SiC encapsulation of (V)HTR components and waste by laser beam joining of ceramics

From the technological point of view as well as under the aspect of increasing safety requirements high-temperature resistant materials gain increasing importance in the nuclear sector. The non-oxide ceramics are characterized by their truly unusual properties. In this field high-tech ceramics such as silicon carbide (SiC) and silicon nitrite (Si3N4) play an outstanding role. However, their application used to be limited by the lack of a really suitable joining technology for high-temperature applications.At the Dresden University of Technology (TUD) an innovative laser beam joining technology for these ceramics has been developed in a joint project over the last few years. This technology makes it possible to join SiC as well as Si3N4 ceramics with high-temperature resistant, vacuum-tight seams that are resistant to most chemical substances. As no protective atmosphere is needed and the joining process takes less than a minute, the complete joining process can be configured very efficiently also in economic terms.For demonstration of the new possibilities SiCeram GmbH has developed several ceramic components which are tailored to V(HTR) requirements in material and geometries. Examples will be demonstrated.The overall ceramic encapsulation of fuel particles provides an additional thick barrier against the release of fission products, increasing the margins for operation at very high temperatures. Simultaneously ceramic encapsulation of the main core components facilitates the approach to the non-catastrophic behaviour of (V)HTR. Additional future research and the qualification of SiC encapsulated pebbles or compacts may result in important benefits also for waste management and final storage.