1 - Pellet Injection into Plasma

Bret Kugelmass: What set you on your current path?

Lou Qualls: Lou Qualls grew up in West Tennessee and went to school at the University of Tennessee at Knoxville, receiving his PhD in nuclear engineering in the fusion area. He developed fueling technology for plasmas. Hydrogen plasma has deuterium and tritium in it. In order to get the fueling into the center of the plasma, it needs to be frozen into a little ball and shot at high velocity so it melts on the way in, which is called a pellet injection system. In his PhD work, Qualls worked on a stellarator the Advanced Toroidal Facility (ATF), a research project at Oak Ridge National Lab (ORNL) at the Y-12 site. A stellarator is a fusion device that has current carried in the coils so it can run in steady state. The alternate type is called a tokamak, like ITER, and is run in an inherently pulsed mode. The tokamak makes a better plasma, giving it the most promise to make a fusion reactor compared to the stellarator. When Japan built tokamaks, they found the physics changed when it was scaled up. Qualls hired into Oak Ridge in the pellet injection group; his job is to shoot pellets into plasma. He worked on the TFTR (Tritium Fusion Test Reactor) at Princeton University as a post-doc for 9 months. Instead of using the tritium pellet injector, they used neutral beam injection. This particle beam of protons goes straight through the plasma. Beams heat the plasma, but pellets cool the plasma. Neutral beams can heat the plasma and also drive the current, which the tokamak needs. Qualls also worked on the Tore Supra overseas in Cadarache. Upon his return to Oak Ridge and settling down in his family life, Qualls switched from the fusion world into the fission world.

2 - High Flux Isotope Reactor

Bret Kugelmass: How did you make your initial connections in the fission world?

Lou Qualls: Lou Qualls eventually switched from the fusion world into the fission world through his network of professional connections. Someone recommended Qualls for a position in the fission division and he accepted an initial job related to building radiation experiments that would go into the HFIR at Oak Ridge National Lab (ORNL). The goal was to test material specimens at various temperatures that would be relevant for the fusion energy program. Qualls worked at the High Flux Isotope Reactor (HFIR), which was first built in 1965. It was designed to produce medical isotopes and heavier than uranium elements. During design, someone had the idea to put beam ports in to provide the capability for neutron beam experiments later on. The shield has a hole which allows neutrons to pass. Materials are placed on a target to undergo experiments with well-aligned neutrons. HFIR is now mostly a science experiment that also makes isotopes and does irradiation experiments. This provides the ability to meet multiple sponsors’ needs.

3 - Space Power & Molten Salt

Bret Kugelmass: How did you get in charge of molten salt reactors?

Lou Qualls: Lou Qualls was doing irradiation while the space program was up and running. The idea for Project Prometheus was to take a nuclear reactor, create electricity, and do electric propulsion for vehicles that would go to the moons of Jupter and get into the gravity weld. Building a vehicle that could orbit for a while, get out, and go to the next moon required a nuclear reactor. When the project and space power program collapsed, but Qualls still thought it was an exciting initiative to work on. The fission surface power initiative was for developing power systems that could be used on the Moon and on Mars. Thermal propulsion is another form of propulsion in nuclear propulsion. Qualls was asked to be the space power program manager at Oak Ridge National Lab (ORNL), which he accepted. ORNL engaged with other national labs and NASA research centers to collaborate across the nation. Around 2010, there was a resurgence in interest for molten salt reactors. In the 1960’s, ORNL hit upon the molten salt reactor as a good, safe, economic possibility for reactor development. It had a high temperature coolant, a low pressure system, and was easy to operate. The molten salt reactor experiment was built to demonstrate the viability of the concept. Molten salt technology was a possible commercial technology, but was competing with other more mature technologies.

4 - Comeback of Molten Salt Technology

Bret Kugelmass: Why did ORNL start looking at molten salt reactors again in 2010?

Lou Qualls: Back in the 1960’s, Oak Ridge National Lab (ORNL) built a molten salt reactor than ran very reliably for a number of years. The technology was demonstrated, but many technical challenges remained and interest and funding shifted to light water reactors. At the same time, the need for breeding fuel lessened. A molten salt reactor is any reactor that uses molten salt to a significant degree in the primary system. A solid-fueled salt-cooled concept is like a traditional reactor except the coolant has been replaced by a low pressure, high temperature coolant that doesn’t require a thick-walled vessel for a high pressure system. The higher temperature gets a higher conversion efficiency in making electricity. Another version of molten salt reactor takes the fuel and dissolves it as a salt into the coolant which flows around the system. There is not a lot of excess reactivity in the system and reduces the possibility of a reactivity event. The poison effect from fission can be minimized. The salts studied back in the day are the same salts being looked at now. Fluoride or chloride salts can be combined with lithium, beryllium, or uranium to make a salt. Chloride-based salts are better suited for fast, high energy neutron spectrums. Lou Qualls is the National Technical Director for a Department of Energy (DOE) advanced reactor technology program, specializing in molten salt reactors. His job is to understand what molten salt developers are doing and to perform research within the DOE system that helps them be successful. Salt material interaction is basic science that can be done to understand what drives corrosion and develop ways to detect and mitigate it. The chemistry of the salt changes over time and the performance impacts of reactor behavior must be understood.

