Breakthrough Institute on Cheap Nuclear Energy
- Jul 7, 2018 1:04 am GMT
Low cost, abundant, carbon free energy that can be quickly available is the key to averting a climate disaster. Wind and solar energy are unreliable and lack the capacity to be produced on demand. Energy storage technology is expensive and may not be ready in the large amounts required to overcome the flaws of wind and solar power. Clearly then, massive amounts of carbon free energy may not be available within the next 40 years, yet the power companies worry about nuclear costs.
The Breakthrough Institution has firmly joined the nuclear side of the energy debate and is paying attention to Generation IV reactor technology. In 2008 Nuclear Green did a case study of the cost lowering potential of Molten Salt Reactor (MSR) technology. I noted strategies for lowering nuclear cost. Breakthrough Institute has now performed a much more comprehensive study of nuclear energy cost lowering strategies.
By nuclear costs, I am referring to two different sorts of costs, the up front capitol costs owed by the owner of a new nuclear power plant, and the cost payed by the consumer for electricity produced by Nuclear Power Plants (NPPs). In Nuclear Green, I offered a case study of what I could call the full court press approach to lowering MSR investment costs. I do not claim originality for all my ideas. The purpose of my case study was to demonstrate that nuclear costs could be substantially lowered.
Fast forward to Summer of 2013, when Breakthrough Institute produced a report, How to Make Nuclear Power Cheap. At first, I expected extensive borrowing from my ideas, but this was not the case. The Breakthrough report is quite original and stands on its own as a major contribution to our understanding of the future of nuclear power. At the same time, the Breakthrough report contains a number of errors and fails to realize the full potential of nuclear power in the Second Nuclear Era.
Breakthrough Institute suggests that four factors effect nuclear costs. The Factors are Inherent Safety, Modular Design, Thermal Efficiency, and Readiness. Since I have been writing about cheap nuclear power for over 6 years, I do have a number of comments to make about the potential for cost saving of these standards.
Let us begin with Inherent Safety. While Inherent Safety is often good, it is not inevitably the best form of nuclear safety. The oldest form of nuclear safety involved the concept of barriers. Barriers can be improved and their cost lowered significantly. It may be desirable to retain one or more barriers, while lowering its cost. For example locating a reactor in an old salt mine might provide a substitute for the concrete and steel reactor dome at a fraction of the cost.
Removing radioactive fission products and undesirable Trans Uranium Elements (TRU) would improve reactor safety and is quite possible at a low price with MSR technology. By removing at least radioactive gases and volatile fission products, together with TRUs, we could improve safety in the event of a nuclear accident. The salt cleaning would offer a large safety advantage over traditional solid fuel reactors, even in a mine located MSR, with significant cost advantages.
At the same time, Inherent Safety features may sometimes create disadvantages for Generation IV Nuclear technology. Sodium is a fire hazard in air, as is plutonium. One would expect sodium fires to be rare in Liquid Sodium Fast Breeder Reactors such as the the Integral Fast Reactor. A large tank of liquid sodium acts as a heat sink in the case of an accident without coolant circulation. However in the rare event of a core breech and sodium fire, the tank would potentially contribute to a safety problem. The Pebble Bed Reactor is often pointed to as an example of Generation IV Inherent Safety, but part of that safety requires a very large core. In fact a core that is larger than the core of commercial Light Water Reactors. The Pebble Bed core costs as much to build as a LWR and thus no one seems to be moving forward with conventional Pebble Bed Reactor projects.
Oak Ridge National Laboratory (ORNL) made considerable progress on developing technology suitable for low cost removal of the most dangerous fission products and TRU elements from MSR core salts. I am not trying to criticize the Breakthrough Institute here. I have just been in the cheap nuclear power game longer than they have and have learned a few tricks they do not know yet.
The second factor which Breakthrough Institute suggests is Modularity. But there is more to the story than manufacturing modules for factory or field assembly. There are several other factors that may contribute to lowering the cost of production. Factory labor is a lot cheaper and more efficient than labor in the field. Some Multi-module reactors still require a great deal of field labor. This would even be the case for small mPower reactors. Some expensive materials can be replaced with cheaper materials. Finally some reactor designs are far simpler than others. Also, it is cheaper per unit to produce large numbers of identical modules, than to produce small numbers. One-off modules will be even more expensive.
