NSE - Nuclear Science & Engineering at MIT


Charles W. Forsberg

Charles W. Forsberg

Principal Research Scientist
Executive Director, MIT Nuclear Fuel Cycle Project
Director and PI, Fluoride Salt-Cooled High-Temperature Reactor Project



Dr. Charles Forsberg directed the MIT Nuclear Fuel Cycle Study and is the principle investigator for the MIT Fluoride Salt-Cooled High-Temperature Reactor Project to build a salt loop at the MIT reactor. Before joining MIT he was a Corporate Fellow at Oak Ridge National Laboratory (ORNL). He is a Fellow of the American Nuclear Society (ANS) and the American Association for the Advancement of Science. Dr. Forsberg received the 2002 ANS Special Award for Innovative Nuclear Reactors (Fluoride-salt-cooled high-temperature reactors and PIUS-BWR), and in 2005 the American Institute of Chemical Engineers Robert E. Wilson Award in recognition of chemical engineering contributions to nuclear energy, including his work on reprocessing, waste management, repositories, and production of liquid fuels using nuclear energy. He received the 2014 Seaborg Award from the ANS for advancements in nuclear energy. He was recently a Director of the American Nuclear Society (2019-2022). Dr. Forsberg holds 12 patents and has published more than 300 papers. Two of his technologies are now being commercialized by startup companies.

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  • B.S., Chemical Engineering, University of Minnesota, 1969
  • M.S., Nuclear Engineering, Massachusetts Institute of Technology, 1971
  • Sc.D., Nuclear Engineering, Massachusetts Institute of Technology, 1974


  • Seaborg Medal (ANS) 2014

Recent Professional Service

American Nuclear Society. Director (2019-2022)

U.S. Department of Energy. Workshop Chair and Organizer, Can a Nuclear-Assisted Biofuels System Enable Liquid Biofuels as the Economic Low—carbon Replacement for all Liquid Fossil Fuels and Hydrocarbon Feedstocks and Enable Negative Carbon Emissions, (3-Day Virtual Workshop), August 2021.

Thermal-Mechanical-Chemical Energy Storage Workshop, Organizer (Yearly)

U.S. Department of Energy Nuclear Energy Innovation Workshop, March 2015.

American Nuclear Society. Director, Nuclear Fuel Cycle and Waste Management Division

National Research Council of the Academy of Science (Planning committee), Improving the Assessment of Proliferation Risk in Nuclear Fuel Cycles: Workshop Summary, Washington D.C., August 1-2, 2011.

U.S. Department of Energy (Organizer), Technology and Applied R&D Needs for Nuclear Fuel Resources (Uranium resources), Norwood, Massachusetts, October 13-15, 2010.


Dr Forsberg’s research interests are in the areas of salt-cooled reactors, integration of low-carbon energy systems (including heat storage) to replace fossil fuels and nuclear fuel cycles. An abbreviated list of publications associated with each research area is included below.

Fluoride Salt-Cooled High Temperature Reactors (FHRs): Ongoing research

The FHR is a new reactor (2001) concept with the goal to create a reactor with three characteristics: (1) deliver high-temperature heat to the customer, (2) increased revenue by 50 to 100% with base-load operation and variable electricity to the grid, and (3) no major fuel failures and thus no significant off-site consequences under severe accident conditions. The FHR was invented by [1] Charles Forsberg while at Oak Ridge National Laboratory, Per Peterson of the University of California at Berkeley and Paul Pickard of Sandia National Laboratories. It is being commercialized by Kairos Power (https://kairospower.com/) with a 35 MWt test reactor to be built in Oak Ridge, Tennessee by 2026 [2]. Per Peterson is the Kairos Chief Nuclear Officer. Dr. Forsberg is working on multiple FHR and molten salt reactor projects

The FHR combines graphite-matrix coated particle fuel with a clean liquid salt coolant. The economics are based on delivery of heat at a higher average temperatures than any other reactor [3-5] that (1) open new industrial markets, (2) enables more efficient electricity generation and (3) enables Nuclear Air-Brayton Combined Cycles [NACC] to provide variable electricity to the grid with very fast response times. The FHR safety case eliminates the potential for large off-site releases of radioactivity by the combination of a high-temperature fuel with failure temperatures above 1600˚C, a coolant with a boiling point above 1400˚C and a coolant that dissolves fission products if there are any fuel failures.  Dr. Forsberg currently leads the third consecutive multi-university Integrated Research Project with the goal to install a flowing salt loop at the MIT reactor that includes MIT, the University of California at Berkeley, North Carolina State University and Oak Ridge National Laboratory.  

