Germany’s infamous Energiewende, or Energy Transition, has seen a massive national investment failing to provide the environmental benefits that were ostensibly the basis for its existence. There is, however, a very different energy transition that is about to take place globally, one that will be far more effective and dramatic in the benefits it will bring to all nations, particularly in developing countries that are in dire need of inexpensive, reliable power.
Last year Russia towed a floating nuclear power plant, the Akademik Lomonosov, to Pevek, a small town on the Arctic Ocean in northeastern Russia. Though nuclear power has been used for decades by military ships and ice breakers, only rarely has such a floating nuclear power plant been deployed to power cities. Yet there are compelling reasons why this is not only possible but inevitable. A small company called Thorcon is pursuing this vision not just for tiny towns like Pevek. They have a design for full-scale ship-borne power plants capable of powering cities and countries just as land-based power plants do today.
Two brothers, Jack and Dave Devanney, who started Thorcon, are accomplished industrialists who designed and oversaw the construction of what were, at the time, the four largest ships in the world, after having successfully designed many other large vessels. They had their ships built in South Korean shipyards that are known for being at the forefront of high-tech shipbuilding technology. When they realized from actual experience how cheaply and quickly they could construct ships that way, it made them wonder if that same technology could be used to mass-produce nuclear power plants. Assembling a small group of engineers and physicists, they soon realized that molten salt reactor technology would be compatible with such mass production.
The molten salt reactor (MSR) technology that they intend to employ is based on a reactor design that was built at Oak Ridge National Laboratory in Tennessee in the USA back in the Sixties. It is arguably the simplest and safest type of nuclear reactor ever created, and the prototype reactor ran successfully for four years before the project was cancelled. The cancellation of such successful national laboratory projects in the USA is, unfortunately, not at all uncommon. They are often the victims of political influence or economic convenience. It wasn’t until nearly 2010 that people began to look back at MSR technology. At about the same time, the idea of building small, modular nuclear reactors also began to take hold. The idea is that small nuclear reactors could be built in factories instead of involving massive building projects that were becoming both slower and far more expensive.
Molten salt reactor technology is the simplest type of nuclear reactor system ever devised. It’s said that you only need 3 P’s: a pipe, a pot, and a pump. The pot is a container filled with slabs of graphite, with channels between them through which the molten salt flows. Uranium or other fissile material is dissolved in the hot salt (which liquifies at about 300°C), and as it passes the graphite the uranium atoms split and thus create heat. The hot molten salt exits the top of the pot where a low-pressure pump (about the same pressure as a garden hose) moves the hot salt into a heat exchanger (the pipe). The now cooler molten salt then reenters the bottom of the pot. Once the heat has been transferred via the heat exchanger the process of converting that heat to electricity is similar to the way any power plant works.
The rebirth of the MSR concept has seen a number of small startup companies tackle the challenge of designing reactors that can run for 60-80 years, like the current light-water reactors that now make up the vast majority of nuclear power plants around the world. But there are some serious materials challenges involved in this transformation. For one thing, MSRs operate at about 700°C, whereas light-water reactors operate at about 350°. And hot molten salt can be highly corrosive, adding more of a challenge to the already hostile environment with embrittlement effects of metals being bombarded by the neutrons in an operating reactor. Unfortunately, the designers of these reactor concepts often seemed overly glib about new alloys that weren’t available in the Sixties when the first MSR was built. No such assurances really seemed to pass the smell test, since nobody had ever actually put them to the test. There are other such material challenges that must be either overcome or sidestepped that are a bit too technical for the purposes of this article.
What set Thorcon apart from the other MSR hopefuls was partly due to their years of experience in actually designing and building industrial projects. They knew from the start that even the metal alloys available half a century ago could withstand the materials challenges of the MSR environment for at least four years, because the original reactor ran that long. The physicists and engineers at Oak Ridge had already designed their next MSR, to be capable of producing 300 megawatts of power, when their project was cancelled. The Thorcon team decided to design a modular MSR of 250MW, clearly a realistic scale-up of the original. What set this plan apart from the rest was the realization that even if the reactors were only built to run for four years, they could be built cheaply enough that the economics would still make the project financially workable. In fact, they would still be cheaper than just about any currently employed power sources.
The original plan envisioned building cylindrical self-contained reactor modules in factories. These would then be loaded onto a “canship” and transported to sites along navigable waterways, where they would be lifted off the canship and placed into silos near the shoreline. The silos, along with the generators, switchyards, cooling and control systems, would all be shore-based. Only the reactor modules themselves would be transported.
