 1 million rems of radiation per hour at a distance of one foot – a fatal dose in seconds, the report says. The radiation is kept in check by tons of water continually flowing around the rod assemblages.

Some 30 million such rods are stored in spent-fuel pools at 51 sites around the country that "contain some of the largest concentrations of radioactivity on the planet," the study said. The rods are usually kept in tightly-packed racks submerged in pool water, which requires a steady flow of electricity to keep from overheating. If water drains from a spent-fuel pool, it can lead to a catastrophic fire that emits dangerous radioactive elements like Cesium 137.

Spent-fuel pools: A public threat?

Typically, spent-fuel pools are rectangular, about 40 to 50 feet deep, and made of reinforced concrete walls four to five feet thick, with stainless steel liners. Those without liners may crack or corrode more often, the report says.

The National Academy of Sciences in 2004 cited the pools as vulnerable to terrorist attack and fires. While the Nuclear Regulatory Commission has said the pools are safe, the Fukushima reactors' core meltdowns and spent-fuel pool fire prompted a new study of the possible impact of an earthquake or electrical blackout on US sites.

Spent-fuel pools need electricity to pump water to cool the fuel rods, as well as to maintain a high water level to prevent radiation from escaping. At present, however, there is no federal requirement for back-up power supplies for spent-fuel pools, to ensure the circulation of water continues in a blackout situation, the report notes.

Dangerous spent fuel pool reactor sites listed in the report include:

Two reactors at Indian Point – about 25 miles from New York City – have spent fuel in their pools containing about three times more radioactivity than the combined total of all four spent-fuel pools at the damaged Fukushima reactors. A spent-fuel fire could cause $461 billion in damage and thousands of deaths from disease, the report says.

At Diablo Canyon, near Los Angeles, nuclear reactors have material with about 2.7 times more radioactivity in their spent-fuel pools than Fukushima’s combined total.

Similarly, reactors at Turkey Point, about 65 miles from Miami, have material with 2.5 times more radioactivity than Fukushima’s combined total.

The venerable Vermont Yankee reactor, which is involved in a battle to win a new re-licensing that would let it operate another 20 years, has a design similar to the Fukushima plant. It holds seven percent more total radioactivity than the four Daiichi reactors combined – and nearly three times the amount of spent fuel that was stored in at Fukushima’s Unit 4 reactor, which caught fire.

The alternative: Yucca Mountain and dry cask storage

With the Yucca Mountain site closed by President Obama, there is no long-term storage available – a problem now being studied by a presidential blue-ribbon commission. But any long-term storage solution could take decades.

In the meantime, the study suggests an interim solution would be to remove spent fuel older than five years – now cool enough to be removed from water – and place it in above-ground "dry casks" that would use passive air cooling. That project would require 10 years and cost of $3 billion to $7 billion, the report acknowledges. But while the expense would "add a marginal increase to the retail price of nuclear-generated electricity of between 0.4 to 0.8 percent," the report says, it would make the reactor sites safer.