Materials in Nuclear Energy Systems (MiNES) 2021: Material Properties Evolution- Session I
Program Organizers: Todd Allen, University of Michigan; Clarissa Yablinsky, Los Alamos National Laboratory; Anne Campbell, Oak Ridge National Laboratory

Wednesday 4:00 PM
November 10, 2021
Room: Allegheny
Location: Omni William Penn Hotel

Session Chair: Stuart Maloy, Pacific Northwest National Laboratory


4:00 PM  
Development of a Multicomponent Ideal-solution (MCIS) Free Energy Phase-field Model for Simulation of Nuclear Materials Microstructural Evolution: Chaitanya Bhave1; Amani Cheniour2; Daniel Schwen3; Michael Tonks1; 1University of Florida; 2Oak Ridge National Laboratory; 3Idaho National Laboratory
    The development of grand-potential (GP) based phase-field models requires an analytical inverse function for the concentration of the chemical components in terms of the chemical potentials. Due to the lack of such an inverse function for multicomponent ideal solution free energy functions, past GP models have required the use of simpler free energy functions, limiting the physical accuracy of the models. In this work, we derive a general inverse function for an ideal solution approximation free energy system with multiple components on a single lattice. This MCIS model is then applied to two problems of interest in nuclear materials evolution – molten salt corrosion of Ni-Cr alloys, and intragranular fission gas bubble growth in UO2. The model predictions are compared against predictions made using the Kim-Kim-Suzuki phase-field model to evaluate model accuracy and computational performance.

4:20 PM  
Effect of the Inner Liner on Radial Delayed Hydride Cracking: Aaron Colldeweih1; Pavel Trtik1; Francesco Fagnoni1; Johannes Bertsch1; 1PSI
    This work investigates radial DHC in unirradiated Zircaloy-2 cladding material with an inner liner. DHC is induced through a three-point bending test from the outside-in direction. Post DHC examinations were conducted with light optical microscopy (LOM), scanning electron microscopy (SEM), and high-resolution neutron radiography. Metallography analysis has characterized the hydrogen precipitation near and around the crack tip, as well as at the liner/matrix interface in front of the crack tip. Fractography analysis was employed to quantify the crack velocities and determine stress intensity factors in combination with finite element modeling (FEM). Through FEM, stress fields as well as stress intensity factors expected at various stages of crack propagation are calculated. At the SINQ spallation neutron source of the Paul Scherrer Institut (PSI), using the Neutron Microscope detector, radiography provided quantitative information about the hydrogen concentration distribution throughout the sample, specifically at and between the liner/matrix interface and crack tip.

4:40 PM  
Effects of Heat Treatment, Build Angle and Radiation Type on the Hardness and Microstructure of Inconel 625 and 718 Fabricated via Laser-powder Bed Fusion Additive Manufacturing: Valentina O’Donnell1; Mohanish Andurkar2; Tahmina Keya3; Ashley Romans3; Greyson Harvill3; John Gahl1; Scott Thompson2; Bart Prorok3; 1University of Missouri; 2Kansas State University; 3Auburn University
    Various Inconel 625 and 718 specimens, manufactured via Laser-Powder Bed Fusion (L-PBF), were investigated for micro and nano-hardness, as well as microstructure, before and after irradiations performed at the University of Missouri Research Reactor Center (MURR). Specimens were exposed to a variety of radiation environments. These included a neutron flux of 6.3x10^13 neutrons/cm²/s in the MURR reactor, an accelerator driven fast neutron flux of 3.0x10^9 neutrons/cm²/s, and a direct proton irradiation in excess of 10^14 protons/cm²/s. The MURR cyclotron facility features a 16.5 MeV GE PETtrace cyclotron situated in a vault, allowing for beam extraction and solid target irradiation as well as fast neutron production. Results indicate that, independent of radiation source/type, all L-PBF specimens harden less due to irradiation relative to the wrought control group. Heat treatments at various time lengths and temperatures were found to produce precipitates in the Inconel alloys that affect hardness and radiation damage.

5:00 PM  
Mechanical Testing of Fuel Cladding Tubes: Benjamin Eftink1; Mathew Hayne1; Thomas Nizolek1; Cheng Liu1; Tarik Saleh1; Stuart Maloy1; 1Los Alamos National Laboratory
    Mechanically evaluating tube material is difficult, particularly in the hoop direction. While tensile samples may be extracted to test along the length of the tube, microstructural anisotropy due to processing means those results do not necessarily represent the tube properties in the hoop direction. Compounding the problem is that common techniques for testing tubes, such as burst tests, are difficult to implement and require large quantities of material. Research will be presented on efforts to refine a ringpull mechanical testing technique using analytical strain calculations and digital image correlation. As a result a test fixture was developed that can accommodate a range of tube diameters while being suited for hot-cell testing environments for activated samples. Test results will be from accident tolerant FeCrAl fuel cladding.

5:20 PM  
Accessing High Damage Level Microstructures Using Combined Ion and Neutron Irradiation of a 304L Stainless Steel: Zhijie Jiao1; Samara Levine2; Miao Song2; Chad Parish3; Gary Was1; 1University of Michigan; 2University of Tennessee; 3Oak Ridge National Laboratory
    Feasibility of extending the neutron irradiated microstructure to high damage level using ion irradiation was investigated on 304L SS. The alloy was previously irradiated in the BOR-60 reactor to 5.5 dpa at 320°C and was subsequently irradiated with a 9 MeV Ni3+ ion beam at 10-3dpa/s to a dose of 47.5 dpa at 380, 400 and 420°C. The irradiated microstructures were compared against those from the neutron irradiated sample at the same dose. Combined irradiation produced a better match of radiation-induced segregation (RIS) profiles compared to the ion-only irradiations. The MIK model revealed that the high sink densities established at 5.5 dpa mitigated dose rate sensitivity of RIS at the grain boundary. While all combined irradiation temperatures failed to reproduce Cu-rich precipitates, combined irradiation at 400°C produced a better overall match of Ni/Si-rich precipitates and RIS observed in neutron irradiated sample.