Dr Charles Forsberg is a nuclear chemical engineer. Before joining MIT, he was a Corporate Fellow at Oak Ridge National Laboratory. He led the MIT Future of the Nuclear Fuel Cycle study and is the PI building a flowing salt loop at the MIT reactor to better understand flowing salts under irradiation fields in support of salt-cooled reactors.. He is one of the three co-inventors of the Fluoride-salt-cooled High-temperature Reactor (FHR). A 35-MWt FHR test reactor is under construction in Oak Ridge, Tennessee by Kairos Power. Dr Forsberg is a co-inventor of electrically conductive firebrick to enable conversion of low-price electricity into stored heat up to 1800˚C. High-temperature heat is used in industry. It is the enabling technology for nuclear thermodynamic power topping cycles to provide dispatchable peak electricity from base-load nuclear power plants. Electrified Thermal Solutions is commercializing the technology. He teaches classes in nuclear chemical engineering and waste management and has published over 300 papers and 13 patents.
The goal is development of salt-cooled reactors including (1) molten salt reactors (fuel dissolved in salt), (2) fluoride-salt-cooled high-temperature reactors (FHRs) with clean salt coolant and solid fuel and (3) future fusion reactors with salt blankets. Salt reactors have potentially major advantages compared to other reactors including delivering higher-temperature heat to the customer (https://doi.org/10.1080/00295450.2020.1743628). There are also safety advantages in the low-pressure systems and other intrinsic characteristics that may improve the economics relative to other reactors. Multiple activities are underway to support their development. The largest project by Dr. Forsberg is building a flowing salt loop at the MIT reactor enabling testing of materials, instrumentation and other technologies required for all salt systems. Other activities include developing methods to lower the cost of irradiated graphite disposal (the highest volume waste) and integration of these reactors with the utility and industrial sectors.
The goal is to productively use all low-price electricity by converting it into high-temperature stored heat up to 1800˚C in low-cost firebrick. Heat is recovered from the firebrick by blowing hot air through the firebrick and using the hot air in industry (cement, steel, etc.). The hot air substitutes for burning fossil fuels that produces hot air. Alternatively, high-temperature heat can be used in nuclear power plants with thermodynamic topping cycles to provide peak power when needed. The work is based on our invention (https://image-ppubs.uspto.gov/dirsearch-public/print/downloadPdf/11877376) that converts cheap insulating firebrick into an electrically conductive firebrick, providing a way to heat firebrick to high temperatures. The technology is being commercialized by Electrified Thermal Solutions. The current focus is how to enable long-duration high-temperature heat storage over many days without excessive heat losses while allowing variable hot air output and low-price electricity input. This increases potential applications and reduces times when one may use fossil-fuel backup if heat storage is depleted.
The Crushed Rock Ultra-large Stored Heat (CRUSH) system goal is to develop a very low-cost heat storage system with incremental capital costs of $5/kWh of heat. At times of low electricity demand, heat from nuclear, Concentrated Solar Power and geothermal plants is stored to produce dispatchable electricity at times of higher demand or heat to industry. The concept (https://doi.org/10.1016/j.apenergy.2023.120753) developed by Dr. Forsberg is at the early stage of development. Heat is stored in very-low-cost crushed rock in piles 20 to 60 meters high inside an insulated building similar to an aircraft hangar. Hot heat transfer fluid from the nuclear reactor is sprayed onto the top of the rock, trickles downward by gravity to the drain pans below while transferring heat from liquid to crushed rock and returning to be reheated. To recover heat from storage, cold heat transfer fluid is sprayed on top of the hot crushed rock, trickles downward through the rock to be heated and sent to the power cycle. The very low cost potentially enables economic storage from hours to seasons to address the viable energy demand. Research is focused on better understanding what may limit performance as scale to a larger size.
The goal is to enable replacement of all crude oil with cellulosic hydrocarbon biofuels (gasoline, diesel, jet fuel and chemical feedstocks) enabled by the massive additions of external heat and hydrogen at the bio-refinery. The use of cellulosic biomass avoids net greenhouse gas emissions. Providing that heat and hydrogen is potentially the largest single market for nuclear energy. Our studies show (https://www.aiche.org/sites/default/files/cep/202504048.pdf) that there is sufficient cellulosic feedstocks (corn stover, trees, kelp, etc.) if the biomass carbon is only used in the final product and is not also consumed in producing heat and hydrogen for the chemical conversion processes. There are many process options and ways to integrate nuclear energy with refinery operations—thus major questions are what combinations of technology provide the lowest cost hydrocarbon biofuels.
Fossil fuels provide over 80% of the total energy for mankind because of their low cost, low-cost storage on an hourly to seasonal basis and low transport costs enabled by their high energy densities. In a low-carbon world, the challenge is not replacing fossil fuels as an energy source but replacing their storability and transportability functions (https://doi.org/10.1016/j.tej.2021.107042). The three big low-carbon energy sources are nuclear, wind and solar—where the last two sources only provide energy some of the time. Nuclear provides heat while wind and solar provide electricity—in a world where only 20% of the energy consumed by the final customer is in the form of electricity. The above activities partly address how to integrate different energy sources together for an affordable low-carbon world without reinventing everything. A series of workshops and studies continue on how to integrate the pieces into an economic system—and an area of active research in the context of the above research initiatives.
22.911 Seminar in Nuclear Engineering
22.912 Seminar in Nuclear Engineering
22.78 Principles in Nuclear Chemical Engineering and Waste Management