The U.S. Department of Energy has awarded Rensselaer Polytechnic Institute $500,000 to research and develop new materials to make nuclear reactors more resilient and efficient. The two-year project involves a number of partners including General Electric and the U.S. Army.
WAMC's Jim Levulis spoke with RPI professor Dr. Jie Lian, the project’s principle investigator.
Lian: Currently nuclear technology generates about 20% of the electricity need in the United States. So nuclear technology is also vital or critical to fulfilling the mission of the net zero transition in 2050. And then to address the critical issues of climate change and global warming. Meanwhile, it's very important to secure our energy future with continuous increases in energy demand.
So in order to achieve this goal, otherwise new technologies are required to improve the efficiency for energy generation and improve the safety and economics and then we also want to achieve the effective utilization of nuclear resources and then to reduce nuclear waste burden. So, there's a number of different concepts, reactor concept or what we call the next generation concepts. Among those concepts, is molten salt. Molten salt is reactor technology that can utilize molten salt as coolant or we have nuclear fuel dispersed into molten salt, this is in contrast to light water in typical or current nuclear reactor fleet using water as coolant. So, a molten salt reactor is a key enabling technology and top priority currently under development and demonstration for future nuclear technology.
So in terms of the goal or the issue we are trying to address for this particular project, basically we want to develop the material with extended performance to be able to address the critical challenge of high temperature molten salt corrosion that it encounters in the molten salt technology. Because in a molten salt reactor we run at high temperatures to improve the efficiency for energy conversion. And also this molten salt is highly corrosive. So, basically the key challenge for the materials utilized in molten salt technology will be corrosion. So, what happens is, because this is unique in contrast to light water reactors, because in light water reactors we have water and the utility around that water reacts for several decades. But in terms of structure materials, so for example the leading material is steel, and then we have this alloy element that can form a protective oxide layer on structure material to protect it against the water corrosion. So this occurs for light water reactors. However for those alloys, for example, if you only have a high chromium element, those elements tend to react actively with molten salt to fluoride molten salt. And then this element was used to protect structure material in light water reactor will be dissolved in the molten salt. So, this is an extremely challenging issue in terms of high temperature corrosion for a molten salt environment.
Levulis: So as you mentioned some of the proposed strategies or methods to improve the life and efficiency of the nuclear reactors, include depositing metallic or ceramic coatings to improve the corrosion resistance is that accurate?
Lian: Yes so the strategy we propose to deposit functional gradient coatings, composite coatings on top of the structure material. So, in that case we’ll be able to improve corrosion resistance in molten salt to address the hot temperature, molten salt corrosion issue. So, you mentioned about the strategy actually the coating is not new. And the strategy for coating is to deposit a different coating material for example, metallic coating or ceramic coating on the alloys and then the coating that improves corrosion resistance. However, this is an issue because the current coating, typical coating material does show mismatched property with the alloy substrate as you can imagine, because if you coated the similar materials on other substrates, and that material may show different physical property. Because this mismatch of properties could generate large residual stress across the interface from the substrate to the corrosion and then leading to the cracking and even degrade the coating and the material performance. So, now, the idea we try to propose is you know, based upon functional graded coasting. So, basically a gradual transition from a substrate to the coating layer and then we have matched the property. So, in that case, we want to effect and mitigate the residual stress and prevent the cracking and meanwhile, we can just improve the materials performance and achieve enhanced corrosion resistance. So, this is the overall idea, you know, to use the functional grade and coating in contrast to current strategies for you know, the single coating materials.
And this is one part of the idea to apply functional graded coating, however, if you look at it functional graded coating, because now we see that it becomes more expensive and technically impractical to search and test different combinations of a large design window because when we talk coating we can have a different protein materials, different composition, because they also have a different geometry from the single coat into multi-layer protein from continuous and discontinuous proteins. So, in that case, they have large design window and they become very expensive, if you want to test every possible combination and then to try to improve the material property.
So instead of a trial-and-error approach, we have proposed an integrated approach or methodology guided by high throughput fine element modeling to guide the coating design. So, basically based upon the element of modeling and then the modeling can guide us about coating design with different compositions and different architecture design. So, in that case we can predict the interfacial property for stress and stress built up and then see how the coating will be able to mitigate cracking. So, in that case can guide us into experiment design and then this modeling will be validated by experiments. So, basically based upon how these materials synthesize and then this coating will also be demonstrated by additive manufacturing. So, that is based upon this integrated approach and methodology, we are able to optimize the design and then to verify the performance and manufacture the assumption breeding protein.
Levulis: Where are you going to be able to test these items out? I understand RPI has a bunch of different partners in this project, where physically are some of the locations the testing take place?
Lian: So, as you said, we're going to collaborate with different partners, particularly from industry, GE Global Research and also Benet Laboratory. So, the additive manufacturer will be delivered at the industrial partner, but before we do that, based upon the fine element modeling to predict the design of the coating and then in our lab we’ll be able to fabricate the composition gradient or functional gradient coating, and then we test the material performance, we test the corrosion resistance in the molten salt. So, all of those will be performed at RPI in my lab. Actually we do have a pretty unique capability to fabricate, to manufacture and to test the materials. So, once we design and verify the coating functionality and the performance and then we provide this information to our industry partner and then they can fabricate using an industrial process at a different manufacturer like at GE and Benet Lab. And then we also will test the materials. And so, in that case, we will be able to close the material design loop. So if we successfully develop this methodology, and then this methodology can be applied widely to design material beyond what we proposed for the molten salt reactor application.
