Take a mental stroll through the streets of Anytown, U.S.A. City hall is on your left, the movie theater on your right. And in the distance, there's the gentle steam plume billowing from the cooling tower of the miniature nuclear reactor that powers the quaint little burg.
Miniature nuclear reactors might be a safe, efficient source of power
Tuesday, September 14, 2010
Correction: It was incorrectly reported that the US has depleted uranium sitting in Portsmouth, NH. It sits in Portsmouth, OH.
Take a mental stroll through the streets of Anytown, U.S.A. City hall is on your left, the movie theater on your right. Smell the delights from the bakery. And in the distance, there's the gentle steam plume billowing from the cooling tower of the miniature nuclear reactor that powers the quaint little burg.
Not your idea of Americana? Wait a decade or two. The government and its private partners are developing reactors that one day might power your home town.
Not long ago, siting a nuclear reactor anywhere near a population center would have been unthinkable. While the 1979 Three Mile Island reactor meltdown didn't cause any deaths or injuries, it soured Americans on nuclear energy. Construction of new reactors came to an abrupt halt. The dramatic Chernobyl meltdown in 1986, meanwhile, created widespread fear that another accident could be even more disastrous.
Then along came carbon dioxide. Writing in The Post in 2006, Patrick Moore, a founding member of Greenpeace who sailed on the group's first protest against nuclear weapons testing in 1971, noted: "More than 600 coal-fired electric plants in the United States produce 36 percent of U.S. emissions -- or nearly 10 percent of global emissions -- of CO2, the primary greenhouse gas responsible for climate change. Nuclear energy is the only large-scale, cost-effective energy source that can reduce these emissions while continuing to satisfy a growing demand for power."
Greenpeace considers Moore a turncoat, and he's not the only one to be tossed out of the environmental establishment for pro-nuclear heresy. Hugh Montefiore, an Anglican cleric who was a stalwart in the movement, was forced to resign from the board of Friends of the Earth in 2004 for advocating nuclear power as a tool to combat global warming.
Back in the mainstream
Today, supporting nuclear power as a green alternative is quite mainstream. In his 2010 State of the Union address, President Obama advocated "building a new generation of safe, clean nuclear power plants." In February, the administration offered to guarantee a loan for construction of the first nuclear plant to be built in the United States since the 1970s. The same month, billionaire Bill Gates gave his backing to the nuclear power renaissance, investing $50 million in TerraPower, a nuclear power research company that is hoping to design a new generation of reactors.
The question for many has shifted from whether to build nuclear plants to where and how. And increasingly there's interest in the idea of mini reactors: power plants that provide energy for only a small area.
When nuclear scientists talk about the size of a reactor, they're talking about maximum electrical output, not square footage. The world's largest reactors generate 1,455 megawatts of electricity, enough to power about 1.5 million households. A program being run by the Department of Energy is focusing on models that would produce about 300 megawatts, enough for Knoxville, Tenn., according to Dan Ingersoll of Oak Ridge National Laboratory. They may go even smaller, producing 50-megawatt reactors that could power small towns or even individual work sites, such as mines, that may be located far from the main energy grid.
There are virtues to local reactors. If a reactor powers only one community, it can be built close to the end users. Between 4 and 10 percent of the electricity produced by U.S. power plants vanishes as it travels through power lines on its way to users. Building smaller plants and putting them closer to population centers could cut that figure significantly.
And doing so can save on construction costs as well. "It's getting very difficult and very expensive to lay new transmission lines," says Ingersoll. "This offers the possibility of providing isolated communities with power."
Believe it or not, living near a nuclear reactor may be safer than living near a coal-fired plant, which spews a host of dangerous chemicals into the air. The only visible emissions from a reactor is steam; the spent fuel is more of a byproduct. (More on that later.).
What about radiation, you ask? The ash coming from a typical coal plant carries plenty of radiation: According to some estimates, it carries 100 times more radiation into the surrounding area than a nuclear reactor producing the same amount of energy.
Smaller reactors might also be cheaper than their bigger siblings, according to Ingersoll. It costs a lot of money to build a gigawatt reactor (i.e., one that produces 1,000 megawatts), in part because it has to be put together on-site, one piece at a time, by expert welding crews. In today's larger reactors, all of which are being built outside the United States, the reactor vessel -- that's the cylindrical vault in which the fission takes place -- is about 90 feet in diameter, much too large to be shipped overland in one piece. Reactor vessels for mini plants would be as small as about 10 feet across and could be loaded onto a train or maybe even onto the bed of a trailer. Once the pieces get to the site, they can be bolted together with far less manpower and equipment.
Small reactors can also be daisy-chained together as a city grows. Consider this: Today's typical 1,000-megawatt reactor can power a city of about a million homes. What happens when the population grows by 20 percent? A second big reactor would be expensive and unnecessary. Smaller increments are more manageable.
