Dr. Tiankai (TK) Yao is a staff scientist at Characterization & Advanced PIE division of Materials and Fuel Complex (MFC) at Idaho National Laboratory. Dr. Yao graduated from Rensselaer Polytechnic Institute with a Ph.D. degree in Nuclear Engineering in 2018. Dr. Yao’s research focuses on the development of advanced nuclear fuel for next-generation nuclear reactors from advanced fabrication methods, such as directed energy deposition and spark plasma sintering, and transmission electron microscopy-based PIE of spent nuclear fuels. His Ph.D. thesis covers the synthesis of various uranium-based fuel compounds by spark plasma sintering and fuel property assessments, primarly the thermo-mechanical behaviors, oxidation resistance, and phase stability under irradiation conditions. Over the 8 years of research activities, He was directly involved in four US Department of Energy Nuclear Engineering University Program (NEUP) projects and two Energy Frontier Research Center (Waste performance and design (PD) and thermal energy transportation under irradiation (TETI)).
Dr. Yao has authored and co-authored more than 60 papers at prestigious journals in the field such as Nature Materials, Science, Nature Materials Degradation, Nature Scientific Report, Scripta Materialia, Journal of American Ceramic Society, Journal of Alloys and Compounds, and Journal of Nuclear Materials. Dr. Yao also holds three patents on the aging of aluminum alloys. As of Sep. 2020, Dr. Yao’s publication has a google citation of ~980 and an h-index of 14. His paper on “Self-accelerated corrosion of nuclear waste forms at material interfaces” has wide media coverage from US ABC News, Fox News, Yahoo News, UK Daily Mails, and official news agencies from many other countries, such as Italy, France, and Sweden.
Outside of academic life, Dr. TK Yao likes soccer with friends and hiking with family.
"Bubble morphology in U3Si2 implanted by high-energy Xe ions at 300ºC"
Yinbin Miao, Jason Harp, Kun Mo, Shaofei Zhu, Tiankai Yao, Jie Lian, Abdellatif Yacout,
Journal of Nuclear Materials
The microstructure modifications of a high-energy Xe implanted U3Si2, a promising accident tolerant fuel candidate, were characterized and are reported upon. The U3Si2 pellet was irradiated at Argonne Tandem Linac Accelerator System (ATLAS) by an 84 MeV Xe ion beam at 300 °C. The irradiated specimen was then investigated using a series of transmission electron microscopy (TEM) techniques. A dense distribution of bubbles were observed near the range of the 84 MeV Xe ions. Xe gas was also found to accumulate at multiple types of sinks, such as dislocations and grain boundaries. Bubbles aggregated at those sinks are slightly larger than intragranular bubbles in lattice. At 300 °C, the gaseous swelling strain is limited as all the bubbles are below 10 nm, implying the promising fission gas behavior of U3Si2 under normal operating conditions in light water reactors (LWRs).
|"Fuel-cladding chemical interaction of a prototype annular U-10Zr fuel with Fe-12Cr ferritic/martensitic HT-9 cladding" Xiang Liu, Luca Capriotti, Tiankai Yao, Jason Harp, Michael Benson, Yachun Wang, Fei Teng, Lingfeng He, https://www.sciencedirect.com/science/article/pii/S002231152031196X#ack0001 Vol. 544 2021 Link
"In situ synchrotron investigation of grain growth behavior of nano-grained UO2"
Jie Lian, Yinbin Miao, Kun Mo, Jun-Sang Park, Tiankai Yao, Jonathan Almer, Sumit Bhattacharya, Abdellatif Yacout,
The study of grain growth kinetics in nano-grained UO2 samples is reported. Dense nano-grained UO2 samples with well-controlled stoichiometry and grain size were fabricated using the spark plasma sintering technique. To determine the grain growth kinetics at elevated temperatures, a synchrotron wide-angle X-ray scattering (WAXS) study was performed in situ to measure the real-time grain size evolution based on the modified Williamson-Hall analysis. The unique grain growth kinetics of nanocrystalline UO2 at 730 °C and 820 °C were observed and explained by the difference in mobility of various grain boundaries.
