Structural nuclear waste is compacted in patties, stacked in a stainless steel container. In these compacting boxes are placed various metal-type materials with the addition of organic matter, including chlorinated waste. By radiolytic degradation, these can lead to the formation of hydrogen chloride HCl. During the storage phase, relative humidity may be present within the container, which, added to the HCl, may lead to a phenomenon of condensation, resulting, on the surface of the materials, of acid and concentrated into chloride ions condensates. In contact with this acid and chloride electrolyte, a pitting phenomenon is likely to begin on the surface of a stainless steel. This is a local phenomenon that can lead to the piercing of the material in extreme cases. The initiation of this phenomenon depends on several factors: the morphology of the electrolyte, its composition and its evolution over time.
If nowadays this phenomenon is well known, modeling it remains a major challenge because it is a coupled multi-physics and multi-parameter problem. Many questions remain open, particularly at the level of the physical and chemical laws to be used or how to represent the corrosion process?
The objective of the post-doctorate is to develop a tool under COMSOL capable of simulating the initiation and the evolution over time of a pit on the surface of a stainless steel. The approach will be based on a mechanistic modeling of the processes (material transport process and all the chemical and electrochemical reactions).
The post-doctorate will take place in several actions:
1- make a state of the art of the bibliography in order to understand the pitting phenomenon and to identify the laws necessary for modeling.
2-simulate the spread of the pit in a chloride environment in order to establish a propagation criterion.
3-the pitting initiation will be implemented in order to obtain a complete tool capable of simulating the pitting process