Material selection for lead cooled fast reactors

Several international projects like ELFR that is the European lead cooled fast reactor or ALFRED a demonstrator, are lead cooled nuclear systems. The selection of structural materials for such systems is essential. The high solubility of steel alloying elements in liquid Pb at reactor relevant temperatures is clearly detrimental. Therefore, all steels that are considered as structural materials have to be protected by dissolution barriers. The common barriers for all steels under consideration are oxide scales that form in-situ during operation. However, increasing the temperature above 500 Celsius degrees will result either in dissolution attack or in enhanced oxidation. For higher temperatures additional barriers like alumina forming surface alloys are discussed and investigated. Mechanical loads like creep stress and fretting will act on the steels. These mechanical loads will interact with the coolant and can enhance negative effects. For ALFRED austenitic steels (316 and 15-15Ti) are selected for most core components. The 15-15Ti is the choice for the fuel cladding of ALFRED while the ferritic martensitic steel T91 was selected as fuel clad material of ELFR. T91 is in both designs the material to be used for the heat exchanger. Surface alloying with alumina forming alloys is considered to assure material functionality at higher temperatures and is therefore selected for fuel cladding of ELFR and for heat exchanger tubes