As weve quantified in prior issues, the most cost-effective and scalable solution for curbing greenhouse gases by 2025 is clearly nuclear fission. However, large-scale nuclear reactors based on uranium and plutonium fuel still have their own serious issues. Perhaps the biggest is the need for complex cooling systems; this factor contributed to both the Three Mile Island incident in 1979 and the recent catastrophes at Japans Fukushima plant following the earthquake and tsunami.
These so-called pressurized-water reactors have been dramatically improved over the past 60 years, but they are still essentially "atomic pressure cookers" that rely on super-heated water for cooling. Interrupt that process for any reason ? as in a tsunami that floods the plant, shorting out the electric motors that pump the cooling water ? and things can go bad very quickly.
On top of these operational issues, nuclear energy poses other challenges ? such as the need to store radioactive waste securely for hundreds of thousands of years, and the risk that nuclear energy programs will enable dictators and terrorists to covertly develop nuclear weapons. For all of these reasons, many U.S. policymakers have written off nuclear energy despite its potential benefits, including low cost and low pollution.
But its critical to understand that the problems lie not so much with nuclear power itself, but with the types of reactor technology that weve used to commercialize it in the past. Fortunately, theres a better alternative.
Writing in the magazine Cosmos,1 Australian journalist Tim Dean summarized perhaps the most succinct case possible for replacing todays nuclear power technology with something radically different:
"What if we could build a nuclear reactor that:
? Offered no possibility of a meltdown ? Generated its power inexpensively ? Created no weapons-grade byproducts ? Could even burn up existing high-level waste, as well as old nuclear weapon stockpiles?
What if the waste produced by such a reactor was radioactive for a mere few hundred years, rather than tens of thousands? It may sound too good to be true, but such a reactor is indeed possible, and a number of teams around the world are now working to make it a reality. What makes this incredible reactor so different is its fuel source: thorium."
This slightly radioactive metal was discovered in 1828 by Swedish chemist Jons Jakob Berzelius whose name for it paid tribute to Thor, the Norse god of thunder. Although thorium is not fissionable, the reactor fuel-cycle breeds fissionable uranium-233 from the thorium.
One of the most attractive features of thorium fuel is that it allows us to get away from the "pressure-cooker paradigm." These reactors do not operate under pressure because their fuel, which is in the form of a molten salt, remains more than 500°C below the boiling point.
Three of the main benefits of a liquid-fuel thorium reactor are:2
Lets look at each of these three benefits in detail.
Many of the environmental safety issues are solved by liquid fuel. Consider these four advantages:
? First, it is physically impossible for there to be a meltdown caused by runaway fission and overheating. In the case of liquid fuel, overheating causes the material to expand, which slows the fission process because the radioactive particles become more separated. This allows the molten salt to cool down. This property eliminates the need for the traditional nuclear power plant cooling system with its associated problems, costs, and risks. ? Second, a liquid-fuel thorium reactor uses a common gas like CO2 rather than water to drive the electric turbine generator. Consequently, if there was a leak, the gas would quickly dissipate and the molten salt, like volcanic lava, would cool off quickly and become inert. ? Third, since a liquid-fuel reactor is air-cooled, it is not necessary to locate it near a lake or ocean shore, where there are greater risks of earthquakes and tsunamis. In fact, sealed underground reactors located in vaults are a real possibility. ? Fourth, a liquid-fuel thorium reactor produces far less radioactive waste material than current uranium and plutonium based reactors. But, more importantly, even the waste produced becomes virtually harmless in just 300 years, rather than tens of thousands. Consider that a 1-gigawatt liquid-fuel reactor, which can supply power for roughly one million homes, can operate on one ton of pure thorium for a year. At the end of that time, the waste products consist of 1,660 pounds of virtually harmless waste from that original ton, and just 340 pounds of radioactive waste.
Adoption of liquid-fuel thorium reactors will also contribute to national security in two key ways:
? First, thorium reactors can be designed and built so they produce little or no weapons-grade byproducts. If terrorists or hostile governments want to get material for fission- or fusion-based nuclear weapons, they will most likely find a way. But by investing in liquid-fuel thorium reactors, we are at least taking away one of the easier avenues. ? A second key national security issue involves our dependence on foreign energy. Thorium, along with uranium resources and reserves, is located in large and accessible quantities in politically stable regions. The largest thorium supplies are in the United States, Australia, and India.