NACC [4-5] is a combined cycle gas turbine using nuclear heat for base-load electricity and peak power provided by a combustible fuel (hydrogen, biofuels, etc.) or Firebrick Resistance-Heated Energy Storage (FIRES, see below). Because the peak power is a thermodynamic topping cycle, the incremental heat to electricity efficiency is above 70%, exceeding any other power cycle.

The same salts that are used in the FHR are proposed for fusion reactor blankets such as the fusion machine being developed by Commonwealth Fusion (https://cfs.energy/). The fusion blanket converts high-energy neutrons into heat for the power cycle, produce tritium fuel and provide radiation shielding. Consequently, some of our work [6, 7] has been to support fusion blanket development with shared facilities at MIT to support fission and fusion salt work.

  1. C. W. Forsberg, P. S. Pickard, and P. F. Peterson, “Molten-Salt-Cooled Advanced High-Temperature Reactor for Production of Hydrogen and Electricity”, Nuclear Technology, 144, pp. 289-302 (December 2003).
  2. Test Reactor Goals, Strategy, and Design: Fluoride-salt-cooled High-temperature Test Reactor (FHTR): Goals, Options, Ownership, Requirements, Design, Licensing, and Support Facilities, MIT-ANP-TR-154, Massachusetts Institute of Technology, Cambridge, MA, Dec. 2014.
  3. C. W. Forsberg. Market Basis for Salt-Cooled Reactors: Dispatchable Heat, Hydrogen, and Electricity with Assured Peak Power Capacity, Nuclear Technology, 2020, https://doi.org/10.1080/00295450.2020.1743628
  4. C. Forsberg and P. F. Peterson, “Basis for Fluoride Salt-Cooled High-Temperature Reactors with Nuclear Air-Brayton Combined Cycles and Firebrick Resistance Heated Energy Storage, Nuclear Technology, 196, October 2016.
  5. C. W. Forsberg, P. J. McDaniel, and B. Zohuri, “Nuclear Air-Brayton Power Cycles with Thermodynamic Topping Cycles, Assured Peaking Capacity and Heat Storage for Variable Electricity and Heat,” Nuclear Technology, 207 (4), 543-557, April 2021. https://doi.org/10.1080/00295450.2020.1785793
  6. C. Forsberg, E. M. Bucci and R. G. Ballinger, Molten-Salt Fusion Liquid-Immersion-Blanket Integrated Validation Plan. MIT-NES-TR-019, PSFC/RR-21-1, Massachusetts Institute of Technology. December 2020
  7. C. Forsberg, G. Zheng, R. Ballinger and S. T. Lam, “Fusion Blankets and Fluoride-salt-cooled High-Temperature Reactors with Flibe Salt Coolant: Common Challenges, Tritium Control, and Opportunities for Synergistic Development Strategies between Fission, Fusion and Solar Salt Technologies”, Nuclear Technology, Dec 2019. https://doi.org/10.1080/00295450.2019.1691400

High-Temperature Electrically Conductive Firebrick: Firebrick Resistance-Heated Energy Storage (Completed)

In a low-carbon world there is the need to convert electricity into very high-temperature heat for direct use in industrial processes and for high-temperature heat storage. The existing technologies (induction heating and plasma torch) are expensive. Firebrick is the only high-temperature low-cost material and is an electrical insulator. Dr Forsberg and his graduate student Daniel Stack developed electrically conductive firebrick that can be used as electric resistance heaters and match the temperatures of burning natural gas. Patents have been filed with Forsberg and Stack as co-inventors. Dr. Stack is now the CEO of Electrified Thermal Solutions (www.electrifiedthermal.com), a start-up company commercializing electrically-conductive firebrick for multiple industrial markets.

