Present practice calls for storing spent fuel rods, which can no longer effectively sustain a chain reaction, in large pools of water, allowing it to slowly cool and preventing the release of radiation, CNN reported Thursday.
But the Japan disaster, where two of the six spent fuel pools at the Fukushima facility were damaged, raises questions about safety at 104 U.S. nuclear reactors which rely on a combination of pools and dry casks to store used fuel.
"I truly believe we must re-think how we manage spent fuel," Sen. Dianne Feinstein, D-Calif., said at a Senate appropriations subcommittee hearing Wednesday.
In California, she said, fuel removed from reactors as long ago as 1984 is still being held in spent-fuel pools, well beyond the minimum five to seven years required by federal regulators.
"It's hard to understand why the Nuclear Regulatory Commission has not mandated a more rapid transfer of spent fuel to dry casks," Feinstein said.
The NRC said there is no maximum time fuel can remain in spent fuel pools.
Industry critics say that as a result nuclear plants have made spent fuel pools the de facto method of storing fuel, crowding the pools with dangerous levels of the still-radioactive material.
"At many sites there is nearly 10 times as much irradiated fuel in spent fuel pools as in the reactor core," David Lochbaum, a nuclear physicist with the Union of Concerned Scientists, said. "The spent fuel pools are not housed in robust concrete containment structures designed to protect the public from the radioactivity they contain."
As of January 2010, an estimated 69,000 metric tons of spent fuel was in storage at U.S. power plants or storage facilities, the NRC said.