The advantages of mass production may outweigh the advantages of thermal efficiency. For example, David LeBlanc notes that the cost of Molten Salt Reactors can be reduced by replacing expensive Nickel alloy with a inexpensive steel. The steel MSR will carry significantly less material costs, 100 C in cost of thermal efficiency. Since fuel costs are a minor factor in the capitol cost of nuclear power, material savings at the cost of 100 C of reactor heat (600 C of heat rather than 700C) might offer advantages. Coolants serve as heat carriers. The least efficient is helium used in gas cooled reactors. The most efficient coolants are found among the molten salts proposed for use in MSRs.
Mass production requires more than building a large number of reactor cores, heat exchanges and generation units. Land must be acquired and appropriate housing constructed. In addition, there must be hookup to the grid and appropriate means of transportation between the factory and the reactor’s home. Transportation issues may contribute to decisions about the reactor module’s size and weight.
Breakthrough Institute’s third factor is Thermal Efficiency. There are, in fact, two different Thermal Efficiencies that can lower nuclear costs. The first is a measure of the reactor system in transforming core heat into electricity. A second Thermal Efficiency would be a measure of the reactor coolant’s ability to transfer heat from the core to a heat exchange, or to provide emergency cooling. Heat transfer efficiency will lead to smaller cores, which in turn require fewer materials and less labor to construct. Helium is the least efficient coolant, while molten salts, for example FLiBe
(lithium fluoride (LiF) and beryllium fluoride. FLiBe is expensive, but it offers many advantages over lower cost salts, especially if your goal is to build LFTRs. However for other MSRs, David LeBlanc tells us that lower cost salts will do nearly as well. Low cost salts with good heat transfer characteristics would seem to be the way to go if you want to build low cost reactors.
The fourth Breakthrough Institute cost factor that could lower nuclear costs is labeled “Readiness.” Exactly what Readiness is, may be open to question. For example, technology that has been already tested is ready. Material and parts that have been tested and certified are ready. But what about parts and technology that require more research and development, but which will be ready in five years given a “business as usual” approach and much sooner given a Manhattan Project approach. Given a Manhattan Project style approach, the most advanced technologies, the LFTR and The IFR breeder could be ready for production in five years. Manhattan Projects are the products of societies operating in a crisis mode. We are not there yet. The public is not yet alarmed about greenhouse gases, but we are beginning to get there. Thus the standard for readiness may be about to shift.
There are several other factors which I have identified on Nuclear Green as offering potentials for lowering nuclear cost. These include the cost of land and reactor housing, the cost of grid connection, and the cost of interest paid for the financial costs of reactor construction. Finally, Breakthrough Institute failed to note the effect of economies of scale on reactor cost.
I have discussed an idea that is not original with me, that the sites of coal fired electrical generating facilities be recycled to house nuclear power plants. Rather than be built on the surface, reactors could be placed in underground silos. The silo would protect the reactor from attacks by aircraft and truck bombs and would cost significantly less to build than above ground concrete and steel protection domes.
Even better than digging a hole in the ground to house reactors, is to find a hole some one else dug and use it for reactor housing. There are a lot of old, abandoned salt mines scattered around the countryside. Many old salt mines might be inappropriate for reactor housing, but some might work.
Simplicity of reactor design, easy to work with and familiar materials, limited material demands all lead to rapid manufacture and final construction. The goal of such a manufacturing process would be to bring the power produced by the reactor system online as quickly as possible. This is highly desirable because interest on money borrowed during the construction period becomes part of the capitol cost of the project. Building cheap reactors means lowering capitol costs any way possible. Quick construction lowers capitol costs.
One final factor that is almost completely ignored in the discussion of lowering nuclear cost is the fuel factor in technology scalability. The Scalability Factor would include the capacity to fuel a large number of reactors quickly. Plutonium fuel for plutonium fueled Fast Reactors represents a bottle neck. There is a limited amount of plutonium available, far less than would be needed to fuel a massive deployment of Fast Reactors. Fast Reactors are excellent plutonium burners and that could serve as a useful role for a limited number of them. Thermal reactors require far less fuel for rated power production. Thus, a Fast Reactor might require 18 tons of reactor grade plutonium if it is rated at 1GW of electrical output while a graphite moderated Molten Salt Reactor might require 1 ton of U-235 or U-233 or even less per GW of output. Plutonium is expensive. Eighteen tons of reactor grade plutonium would cost one billion dollars while one ton of U-235 would cost far less.
All in all, Breakthrough Institute seems to be moving in the right direction towards understanding the control of nuclear costs. My comments suggest that they still have a ways to go. We are learning and I would include myself in the “we”. We still have a way to go, but with the dawning of the second nuclear era, comes the realization that nuclear costs can be made cheaper; perhaps much cheaper.
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