This technology may enable decarbonisation of high temperature industrial processes (steel, cement, glass, etc.) and high-temperature heat storage in firebrick recuperators. Heat storage enables buying electricity at times of low prices to deliver heat whenever needed. High-temperature heat storage also creates the option for the utility to control when electricity is charging storage—dispatching demand rather than just dispatching generation units to meet variable electricity demand. Very high-temperature heat storage enables Nuclear Air-Brayton Combined Cycles coupled to FHRs where base-load electricity is provided by an FHR and peak electricity using stored very-high-temperature heat in a Firebrick Resistance-Heated Energy Storage (FIRES) system. FIRES also enables combined cycle gas turbines that operate like batteries for the electricity grid. The round-trip efficiency of this storage system is slightly below batteries but the capital costs are much less and there is the backup option to burn a combustible fuel (jet fuel, biofuel, hydrogen, etc.) if insufficient heat storage.

  1. D. C. Stack (C. Forsberg advisor), Development of high-temperature firebrick resistance-heated energy storage (FIRES) using doped ceramic heating system, in Nuclear Science and Engineering. 2021, PhD Thesis, Massachusetts Institute of Technology. https://dspace.mit.edu/handle/1721.1/130800
  2. D. Stack and C. Forsberg, “Combined Cycle Gas Turbines with Electrically-heated Thermal Energy Storage for Dispatchable Zero-Carbon Electricity,” POWER2021-65529, Power 21 Power Conference A Legacy to Power the Future, American Society of Mechanical Engineers, Virtual Conference, July 20-22, 2021
  3. D. C. Stack, D. Curtis, and C. Forsberg, “Performance of Firebrick Resistance-Heated Energy Storage for Industrial Heat Applications and Round-Trip Electricity Storage”, Applied Energy, 242, 782-796 (2019) https://doi.org/10.1016/j.apenergy.2019.03.100
  4. C. Forsberg, D. Stack, D. Curtis, G. Haratyk, N. A. Sepulveda, “Converting Excess Low-Price Electricity into High-Temperature Stored Heat for Industry and High-Value Electricity Production,” 30, 42-52,  Electricity Journal, July 2017, https://doi.org/10.1016/j.tej.2017.06.009

Crushed Rock Ultra-Large Stored Heat (CRUSH) System with Hourly to Seasonal Energy Storage: Early stage research project

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 $2-4/kWh of heat. The concept [1-3] was originated by Dr. Forsberg. Very-low cost heat storage enables hourly to seasonal heat storage.  Heat can be provided by a nuclear reactor, conversion of low-price electricity into heat or a concentrated solar power (CSP) plant. Heat is stored as sensible heat in a crushed rock pile 20 to 60 meters high inside an insulated building like an aircraft hangar. A rock pile 20 m by 250 m by 250 m could store 100 GWh of heat. The hot heat transfer fluid 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 power cycle output may be several times the base-load output of the nuclear reactor to enable meeting peak electricity demands. If the heat is from a high-temperature reactor such as the FHR or by conversion of low-price electricity to heat, the heat transfer fluid is nitrate salt. If the heat is from a lower temperature reactor such as a light-water reactor, the heat transfer fluid is an organic heat transfer fluid with peak temperature limits near 400˚C. This system may enable base-load nuclear plants to replace today’s gas turbine using stored natural gas to provide variable electricity to the grid. Research is at an early stage of development. While CRUSH is a new heat storage technology, most of the subsystems have been developed for other industrial applications; thus, much of the work is to integrate these technologies into a new system.

