Part Of America’s Long-Term Energy Future?
The Electric Generation Fleet Is Changing
In the coming decades, an increasing number of coal and nuclear baseload electricity plants will be retired. Coal is under growing environmental pressure and a significant number of plant retirements are in the pipeline. Meanwhile, the hoped-for nuclear renaissance has fallen short of the initial anticipations, a casualty of concerns raised by the catastrophe at Fukushima, as well as low natural gas prices that have rendered uneconomic operation of even some current plants. (In the United States a plant previously held in abeyance, Watts Bar, is about to be licensed and four other plants are under construction. However, the future pipeline is limited.) However, this leaves many to wonder what will replace the power lost by these plant shutdowns. Wind and solar resources can do their part, and are growing rapidly, but they are intermittent sources of power and will require other resources (such as gas-fired plants or storage) to complement them.
Gas plants are expected to fill much of the generating void. But even with abundant shale gas reserves, supplies are not limitless and new claims on the resource are rapidly emerging. These demands include Liquid Natural Gas (LNG) conversion plants which ready gas for export to overseas markets, gas-to-liquid facilities that convert methane to diesel fuel, and an enormous potential growth in the petrochemical industry eyeing domestic gas as a competitive feedstock.
As a consequence, a small number of analysts and companies are suggesting that it is time to re-evaluate various molten salt reactor technologies using thorium, spent nuclear fuel, or low enriched fuel. And it is not only the U.S. that is looking at this technology. China is forging ahead with plans to have both liquid and solid fuel salt-cooled test reactors by 2017, while India is also evaluating the technology (especially reactors powered by thorium – which it possesses in abundance).
A Brief History Lesson
In 1946, a year after the U.S had dropped atomic bombs on Japan, it was already evident that nuclear fission could be used not only for bombs but for electricity production as well.
That year, Admiral Hyman Rickover began his program to power the U.S. Navy’s vessels with nuclear reactors. A naval propulsion system based on nuclear fission required the development of a relatively small reactor, and the Navy ultimately settled on a pressurized water reactor (PWR) that utilized solid fuel assemblies within a reactor vessel. The pressure inside this vessel was equal to approximately 160 atmospheres, allowing heated water – which otherwise would have turned to steam – to remain in a liquid state at 330°C. This was useful in the production of hot steam for electricity and propulsion. The Navy used the PWR technology as its mainstay, installing PWRs in both nuclear submarines and aircraft carriers.
In the early 1950’s, the U.S. began to focus on civilian energy applications, which eventually led to the deployment of a 60 megawatt nuclear plant (originally designed for aircraft carriers) being used to power the domestic grid at Shippingport, Pennsylvania. The PWR reactor technology was subsequently adopted for all future U.S. nuclear power plants.
Later another version of this Light Water Reactor (LWR) technology, called the Boiling Water Reactor (BWR) was also used in commercial applications. Similar to the PWR, the BWR used essentially the same solid fuel. However, the coolant actually boiled in the reactor and was then sent directly to the turbine generators (without generating steam). While BWRs had higher plant efficiencies, maintenance was more complicated.
In the meantime, a competing nuclear technology was also being developed by another branch of the U.S. Armed Forces. During the Cold War against the Soviet Union, Air Force General Curtis LeMay wanted the equivalent of a perpetually fueled nuclear submarine in the sky. His goal was to develop a bomber fueled by a reactor that could keep the plane endlessly circling the Soviet Union. Such a reactor would have to be far lighter than that designed for submarines. It could not use the thick container vessel and reactor shields associated with a PWR; another technology would be needed. So in the early 1950’s Oak Ridge National Laboratories (ORNL) was assigned to begin working on the project.
The design ORNL came up with involved a small experimental 100 kilowatt reactor using molten uranium salts as its fuel. In 1954, the first molten salt reactor (MSR) was built and operated successfully for a brief period. High temperature salts were developed to deliver high-temperature heat to the jet engines.
The Advantage of MSRs
The molten salt technology had several distinct advantages over the light water reactors:
Operating Pressure: The first inherent virtue was the fact that MSRs operate at a much higher temperature without the need for high pressure. While failure of the primary system at a PWR can result in a highly pressurized release of radioactive material, MSRs operate at atmospheric pressure. A failure would therefore not lead to dispersion of radioactive materials such as was seen at Chernobyl.