Any such project like this involves a number of risk factors, though. For one thing, any country that invests in building a power plant usually insists on having that project be a source for local employment. That brings into question a host of quality control issues that can be especially acute in less-developed countries where technical expertise is often minimal. Potential work stoppages, the potential for graft and corruption, protests by environmental groups, and other such impediments have often hobbled nuclear reactor projects in many countries.
Contemplating these challenges, the Thorcon team arrived at an elegant solution. They already knew how to design the biggest ships in the world. Why not build the entire power plant at the shipyard, self-contained and ready to connect to the power grid in any country? Quality control (and, importantly, cost control) could be assured, as would the construction time. The size of the ship necessary to house a fully-functional 500MW or 1,000MW power plant would be considerably smaller than ships they’d already built with great success. Such power ships with multiple reactor modules could be scaled to even larger sizes to power major cities.
Two Thorcon power ships of 500MW each, fully self-contained power plants
The advantages to such a system are many, if the economics will work. But will they? Once the power ship was designed by Thorcon, quotes from reputable shipyards and companies that supply nuclear power plant components verified the cost estimates that Thorcon had been claiming to the incredulity of many observers. Such power ships can realistically be expected to cost about one dollar per watt. That price has been the holy grail of solar panel designers for decades, but unlike solar panels the power ships would be available 24/7 at full power. Since the cost of fuel for such reactors is trivial, they would be cheaper than any other source of commercial electrical power, with perfectly reliable on-demand power.
Whatever countries or companies built such power ships could retain ownership rather than selling them. Fleets of power ships could be built and floated to nearly any country on earth. Yes, such modules could also be shipped to landlocked countries, but the vast majority of countries would be accessible either along seacoasts or major rivers. Developing nations with little or no money available for large capital-intensive projects like power plants wouldn’t have to invest anything beyond their own grid development costs. The ship owners would sell electricity just as utility companies sell it to their customers all over the world. If the electricity were to be sold at about half the average cost of electricity in Europe today, a power ship would be paid for in less than a year and a half. After that, it becomes a money machine for its owners, while providing clean, economical electricity for its customers.
An oft-cited argument against deploying nuclear power widely around the world is the risk of nuclear proliferation. With this system, that risk would be reduced to virtually zero. The power ship owners would be the operators. No nuclear technology whatsoever would have to be transferred to the customer country. In the event of extreme political instability, the ship could even be removed. Even if such a power ship were to be commandeered by hostile actors bent on building nuclear weapons, the nature of the MSR technology isn’t conducive to creating weapons.
Safety is clearly the main issue with nuclear power, and here the MSR shines. Unlike light-water reactors that operate at high pressures, MSRs operate at atmospheric pressure. Well, there’s actually a pump that moves the molten salt around with about the pressure of a garden hose, but in terms of safety issues we’re talking about a no-pressure system. In nuclear accidents like those that happened at Chernobyl and Fukushima, troublesome radioactive elements like Cesium-137, Iodine 131, and Strontium 90 are ejected into the air and can contaminate surrounding areas. But in an MSR these and other potentially dangerous elements are chemically bound to the fuel salt.
If one were to consider a worst-case scenario for such a power ship, it would probably be some sort of terrorist attack involving a large conventional explosive blowing up one or more modules. It’s not hard to create security systems that would be nearly invulnerable to such a situation, but that’s what worst-case scenarios are meant to supersede. So suddenly there’s a massive explosion and radioactive molten salt is thrown into the air. What would happen?
There are a number of different salt combinations that can be used in MSRs, but in general they melt at about 300°C. Assuming the reactors were blown up while operating at 700°, the molten salt would almost immediately solidify as it would quickly cool to below 300°, dropping to the earth along with its component radioactive elements. The radioactive salt that dropped onto the ground would make for a mess that would have to be cleaned up, but people living in the vicinity would have nothing to fear. Any salt that fell in the water would immediately be diluted to levels that would pose no meaningful hazard. It must be noted that we’re talking about this from a scientifically justifiable position, not from an alarmist nonsensical one. There are some people (including a few scientifically literate people who know better) who were so ridiculously alarmist about Fukushima that they warned people that they might not be able to swim in the waters off Hawaii because of radiation from Fukushima. This is utterly absurd. The ocean contains vast amounts of naturally radioactive material. In fact, if the ocean water that runs through an ocean-side power plant’s cooling system were to have filters put in place to extract the uranium from the seawater (yes, that technology already exists), the uranium thus obtained would be more than sufficient to fuel the power plant.
