Metal Matrix Integrity and Related Technology Development in the Canadian Nuclear Fuel Waste Management Program

Abstract

ABSTRACTOne of the concepts under development as a nuclear fuel waste isolation container is a thin-wall corrosion-resistant shell, supported internally by a cast metal matrix in which intact used fuel bundles are invested. The integrity of the metal matrix can be influenced by metallurgical factors and by process parameters. Finite element solidification modelling and laboratory experiments with lead as an investment material have shown the influence of heat transfer parameters on matrix integrity. Controlled cooling of the container walls, for example, can be used to reduce the interaction time between the molten matrix, the fuel sheathing and the container wall, and achieve a void-free matrix. The results of the computer simulations have been used to design an improved casting system, based on controlled wall cooling, for investing nuclear fuel waste containers. Ultrasonic testing of bonds between some candidate container and metal matrix materials, in combination with the metallurgical characterization of the interface region, has allowed differentiation between bonded and unbonded regions. Matrix cracking near bonded interfaces was identified as a potential problem, which could limit the use of the ultrasonic scanning technique for matrix inspection. To produce a high quality interface with good chemical bonding, induction skin melting looks promising and is being further evaluated.