Risk of Meltdown: Since an MSR is already operating in a liquid form with molten salts, by definition it cannot have a meltdown. A rupture of a pipe or the containment vessel would simply result in solidification of the molten salts with the radioactive elements remaining inert in a crystallized form.
Overall Stability: If the MSR creates too much heat, the molten salts expand into the surrounding pipes. In such a case, the chain reactions are reduced and the heat levels fall.
Passive Safety Systems: Oak Ridge created a simple back-up safety system in the event of failure, in the form of a ‘freeze plug,’ a salt plug kept cool by a fan. If the system loses power, the salt plug melts and the liquid salt flows into a geometrically designed tank where fission ceases to occur. This is significant, particularly when compared to the systems utilized at today’s light water reactors such as Fukushima. Although the Japanese facilities shut down immediately after the initial earthquake, the resulting tsunami overwhelmed the back-up electrical generators and battery systems necessary to keep the system cool and stable. The reactors overheated, resulting in a reaction that released hydrogen which accumulated in the containment. This ultimately led to the explosions that ruptured the containment.
Lower Proliferation Risk:
Another advantage of the molten salt reactor is that it can run on thorium, making it unsuitable for weapons use and therefore possessing non-proliferation characteristics. Partly for that reason, in 2002 the Generation IV International Forum (GIF – led by the European Atomic Energy Community) anointed the MSR technology as one of six most promising for future development.
While the bomber concept was eventually laid to rest, ORNL continued to develop the technology for civilian purposes, and successfully ran a 7.4 megawatt (MW) molten salt reactor experiment (MSRE) from 1965 to 1969. However, in the early 1970s the federal government increased its research and funding focus on other competing technologies and abandoned the salt-based reactor technologies.
The Molten Salt Reactor Concept Resurrected
In the U.S., a small but growing community of advocates and investors is actively pushing for an MSR renaissance utilizing thorium or other fuel sources. These include – among others: the Energy From Thorium Foundation (EFTF) of Cleveland, Ohio; Flibe Energy of Huntsville, Alabama; a U.S. Department of Energy led consortium including the Massachusetts Institute of Technology, the University of California, and the University of Wisconsin; and Transatomic an MIT based start-up with $2 million in seed funding from the Founders Fund (led by Peter Thiel, Founder of PayPal).
The EFTF’s Nuclear Operations and Project Management Consultant Dave Amerine is a converted former nuclear engineer with 45 years in the nuclear industry, a storied career, and experience on the leadership teams of eight different nuclear plants. He’s a passionate believer in salt-based nuclear technologies and convinced that a thorium-based MSR would ultimately be safer and cheaper than the current pressured light water technologies in use today. Amerine comments that, in particular, the nuclear waste issue is a huge comparative advantage worthy of consideration:
Unlike light water reactors where we only consume about 5% of available fuel and then we remove the rods for structural integrity considerations, with fuel in a hot and highly radioactive state, in the LFTR (liquid fluoride thorium reactor), almost 100% of the fuel is consumed.
The resultant waste when you shut down a molten salt reactor is a lot less in volume and over 80% is short lived, with most decaying to acceptable levels in approximately ten years…A small amount would take 300 years to reach safe radioactive levels, but that is more manageable compared with 10,000 years with waste from a light water reactor.
There is still little practical experience with MSR technologies, but Amerine believes that the lifespan of an MSR could be considerable.
They are building naval light water reactors to last 60 years…they (MSRs) could probably last even longer, perhaps 80 years or more.
He believes decommissioning would probably cost a lot less than a traditional light water reactor as well. He also mentioned that fuel enrichment and fabrication costs could also be avoided and containments would not have to be as robust, resulting in costs being as much as 50% less than today’s LWRs.
Meanwhile, other countries are forging ahead and Amerine is concerned that the U.S. may lose its original leadership role in this technology in particular and nuclear power in general, because there is little government support to explore the possibilities.
China, India, the Czech Republic and Russia are exploring this technology. We are virtually stalled because we don’t have a national resolve to address a pending problem, which is our energy crisis… If you read Dr. Moniz’s (the current Secretary of Energy) strategic plan for the DOE, it does not mention nuclear. Instead it is in pursuit of solar, wind, and biomass. None of these technologies would be sustainable without significant government subsidies.
The Challenge of Promoting and Developing a New Technology
Amerine opines that the slow pace relative to the MSR technology in the U.S. is partially a result of the regulatory and government mindset. Those who do have an understanding of nuclear-related technologies have generally become “light water reactor centric,” which he fears will keep the U.S. from seriously evaluating the molten salt reactor path.
