The travails of the Fukushima Daiichi nuclear power plant in Japan are highlighting a key question for the US: Why are America's nuclear power plants allowed to store tons of used but still highly radioactive fuel in pools for as many as 100 years – despite the fact that those pools are far more vulnerable to terrorist attack than the reactors themselves?
In Japan, a relatively small amount of used-up fuel was sitting in Fukushima's seven spent-fuel pools when disaster occurred. Yet after just days without a cooling system, most water in at least one pool had apparently boiled away, a fire was reported, and radiation levels soared.
By contrast, nuclear utilities in the US have over decades accumulated some 71,862 tons of spent fuel in more than 30 states – the vast majority of it sitting today in pools that are mostly full, according to a recent state-by-state tally by the Associated Press. It's a huge quantity of highly radioactive material equal to a great many Chernobyls' worth of radioactivity, nuclear experts say.
The reason is the lack of a national repository for spent fuel – meaning it must be stored on site – as well as the lack of a coherent nationwide policy, experts told Congress Wednesday.
"From the history of our nuclear power program, storage of spent fuel – between the reactor and the presumed repository – has been an afterthought," said Ernest Moniz, a nuclear expert at the Massachusetts Institute of Technology, at a Senate hearing. "It has not really been part of our serious policy discussion about fuel cycle design."
"What we need to do is to stand back and say: What is our whole integrated system?" he added. "We should really start thinking hard about that view."
Warnings years ago
The risks posed by spent fuel held in such pools are hardly new or unknown. A 2006 study by the National Academy of Sciences (NAS) warned Congress and the Nuclear Regulatory Commission (NRC) that spent fuel pools were vulnerable to terrorist attack, with some nuclear plant designs more than others. With water gone from the pools, the spent fuel could easily catch fire and see "the release of large quantities of radioactive materials to the environment," the study found.
The NAS report found that another method of storing spent fuel, called "dry cask" storage, did not require on complex power systems. Dry-cask storage involves putting older spent fuel into concrete- and steel-lined cylinders to allow natural air circulation for cooling. Dividing up spent fuel among a large number of such cylinders also makes "it more difficult to attack a large amount of spent fuel at one time" and also reduces "the consequences of such attacks," the report found.
Echoes of that report could be heard in Congress Wednesday, with several experts testifying that finding a new way to deal with spent fuel was a key takeaway from Fukushima.
For instance, the Fukushima General Electric Mark 1 Boiling Water Reactor design, which has a spent-fuel pool near the top of the building where it's easy for loading cranes to access, is one of the most vulnerable reactor designs, some experts say. At least 28 of America's 104 reactors are of that type.
The Fukushima problems of spent-fuel pools located on the same site with the reactors "will undoubtedly lead to a reevaluation of spent nuclear fuel management strategy," said Professor Moniz.
Protection akin to a 'Sears storage shed'
David Lochbaum, a nuclear engineer who spent years working in power plants with the same design as the Fukushima plant, told the Senate Energy and Water Development Appropriations subcommittee today that spent fuel was a huge risk.
While nuclear fuel in the reactor is carefully safeguarded with heavy shielding and multiple redundant cooling systems, that all changes once the still highly radioactive fuel is no longer productive, he said.
"Irradiated fuel sits in temporary spent-fuel pools with almost no protection," he said. "For unfathomable reasons, irradiated fuel is considered benign after it is taken out of the reactor core" even though it will be many years before a final repository can be agreed upon and built.
Today, many US reactor operators' spent-fuel management strategy is "to nearly fill the spent-fuel pools to capacity, and then to transfer fuel into dry-cask storage to provide space for the new fuel discharged from the reactor core," Dr. Lochbaum said at the hearing. But the result is that spent-fuel pools are kept nearly full of highly radioactive fuel, "maintaining the risk at about as high a level as possible."
At many reactor sites today, there is nearly 10 times as much irradiated fuel in the spent fuel pools as in the reactor cores, Lochbaum said. Yet those pools "are not cooled by an array of highly reliable emergency-cooling systems capable of being powered from the grid, diesel generators, or batteries. Instead, the pools are cooled by one regular system sometimes backed up by an alternate makeup system."
The spent-fuel pools are also not housed within robust concrete containment structures. Instead, "the pools are often housed in buildings with sheet metal siding like that in a Sears storage shed," Lochbaum said.
To solve the problem, he and others argue that spent fuel needs to be transferred to dry-cask storage after cooling for five years. In addition, he says, emergency procedures and operator training for spent-fuel pool accidents needs a major upgrade.
But Gregory Jaczko, chairman of the Nuclear Regulatory Commission, says the US reactors and spent-fuel pools remain safe. He assured the senators that a complete review of the safety of all 104 reactors in the US was under way, including issues such as the security and safety of spent-fuel pools.
Asked by Sen. Diane Feinstein (D) of California why commission policy permitted storing spent fuel in pools for up to 100 years, Dr. Jaczko said the NRC requires reactor operators to intersperse new and old fuel in the pools, lowering the threat if water is lost. But he acknowledged that this long-standing policy was now under review, he said.
"So why does industry practice appear to be to keep spent fuel in pool much longer than five to seven years?" Ms. Feinstein asked Moniz and William Levis, president of PSEG Power. "Why not move to dry cask?"
The industry, Mr. Levis explained, wanted to limit the number of times it moved and handled spent fuel because of the costs associated with that.
"I would not characterize the industry as having a reluctance for putting fuel bundles into cask storage," Levis said. "One of the impactful items is lack of a national strategy and policy as to what we're going to do with it."
For his part, professor Lochbaum emphasized the need for spent-fuel storage to get a hard look.
"The irrefutable bottom line is that we have utterly failed to properly manage the risk from irradiated fuel stored at our nation’s nuclear power plants," he said in his opening remarks. "We can and must do better."