5 - Fission Products and Salt

Bret Kugelmass: Do fission products interact with the salt in molten salt reactors to form new compounds?

Lou Qualls: Fission products are put into the salt as the as the reactor runs and they are tracked over time and grouped into classes. Noble gases come out of the system because they don’t react with anything and a system in the reactor lets them escape. Some fission products react with the salt, the fluoride or chloride, and can become soluble in the system. Soluble products have an impact on reactor behavior, but as more soluble fission products are in the salt, there is less room in the salt for uranium. A solid can be formed within the liquid salt and can nucleate and begin to grow. This same particle could end up in a filter somewhere, leaving the salt but still in the system. Other things can stick to the wall, such as noble metals that don’t react or create salt solutions. This may disrupt the flow, impact the dose in the area, or put a heat load on the component that is serious enough to worry about getting over temperature if not properly cooled.

6 - Design of Molten Salt Reactors

Bret Kugelmass: What are the impacts of a hot spot in a molten salt reactor?

Lou Qualls: Hot spots could create a problem with a specific component. If maintenance has to be done on that component, there is no longer an easy way to access it to do deposits stuck on the wall. Monitoring and maintenance of a molten salt reactor is going to have challenges because of the distributed dose that is around the plant, not just in the fuel in the core underwater. Molten salt reactors don’t have a water pool above them so there must be different ways to shield and access. Camera systems that are tolerant to high doses of radiation and temperature must fit into the primary system. Components can be designed to last the lifetime of the plant or they can be designed to be replaced if they were not going to last the lifetime of the plant. This must be a thoughtful upfront design decision. The normal nuclear business thinks of everything as fixed and permanent, but molten salt reactors are more like a steam plant in which it is rebuilt over the span of its lifetime. The logistics of getting into the molten salt reactor business are challenges. Getting salts fabricated, transported, irradiated must be thought about. Supply chain on the front end must be created to make pumps and heat exchanges for molten salt reactors and have different design rules because of higher temperatures. This information must be shared with the NRC (Nuclear Regulatory Commission) and developers to get it into the design real-time. The nuclear business is in a difficult spot right now and needs a change. Evolutionary change is not always healthy; a revolutionary change is needed and molten salt can bring that to nuclear.

1 - Pellet Injection into Plasma

Bret Kugelmass: What set you on your current path?

Lou Qualls: Lou Qualls grew up in West Tennessee and went to school at the University of Tennessee at Knoxville, receiving his PhD in nuclear engineering in the fusion area. He developed fueling technology for plasmas. Hydrogen plasma has deuterium and tritium in it. In order to get the fueling into the center of the plasma, it needs to be frozen into a little ball and shot at high velocity so it melts on the way in, which is called a pellet injection system. In his PhD work, Qualls worked on a stellarator the Advanced Toroidal Facility (ATF), a research project at Oak Ridge National Lab (ORNL) at the Y-12 site. A stellarator is a fusion device that has current carried in the coils so it can run in steady state. The alternate type is called a tokamak, like ITER, and is run in an inherently pulsed mode. The tokamak makes a better plasma, giving it the most promise to make a fusion reactor compared to the stellarator. When Japan built tokamaks, they found the physics changed when it was scaled up. Qualls hired into Oak Ridge in the pellet injection group; his job is to shoot pellets into plasma. He worked on the TFTR (Tritium Fusion Test Reactor) at Princeton University as a post-doc for 9 months. Instead of using the tritium pellet injector, they used neutral beam injection. This particle beam of protons goes straight through the plasma. Beams heat the plasma, but pellets cool the plasma. Neutral beams can heat the plasma and also drive the current, which the tokamak needs. Qualls also worked on the Tore Supra overseas in Cadarache. Upon his return to Oak Ridge and settling down in his family life, Qualls switched from the fusion world into the fission world.

2 - High Flux Isotope Reactor

Bret Kugelmass: How did you make your initial connections in the fission world?

Lou Qualls: Lou Qualls eventually switched from the fusion world into the fission world through his network of professional connections. Someone recommended Qualls for a position in the fission division and he accepted an initial job related to building radiation experiments that would go into the HFIR at Oak Ridge National Lab (ORNL). The goal was to test material specimens at various temperatures that would be relevant for the fusion energy program. Qualls worked at the High Flux Isotope Reactor (HFIR), which was first built in 1965. It was designed to produce medical isotopes and heavier than uranium elements. During design, someone had the idea to put beam ports in to provide the capability for neutron beam experiments later on. The shield has a hole which allows neutrons to pass. Materials are placed on a target to undergo experiments with well-aligned neutrons. HFIR is now mostly a science experiment that also makes isotopes and does irradiation experiments. This provides the ability to meet multiple sponsors’ needs.