  1. C. W. Forsberg, “Low-cost Crushed Rock Heat Storage with Oil or Salt Heat Transfer”, Applied Energy 335. 120753, March 2023. https://doi.org/10.1016/j.apenergy.2023.120753
  2. D. Bandyopadhyay and C. Forsberg, “Selecting Rock Types for Very-low-cost Crushed Rock Heat Storage Systems with Nitrate Salt Heat Transfer”, Journal of Energy Storage,  Vol. 61, 106664, Journal of Energy Storage, May 2023.  https://doi.org/10.1016/j.est.2023.106664 
  3. C. W. Forsberg and G. Preston, “Long Duration Heat Storage Using Crushed Rock and Nuclear Heat: Impact on Grid Design”, Transactions American Nuclear Society, 127 (1), 820-823, November 13-17, 2022. doi.org/10.13182/T127-39519

Replacing All Crude Oil with Nuclear-Assisted Cellulosic Hydrocarbon Biofuels: New research initiative.

The goal is to enable replacement of all crude oil with cellulosic hydrocarbon biofuels (gasoline, diesel, jet fuel, chemical feed stocks) enabled by the massive additions of heat and hydrogen at the bio-refinery. This is potentially the largest domestic and global market for nuclear energy. The work is in cooperation with Professor Bruce Dale at the Michigan State University. The United States currently consumes 18 million barrels per day of crude oil. We are developing a pathway [1-4] to replace all crude oil with cellulosic hydrocarbon drop-in fuels that (1) could produce 25 million barrels of hydrocarbon liquids per day without significant impacts on food and fiber prices and (2) large-scale sequestration of atmospheric carbon dioxide and (3) recycle of plant nutrients for long-term agricultural and forest sustainability. Cellulosic (non-food) biomass is the most abundant form of biomass on earth and includes corn stover, trees and kelp. Plants remove carbon dioxide from the atmosphere. If we use them to make liquid fuels, the burning of the fuel returns that carbon dioxide from the atmosphere with no net addition of carbon dioxide to the atmosphere.

Gasoline, diesel and jet fuel are made of carbon and hydrogen. Most current biofuels strategies use biomass as (1) a carbon source to produce the hydrocarbon product and (2) an energy and chemical source for the chemical conversion process into liquid fuels. The traditional conversion of biomass into gasoline, diesel and jet fuel involves using some of the biomass carbon for (1) removal of 40% by weight of the oxygen in biomass as carbon dioxide, (2) the production of hydrogen incorporated into the hydrocarbon product and (3) the energy to operate the process. Only a fraction of the biomass carbon ends up in the final product. Our cellulosic biofuels strategy uses massive quantities of external heat and hydrogen for converting cellulosic biomass into hydrocarbon liquids. With the conventional strategy, U.S. biofuels production is limited to ~6 million barrels per day versus 25 million barrels per day with external heat and hydrogen inputs to the bio-refinery. The use of external heat and hydrogen inputs have two effects: (1) doubles hydrocarbon liquid fuels produced per ton of cellulosic biomass feed stock and (2) makes hydrogen (not biomass) the primary cost of liquid fuels to enable paying more for biomass without large impacts on final liquid hydrocarbon fuel prices. The U.S. currently consumes 18 million barrels of crude oil per day.

  1. C. W. Forsberg, “What is the Long-Term Demand for Liquid Hydrocarbon Fuels and Feedstocks?” Applied Energy, 341, 121104 (1 July 2023). https://doi.org/10.1016/j.apenergy.2023.121104
  2. C. W. Forsberg and B. Dale, “Can large integrated refineries replace all crude oil with cellulosic feedstocks for drop-in hydrocarbon biofuels?”, Hydrocarbon Processing, January 2023. Can large integrated refineries replace all crude oil with cellulosic feedstocks for drop-in hydrocarbon biofuels? (hydrocarbonprocessing.com)
  3. C. W. Forsberg and B. Dale, Can a Nuclear-Assisted Biofuels System Enable Liquid Biofuels as the Economic Low-carbon Replacement for All Liquid Fossil Fuels and Hydrocarbon Feedstocks and Enable Negative Carbon Emissions?, Massachusetts Institute of Technology, MIT-NES-TR-023. April 2022.  https://canes.mit.edu/download-a-report 
  4. C. W. Forsberg, C. W, B. E. Dale, D. S. Jones, T. Hossain, A.R.C. Morais and L. M. Wendt, “Replacing Liquid Fossil Fuels and Hydrocarbon Chemical Feedstocks with Liquid Biofuels from Large-Scale Nuclear Biorefineries”, Applied Energy, 298,  117525, 15 September 2021. Replacing liquid fossil fuels and hydrocarbon chemical feedstocks with liquid biofuels from large-scale nuclear biorefineries - ScienceDirect

