Microstructural Processes in Irradiated Materials: Zr-Alloys and Advanced Modeling
Sponsored by: TMS Structural Materials Division, TMS: Nuclear Materials Committee
Program Organizers: Thak Sang Byun, Pacific Northwest National Laboratory; Chu-Chun Fu, Commissariat Ó l'Únergie atomique et aux Únergies alternatives (CEA); Djamel Kaoumi, University of South Carolina; Dane Morgan, University of Wisconsin-Madison; Mahmood Mamivand, University of Wisconsin-Madison; Yasuyoshi Nagai, Tohoku University

Thursday 8:30 AM
March 2, 2017
Room: Del Mar
Location: Marriott Marquis Hotel

Session Chair: Enrique Martinez Saez, Los Alamos National Laboratory; Fabien Onimus, CEA-Saclay

8:30 AM  Invited
Deformation Mechanisms and Radiation Induced Damage in Zirconium Alloys: A Multi-scale Approach: Fabien Onimus1; L. Dupuy1; Frederic Mompiou2; M. Bono1; 1CEA; 2CEMES-CNRS
    Zirconium alloys are used as cladding tubes for the fuel of nuclear water reactors. In-reactor, zirconium alloys are subjected simultaneously to mechanical loadings and neutron irradiation. In order to gain a better understanding of the radiation effect on deformation mechanisms and on the resulting mechanical behavior, a multiscale study has been undertaken. Mechanical tests have been conducted on neutron irradiated tubes. The deformation mechanisms have been analyzed by TEM. A process of removal of irradiation defects by gliding dislocations has been observed. Then Zr ion irradiations have been performed allowing conducting tensile tests in situ, inside the TEM. Interactions between dislocations and irradiation defects have been observed in situ and also simulated using a novel dislocation dynamics code. Finally, a polycrystalline model, that takes into account these mechanisms, has been developed and compared, with success, to both loading path change tests and TEM observations.

9:00 AM  
Quantifying Irradiation-induced Defect Densities in Zr Through Changes in X-ray Diffraction Line Profiles - Insights from Atomistic Modeling.: Rory Hulse1; Christopher Race1; Michael Preuss1; 1University of Manchester
    Irradiation-induced growth (IIG) of Zr-alloy nuclear fuel cladding under irradiation can limit the service life of nuclear fuel. IIG is believed to occur due to the formation and growth of dislocation loops. Current efforts to create Zr-alloys that are resistant to IIG rely on accurate determination of dislocation density and type in irradiated candidate alloys. X-ray diffraction (XRD) can, in principle, provide this information via an analysis of changes to the diffraction peak shapes. However uncertainty exists in correlating XRD data to defect density and type for the case of irradiation-induced defects. We have utilized atomistic models of controlled defect populations in pure Zr to generate theoretical XRD profiles. These are compared with experimental profiles and changes in line shape are analyzed in terms of contributions from the strain fields of individual defects. These insights will allow more accurate quantification of irradiation-induced defects with XRD.

9:20 AM  Cancelled
Effects of Heavy-ion (Zr+) Irradiation on Zr-2.5Nb Alloy Studied by X-ray Diffraction, Nanoindentation, and TEM: Qiang Wang1; Levente Balogh1; Mark Daymond1; Zhongwen Yao1; 1Queen's University
    Zr-2.5Nb pressure tube alloy was irradiated by Zr+ along both transverse and axial directions of the tube at room temperature. X-ray diffraction and nanoindentation test have been carried out to investigate the developments of irradiation defects and hardness. The X-ray diffraction was conducted at room temperature while the hardness was test from room temperature to 350░C. The dislocation densities, arrangements, and characters were quantitatively determined by modern whole pattern diffraction line profile analysis (DLPA). Both X-ray diffraction and hardness results showed obvious orientation dependence. Hardness of the cross-sectional samples was also tested. Post-mortem studies of the irradiated and deformed samples were conducted by Transmission Electron Microscope (TEM). The results were discussed in terms of irradiation effects, microstructural distributions and plastic deformation mechanisms.

9:40 AM  
In-Situ TEM Triple Beam Irradiation of Zirconium Alloys at Elevated Temperature: Brittany Muntifering1; Khalid Hattar1; David Senor2; Clark Snow1; 1Sandia National Laboratories; 2Pacific Northwest National Laboratory
    The aggressive environment of nuclear reactors present a wide range of material challenges. This is exemplified in the tritium-producing burnable absorber rod (TPBAR), in which displacement damage, helium production, and hydrogen isotope production all occur simultaneously at elevated temperatures. In this in-situ ion irradiation transmission electron microscope (TEM) experiment, we examined the effects of zirconium alloys to both sequential and concurrent implantations of 10 keV D2 and He ions, as well as 3 MeV zirconium ions, all done at 300 ˚C. Defect evolution, including dislocation loop and cavity growth, was characterized as a function of irradiation order and synergy. The culminating study of this investigation was an overnight in-situ triple beam irradiation experiment at elevated temperatures. Finally, detailed post-irradiation examination was done to understand the long term stability of zirconium alloys exposed to these combinations of aggressive and complex environments.

10:00 AM Break