Liquid salt for new reactor concepts

In the future, liquid molten salts could contribute to more efficient, climate-friendly energy generation. At FRM II, PhD student Liliana Quintero Zambrano is researching the use of liquid salt as a cooling and heat transfer medium in new reactor designs. The project is funded by TÜV NORD.

Doctoral student Liliana Quintero Zambrano Doctoral student Liliana Quintero Zambrano in front of the THOR test rig, which simulates the thermohydraulic parameters of an FRM II cooling channel. © Laura Richter, TUM/FRM II

Doctoral student Liliana Quintero Zambrano in front of the THOR test rig, which simulates the thermohydraulic parameters of an FRM II cooling channel. © Laura Richter, TUM/FRM II

Technologies to reduce CO₂ emissions are being developed worldwide. These include innovative reactor concepts, such as small modular reactors (SMRs). One subgroup is molten salt reactors, which use liquid salt instead of water for cooling purposes. “Molten salts as heat transfer media offer great potential for making energy systems more efficient, powerful, environmentally friendly and economical. Further developing these technologies will enable us to play a key role in decarbonising the energy sector and thus contribute to climate protection,” says Liliana Quintero Zambrano, PhD student at the TUM Centre for Nuclear Safety and Innovation at FRM II, who is researching on the TÜV NORD-funded project.

Characterisation of the flow behaviour of salts

The project aims to characterise various molten salts and investigate their thermo-hydraulic properties over a wide range of high heat fluxes and power densities. Additionally, heat transfer between surfaces and different molten salts will be analysed. This will enable the cooling capacity of molten salts to be determined and potentially establish new correlations for safety analyses.

TÜV News Kick-off of the research project in Garching: Prof. Christian Reiter, TUM, Frank Blömeling and Frank Meissner, both TÜV NORD EnSys, Liliana Quintero Zambrano, at TUM CNSI, and Tilmann Schlitt, research assistant, TUM (from left to right). © Laura Richter, TUM/FRM II

Kick-off of the research project in Garching: Prof. Christian Reiter, TUM, Frank Blömeling and Frank Meissner, both TÜV NORD EnSys, Liliana Quintero Zambrano, at TUM CNSI, and Tilmann Schlitt, research assistant, TUM (from left to right). © Laura Richter, TUM/FRM II

Why liquid salt?

Liquid salt is particularly effective at transporting heat and remains stable even at very high temperatures. ”Molten salt is proving to be a promising heat transfer medium for both small reactors and solar thermal energy,” explains Frank Meissner, Head of Reactor Technologies at TÜV NORD EnSys. “However, due to the high melting temperatures and aggressive corrosion behaviour of the materials used in the temperature range above 550°C, using molten salts is very challenging.” The aim of the research project is therefore to investigate the properties of molten salts and their flow behaviour under the respective thermal conditions in even greater detail, with the ultimate goal of enabling their use in commercial applications.

Comparing measurements with simulations

As part of the doctoral programme, a thermohydraulic test bench is being set up to test molten salts under extreme conditions. The measurement data will then be compared with computer simulations. The aim is to improve models that will later assist with the design and safety assessment of new plants. “This enables Liliana to work in a field ranging from development to operation as a PhD student and gain first-hand knowledge of the topics involved,” says Prof. Christian Reiter from the Chair of Applied Nuclear Technologies at TUM, who is supervising the work.

Close cooperation with TÜV NORD

“With the financial support of the TÜV NORD associations, we are very pleased to be able to advance the application of innovative technologies for a climate-neutral energy future,” says Thomas Rappuhn, Chairman of the Supervisory Board of TÜV NORD AG.

“With this joint research work, we are expanding our expertise in a new, promising approach to heat transfer materials and reactors and the associated system requirements. This means that we are not only learning more about the properties of very hot molten salts, but also about the parameters required to test the associated phenomena,” adds Frank Meissner.