A European manufacturing line for monolithic U–Mo bare foil production

Abstract

The nuclear research reactor Forschungs-Neutronenquelle Heinz Maier-Leibnitz (FRM II), operated by the Technical University of Munich (TUM) in Germany, provides intense thermal neutron beams for the international scientific community. The uranium fuel currently used for the compact core is an assembly of fuel plates composed of dispersed U3Si2 powder with an enrichment up to 93%, dispersed in aluminium (Al) powder and cladded with an Al alloy. Within the international efforts to minimise the usage of HEU (Highly Enriched Uranium), the FRM II aims to convert its compact core to LEU (Low Enriched Uranium), i.e., a fuel with an enrichment in 235U lower than 20%. The most promising candidate is the metallic monolithic uranium–molybdenum alloy (U–Mo) with zirconium (Zr) coating and Al-based cladding. Here, we show the first European pilot line for U–Mo bare foil manufacturing, implemented in collaboration with the European fuel manufacturer Framatome-CERCATM in Romans-sur-Isère, France. This line involves innovative manufacturing processes, including casting, laser welding, hot rolling, and laser cutting. An overview of the bare foil development with the first results is presented, including visual inspections of foils produced from the hot rolling, the laser cutting and the manufacturing tools used. These first depleted uranium (DU) bare foils are analysed to extract the best manufacturing parameters for future industrialisation. This European manufacturing process gives an alternative solution to the US development for U–Mo monolithic bare foil manufacturing. It represents the first step for European monolithic fuel manufacturing, which could push other European research reactors to use the monolithic U–Mo for their conversion.