When one of the earth’s great tectonic plates thrust under another off the east coast of Japan in March 2011, it generated a violent earthquake and set off a tsunami with waves that reached heights of 20 feet or more. This devastating combination left tens of thousands of people dead and set off a nuclear crisis when seawater flooded the site of the Fukushima Daiichi Nuclear Power Plant , cutting power and disabling backup safety equipment.
Crews were unable to keep the reactors cool, which led to fuel melting, hydrogen explosions and the release of radioactive material. More than nine months passed before authorities announced the reactors had been brought to a stable state of cold shutdown. Safety concerns also led to the shutdown of nearly all of Japan’s other nuclear plants.
The Fukushima event—the worst nuclear accident since Chernobyl in 1986—has cast a shadow over atomic energy and the industry's burgeoning hopes for a "nuclear renaissance." More than two years later, Japan has restarted only two of the nation's 54 reactors, and dangers persist at Fukushima as workers struggle to contain radioactive wastewater leaks. Germany and Switzerland have decided to phase out nuclear power, and many other nations are reassessing their nuclear ambitions. In June 2011, Italian voters rejected their country’s nuclear program in a referendum.
Yet for an increasingly energy-hungry world, nuclear remains a tantalizingly reliable, carbon-free power source, and an attractive way to diversify energy supplies and move away from sources including coal that contributes to climate change. "We need a renaissance of some technology that can take the place of coal," says Per Peterson, a professor of nuclear engineering at the University of California, Berkeley. Both coal and nuclear plants are costly to build but able to provide reliable power around the clock with relatively low fuel costs. "It's difficult to see how you could possibly displace coal if you don't include nuclear," Peterson says.
Globally, the future of nuclear lies increasingly in China and India. "The nuclear renaissance is currently underway but primarily outside the United States," says Dan Lipman, executive director of strategic supplier programs for the Nuclear Energy Institute, an industry group. Seven of the 66 plants now under construction worldwide are in India. And China linked its 17th nuclear reactor to the power grid in February.
The story is more mixed in the United States, though the country leads the world in nuclear electricity output. Until recently, 104 reactors in 31 states provided about 19 percent of the nation's electricity. The U.S. Energy Information Administration anticipates new reactors will add about 5.5 gigawatts—comparable to nearly three Hoover Dams—of nuclear capacity by 2025. This spring, construction of two new reactors began for the first time in 30 years.
But low natural gas prices have taken a bite out of revenues for plant owners. The fleet dropped to 102 reactors this spring due to plant closures, the most recent example being Wisconsin’s Kewaunee nuclear station, which saw its profits eaten away by the natural gas glut. The shutdown has fueled predictions that more closures may be on the way as older nuclear plants struggle to compete. Duke Energy dropped plans for two new reactors in North Carolina and officially retired its Crystal River reactor—offline for two years—in Florida after decades of operation, having opted for shutdown rather than repair. EIA forecasts see natural gas and renewables taking up larger slices of a growing U.S. energy pie, depending on prices and subsidies.
The 1979 nuclear accident at Three Mile Island in central Pennsylvania, like Fukushima, came at a similar time of nuclear growth. By the time of the Chernobyl disaster, though, that growth had begun to slow. It stagnated not only because of heightened safety concerns but also due to a drop in fossil fuel prices in combination with the long delays, ballooning budgets and high financing charges that were the hallmarks of new-plant construction in the 1980s and '90s. Then, as now, the economics of nuclear proved daunting.
Interest in nuclear eventually rekindled. From around 2005, Lipman says, a confluence of factors fired up construction. Economic growth boosted electricity demand, and historically volatile natural gas prices were on an upswing. The Energy Policy Act of 2005 provided loan guarantees and other incentives for new nuclear plants, and residential electricity demand in southeastern states—particularly Florida—"was growing like gangbusters," he says. Plus, for a moment, it seemed possible that climate regulation might make coal power more costly.
The timing was perfect. "A younger generation [had] forgotten about or had not lived through Three Mile Island and Chernobyl," says Edwin Lyman, a senior scientist in the Global Security Program at the Union of Concerned Scientists in Washington, D.C.
While some Americans have warmed to the idea of increasing nuclear power, the public remains split on the issue. Five months before the Fukushima disaster, 47 percent of Americans surveyed by the Pew Research Center favored increasing use of nuclear power. Immediately following the crisis, support fell to 39 percent, but opinions have mellowed somewhat since then.
A more-receptive public can open the door only so far for nuclear. "They could not get around the economics issues of nuclear power, even before Fukushima happened," Lyman says. The 2011 crisis in Japan "threw another monkey wrench in the works."
Nuclear has sometimes been promoted as an important weapon in the fight against climate change, but "the level of deployment of nuclear power you would need over the next couple decades to make a dent in global warming emissions would be so enormous, it's just not feasible," Lyman says.
