Mechanical Behavior and Degradation of Advanced Nuclear Fuel and Structural Materials: Poster Session
Sponsored by: TMS Structural Materials Division, TMS: Mechanical Behavior of Materials Committee, TMS: Nuclear Materials Committee
Program Organizers: Dong Liu, University of Oxford; Peng Xu, Idaho National Laboratory; Simon Middleburgh, Bangor University; Christian Deck, General Atomics; Erofili Kardoulaki, Los Alamos National Laboratory; Robert Ritchie, University of California, Berkeley

Tuesday 5:30 PM
March 1, 2022
Room: Exhibit Hall C
Location: Anaheim Convention Center


N-32: Dynamics of Helium Bubbles during Thermal Annealing: A Data-driven Approach: Kory Burns1; Kayvon Tadj1; Assel Aitkaliyeva1; Khalid Hattar1; Mary Scott1; 1University of Florida
    Helium atoms are immiscible in most metals and can diffuse until they become trapped, agglomerate, and form helium bubbles. With additional energy, these bubbles can also migrate and coalesce into large voids of various size and shapes at grain boundaries, surfaces, or in the matrix. This study aims to couple in-situ transmission electron microscopy (TEM) with deep learning methods to gain a richer understanding of helium bubbles evolution in extreme environments. First, we implant He atoms into a Palladium target and verify their presence. Then, we use in-situ TEM annealing to track the movement and changes in areal density, size, and shape of the resulting cavities. Finally, we employ a U-Net model to characterize the annotated micrographs in their completeness. We expect this method to become widely adopted to help unveil the underlying physics in in-situ TEM experiments. SNL is managed and operated by NTESS under DOE NNSA contract DE-NA0003525.

N-34: Influence of the Bulk Chemical Composition on the Microstructure Evolution of Irradiated Chemically-tailored Nuclear RPV Steels: Aidar Zakirov1; Bertrand Radiguet1; Rachid Chaouadi2; Philippe Pareige1; 1Groupe de Physique des Matériaux - Université de Rouen Normandie; 2SCK CEN
     Irradiation embrittlement of reactor pressure vessel (RPV) steel, partly due to the formation of solute clusters, is one of the main lifetime limitations of nuclear power plants. The bulk concentration of irradiation-sensitive elements such as Cu, P, Ni, Mn and Si impacts the mechanisms and kinetics of formation of these clusters. To study the synergy between Cu and P, Ni and Mn, chemically-tailored steels with variable compositions were irradiated in BR2 reactor. The effect of irradiation on the mechanical properties was measured by tensile tests at room temperature.Microstructural changes after irradiation were studied by Atom Probe Tomography. In this presentation, the evolution of microstructure due to neutron irradiation in RPV steels with different Cu, P, Ni, Mn contents will be reported and discussed, to understand the synergetic effects between these solutes and to improve the prediction of the post-irradiation behavior of RPV steels.

N-35: Investigation of Ion Irradiation Effects on Mineral Analogues of Concrete Aggregates: Zehui Qi1; Steven Zinkle1; Yann Le Pape2; Elena Rodriguez2; Xin Chen3; Gaurav Sant3; 1University of Tennessee, Knoxville; 2Oak Ridge National Laboratory; 3University of California, Los Angeles
    Amorphization and radiation induced volume expansion (RIVE) are considered as the primary causes that limit long-term performance of reactor concrete. To develop a consistent knowledge of irradiation effects in concrete, selected mineral analogues of concrete aggregates were irradiated by light ions. Three minerals (limestone, marble and quartzite) were irradiated by 5.5 MeV He^+ ions at room temperature producing doses of ~0.05, ~0.075 and ~3 dpa for surface, mid-range and peak damage regions (ion fluence of 2.5e17 ions/cm^2). The ion penetration depth was ~23 μm. Irradiation induced cracks were characterized by SEM and EBSD. GIXRD and nanoindentation were used to observe amorphization, RIVE and hardness change. No amorphization was observed in any irradiated mineral, while additional cracks and moderate lattice parameter swelling existed in some of the minerals. Hardness increased in marble and limestone by ~20% while quartzite softened by ~3%. Elastic modulus decrease was observed in all three minerals.

N-36: Stress Distribution of Disk Geometry Under Three-point Bending Tests to Evaluate Mechanical Properties of Neutron-irradiated Tungsten for Future Fusion Devices: Trevor Marchhart1; Nathan Reid2; Lauren Garrison3; Jean Paul Allain1; 1Penn State University; 2University of Illinois; 3Oak Ridge National Laboratory
    Advanced tungsten alloys have shown promise in future nuclear fusion reactors as plasma-facing components. The High Flux Isotope Reactor at Oak Ridge National Laboratory is used to screen potential fusion materials by irradiating 3 mm diameter disks. A miniaturized three-point bend test has been developed to test the mechanical properties of these neutron-irradiated disks. Three-point bend tests create both bending stress and shear stress within a sample, the amount of which is a function of the span-thickness ratio of the sample geometry. A finite element analysis simulation of the experimental set-up using ANSYS was conducted in order to understand the internal stress state of the materials during the three-point bend test and the influence of the sample thickness from 0.1 to 1 mm. The model was validated with experimental results and gives additional insight beyond what can be experimentally measured during the tests.

N-37: Study of Microstructure, Hydrogen Solubility and Corrosion of Ta-modified Zr-1Nb Alloys for Nuclear Applications: Pedro Ferreirós1; Estefanía Savoy Polack2; Liliana Lanzani2; Paula Alonso2; Dante Quirós2; Juan Mieza2; Eugenia Zelaya3; Alexander Knowles1; Gerardo Rubiolo3; 1University of Birmingham; 2Comisión Nacional de Energía Atómica; 3Consejo Nacional de Investigaciones Científicas y Técnicas
    Modified Zr-1Nb alloys with Ta additions is a potential strategy to improve structural alloys for nuclear reactors. The effects of Ta on microstructural stability and resistance to corrosion of Zr–1Nb alloys were systematically investigated and elucidated. The (α+β) microstructure in Zr-1.05Nb, Zr-0.85Nb-0.20Ta and Zr-0.85Nb-0.40Ta (wt.%) alloys were obtained with the following two thermo mechanical processes after a water quenching from βZr: a) annealed at 570 °C for 3840 h and b) a combination of intermediate annealing temperatures and cold rolled steps. Quantitative EDS-TEM analysis together with DSC measurements were used to characterise the changes in phase compositions and the fraction of beta-phase precipitates. Hydrogen solubility was measured in alloys with the first annealed condition. The Ta additions increase the monotectic transformation temperature, improves the steam corrosion at 400 °C and 10 MPa up to 14 days, and decreases slightly the hydrogen solubility. The higher thermal microstructural stability compared to Ta-free Zr-1Nb alloys provide potential advantages for increases in operating temperature or acceleration of precipitation kinetics during thermomechanical processing.