Developments in nuclear liquid metal technology

Current trends in the nuclear technology either in fission fusion or structure of matter research towards component solutions with high power densities led to a renaissance of the liquid metal related thermal-hydraulic and material research. Since liquid metals independent if they belong to the high or low Z-range offer the unique capability to act both as neutron source and as coolant they facilitate simple and robust structures within the reaction zone enabling compact designs at low capital investment. Due to their high specific electric and thermal conductivity they allow unique measurement and pumping techniques minimizing the effort for in-service inspection issues at simultaneously relatively moderate temperatures and temperature gradients within the structure. But, both the thermo-physical and the thermochemical properties of liquid metals require specific adapted solutions in order to match the individual goals. In this context the KAlrsruhe Liquid metal LAboratory (KALLA) consisting of several stagnant and circulating liquid metal systems using both low and high Z- fluids has been erected and set into operation. KALLA is dedicated to investigate crucial thermal-hydraulic and material problems together with the development of adequate measurement and sensing techniques in the nuclear field. The aim of this article is to discuss significant developments conducted at KALLA supporting the research in the field of fusion. Moreover, it is aimed to overview the experiences gained with the operation of liquid metal facilities and to illustrate cross-cutting issues appearing not only in fusion research. The individual KALLA experimental facilities are now operated continuously since several years and a broad experience has been gained for components typically appearing in nuclear systems like pumps (both electromagnetic and mechanical), oxygen monitoring and control systems, etc. (orig.)