And after Fukushima, safety is again a concern. Among the lessons to emerge from the disaster is the need to prepare for improbable sequences of events, says Berkeley’s Peterson. After 9/11, the Nuclear Regulatory Commission, responsible for regulating the U.S. nuclear industry, began examining overlooked, if not improbable, threats of widespread damage—issues, such as "what would we do if terrorists hijacked an airplane and decided to fly it into a U.S. nuclear plant,” Peterson says. The NRC looked at the damage that would happen to a plant’s safety systems in such a scenario, he says, and now requires that plants acquire portable emergency equipment as a backup.
What was not accounted for was the possibility of one event or a combination of natural hazards bringing down multiple reactors at a plant, each one demanding emergency response and the efforts of trained staff. More than one-third of nuclear power plants in the United States currently have two or more reactors. And yet emergency response plans allowed for only one failure. "In the U.S., our preparation was always that it would happen to one of the units," says Joe Pollock, vice president of nuclear operations for the Nuclear Energy Institute. "We have to be able to deal with all the units simultaneously in all our plans and preparation."
Pollock says nuclear plants in the U.S. are now better equipped for emergencies, but critics say reforms have not gone far enough. The Union of Concerned Scientists has warned that many reactors in the United States could have fared far worse than Fukushima Daiichi in the event of cooling system failures, because their spent fuel pools are more densely packed and more difficult to keep cool in an emergency. The group contends plants ought to be capable of withstanding a 24-hour station blackout without resorting to portable equipment, rather than the eight hours recommended, though not required, by an NRC task force organized in response to Fukushima, and they should be ready to function for a full week without off-site support, as opposed to only three days.
Newer reactors with passive cooling systems, such as Westinghouse's AP1000, show steps toward improved safety. Rather than pumps and diesel generators, the AP1000 uses natural convection, gravity and water evaporation to prevent overheating and pressure buildup without needing offsite power or even operator action. It's designed to withstand 72 hours of full station blackout. Four AP1000 reactors are under construction in China and two units are planned for the VC Summer nuclear plant in South Carolina.
Even in this advanced model, Westinghouse was able to identify potential areas for improvement after the Fukushima accident. Lipman says the company "went back and examined the design very significantly to see what kind of changes needed to be made,” discussing design changes such as positioning batteries higher up or installing watertight doors for flood resistance. Nonetheless, the company has concluded that the AP1000 could endure an event similar to the one that crippled Fukushima Daiichi.
Future nuclear reactors may sidestep some of the cost and safety challenges associated with today's 1,000-plus-megawatt giants by downsizing. The U.S. Department of Energy has an ambitious goal of seeing technology for smaller, self-contained and mostly factory-built reactors deployed within the next decade. Known as small modular reactors, or SMRs, these mini nuclear plants would have electric power equivalent to less than 300 megawatts and would be compact enough to ship by rail or truck. Already, researchers are working on dozens of different concepts worldwide.
One promising type is known as an integral pressurized water reactor. Named the mPower, this model from the nuclear equipment firm Babcock & Wilcox calls for a pair of 180-megawatt-equivalent modules that can run for four years without refueling—twice as long as today's reactors. And they are small enough to potentially use existing infrastructure at aging coal plants, raising the possibility of giving new, nuclear-fueled life to 1950s-era coal plants after their retirement. Estimated costs to deploy SMRs range from $800 million to $2 billion per unit—about one-fifth the cost of large reactors.
"It really is much easier to design safe, small reactors," says Peterson. With large reactors, there’s a danger of developing "hot spots" in the fuel. “Once fuel is damaged, it becomes more difficult to cool, and thus the damage can propagate,” Peterson explains. Well-designed smaller reactors that can avoid this problem and perhaps even quash the need for external equipment and fallible human decision-making in a time of crisis, can be “intrinsically safer,” he says. However, the degree to which small modular reactors might improve safety in real-world use remains uncertain.
The cost advantages are not guaranteed, either. "The history of nuclear power has driven reactors to get larger and larger," to take advantage of economies of scale, says Lyman. "If you're going to make small reactors competitive with large reactors, you have to reduce operating costs,” he says. “You need to slash labor costs in a way which is irresponsible. It's unproven that it's safe to reduce the number of operators [and] security personnel and still maintain safety." It's possible to make a small reactor safer than a larger reactor, he adds, "but it's not going to happen automatically."
For any innovative technology that might replace or succeed today's reactors, a long road lies ahead. “Even the best-studied plants have a lot of mysteries," says Lyman. The post-Fukushima drive to scrutinize those unknowns and eliminate needless risk may be all too brief to deliver lasting change. This time, Lyman says, "It would be nice if change were to occur before catastrophe strikes."