Zero-Carbon Integrated Energy Systems: Ongoing activity

Fossil fuels provide over 80% of the total energy for mankind because of their low cost, low-cost storage and low transport costs enabled by their high energy densities. The challenge [1] is not replacing fossil fuels as an energy source but replacing their storability and transportability functions. To use an example, solar electricity is inexpensive in many locations but the cost of electricity storage is four times the cost of the solar electricity.  Today affordable solar energy depends upon gas turbines using cheap-to-store natural gas to provide electricity when the sun is not shining.  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 energy sources together in a low-carbon world for specific technology options. 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.

  1. C. Forsberg, “Addressing the Low-Carbon Million Gigawatt-Hour Energy Storage Challenge“, The Electricity Journal, December 2021. https://doi.org/10.1016/j.tej.2021.107042.
  2. C. W. Forsberg, “Variable and Assured Peak Electricity from Base-Load Light-Water Reactors with Heat Storage and Auxiliary Combustible Fuels”, Nuclear Technology; 205, 377-396, March 2019.  https://doi.org/10.1080/00295450.2018.1518555
  3. C W. Forsberg, “Separating Nuclear Reactors from the Power Block with Heat Storage to Improve Economics with Dispatchable Heat and Electricity”, Nuclear Technology, 2021. https://doi.org/10.1080/00295450.2021.1947121
  4. Charles Forsberg, Stephen Brick, and Geoffrey Haratyk, “Coupling Heat Storage to Nuclear Reactors for Variable Electricity Output with Base-Load Reactor Operation, Electricity Journal, 31, 23-31, April 2018, https://doi.org/10.1016/j.tej.2018.03.008
  5. C. Forsberg, B. Dale and E. Ingersoll, “Nuclear Energy Drop-In Replacements for Gas Turbines, Natural Gas and Fossil Liquid Fuels”, Applied Energy Symposium: MIT A+B, August 11-13, 2021 • Cambridge, USA. https://www.energy-proceedings.org/category/mitab2021/
  6. Forsberg and S.M Bragg-Sitton, “Maximizing Clean Energy Utilization: Integrating Nuclear and Renewable Technologies to Support Variable Electricity, Heat and Hydrogen Demands, The Bridge, 50 (3) National Academy of Engineering, Fall 2020. https://www.nae.edu/239450/Maximizing-Clean-Energy-Use-Integrating-Nuclear-and-Renewable-Technologies-to-Support-Variable-Electricity-Heat-and-Hydrogen-Demands

Nuclear Fuel Cycles: Rethinking How Fuel Cycles are Organized

Nuclear fuel cycles, including disposal of wastes, are central to nuclear power. Dr. Forsberg was the executive director of MIT Future of the Nuclear Fuel Cycle study that issued its report in 2011 [1]. One top-level question is how the fuel cycle should be organized—including whether backend fuel cycle facilities should be collocated at the repository to improve economics, repository performance, nonproliferation characteristics, and public acceptance. The evidence strongly supports such a conclusion with continued work in this area.

