Heavy liquid metal cooled reactors are currently in development worldwide as an alternative for an affordable energy system aiming at net-zero emissions. Among those, small modular reactors (SMR) play a significant role. The first design expected to be deployed is based on the use of water as coolant of the reactor. Resorting to the experience gained in the framework of the R&D for the MYRRHA (Multi-purpose hYbrid Research Reactor for High-tech Application) project, an accelerator driven system conceived as the coupling of a proton accelerator and a subcritical reactor cooled by lead bismuth eutectic, Belgium would be using a heavy liquid metal, Pb, as coolant of their innovative SMRs. The main challenges related to the chemistry of this coolant focus on the corrosion of materials and release, precipitation and filtration of highly radiotoxic radionuclides.
During the operation of Lead Fast Reactors (LFR), the coolant will have various radionuclides produced by nuclear reactions. Understanding the release of these radionuclides from the coolant and their interactions with other impurities, in Pb and/or cover gas, and surfaces are major questions related to the chemistry of Pb-cooled reactors. Among the most important scenarios from the safety perspective one could highlight a failed fuel pin that would lead to the ingress/contact of fission products (e.g. Cs, I and Te) with the lead coolant.
To characterize the release behavior of these aforementioned elements, the main objectives of this work are the following:
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conducting transpiration experiments to determine the vapor pressure of elements of major interest (I, Cs and Te) above Pb. The influence of variables such as temperature, flow rate and nature of the gaseous atmospheres, concentration of the fission products in Pb and the interaction among them (mainly focusing on the interaction between Cs and I) will be investigated. To this aim, inactive samples will be used, doping Pb with various concentrations of the stable elements.
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validate and refine thermochemical models currently under development in our group using the obtained experimental results. These results will allow a more accurate determination of thermodynamic properties of great importance such as the activity coefficients of the investigated elements in lead and the main chemical interactions between them in Pb describing their release into the gas phase