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Low temperature diffusion bonding – aluminosilicate ceramics

ANDRA is the French national radioactive waste management agency. The company is responsible for the long-term management of radioactive waste produced in France. ANDRA approached TWI for help in developing a long-term disposal solution based on encapsulation in ceramic overpacks.

The Challenge

ANDRA was commissioned to undertake a study of ceramic materials that could be used to enclose canisters used for waste encapsulation. Aluminosilicate ceramics were identified as a potential option with the right properties, however to use them it was necessary to find a way to hermetically seal the lid to the body of the canister without damaging the vitrified radioactive waste. The latter constraint imposes a limit on the inner temperature of 600°C whilst the ceramic diffusion bonding temperature is around 1150°C.

TWI’s contribution

Radiant heating was successfully used to prove that aluminosilicate ceramic components could be diffusion bonded. TWI’s vacuum furnaces were adapted to install an induction heating system. Diffusion bonding trials were performed under vacuum with a back fill of Argon for safety reasons, linked to the use of a graphite susceptor. This technique showed efficiency in heating a controlled area at the joint, demonstrating proof of principle to the client. 

Value to the client

The client was provided with a report detailing the parameters that were used to run the experiments and the associated results and conclusions. This provided a route forward for further development to control the process in line with the inner temperature limit. Work to continue this development is currently being reviewed by ANDRA, looking for a lower temperature process tailored to its project requirements. For further information please see the diffusion bonding section of our website or email contactus@twi.co.uk. 

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