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Thorium, The Green Energy Source For The Future
By Richard Martin
Palgrave Macmillan Copyright © 2012 Richard Martin
All rights reserved.
THE LOST BOOK OF THORIUM POWER
Kirk Sorensen was a rookie engineer at the Marshall Space Flight Center in Huntsville, Alabama, when he stumbled on the book that would change his life. This was in 2000. Sorensen was part of a team of engineers and physicists studying ways to use nuclear energy to power rockets to carry cargo into space. It was, as engineers like to say, a multivariable problem: the scientists had to consider the weight of the launch vehicle, tight confines of the engine compartment, extremes of temperature and atmospheric pressure as the rocket ascended beyond the atmosphere, risk of catastrophic accident, and so on. They quickly realized that conventional nuclear reactors would not do the job. And so they began looking into alternative reactor designs.
One afternoon that spring, Sorensen stopped by the office of his older colleague, Bruce Patton, a long-time nuclear engineer on assignment at the Marshall Center from Oak Ridge National Laboratory in Tennessee. Patton, who had lived through many changes of administration and many dead-end research programs at the national lab, had taken a liking to the young Mormon from Utah with a linebacker's build, a rocket scientist's intellect, and the temperament of a cattle-dog puppy.
Sorensen leaned against the door frame, his bulk filling the opening. The offices of chief scientists at Oak Ridge are not large, and Patton was not a chief. As technologists do, they chatted for a while in a language foreign to nonspecialists—Sorensen recalls it was about his growing frustration with the search for inexpensive ways to get heavy payloads into orbit. On the bookshelf in Patton's office he noticed a book with an intriguing title: Fluid Fuel Reactors. He picked it up and started leafing through it.
It was a book only an engineer could love. Published by the Atomic Energy Commission in 1958, during the Atoms for Peace era under President Dwight D. Eisenhower, and written by a group of contributors under the editorship of the Oak Ridge scientist James Lane, it ran 945 chart- and graph-crammed pages and weighed in at a biblical three pounds. Featuring chapter titles like "Integrity of Metals in Homogeneous Reactor Media" and "Chemical Aspects of Molten Fluoride Salt Reactor Fuels," Fluid Fuel Reactors details the work carried out in the 1950s at Oak Ridge, under then-director Alvin Weinberg. It describes nuclear power reactors with cores that were liquid, not solid, and that offered some intriguing advantages over the conventional light-water reactors (cooled by ordinary water) that make up nearly 90 percent of the reactors in operation today. It also describes the use of a novel nuclear fuel, an alternative to uranium and plutonium: the radioactive element thorium.
Sorensen took the book home and devoured it within days. His sleep suffered. A devout Mormon and a linear-thinking engineer, Kirk Sorensen was an unlikely revolutionary. But Fluid Fuel Reactors dropped a lit match into the dry tinder of his mind.
Here, he realized, was a potential solution—not to the problem of nuclear- powered spaceflight, which he had by that time decided was a pipe dream anyway, but to society's insatiable thirst for energy. Like most engineers of his generation, he knew that thorium is an actinide—one of the heavy elements on the bottom row of the periodic table of elements, a group that includes uranium and plutonium—and he vaguely remembered that the United States had done some work on thorium reactors in the two decades after World War II.
That work had gone far beyond calculations and experiments to an actual working reactor, and a sizable contingent of scientists, including Weinberg, believed that thorium-fueled reactors, with fluid cores of molten salt, should have been the future of nuclear energy. Outraged, Sorensen asked himself the question that has become a persistent refrain among thorium advocates: Why has this never been pursued?
Thorium is around four times as abundant as uranium and about as common as lead. Pick up a handful of soil at your local park or ball-field; it contains about 12 parts per million of thorium. The United States has about 440,000 tons of thorium reserves, according to the Nuclear Energy Agency; Australia has the world's largest resources, at about 539,000 tons. Like uranium and plutonium, thorium makes a dense and highly efficient energy source: scoop up a few ounces of sand on certain beaches on the coast of India, it's said, and you'll have enough thorium to power Mumbai for a year.
Used properly, thorium is also far safer and cleaner than uranium. Thorium's half- life, the time it takes for half of the atoms in any sample to disintegrate, is roughly 14.05 billion years, slightly more than the age of the universe; the half-life of uranium is 4.07 billion years. The longer the half-life, the lower the radioactivity and the lower the danger of exposure from radiation. Thorium's rate of decay is so slow that it can almost be considered stable; it's not fissile (able to sustain a nuclear chain reaction on its own), but it is fertile, meaning that it can be converted into a fissile isotope of uranium, U-233, through neutron capture, also known as "breeding." You can't mash together two lumps of thorium, even highly purified thorium, and trigger a nuclear explosion. Left alone, a chunk of thorium is no more harmful than a bar of soap. In fact, for a period before World War II, a thorium-laced toothpaste was marketed in Germany under the brand name "Doramad." Because of its unusually long decay process and its rare ability to breed through neutron capture, thorium is a more energy dense and efficient source of energy than uranium or plutonium: As a nuclear fuel, thorium reserves carry enough energy to power humanity's machines for many millennia into the future.
