University of Wisconsin–Madison

Welcome to Heat and Mass Transport group at UW Madison Nuclear Engineering

We work on molten salt technology and the next generation of nuclear reactors to provide options for sustainable energy production.

We have activities in the areas of molten salt chemistry, heat and mass transport, thermal-hydraulic analysis, safety analysis, code verification and validation, and engineering ethics.

Molten  salts have good performance as heat transport fluids and fuel solvents. Advanced reactor designs can take advantage of the properties of the molten salts in the design of simpler and more economically competitive nuclear reactors than existing nuclear technology. An experimental molten salt reactor was operated in United States in the 1960s. To date, the use of molten salts in nuclear reactors has been limited, but activity in the commercial sector is exciting and growing.

Molten salts offer fertile ground for scientific studies of their chemical and thermal-hydraulic behavior, and fundamental studies may open doors to the development of even more highly performant technology than what we envision today.

Our group also has the educational mission to develop teaching curriculum relevant to molten salts. We welcome you to browse through the material from the Molten Salt Technology course from Spring 2017.

flibe phase diagram

Phase Diagram of LiF-BeF2 (Flibe) the Primary Coolant of the FHR Nuclear Reactor [Romberger K. A. et al. J. Phys. Chem. 76(8) 1972. 1154-1159.]

Nuclear Reactors (the next generation)

Nuclear reactors can be used for electricity production, process heat production for industrial plants, water desalination and purification, and medical isotope production. Can you think of other uses? don’t hesitate to share your ideas with us.

Advanced reactors that employ molten salts can be (1) solid-fueled, using the molten salts as coolants, or (2) liquid fueled, using the molten salts as solvents in which nuclear fuel (uranium, thorium, or other actinides) and the products of the nuclear reactions are dissolved. Solid-fueled reactors are termed Fluoride Salt-Cooled High Temperature Reactors (FHRs), and liquid-fueled reactors are termed Molten Salt Reactors (MSRs).

FHR combines high temperature fluoride salt coolants with solid fuel elements containing particle encapsulated (TRISO) fuel. The objective of the FHR technology is to be commercially competitive with natural gas plants while providing a low carbon-emission source of energy, and to achieve this with a short commercialization timeline. Conventional nuclear plants (and coal plants) produce heat at 400°C and below and are limited to running steam turbines with power conversion efficiencies below 34%. FHRs generate heat in the 600 – 700°C range, and can be coupled to commercially available gas turbines that enable combined-cycle efficiencies of 65% and above. Furthermore, this provides the capability of natural gas co-firing for rapid-deployment of peaking power. This provides a revolutionary advantage over all other nuclear reactor concepts.


PB-FHR Mark 1 Reactor Schematic [FHR@UCB website]

Our research activity has applications beyond the FHR and MSRs, including pyro-processing separations for the recycling of used nuclear fuel, fusion energy production, solar thermal systems, thermal energy storage,  batteries, metals production, and fluoride glasses.


If you would like to donate to the Molten Salt and Heat and Mass Transport Fund, your gift goes towards supporting research and outreach activities related to molten salt technology, advanced advanced nuclear energy, clean energy technology, and safety analysis.

More information about our research can be found on the Current Projects page, the People page, and the Publications page.


Our group is strongly committed to serving the diversity and inclusion responsibilities that the university has because equal access to education is an important value of democracy and furthermore because the university shapes the fabric of the culture and the values of future generations.

Related post:  A thought on diversity and inclusion