Tritium, the radioactive isotope of hydrogen, is used as fuel for nuclear fusion, particularly in the ITER research reactor currently under construction in Cadarache (France). Its small size allows it to easily diffuse into materials, which will lead to the production of waste containing tritium after the operational phase of ITER.
To optimize the management of this tritiated waste, the CEA is developing technological solutions aimed at extracting and recycling tritium, as well as limiting its migration to the environment. The effectiveness of these solutions largely depends on the chemical form in which tritium is released. Experience from the outgassing of tritium from various types of waste indicates that it is released in two main chemical forms: tritiated hydrogen (HT) and tritiated water vapor (HTO), in varying proportions.
However, the mechanisms determining the distribution of tritium between these two species are not well understood. Several factors, such as oxygen and water concentrations, the nature and surface state of the waste, and the concentration of tritium, can influence this speciation.
The objectives of this thesis are as follows:
- To identify the phenomena affecting the speciation of tritium during the outgassing of tritiated waste.
- To conduct an experimental study to verify the proposed hypotheses.
- To develop a numerical model to predict the proportions of HT and HTO released, in order to optimize the management of this waste.
The thesis will be conducted within the IRESNE Institute (Institute for Research on Nuclear Systems for Low Carbon Energy Production) at the CEA site in Cadarache, in a laboratory specialised in tritium studies. The PhD candidate will work in a stimulating scientific environment and will have the opportunity to showcase their research work. The candidate must hold an engineering degree or a master’s degree in Chemical Engineering, Process Engineering, or Chemistry.