Thorium advocates point out that it's impossible to make a bomb from thorium, and significantly more difficult to make a bomb from uranium bred in thorium reactors than from enriched natural uranium. U-233 bred from thorium includes other undesirable isotopes, namely uranium–232, that provide built-in proliferation resistance. Nuclear waste from the thorium fuel cycle is also less hazardous to future generations. Fluid-fueled reactors known as liquid fluoride thorium reactors (LFTRs, pronounced lifters) can act as breeders, producing as much fuel as they consume. In LFTRs, thorium offers what nuclear reactor designers call higher burnup—there's less of it in terms of volume and less long-lived radioactive wastes to deal with afterwardthan uranium. They can even consume highly enriched fissile material from dismantled warheads and long-lived transuranics in spent fuel from other reactors, turning it into a relatively benign and shorter-lived form of spent fuel, thus eliminating the need for geologic storage for thousands of years. What's more, LFTRs are inherently safe: The fission reactions occur in a radioactive cocktail of molten salt containing uranium-233 and jacketed by a blanket of thorium for breeding, requiring only a small start-up charge of enriched uranium, with thorium as the sole input thereafter. As the liquid fuel in the core heats up, it expands, decreasing the amount of fuel available, slowing the rate of fission reactions and cooling the fuel. It's like doubling the size of a pool table while keeping the number of balls on the table the same: fewer collisions occur, resulting in an extremely stable and responsive operation. The reactor core in a LFTR includes a "freeze plug" of frozen salt at the bottom, like the plug in a bathtub drain. Any power outage or unexpected deviation causes the freeze plug to melt, and allows the fuel in the core to drain into a shielded container designed to withstand the residual heat from the decay of fission products in the fuel. Because the reactor is inherently stable and the liquid fuel can be readily drained from the reactor core, a meltdown is physically impossible.
Thorium could provide a clean and effectively limitless source of power while allaying all public concerns—weapons proliferation, radioactive pollution, toxic waste, and fuel that is both costly and complicated to process. These concerns have crippled the nuclear power industry since the early 1980s.
Today, with global warming accelerating, climate-neutral nuclear power is poised for a worldwide comeback commonly referred to as the nuclear renaissance. At the same time, it's clear that the flaws of conventional, uranium-based nuclear power—which accounts for no more than one-fifth of power generation in the United States and less than that worldwide—make it an unsuitable replacement for fossil fuels in the near term. The nuclear accident that followed the earthquake and tsunami in Japan in March 2011 caused many countries to reconsider their ambitious nuclear agendas.
The problem is that only by shifting to non–carbon-emitting energy sources, like nuclear power, will we avoid catastrophic global climate change. Outside of the right wing of the Republican Party, hardly anyone today questions the worldwide scientific consensus that human-caused global warming, if left unchecked, will result in disruptions of a civilization-threatening nature: coastal cities like Calcutta and Miami inundated by seawater, huge swathes of farmland desertified, many now-populated areas uninhabitable, prolonged drought, and so on.
According to the International Energy Agency, worldwide demand for energy will rise by nearly 40 percent by 2035—a figure that many analysts, citing booming economic growth in the booming nations of China, India, and Brazil, consider low. Meeting that demand with current energy technologies would result in the addition of many billions of tons of carbon into Earth's atmosphere—and, most likely, in resource wars, famine, and the effective collapse of functioning society in many regions. The fossil fuel society on which we have built our civilization is simply no longer tenable.
Many well-meaning observers argue that by shifting to renewable sources, like wind and solar, and reducing energy demand through conservation and increased efficiency, we can shift away from fossil fuels in time to avert this disastrous scenario. Unfortunately, those hopes are illusory.
TH90 TH90 TH90
I FIRST MET KIRK SORENSEN in early 2009, when I was researching a feature for Wired magazine on the thorium power movement. I'd been covering energy for the better part of two decades. Since 2002 I'd been based in Boulder, Colorado, and had gotten a close-up view of both the natural gas boom that took hold in the northern Rockies in the first decade of the new century and the renewables push crystallized by Colorado's new governor, Democrat Bill Ritter. Like many of my generation, I had a deep foreboding about what rampant use of fossil fuels was doing to our planet and a conflicted attitude toward nuclear power.