"In-situ TEM study of the ion irradiation behavior of U3Si2 and U3Si5"
Tiankai Yao, Bowen Gong, Yinbin Miao, Jason Harp, Jie Lian,
Journal of Nuclear Materials
U3Si2 and U3Si5 are two important uranium silicide phases currently under extensive investigation as potential fuel forms or components for light water reactors (LWRs) to enhance accident tolerance. In this paper, their irradiation behaviors are studied by ion beam irradiations with various ion mass and energies, and their microstructure evolution is investigated by in-situ transmission electron microscopy (TEM). U3Si2 can easily be amorphized by ion beam irradiations (by 1 MeV Ar2+ or Kr2+) at room temperature with the critical amorphization dose less than 1 dpa. The critical amorphization temperatures of U3Si2 irradiated by 1 MeV Kr2+ and 1 MeV Ar2+ ion are determined as 580 ± 10 K and 540 ± 5 K, respectively. In contrast, U3Si5 remains crystalline up to 8 dpa at room temperature and is stable against ion irradiation-induced amorphization up to ∼50 dpa by either 1 MeV Kr2+ or 150 KeV Kr+ at 623 K. These results provide valuable experimental data to guide future irradiation experiments, support the relevant post irradiation examination, and serve as the experimental basis for the validation of advanced fuel performance models.
"Nano-crystallization induced by high-energy heavy ion irradiation in UO2"
Yinbin Miao, Tiankai Yao, Jie Lian, Shaofei Zhu, Sumit Bhattacharya, Aaron Oaks, Adbdellatif Yacout,
Advanced microstructure investigations of the high-burnup structure (HBS) in UO2 produced by high-dose 84 MeV Xe ion irradiation are reported. Spark plasma sintered micro-grained UO2 was irradiated to 1357 dpa at 350 °C. The characteristic nano-grains and micro-pores of the HBS were formed. The grain size and grain boundary misorientation distributions of the HBS were measured using transmission electron microscopy based orientation imaging microscopy. Grain polygonization due to accumulation of radiation-induced dislocations was found to be the mechanism of nano-crystallization. The morphology of Xe bubbles was quantitatively investigated. This study provides crucial references for advanced fuel performance modeling of high-burnup UO2.
"Radiation-induced grain subdivision and bubble formation in U3Si2 at LWR temperature"
Bowen Gong, Jason Harp, Jie Lian, Tiankai Yao, Lingfeng He, Michael Tonks,
Journal of Nuclear Materials
U3Si2, an advanced fuel form proposed for light water reactors (LWRs), has excellent thermal conductivity and a high fissile element density. However, limited understanding of the radiation performance and fission gas behavior of U3Si2 is available at LWR conditions. This study explores the irradiation behavior of U3Si2 by 300 keV Xe+ ion beam bombardment combining with in-situ transmission electron microscopy (TEM) observation. The crystal structure of U3Si2 is stable against radiation-induced amorphization at 350 °C even up to a very high dose of 64 displacements per atom (dpa). Grain subdivision of U3Si2 occurs at a relatively low dose of 0.8 dpa and continues to above 48 dpa, leading to the formation of high-density nanoparticles. Nano-sized Xe gas bubbles prevail at a dose of 24 dpa, and Xe bubble coalescence was identified with the increase of irradiation dose. The volumetric swelling resulting from Xe gas bubble formation and coalescence was estimated with respect to radiation dose, and a 2.2% volumetric swelling was observed for U3Si2 irradiated at 64 dpa. Due to extremely high susceptibility to oxidation, the nano-sized U3Si2 grains upon radiation-induced grain subdivision were oxidized to nanocrystalline UO2 in a high vacuum chamber for TEM observation, eventually leading to the formation of UO2 nanocrystallites stable up to 80 dpa.
|"High-Resolution TEM Characterization of Neutron-Irradiated U-10Mo Fuel in the Low Temperature and Low Burnup Regime" Sukanya Majumder, Gyuchul Park, Tiankai Yao, Kaustubh Bawane, Cameron Howard, Kourtney Wright, Laura Hawkins, Brandon Miller, Jonova Thomas, Benjamin Beeler, Maria Okuniewski, Materials in Nuclear Energy Systems (MiNES) December 11-14, (2023)
|"Influence of Irradiation-induced Microstructural Defects on the Thermal Conductivity of Single Crystal Thorium Dioxide" Marat Khafizov, Amey Khanolkar, Zilong Hua, Cody Dennett, wangthink Wang, Tiankai Yao, Lingfeng He, Jian Gan, David Hurley, TMS 2020 February 23-27, (2020)
|RTE 1st Call Awards Announced - Projects total approximately $1.4 million These projects will continue to advance the understanding of irradiation effects in nuclear fuels and materials in support of the mission of the DOE-NE. Friday, February 8, 2019 - Calls and Awards
|RTE 2nd Call Awards Announced - Projects total approximately $1.6 million These project awards went to principal investigators from 26 U.S. universities, eight national laboratories, two British universities, and one Canadian laboratory. Tuesday, May 14, 2019 - Calls and Awards
|Outside looking in: Remote capabilities at Research Collaboration Building improve ease of research - Monday, January 15, 2024 - Facility Highlight
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