Work Package 3
Safety of the reactor containment system
to prove the ultimate retention capabilities of the coolant-containment pair
In a nutshell

ork Package 3 investigates experimentally the mechanisms of fission product release and of aerosol formation and transport in a heavy-liquid-metal-cooled system, to provide elements for the development and validation of simulation models relevant for LFRs.

Work scope
Task 3.1
Fission product release from HLM
and deposition from the gas phase

The proposed R&D efforts will build on the results obtained in previous H2020 projects and will consist of three actions.

In the first action, the effect of interactions between Cs and I in heavy-liquid-metal (HLM) on the release of these elements by evaporation will be investigated. Suitable Cs and I doped HLM samples will be prepared, and combined in various proportions for use in transpiration-type evaporation experiments. If applicable, thermodynamic properties such as Henry constants will be derived from these data. These are needed in thermochemical simulations. Thermochromatography will be used to gain insight in the volatility and speciation of the vapors, and the existing models will be adapted according to the results obtained.

In the second action, the release behavior of tellurium (one of the elements forming the JOG phases investigated in WP1) will be studied in more detail by transpiration experiments and thermochromatography to quantify the effect of the cover gas on the release. The study of tellurium also allows better understanding and modeling of its heavier homologue polonium, which is difficult to study experimentally: these studies will permit to validate the simulations of enhanced released from the HLM due to interaction with vapor in the cover gas. Transpiration evaporation experiments (which measure the total Te release) will be used in combination with thermochromatography experiments, to gain qualitative insight in the volatility and speciation of the vapors.

In the final action, the evaporated fission product molecules will be studied using molecular beam mass spectrometry adapted for the sampling and analysis of condensable vapors at atmospheric pressure and high temperatures will be used for the preliminary characterization of I, Te and Cs gas molecules released from HLM.

Task 3.2 deals on the formation and transport mechanisms of nanometer to micron size aerosols, observed in various experiments but never studied systematically.

At SCK CEN, aerosol formation mechanisms relevant to HLM reactors will be examined, and formation yields and particle size distributions will be determined. Studying the LBE/Pb aerosol transport in a gas stream, transport rates (and factors that influence these rates such as deposition on tube walls) as function of aerosol particle size will then be determined.

The outcomes of experimental work will then be integrated by KTH into the development of models for the prediction of aerosol formation and transport in the containment system of an HLM-cooled reactor, using the containment code GOTHIC as platform. Aerosol formation models will be developed in cooperation with PSI and SCK CEN in order to model the source of aerosols in different relevant scenarios. Selection of relevant design features of the containment and accident scenarios will be carried out in collaboration with LFR designers. The work will also include the assessment of the importance of different uncertain modeling parameters on the release characteristics.

Task 3.2
Pb/LBE aerosol formation and transport