I also had one overriding belief: A new technology that promises to improve life or provide people with new goods or make things less expensive cannot be stopped. You can delay it, regulate it, boycott it, or ban it, but eventually the technology will triumph.
I first read about thorium in a blog post by Charles Barton Jr., the son of one of the scientists who'd collaborated on experiments with thorium-based molten salt reactors in the 1960s. The blog ran on The Oil Drum, a "peak-oil" blog that examines the consequences of dwindling fossil fuel resources. At the same time, I was researching a report for Pike Research, a clean-tech energy research firm based in Boulder, on carbon capture and sequestration (CCS). CCS has been touted in some quarters as the answer to the evils of coal-fired power plants, which are by far the largest emitters of carbon per unit of power provided by any electricity source. Governments, including that of the United States, are pouring billions into developing systems that will separate the carbon from coal plant smokestack emissions (the capture) and then bury it permanently in underground reservoirs (sequestration). As I got deeper into the research, it became more and more clear that the numbers just didn't add up: CCS is an unproven, hugely expensive technology that is unlikely to be adopted at commercially significant levels in anything close to the time frames predicted by its supporters.
"Many of the current goals and targets for emissions captured between now and 2030 are overly optimistic," I wrote. This was a conclusion that was bolstered by studies from MIT, Stanford's Program for Energy and Sustainable Development, and Harvard's Belfer Center, among others.
Unfortunately, the same is true of many projections for renewable energy—especially solar and wind power. In the same period, I was doing some reporting for a website called Energy Tribune, run by Robert Bryce. A conservative journalist and energy analyst, Bryce has become one of the principal skeptics of green energy. I already had doubts about whether the glowing predictions for wind, solar, biofuels, and other forms of green energy could fulfill their promise in time to limit catastrophic global warming in my lifetime or that of my son, born in 1999. Bryce's work cemented those doubts.
In two books, Gusher of Lies (2008) and Power Hungry (2010), Bryce convincingly demonstrates that placing our faith in renewables, as that term is conventionally understood, is a "dangerous delusion." "The deluge of feel-good chatter about 'green' energy has bamboozled the American public and U.S. politicians into believing that we can easily quit using hydrocarbons and move on to something else that's cleaner, greener, and, in theory, cheaper."
In fact, there is only one way to transition from an energy economy based largely on fossil fuels to a sustainable "New Energy Economy," as politicians like Colorado's Ritter like to call it: moving quickly to what Bryce calls N2N, a combination of natural gas and nuclear power for production of baseload electricity. (Baseload is the minimum amount of electricity that a power company must consistently generate to meet the demands of its business and residential customers.) In the liberal green circles in which I moved in Boulder, this amounted to right-wing heresy. But, while I didn't agree with some of Bryce's harder conclusions ("MYTH: Wind Power Reduces CO2 Emissions"), the numbers were unassailable.
To take one example, the International Energy Agency has projected that new nuclear power plants will produce electricity for approximately $72 per megawatt-hour (one hour of operation at a rate of one megawatt). Electricity from onshore wind farms will cost up to $94 per megawatt-hour.
What's more, to build enough wind, solar, and other renewable energy projects to significantly reduce coal and oil use would require time and resources we simply do not have. In considering the real costs of different energy sources, it's important to take into account not just construction and operating costs but secondary factors like transmission, road building, resource extraction (of petroleum, coal, uranium, and so on), and real estate. Way back in the late 1970s, I took a course at Yale called "The Physics of Energy." The first assignment was to calculate how big a solar plant, in an ideal sun-drenched location like the American Southwest, would be required to supply 90 percent of U.S. electricity demand at the time. I'll spare you the calculations, but the answer was "roughly the size of the state of Arizona."
"Renewable sources such as wind and solar ... require hundreds—or thousands—of square miles of land for power generation," Bryce noted. "The same problems of energy sprawl hamper the development of hydro-power and biofuels."
To give one more example, the local utility in Austin, Texas, where I spent a year in graduate school, announced in early 2009—just as I was becoming fascinated by the thorium movement—that it would spend $180 million on a 30-megawatt solar plant. Officials said the new sun farm would run at an average 23 percent of capacity, producing power at a construction cost of $6,000 per kilowatt of capacity. "Thus, Austin Energy has agreed to build a solar plant that will operate about one-fourth as often as a nuclear plant and cost about 25 percent more on a per-kilowatt basis," Bryce scoffed.
Excerpted from SuperFuel by Richard Martin. Copyright © 2012 Richard Martin. Excerpted by permission of Palgrave Macmillan.
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