If you look at the generation 4 reactors which are the future reactors on the DOE nuclear power list, the MSR is at the bottom of the list.
Amerine acknowledges that it is a heavy lift – potentially involving several decades of research, money, and regulatory processes – to get from MSR concept to commerciality. The first thing one would need is a small research reactor to (re)prove the concept and address unresolved technology issues from the 1960s. That would likely then lead to a test reactor and finally to a demonstration reactor. The problem is that this would fall under DOE auspices and require congressional support – at a time when the dysfunctional congress cannot agree on anything, let alone a potentially promising energy technology that requires long lead times and potentially billions of dollars.
Amerine’s colleague at EFTF, lawyer Michael Goldstein, who has experience as an electric utility attorney at a nuclear power plant and Navy nuclear submarine duty, comments that licensing is a very big issue and that the existing regulatory structure is not established to address the thorium or other molten salt technologies. There are no current regulations applicable specifically to molten salt reactors, and these rules will have to be created before licensing. He notes that there is investor interest, but money will likely stay frozen until regulatory issues get ironed out.
Nobody’s willing to wait 20 years to find out if they could get a return on their investment…People and technologies are ready if there were a path to licensing.
Transatomic Power: A Promising Company Making Steps Forward
Even as most of the investment community waits on the sidelines, there are a few initiatives that continue to advance. One of the most interesting is the work of Transatomic Power. Co-founded by two MIT Ph.D. students, the company is focused on developing a molten salt reactor fueled with nuclear waste. Conventional light water reactors consume less then 5% of the potential fission energy in uranium. The Transatomic Power reactor design is focused on harvesting the 95% or more energy in the fuel that remains. CEO Leslie Dewan and CTO Mark Massie examined existing nuclear technologies and quickly became convinced that the molten salt reactor was the best technology for today’s world.
The ability to achieve high burn-up rates at atmospheric pressure was desirable. We also liked that one had been tested at Oak Ridge National Labs which ran for 20,000 hours. That showed this type of plant was viable.
The team felt that the ORNL design needed some significant re-design: It was bulky, expensive, had a low power density, and required highly enriched fuel. The design was highly accident-resistant, but its high cost and low power density prevented its broader adoption, Dewan notes, “in part because there had been no nuclear accidents at that point, and nobody wanted to make the trade-off (between cost and safety).”
Transatomic Power opted to change the ORNL design in some fundamental ways. The first thing they did was to determine how to make the plant run on nuclear waste. The company then changed the moderator. The ORNL design used graphite as a moderator (a moderator slows neutrons down to the correct energy level, to make them more likely to induce fission), but it required approximately 90% of its core to be graphite. For its moderator, Transatomic uses zirconium hydride, clad with a silicon carbide based composite. Zirconium hydride is much more effective at slowing down neutrons, so only 50% of its core has to be moderator.
The company also changed the salt. The ORNL design used a lithium fluoride – beryllium fluoride salt, but this salt can only contain a very small amount of dissolved uranium. Transatomic instead uses a lithium fluoride – uranium fluoride salt, which can contain about 27 times more uranium. Together, these two changes to the moderator and salt allow the reactor to run on either very low-enriched fresh uranium fuel or spent nuclear fuel.
Dewan is looking to the future when coal plants are retired en masse, and she has designed the new units to be suitable as similarly sized replacements, at 520 megawatts of electric generating capacity. But much stands between today’s blueprints and future commerciality, and the company is focused on key experimental tests.
The main thing we are starting to do is to start tests concerning corrosion effects and component lifetimes in the reactor itself.
Transatomic’s CEO is reluctant to offer a timeline for commercialization, noting that the outcome will be heavily driven by the regulatory process.
It’s one of the biggest hurdles. On the technology side, we will have all of the technical and design work done within the next two or three years. Then we will need to build a demo site at a national laboratory to get data for the Nuclear Regulatory Commission (NRC).
Dewan estimates that the demonstration site would likely cost three hundred million dollars for licensing, construction, and operation. To date, the company has had only informal discussions with the NRC. It has been in conversations with a joint DOE and NRC initiative for developing a licensing pathway for advanced reactor technology, and the DOE has been working on this for over a year.
Finally, Dewan observes that Transatomic Power’s reactor could run on thorium, but she believes it will be easier to obtain the uranium fuel. The key, though, is not the underlying fuel, but the molten salt reactor technology.
