NSUF 18-1434: Study on defect evolution and stability of Y-Ti-O nano-oxides in 14YWT alloys under heavy ion irradiation

Next generation fast spectrum reactors require structural materials that can tolerate higher temperature and radiation damage compared to the currently used metal alloys. Nanostructured ferritic alloys (NFAs) are considered to be one of the best candidates for structural components in advanced nuclear reactors due to their excellent irradiation resistance, high strength and resistance to oxidation/corrosion under extreme conditions of temperature and pressure. The presence of a high density of nano-oxides (NOs) having sizes <5 nm provides higher strength, better thermal stability and creep resistance to NFAs in comparison to conventional ODS alloys. NOs hinder the recovery and creep by pinning the dislocations and grain boundaries. This results in fine microstructures with high density dislocations which create high sink densities and enhanced radiation damage resistance in NFAs. Moreover, NOs are reported to serve as sinks for He gas, effectively trapping it in extremely small bubbles during neutron irradiation. In this project, 14YWT NFAs will be used to study the interaction of NOs with defects and their stability under irradiation to a dose of ~ 10 dpa at various temperatures. Together with this, the effect of size and number density of the NOs on the defect evolution in NFAs will be studied. We have found that the size and number density of the NOs vary extensively in large and small grains in these NFAs. Therefore, samples for these experiments are annealed at 1100 °C and partly recrystallized to obtain abnormally grown large grains together with small unrecrystallized grains. Detailed high resolution TEM (HRTEM) on their crystal structure and energy filtered TEM (EFTEM) on their size and number density will be performed at Los Alamos National Laboratory (LANL) before the irradiations at the IVEM. The main work performed at the IVEM will include in-situ heavy ion irradiations (Kr) on 14YWT NFAs at room temperature, 300, 450, 600 and 1000 °C under bright-field TEM at around 150kx magnification. In-situ irradiations will enable us to observe the defect formation and evolution, and NO-defect interactions. After the irradiations, detailed HRTEM for crystal structure investigation of the NOs and EFTEM analyses for NO size and number density quantification will be performed at LANL. The results of this project will clarify the reason why NFAs are radiation tolerant and how the NOs play a role on this characteristics. This project will have a universal impact on the materials and nuclear fission communities and will help predicting the performance of the structural materials in neutron irradiation environments in advanced nuclear reactors. We ask for 10 days of beam time at IVEM as we want to go up to relatively high dpa (~10 dpa) levels at various temperatures. The expected period to run this project is 6 months starting from June 2018.

Additional Info

Field	Value
Abstract	Next generation fast spectrum reactors require structural materials that can tolerate higher temperature and radiation damage compared to the currently used metal alloys. Nanostructured ferritic alloys (NFAs) are considered to be one of the best candidates for structural components in advanced nuclear reactors due to their excellent irradiation resistance, high strength and resistance to oxidation/corrosion under extreme conditions of temperature and pressure. The presence of a high density of nano-oxides (NOs) having sizes <5 nm provides higher strength, better thermal stability and creep resistance to NFAs in comparison to conventional ODS alloys. NOs hinder the recovery and creep by pinning the dislocations and grain boundaries. This results in fine microstructures with high density dislocations which create high sink densities and enhanced radiation damage resistance in NFAs. Moreover, NOs are reported to serve as sinks for He gas, effectively trapping it in extremely small bubbles during neutron irradiation. In this project, 14YWT NFAs will be used to study the interaction of NOs with defects and their stability under irradiation to a dose of ~ 10 dpa at various temperatures. Together with this, the effect of size and number density of the NOs on the defect evolution in NFAs will be studied. We have found that the size and number density of the NOs vary extensively in large and small grains in these NFAs. Therefore, samples for these experiments are annealed at 1100 °C and partly recrystallized to obtain abnormally grown large grains together with small unrecrystallized grains. Detailed high resolution TEM (HRTEM) on their crystal structure and energy filtered TEM (EFTEM) on their size and number density will be performed at Los Alamos National Laboratory (LANL) before the irradiations at the IVEM. The main work performed at the IVEM will include in-situ heavy ion irradiations (Kr) on 14YWT NFAs at room temperature, 300, 450, 600 and 1000 °C under bright-field TEM at around 150kx magnification. In-situ irradiations will enable us to observe the defect formation and evolution, and NO-defect interactions. After the irradiations, detailed HRTEM for crystal structure investigation of the NOs and EFTEM analyses for NO size and number density quantification will be performed at LANL. The results of this project will clarify the reason why NFAs are radiation tolerant and how the NOs play a role on this characteristics. This project will have a universal impact on the materials and nuclear fission communities and will help predicting the performance of the structural materials in neutron irradiation environments in advanced nuclear reactors. We ask for 10 days of beam time at IVEM as we want to go up to relatively high dpa (~10 dpa) levels at various temperatures. The expected period to run this project is 6 months starting from June 2018.
Award Announced Date	2018-05-17T11:05:59.783
Awarded Institution	None
Facility	None
Facility Tech Lead	Wei-Ying Chen
Irradiation Facility	None
PI	Ben Eftink
PI Email	[email protected]
Project Type	RTE
RTE Number	1434