3 - Space Power & Molten Salt

Bret Kugelmass: How did you get in charge of molten salt reactors?

Lou Qualls: Lou Qualls was doing irradiation while the space program was up and running. The idea for Project Prometheus was to take a nuclear reactor, create electricity, and do electric propulsion for vehicles that would go to the moons of Jupter and get into the gravity weld. Building a vehicle that could orbit for a while, get out, and go to the next moon required a nuclear reactor. When the project and space power program collapsed, but Qualls still thought it was an exciting initiative to work on. The fission surface power initiative was for developing power systems that could be used on the Moon and on Mars. Thermal propulsion is another form of propulsion in nuclear propulsion. Qualls was asked to be the space power program manager at Oak Ridge National Lab (ORNL), which he accepted. ORNL engaged with other national labs and NASA research centers to collaborate across the nation. Around 2010, there was a resurgence in interest for molten salt reactors. In the 1960’s, ORNL hit upon the molten salt reactor as a good, safe, economic possibility for reactor development. It had a high temperature coolant, a low pressure system, and was easy to operate. The molten salt reactor experiment was built to demonstrate the viability of the concept. Molten salt technology was a possible commercial technology, but was competing with other more mature technologies.

4 - Comeback of Molten Salt Technology

Bret Kugelmass: Why did ORNL start looking at molten salt reactors again in 2010?

Lou Qualls: Back in the 1960’s, Oak Ridge National Lab (ORNL) built a molten salt reactor than ran very reliably for a number of years. The technology was demonstrated, but many technical challenges remained and interest and funding shifted to light water reactors. At the same time, the need for breeding fuel lessened. A molten salt reactor is any reactor that uses molten salt to a significant degree in the primary system. A solid-fueled salt-cooled concept is like a traditional reactor except the coolant has been replaced by a low pressure, high temperature coolant that doesn’t require a thick-walled vessel for a high pressure system. The higher temperature gets a higher conversion efficiency in making electricity. Another version of molten salt reactor takes the fuel and dissolves it as a salt into the coolant which flows around the system. There is not a lot of excess reactivity in the system and reduces the possibility of a reactivity event. The poison effect from fission can be minimized. The salts studied back in the day are the same salts being looked at now. Fluoride or chloride salts can be combined with lithium, beryllium, or uranium to make a salt. Chloride-based salts are better suited for fast, high energy neutron spectrums. Lou Qualls is the National Technical Director for a Department of Energy (DOE) advanced reactor technology program, specializing in molten salt reactors. His job is to understand what molten salt developers are doing and to perform research within the DOE system that helps them be successful. Salt material interaction is basic science that can be done to understand what drives corrosion and develop ways to detect and mitigate it. The chemistry of the salt changes over time and the performance impacts of reactor behavior must be understood.

5 - Fission Products and Salt

Bret Kugelmass: Do fission products interact with the salt in molten salt reactors to form new compounds?

Lou Qualls: Fission products are put into the salt as the as the reactor runs and they are tracked over time and grouped into classes. Noble gases come out of the system because they don’t react with anything and a system in the reactor lets them escape. Some fission products react with the salt, the fluoride or chloride, and can become soluble in the system. Soluble products have an impact on reactor behavior, but as more soluble fission products are in the salt, there is less room in the salt for uranium. A solid can be formed within the liquid salt and can nucleate and begin to grow. This same particle could end up in a filter somewhere, leaving the salt but still in the system. Other things can stick to the wall, such as noble metals that don’t react or create salt solutions. This may disrupt the flow, impact the dose in the area, or put a heat load on the component that is serious enough to worry about getting over temperature if not properly cooled.

6 - Design of Molten Salt Reactors

Bret Kugelmass: What are the impacts of a hot spot in a molten salt reactor?

Lou Qualls: Hot spots could create a problem with a specific component. If maintenance has to be done on that component, there is no longer an easy way to access it to do deposits stuck on the wall. Monitoring and maintenance of a molten salt reactor is going to have challenges because of the distributed dose that is around the plant, not just in the fuel in the core underwater. Molten salt reactors don’t have a water pool above them so there must be different ways to shield and access. Camera systems that are tolerant to high doses of radiation and temperature must fit into the primary system. Components can be designed to last the lifetime of the plant or they can be designed to be replaced if they were not going to last the lifetime of the plant. This must be a thoughtful upfront design decision. The normal nuclear business thinks of everything as fixed and permanent, but molten salt reactors are more like a steam plant in which it is rebuilt over the span of its lifetime. The logistics of getting into the molten salt reactor business are challenges. Getting salts fabricated, transported, irradiated must be thought about. Supply chain on the front end must be created to make pumps and heat exchanges for molten salt reactors and have different design rules because of higher temperatures. This information must be shared with the NRC (Nuclear Regulatory Commission) and developers to get it into the design real-time. The nuclear business is in a difficult spot right now and needs a change. Evolutionary change is not always healthy; a revolutionary change is needed and molten salt can bring that to nuclear.