A big 'but'
Not convinced? You're not alone. Opponents point out that small reactors don't begin to solve the most worrisome aspects of nuclear energy: dangerous waste and the potential that the fuel could be used to build a weapon.
When you remove used-up fuel from a reactor, it's incredibly hot and very radioactive. The spent rods are moved into a concrete-encased pool, where they spend years cooling off. Eventually, they should be moved to a long-term storage facility, but one doesn't exist yet. (No one wants nuclear waste stored in their state.) As a result, there are more than 50,000 tons of uranium soaking in pools next to U.S. reactors, waiting for a permanent home.
As for the risks of nuclear proliferation, it's hard to separate generating nuclear power from building nuclear weapons, because the first few steps of the process are nearly identical.
Uranium can take several forms, which differ based on the number of neutrons in the nucleus. When miners pull uranium from a mine, more than 99 percent of what they get is U-238, which isn't all that useful for either power or weapons.
Today's nuclear reactors want the slightly lighter U-235. So the uranium ore is hauled off to enrichment plants, which keep pulling U-238 out of the sample until 3 to 5 percent of what's left is U-235. At that point, the sample can power a reactor.
"But you can use the same enrichment plant and just keep putting the stuff through over and over again until you get into the 90 percent range," says nuclear scientist John Gilleland, who runs TerraPower. "At that level, you can pipe all that stuff together and make a bomb."
Since you use the same ingredients, equipment and processes to create reactor and bomb fuel, countries such as Iran, which is suspected of having nuclear-weapons ambitions, can plausibly tell the world they're enriching for power-generation purposes for a long time before their true intentions are undeniable.
Many also fear that a nuclear cooling tower might look like a bull's-eye to a terrorist. The towers on small reactors would be narrower and shorter than those at big plants, since most of the reactor can be buried. While there has never been an attack on a nuclear plant, it remains a concern.
If it works . . .
TerraPower, the venture that has received Gates's backing, is working to develop a system that will solve some of the problems with today's nuclear reactors. Its "traveling wave reactor" would be powered almost completely by fuel rods containing depleted uranium, the concentrated U-238 that enrichment plants throw away after extracting U-235. (TerraPower plans to start with a 500-megawatt reactor, but it could be scaled smaller or larger as needed.)
Here's how it would work: A tiny amount of U-235 is introduced and split open, releasing a whole bunch of neutrons. The depleted uranium in the fuel rod absorbs one of the neutrons. The resulting form of uranium soon decays into plutonium, a very potent fissile material. When more neutrons strike the plutonium, huge amounts of energy are released, as well as some more neutrons to keep the reaction going.
The "traveling wave" term is fitting because this process starts at one end of the fuel rod and creeps slowly forward, burning up the U-238 as it goes. The progression could take as many as 60 years, another major advantage of the new reactor. Traditional reactors have to be stopped, opened and refueled every 18 months or so.
If it works, a traveling wave reactor would probably be cheaper than a similarly sized plant running on enriched uranium, since its fuel would be so plentiful. The United States has about 775,000 tons of depleted uranium sitting in steel cylinders in Paducah, Ky., Portsmouth, OH, and Oak Ridge, Tenn. In the long run, countries would no longer be able to disguise their bomb factories as power plants, because running a reactor with enriched uranium wouldn't make economic sense. And the world could stop mining uranium, a process fraught with political and environmental hazards. According to Gilleland, there's already enough depleted uranium to satisfy the power needs of 10 billion Americans for 100 millennia.
So what are the chances a nuclear reactor will soon join the skyline of New Orleans, a city that's about the right size for TerraPower's envisioned 500 megawatt plant? It will probably all come down to economics, says Amory Lovins, chairman of the Rocky Mountain Institute, an environmental think tank focused on the future of energy.
Lovins thinks that proponents of nuclear power are missing the bigger picture: The issue isn't whether nuclear energy can be made safely, it's whether it is the best option among the many sources of energy available.
According to Lovins, small modular reactors, whether based on traditional or traveling wave technology, are doomed to fail simply because the other options are cheaper. He notes that only one-third of the cost of nuclear power has anything to do with the reactor core. The majority of the cost is the steam-turbine machinery needed to convert the heat into electricity.
Even if small modular reactors are cheaper to assemble and the depleted uranium is free, he argues, nuclear will never be able to compete with wind and solar power, which also rely on free fuel but require far less capital investment.
The race for America's energy future is coming to a town near you. Will it be windmills or cooling towers? It all depends on the dollars and cents.
Hyperion, a New Mexico-based manufacturer, has said it plans to start delivering 25-megawatt reactors, which are about the size of a garden shed and cost around $25 million, in 2013. The first units will probably be installed in Eastern Europe. A few other companies, including Toshiba, are applying to the federal government for the right to build small reactors. And Oak Ridge's Ingersoll targets 2020 as the earliest date a U.S. city might come online.
Palmer is a freelance writer based in New York and a regular columnist for the Health and Science section's How and Why column.