Mechanical Behavior and Degradation of Advanced Nuclear Fuel and Structural Materials: Structural Materials Characterization & Modelling I
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 2:30 PM
March 1, 2022
Room: 204A
Location: Anaheim Convention Center
Session Chair: Erofili Kardoulaki, LANL; Joshua White, LANL
2:30 PM Invited
Degradation Modes of Core Materials under Multiple Components of the Reactor Environment: Gary Was1; 1University of Michigan
Both current and advanced reactors require that materials operate in extreme environments consisting of high temperature, irradiation, stress, and chemical aggressiveness. Depending on the reactor design and degradation mode, different combinations of these environmental components come into play. Swelling is of greatest concern in sodium cooled reactors and the primary environmental components are temperature and damage. Irradiation creep is of concern in both LWRs as well as high temperature concepts with components under stress, in addition to a high temperature and radiation. Finally, irradiation assisted stress corrosion cracking remains a vexing problem in LWRs and requires all of the environmental components to be at work for the process to occur. These degradation modes occur in progressively more complex environments that make for difficult experimentation. This talk will focus on strategies to capture the effect of multi-modal environments on the various degradation modes in an effort to improve our mechanistic understanding.
3:00 PM
Study of the Irradiation Induced Microstructure and Mechanical Properties in Low Alloyed Ferritic Steels: Maria Vrellou1; Bertrand Radiguet1; Akiyoshi Nomoto2; Philippe Pareige1; 1Groupe de Physique des Matériaux - Université de Rouen Normandie; 2Central Research Institute of Electric Power Industry
Irradiation modifies the microstructure of the Nuclear Power Plant’s structural materials, causing embrittlement and thus possibly limiting their integrity for long term operation. Some details of underlying mechanisms driving this process remain still unclear since the induced microstructure depends on many parameters concerning both irradiation conditions and material history and environment. This study aims to evaluate the impact of Ni, Mn, their synergistic effect and the effect of Cu, on the neutron irradiation induced microstructure of 4 selected model alloys (Fe-1.1Mn-0.7Ni, Fe-1Mn, Fe-1Ni and Fe-0.1Cu), correlating it with the change in their mechanical properties. For this, the unirradiated and irradiated alloys’ microstructure is determined by APT. Irradiation induced hardening calculated from the stress-strain curves is obtained by in-situ micro-compression of FIB-fabricated micropillars. To corelate the irradiation induced microstructure with measured hardening, APT tips and TEM lamellas are lifted out from the compressed pillars. The results will be presented and discussed.
3:20 PM
Neutron Irradiation Effects on Mechanical Anisotropy in Alloy 625: Caleb Clement1; Megha Dubey2; Yu Lu2; Sheng Cheng2; Donna Guillen3; David Gandy4; Janelle Wharry1; 1Purdue University; 2Boise State University/ Center for Advanced Energy Studies; 3Idaho National Laboratory; 4Electric Power Research Institute
The objective of this talk is to understand the effects of neutron irradiation on grain orientation mechanical anisotropy of Ni-based Alloy 625 fabricated by powder metallurgy with hot isostatic pressing (PM-HIP) as compared to traditional forging. Alloys can exhibit considerable orientation anisotropy of yield strength, but it is not well understood how irradiation affects this anisotropy. In this study, Alloy 625 was neutron irradiated in the Advanced Test Reactor to 1 displacement per atom (dpa) at 300°C. Grain structure of irradiated and as-received specimens were observed via electron backscatter diffraction (EBSD), and targeted nanoindentation on [001], [110], and [111] grains was performed. The deformation microstructures were then studied via bright field scanning transmission electron microscopy (STEM). The PM-HIP variant shows less orientation anisotropy in nanoindentation yield strength as compared to its forged counterpart. The deformation microstructures are discussed in the context of Schmid factor and twinning versus slip localization.
3:40 PM Break
4:00 PM
Micromechanical Testing of Femtosecond Laser Machined Tensile Samples of Varied Geometries: Jason Duckering1; Andrew Dong1; Peter Hosemann1; Stuart Maloy2; 1University of California Berkeley; 2Los Alamos National Laboratory
Mechanical testing of materials at smaller length scales enables targeted studies into microstructural features while considering the limitations and handling of irradiated samples. Typical small scale sample preparation techniques require the use of focused ion beam milling which can be both time consuming and infeasible for samples larger than a few tens of microns. Traditional mesoscale machining techniques generally leave a surface finish unsuitable for samples in the tens of microns. This results in an observable data gap and concern in the fidelity and extendibility of small-scale data to bulk scale applications. Femtosecond laser machining enables the rapid and consistent fabrication of micro-mesoscale samples that can fill this data gap. This presentation showcases data obtained from a series of micromechanical tensile samples machined to a range of geometries <100um via femtosecond laser machining. The objective is to elucidate potential size effects in investigating samples at reduced geometries.
4:20 PM
Through-thickness Microstructure Characterization in a Centrifugally Cast Austenitic Stainless Steel Nuclear Reactor Primary Loop Pipe Using Time-of-flight Neutron Diffraction: Matthew Schmitt1; Daniel Savage1; James Wall2; John Yeager1; Chanho Lee1; Sven Vogel1; 1Los Alamos National Laboratory; 2Electric Power Research Institute
Inspection of centrifugally cast austenitic stainless steel pipe, commonly used in primary cooling loops in light-water nuclear reactors, using ultrasonic techniques is not reliable as the microstructure strongly attenuates ultrasonic waves. In order to account for elastic anisotropy in the material, the texture in the steel was measured as a function of radial distance though the pipe wall using the HIPPO time-of-flight neutron diffractometer at the Los Alamos Neutron Science Center (LANSCE, Los Alamos, NM, USA). Strong textures dominated by a small number of austenite grains with their (100) direction aligned in the radial direction of the pipe were observed. ODF analysis indicated that up to 70% of the probed volume was occupied by just three single-grain orientations, consistent with grain sizes of almost 1 cm. Texture and phase fraction of both ferrite and austenite phases were measured along the length of the samples.