The molten salt reactor and thorium salt reactor each have same safety features and fuel burn-up. If you changed the moderator arrangement you could get each to run on the other fuel. They are cousins. We’ve been seeing benefits of molten salt reactors independent of whether they run on thorium or uranium. The molten salt is what makes it valuable. One key benefit is the ability to have a valve at the bottom, so if the system were to fail, it fails in a solid form rather than liquid or gaseous. The worst-case accident is confined to the site.
Another Approach: A Hybrid Market-Focused Initiative Using Solid Fuel And A Gas Generator
Transatomic Power is not the only group focused on a salt-cooled nuclear technology. Another group involving the DOE, the Universities of California and Wisconsin, and MIT is focused on a fluoride-salt-cooled high temperature reactor (FHR) technology, combined with a heat storage technology and gas turbines to create power that can be dispatched as needed.
Charles Forsberg, director of the Integrated Research Project Initiative, notes that the FHR approach – using low-enriched uranium – may serve as a ‘halfway house’ to full development of a molten salt reactor. A former Corporate Fellow at Oak Ridge and former Executive Director of the Nuclear Fuel Cycle Study at MIT, with a long and distinguished resume, Forsberg ran the salt-cooled projects at ORNL in the 2000 timeframe.
He draws a distinction between salt-cooled reactors and molten salt reactors where the fuel is actually dissolved in the salt itself. Forsberg indicates that the Chinese are making significant investments in both technologies, with plans to complete both a solid-fuel 10 MW fluoride salt-cooled reactor and a liquid-fueled 2 MW molten salt reactor within the next three years. According to Forsberg, the Chinese have half a billion dollars invested in the program to date, with more investment coming as they move towards commercialization in the foreseeable future (the U.S. and China have a Memorandum of Understanding to share information on the technologies).
Forsberg’s team believes that the solid fuel approach is the best way to approach the regulatory challenge.
Our perspective is that the solid fuel is a whole lot easier to develop and is the logical starting point. Get it to work and you have a smaller jump to the molten salt reactor where you have the fuel dissolved in the coolant. With permitting and regulatory, any time you go from solid fuel to liquid fuel you have to rethink the regulatory world.
Forsberg says that work with a clean salt cooled approach would probably be viewed by the NRC as a variant of something they have seen before, which is one reason to start with this approach. However, the main challenge is economics, and here his team may have an advantage, as they focus on using a hybrid reactor and turbine to create higher value and dispatchable peak power.
What the team has done here is to re-think the nuclear process by combining the reactor with a firebrick storage option. The latter facilitates the relatively long-term storage of heat, which can then be used when needed in the form of 600-700 degree centigrade air to power a gas turbine for production of added electricity at times of high demand and high prices.
Forsberg says the firebrick technology actually allows one to do this faster than it can be done with a conventional gas turbine. It could not have been done until recently: the previous gas turbines were not good enough to integrate into the system. The firebrick technology is over a century old and has seen long use in the steelmaking process, while the FHR team plans to utilize modified GE turbines to produce power. “Never invent a technology if you can borrow it,” he says.
Forsberg takes pains to point out that the gas turbine approach could also be applied to molten salt technologies and thorium reactors to improve the economics. And he’s convinced this technology could do a better job than today’s batteries.
What happens if you bet on batteries? You could have several days of no wind or sun, so you need gas turbine backup. The actual cost of a battery is the cost of the battery plus back up generation capacity. In my case, I already own the gas turbine and I operate storage in the gas turbine.
As with the MSR, Forsberg is clear that the federal government will have to play a role if this technology is ever to see the commercial light of day.
The first case would have to be built by Uncle Sam…After a test reactor, getting vendors in would not be a big issues. All vendors say you need a test reactor before you get any serious money. The timeline is too long otherwise… We realize it’s going to require a heavy lift.
All in, Forsberg estimates this project will cost approximately two billion dollars.
The idea would be to get a test reactor, a 30-40 MW reactor…This (estimate) is based on looking at other projects with similar complexity…It’s a big integration project. The concrete and steel would probably cost $150-200 million. It’s the R&D necessary to get enough confidence that after you get done, you can say ‘I think we want a pre-commercial plant.’
That’s a big price tag, but not an enormous one in the scheme of things. Given the opportunities at stake and the challenges faced by a world that must move to cheaper and cleaner energy technologies, at least some very smart people would argue that this is an investment worth seriously considering.