Finally, thorium-based nuclear power offers two major cost advantages:
? First, the costs of building liquid-fuel reactors are lower than uranium-based reactors. Why? Because the latter operate at extremely high pressure and use elaborate mechanical cooling systems. Thats why each plant is virtually a custom design, with the required design work alone costing up to $100 million per plant. The total cost to build a 1-gigawatt uranium-fueled plant today runs around $1.1 billion. By contrast, estimates for building a liquid-fuel reactor run as low as $220 million, because it isnt necessary to add expensive, anti-meltdown measures such as emergency cooling systems, control rod mechanisms, and spent fuel storage pools. Also, liquid-fuel reactors would be smaller and very standardized, which would allow them to be mass-produced in factories. ? Second, the costs to operate a thorium-based plant are also estimated to be lower than a uranium power plant. A 1-gigawatt uranium-fueled plant today requires around 500 personnel to run, costing $50 million a year. Estimates put the cost to run a liquid-fuel plant at about $5 million, or one-tenth the expense. The cost of fuel is another consideration. Thorium is 3 to 4 times more abundant and does not require enrichment, only purification. The annual cost to supply fuel to a 1-gigawatt uranium plant today is $30 million. Fuel for the thorium plant of the same size is expected to cost only about $1 million annually. Because of economies of scale, thorium is currently mined as "a rare-earth specialty metal," so it costs more than uranium. However, when its produced on the same scale as uranium, expect a precipitous price drop.
These rough numbers tell us that over the 60-year life of a liquid-fuel nuclear plant, electrical capacity would cost $8.2 million per gigawatt-year. That is a ten-fold reduction compared to the $81.6 million per gigawatt-year for a uranium plant of the same capacity.
So, with all of these benefits, why wasnt a thorium reactor commercialized long ago? The answer goes back to a working prototype built at the Oak Ridge National Laboratory over 50 years ago. It worked as expected. However, it was mothballed after a number of years because it was not compatible with nuclear weapons production research involving plutonium and uranium. A handful of liquid-fuel thorium reactors were subsequently developed in other countries, as well. But, all these projects were overshadowed when the Three Mile Island and Chernobyl catastrophes put a cloud over all nuclear energy development.
Its really been the pressure over the last two decades to find a cost-effective green energy solution thats put thorium back in the spotlight.3 Today, a number of countries and companies are aggressively pursuing the dream of a thorium-powered world. For instance, Lightbridge Corporation, a pioneering nuclear-energy start-up company based in McLean, Virginia, is developing the Radkowsky Thorium Reactor in collaboration with Russian researchers. In 2009, Areva, the French nuclear engineering conglomerate, recruited Lightbridge for a project assessing the use of thorium fuel in Arevas next-generation nuclear reactors being built in Finland and France. Then, in China, Atomic Energy of Canada Limited and a team of Chinese companies and agencies began an effort in mid-2009 to use thorium as fuel in nuclear reactors in Qinshan, China.
Given this trend, consider the following four forecasts:
First, with the right incentives, the U.S. will become one of the worlds largest suppliers of thorium.
American thorium is in large supply, but has traditionally been considered of low value. Because it comes out of the ground as a byproduct of uranium and rare-earth mining, there are estimates that we already have a 400-year supply on hand in ? or adjacent to ? uranium and rare-earth mines. Rather than being an energy importer, the U.S. could quickly become a major energy supplier to the world, but that would require us to jump-start global demand. Under this scenario, we would export fuel, as well as our expertise in building thorium-based reactors, to countries in need of cheap, clean power from a friendly and reliable source.
Second, since safety and weapons proliferation are greatly reduced issues for thorium-based reactors, there will be a wider acceptance of this form of nuclear power around the world.
Already, several "green groups" with a strong tradition of anti-nuclear bias have cautiously given their approval for this type of safe nuclear energy. As the benefits and safety of thorium plants become established, they are likely to replace aging coal plants, as well as provide new incremental capacity. Because liquid-fuel plants are scalable and can be built small enough to serve a community of only 1,000, its conceivable that we could eventually have thousands of decentralized thorium plants targeting the needs of communities, large and small.
Third, thorium fuel will be used to make conventional pressurized-water reactors safer and more cost-effective.
Several companies are pioneering technology for retrofitting todays reactors with thorium fuel. This will not lower plant construction costs nor reduce cooling system complexity. However it will enable the same plant to produce up to 30 percent more output, as well as minimizing nuclear waste and eliminating weapons proliferation issues.
Fourth, widespread adoption of liquid-fuel thorium reactors would also permit disposal of all of the existing nuclear waste from a half-century of uranium reactor operation.
Since America abandoned its plan to store its current waste permanently at Yucca Mountain, Nevada, there has been a huge question mark hanging over U.S. energy policy. Now there is a solution: Use the existing waste in the fuel cycle of the new plants and ultimately store the new, less-hazardous waste at each new plant for just 300 years. This one benefit alone justifies serious development of the technology.
References1. Cosmos, April 2006, "New Age Nuclear," by Tim Dean. ⓒ Copyright 2006 by Luna Media Pty. Ltd. All rights reserved. http://www.cosmosmagazine.com 2. For more information about the benefits of using a liquid-fuel thorium reactor, visit the Blue Ribbon Commission on Americas Nuclear Future website at: http://brc.gov 3. Discovery News, October 7, 2011, "Is Thorium the Future of Nuclear?" by Eric Niiler. ⓒ Copyright 2011 by Discovery Communications LLC. All rights reserved. http://news.discovery.com