  1. M. Kazimi, E. Moniz, C. Forsberg, et. al., The Future of the Nuclear Fuel Cycle, an Interdisciplinary Study, Massachusetts Institute of Technology, April 2011. https://energy.mit.edu/wp-content/uploads/2011/04/MITEI-The-Future-of-the-Nuclear-Fuel-Cycle.pdf
  2. C. Forsberg and W. F. Miller, “Coupling Fuel Cycles with Repositories: How Repository Institutional Choices May Impact Fuel Cycle Design,” Paper 7902, Global 2013, Salt Lake City, Utah, September 29-October 3, 2013. https://www.osti.gov/biblio/22264142
  3. C. W. Forsberg, “Coupling the Back End of Fuel Cycles with Repositories,” Nuclear Technology, 180 (2), pp 191-204, November 2012. https://ans.tandfonline.com/doi/10.13182/NT12-A14633#.ZGq283bMI2w
  4. C. W. Forsberg, J. Buongiorno and E. Ingersoll, “Nuclear Tech Hub: Co-siting Cutting Edge Nuclear Facilities with Waste Management Sites” Radwaste Solutions, Spring 2022. https://www.ans.org/news/article-3726/nuclear-tech-hub-cositing-cuttingedge-nuclear-facilities-with-waste-management-sites/

Other Studies

Several other studies are underway or completed—coupled by technology to the activities above. This includes work on two advanced concentrate solar power (CSP) systems [1, 2] that use some of the same liquid salts as in the above systems. Dr. Forsberg has also written on methods to stop air-borne pandemics [3] using the same filter technologies originally developed for nuclear facilities. There have been multiple projects on inherent and passive safety for different reactor types [4-5]  including his invention of the PIUS-BWR [6] and recent work on fission batteries [7] where the largest market may be for liquid fuels production from cellulosic feed stocks.

  1. A. H. Slocum, D. S. Codd, J. Buongiorno, C. Forsberg, T. McKrell, J. Nave, C. N. Papanicolas, A. Ghobeity, C. J. Noone, S. Passerini, F. Rojas, and “A. Mitsos “Concentrated Solar Power on Demand,” Solar Energy 85, 1519-1529 (2011)
  2. C. W. Forsberg, “1000-MW CSP with 100-Gigawatt-Hour Crushed-Rock Heat Storage to Replace Dispatchable Fossil-Fuel Electricity”, SolarPaces2021; Paper 7281, September 27-October 1, 2021
  3. C. Forsberg, “Public Health is a Job for Engineers”, Mechanical Engineering, 36-41, February-March 2022. Pandemic Shows Public Health is a Job for Engineers - ASME
  4. C. W. Forsberg and A. M. Weinberg, “Advanced Reactors, Passive Safety, and the Acceptance of Nuclear Energy”, Annual Reviews of Energy, 15: 133-152 (1990). https://www.annualreviews.org/doi/pdf/10.1146/annurev.eg.15.110190.001025
  5. C. W. Forsberg, D. L. Moses, E. B. Lewis, R. Gibson, R. Pearson, W. J. Reich, G. A. Murphy, R. H. Staunton, and W. E. Kohn, Proposed and Existing Passive and Inherent Safety-Related Structures, Systems, and Components (Building Blocks) for Advanced Light-Water Reactors, ORNL‑6554, Oak Ridge National Laboratory, Oak Ridge, Tennessee, October 1989. https://doi.org/10.2172/7023863
  6. C. W. Forsberg, “A Process Inherent Ultimate Safety Boiling Water Reactor”, Nucl. Technol., 72: 121-134 (February 1986). https://www.tandfonline.com/doi/abs/10.13182/NT86-A33735
  7. C. Forsberg and A. Foss, Fission Battery Markets and Economic Requirements, Applied Energy, 329, 2023, 120266. https://doi.org/10.1016/j.apenergy.2022.120266


22.911 Seminar in Nuclear Engineering
22.912 Seminar in Nuclear Engineering
22.78   Principles in Nuclear Chemical Engineering and Waste Management


Recent News

Recent Invited Lectures

Oxford University, Alternative Nuclear Energy Futures: Peak Electricity, Hydrogen, and Liquid Fuels, 2011 World Nuclear University Institute, Christ Church, England, July 10, 2011.

National Renewables Energy Laboratory, Nuclear Wind Hydrogen Systems for Variable Electricity and Hydrogen Production, Bolder, Colorado, September 12, 2011.

National Association of Regulatory Utility Commissioners, The MIT Future of the Nuclear Fuel Cycle Study, Los Angeles, California, July 19, 2010.