University of Wisconsin–Madison

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

Our research investigates the transport of tritium and other radioisotopes in molten fluoride salts and graphite fuel elements. We also study freezing transients of fluoride salt coolants from the point of view of thermal-hydraulic phenomenology, nuclear reactor transients, and safety analysis. 

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.

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.]

These studies have application to the thermal-hydraulic and mass transport studies for advanced Fluoride Salt-Cooled High Temperature Reactors (FHR). FHR is a Gen IV reactor concept that 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.

Molten fluoride salts have very good performance as heat transport fluids, and FHR designs take advantage of the inherent and passive safety features enabled by the properties of the fluoride salts and the robust fuel elements employed in FHR. However, to date the use of fluoride salt coolants has been limited, and they offer fertile ground for scientific studies of their chemical and thermal-hydraulic behavior.

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

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

More information about our research can be found on the Current Projects page, the People page, and the Publications page. Additional information and references for the FHR technology are found on the FHR Reactors page.

Group News

Congratulations to Kazi Ahmed for winning the Best Poster Award at the MSR Workshop.

Congratulations to Louis Chapdelaine for being awarded the DOE NEUP Fellowship! He joins Kazi Ahmed, and Michael Young, as the third NEUP fellow in our group.

Upcoming Conferences and Workshops



More upcoming conferences and workshops that our group will be attending can be found HERE.

Previous Presentations

Slides and abstracts from previous presentations given by our group can be found HERE.