Estimates of how many power ships like this can be built vary a bit, but the most credible is probably that of an environmental organization in Boston, Massachusetts that did a survey of existing shipyards around the world. They concluded that just utilizing currently unused shipyard capacity could produce about 400 gigawatts (that’s 400,000 megawatts) of power ships per year! That’s equivalent to the capacity of the entire world’s current nuclear power plants. If you want to talk about power transformations that can deal meaningfully with climate change, look no further.
Since nuclear power plants are perfectly suited to operating at full power around the clock, the ideal configuration for power ships will ultimately be to make them hybrids that can produce electricity as needed but will be able to divert any excess heat to either desalination or other ancillary services, such as hydrogen production. The Soviet Union demonstrated this concept with the BN-350 on the shores of the Caspian Sea, which operated for two decades from 1973 to 1994. All the technology needed to implement such hybrid power plant systems is already well-known. One can only imagine the benefits to arid and semi-arid countries that would be able to benefit not only from cheap, clean electricity but from the vast amounts of fresh water that could enable substantial agricultural development.
The benefits of providing power to the world using such a system are so compelling that it seems inevitable that we’ll see it deployed in the near future. South Korea, while pioneering high-tech shipbuilding, isn’t the only country that currently has those capabilities. Both Russia and Saudi Arabia have recently constructed similar shipyards, and even relatively low-tech shipyards can build good ships without the reactors, into which the reactor modules (built at new shipyards or other fabrication facilities) could be placed.
As electric cars and trucks become more common, the demand for petroleum will certainly drop. Many countries whose economies are overly dependent upon oil and gas could suffer economic dislocation in the near future because of this electrification of transport. What better way to diminish such economic stress than to have such countries build fleets of power ships and continue to power the world, not with fossil fuels but with clean, plentiful, cheap electricity. It’s going to happen. The only question is which country will recognize this truly disruptive energy future and decide to become the world’s largest utility company?
P.S. Upon the request from the Global Energy Association another distinguished expert Tony Roulstone, Lecturer in Nuclear Energy, University of Cambridge has shared his ideas about this new technology.
There seem to be two technological innovations being proposed:
1. Commercial floating power stations
2. Offshore molten salt reactors, which is a compounding of molten salt technology and its outside the physical boundary of a country.
Stimulated by the Russian barge mounted reactor plant, this concept of large reactor systems floating on their means of cooling has been studied by inventors in US and India. There are a few academic studies one done by MIT and also we have done one in Cambridge England. It is clear that ships large enough to accommodate a commercial power plant are feasible but do not have clear economic advantages except perhaps of building a series of such reactors in one shipyard where productivity could be higher and cost reduction gained from production learning. This would be a massive undertaking with the largest ships in the world with the largest reactors in the world installed. This concept might turn out to be economic but there is almost no evidence one way or another.
The security and regulation issues could be more difficult. Even for coastal waters there is almost no legislation that would apply for commercial plants – I take both the Russian barge and the Chinese ACP-100 not to be commercial plants. If the plant were to be located outside territorial waters the legal problems would be compounded. Both our and MIT’s paper pointed to specific problems of physical security against terrorist attacks which perhaps not insurmountable would add complexity and cost.
The safety issues of a floating nuclear plants are different in detail but not necessarily different in kind. Both the MIT and our studies used established LWR technology. For these thе main additional risk would be sinking. While this would represent an economic loss, it is not clear that it would pose a major nuclear safety hazard.
The use of molten salt reactor technology bring new issues along with it new opportunities and benefits. Because it breeds new fissile material from widely available thorium it appear to have virtually limitless fuel. It is a low pressure system with a lower sensitivity to leaks of the primary coolant, even if this coolant will be highly radioactive. However, the technology is not at all proven though there are a number of design teams around the world proposing molten salt reactors.
There are many differences between the designs of molten salt reactor being proposed. Some are thermal neutron systems and some fast neutron systems. Thorcon design is a breeding system using highly enriched uranium and thorium . The fissile share in the fuel would be high ~20% or more – occasioning proliferation problems. The fuel cycle being considered is new. Though there are technical theoretical arguments that the issues of mobile fission product and reactor wastes can be addressed there is little or not experimental evidence to back up these arguments.
Before the technology could be commercialized there would need to be technology demonstrator built and it operated for a number of years to gain experience and confidence in the design. One would expect the technology to be first proven on land before being used on water. These necessary developmental steps make the possibility of a floating molten salt reactor before 2040 or perhaps 2050 is remote.