Materials in Nuclear Energy Systems (MiNES) 2021: Integrated Phenomena- Session III
Program Organizers: Todd Allen, University of Michigan; Clarissa Yablinsky, Los Alamos National Laboratory; Anne Campbell, Oak Ridge National Laboratory
Wednesday 1:30 PM
November 10, 2021
Room: Allegheny
Location: Omni William Penn Hotel
Session Chair: Michael Short, Massachusetts Institute of Technology
1:30 PM Invited
Irradiation Creep and Fatigue Observed via In-situ Electron Microscopy: Khalid Hattar1; Eric Lang1; Shen Dillon2; 1Sandia National Laboratories; 2University of Illinois, Urbana-Champaign
To predict the lifetime of any current or future component in a fission reactor with any degree of certainty requires a fundamental understanding of the materials response to coupled extreme environments. Many recent studies have highlighted that the response of material to two independent sequential harsh environments does not dictate the response to the same environmental exposure when they are simultaneous. We have developed an in-situ Scanning Electron Microscope (SEM) and a Transmission Electron Microscope (TEM) to elucidate the nuances of materials response to these coupled environments. In-situ TEM examples on quantitative room temperature irradiation creep, creep at 1200 °C, high temperature irradiation induced creep, and high cycle fatigue will be presented. Finally, recent efforts to explore coupled liquid, stress, temperature, and radiation environments in both TEM and SEM will be highlighted.SNL is managed and operated by NTESS under DOE NNSA contract DE-NA0003525
2:10 PM
Wear and Friction Behavior of Fuel Pebbles in Molten Fluoride Salt: Gabriel Meric1; Lorenzo Vergari2; Jake Quincey3; Raluca Scarlat2; Terry Merriman4; Micah Hackett1; 1Kairos Power LLC; 2University of California Berkeley; 3Kairos Power/Oregon State University; 4Tribology Associates
Kairos Power’s fluoride-salt-cooled, high-temperature reactor (KP-FHR) technology uses a novel combination of existing technologies to achieve unique levels of economy, safety, flexibility, modularity and security for nuclear power production. The KP-FHR is a pebble-bed design that relies on TRISO fuel particles embedded in a graphite-like pebble as a fuel form. During online refueling and operation, fuel pebbles are continuously circulating through pebble handling systems and the core. Characterizing the friction and wear behavior of pebbles as they roll and slide against structural component surfaces and against each other is important for accurate modeling of the core behavior and to predict pebble wear and wear dust production. This talk will present tribology data and microstructural characterization for graphite sliding against 316H stainless steel and graphite in inert gas and in molten fluoride salt. The results exhibit the lubrication effect of fluoride salts.
2:30 PM
Thermal Gradient Effect on the Helium and Intrinsic Defects Transport Properties in Tungsten: Enrique Martinez Saez1; Dimitrios Maroudas2; Danny Perez3; Nithin Mathew3; Brian Wirth4; 1Clemson University; 2University of Massachusetts; 3Los Alamos National Laboratory; 4University of Tennesse
Materials in a fusion reactor are expected to withstand stringent conditions, with high heat and particle fluxes that will create strong gradients of temperature and concentration of diverse species. Defects and He migrate in the presence of the afore-mentioned gradients. We use nonequilibrium molecular dynamics to study the transport properties of He, and self-interstitials in the presence of a thermal gradient in W. We observe that in all cases, the defects and impurity atoms tend to reside in the hot regions of the system. The concentration profile results in an exponential distribution, in agreement with irreversible thermodynamics. We compute the heat of transport for each species resulting in negative terms, indicating that the mass flux is opposite to the heat flux. These results have important implications to plasma-facing materials in fusion environments. We demonstrate that the steady-state profiles when the mass-heat coupling is considered varies significantly from the decoupled case.
2:50 PM
Dependence of Sink Strength Effects on Defect Evolution in Dual-ion Irradiated Additive-Manufactured HT9: Pengyuan Xiu1; Niyanth Sridharan2; Kevin Field1; 1University of Michigan; 2Lincoln Electric
Additive-manufacturing (AM) is attracting attention in the nuclear materials community for the fabrication of ferritic-martensitic steels due to the flexibility of composition and geometry control of structural components during the build. In this study, the dual-ion-irradiation responses of three conditions of AM-HT9 are evaluated including the as-built (ASB) from the direct-energy-deposition as well as two other conditions from the same build with different post-build heat-treatments (ACO3 and FCRD). The test matrix includes varying irradiation dose from 16.6 dpa to 250 dpa at 445°C, and varying temperatures from 400°C to 480°C with constant injected helium appm/dpa ratio of 4. Significant disparity of radiation responses among the three conditions of AM-HT9 is observed, with ASB condition exhibiting much more retarded defect evolution including Ni-rich clusters and cavity swelling compared to ACO-3 and FCRD. This is probed by discussing the effects of sink strengths in these alloys tailored by AM and heat-treatment processes.
3:10 PM Break