Materials qualification testing for next generation nuclear reactors

The development of next generation, innovative nuclear fission reactors, needed to replace or supplement the current designs of nuclear reactors within the next say 30 years, critically depends on the availability of advanced structural and functional materials systems which must withstand extreme conditions: intense neutron irradiation, high temperatures, and potentially strongly corrosive coolant environments, in combination with complex loading states and cyclic loading histories. The mechanical performance and reliability of those materials depends on the service and off-normal conditions in whichever of the six candidate systems for Generation IV reactors, under the global Generation IV International Forum (GIF) agreement, they will be applied. This paper gives an overview of the suite of six selected reactor systems indicating where research on materials and structural integrity is still needed. Some of these reactor systems have been under study for many years whereas others are relatively new concepts but all still require a major expenditure of effort before they can be considered as realistic contenders. In particular the materials selection and component integrity for service will play a major role in a final successful design. Specific issues include: the endurance and stability with respect to creep, fatigue and fracture mechanics loading, the need for in situ environmental testing versus pre-exposure of materials and advanced structural-functional materials systems for specific applications. Using examples taken from research projects in which the authors' laboratory has participated, the materials qualification high temperature testing for three crucial components, reactor pressure vessel and piping, gas turbines and heat exchangers is described in some detail. Finally pointers are derived as to not only the scale of the remaining research needs but also the mechanisms which are planned to be followed in Europe, not to mention globally, to obtain the required data and understanding.