Joining process by microwave heating at moderate temperature of an aluminosilicate ceramic material for radioactive waste containers

The Cigeo project developed by Andra consists in creating a deep geological repository where containers for high-level and long and intermediate level wastes will be deposited. The material currently used for high-level radioactive waste containers is an unalloyed steel. In order to optimize the concept of the container, Andra plans to develop an alternative solution using an aluminosilicate ceramic container. The current problem remains to find a joining process for this containers. Sealing glasses are used for that. The selection criteria for these sealing glasses are numerous: melting temperature lower than 800 deg. C, coefficient of thermal expansion close to the ceramic, mechanical strength greater than 100 MPa,... Microwave heating was chosen because it allows controlled and localized heating. The thesis has several objectives: a major theme is the deepening of the understanding of the interaction between microwaves and the materials involved, in order to obtain efficient joining. We present here comparative tests of coupling of the ceramic, glasses alone or added of material which can make it possible to modulate the coupling. The second objective is to realize and optimize the joining by altering several parameters of the heating process (temperature, dwell time...), the implementation of the glasses (wt%, mass deposited) but also on coating methods. Finally, another aspect is to establish relationships between the process parameters and the properties of the joining (interface analysis, mechanical properties). (author)