The promise for developing new, advanced nuclear reactor concepts that significantly improve on commercial nuclear power reactors, and the extension of life of existing light water nuclear reactors rests heavily on understanding how neutron irradiation can degrade the properties of materials that serve as the structural components in reactor cores. In high-dose fission reactor concepts such as the sodium fast reactor (SFR), lead fast reactor (LFR), molten salt reactor (MSR) and the traveling wave reactor (TWR), structural materials must survive up to or over 200 dpa of damage at temperatures in excess of 400°C. A promising solution to achieving such high doses in a rapid and economical manner is ion irradiation. Challenges to the implementation of ion irradiation as a surrogate for neutron irradiation include accounting for rate effects, small irradiation volumes, accounting for transmutation and the lack of data to establish the equivalence of the resulting microstructures. Addressing these challenges constitutes the main focus of this program. This program consists of four major elements, or thrusts: 1) establishment of the capability to conduct dual- and triple- ion irradiations that capture the key elements of the BOR-60 reactor neutron spectrum and development of both ion and reactor irradiation programs, 2) characterization (both experimental and computational) of the evolution of the irradiated microstructure over a wide dose range relevant to fast and thermal reactors, and 3) establishment of the microstructure - property relationship for irradiated materials, and 4) engagement the worldwide radiation effects community through the creation of workshops and working groups to address ion irradiation techniques, irradiated sample preparation and the analysis of microstructure defects. Key elements of the program are A) both ion and neutron irradiation will be performed on the same alloys/heats, B) both damage and transmutation effects will be incorporated seamlessly into the irradiations, and C) the meshing of experiment and modeling efforts will occur across all length scales and all aspects of the program. The program will focus on a set of alloys chosen because: 1) they represent potential candidate alloys for fast reactors (T91 and HT9) and as can be considered as candidate replacement alloys for LWRs at high doses (800H). Importantly, complementary neutron irradiation data exists for several of these alloy heats. Finally, they are amenable to inclusion in a fast reactor irradiation campaign designed to produce a substantive set of data set to allow for a comprehensive comparison of ion and neutron irradiation effects. This project will demonstrate the capability to evaluate the behavior of reactor materials at high irradiation doses. Key to this effort is benchmarking of the microstructures formed under ion irradiation and neutron irradiation by a combined experimental and analytical approach. This RTE will generate valuable data on the microstructure of candidate alloys exposed using ion irradiation for comparison against that from neutron irradiation. The final product will provide a path and a methodology for qualifying materials for service at very high doses.

The mission of the DOE Office of Nuclear Energy is to advance nuclear power to meet the nation's energy, environmental, and national security needs. This RTE focuses on the generation of data on high dose ion irradiation for the purpose of benchmarking it against neutron irradiation to establish it as a viable technique for rapidly advancing the development of materials for advanced reactor concepts and core structural components in life-extended LWRs. The focus on candidate alloys T91 and HT9 in this RTE addresses the goal of the Advanced Reactor Technologies (ART) program to conduct R&D on advanced reactor concepts. Since these alloys are also considered for fuel cladding and duct components, the project also supports the mission of the Fuel Cycle Research and Development (FCRD) program to conduct R&D to develop sustainable fuel cycles. The inclusion of candidate core structural alloy 800H supports the mission of the Light Water Reactor Sustainability (LWRS) program of conducting R&D to develop the scientific basis for understanding and predicting long-term environmental degradation behavior of material in nuclear power plants. Finally, the inclusion of collaborators from England, Japan and Australia, and a collaborative benchmarking effort led by the IAEA supports the mission of the Office of International Nuclear Energy Policy and Cooperation (INEPC) to encourage international participation in the development of nuclear energy.