Materials in Nuclear Energy Systems (MiNES) 2021: Fundamental Irradiation Damage- Session I
Program Organizers: Todd Allen, University of Michigan; Clarissa Yablinsky, Los Alamos National Laboratory; Anne Campbell, Oak Ridge National Laboratory
Tuesday 8:00 AM
November 9, 2021
Room: Allegheny
Location: Omni William Penn Hotel
Session Chair: Grace Burke, Oak Ridge National Laboratory
8:00 AM Cancelled
On the Exploitation of Databases to Predict the Embrittlement of Reactor Pressure Vessels: Marta Serrano1; Lorenzo Malerba1; Diego Ferreño2; 1Ciemat; 2Universidad de Cantabria E.T.S. de Ingenieros de Caminos
The integrity assessment of the RPV is traditionally based on the estimation of the radiation damage (hardening and embrittlement) by means of generic embrittlement trend curves (ETC). In this paper, the first results of tasks 4.2 “Machine learning to model RPV LTO” of the EU-funded project ENTENTE, on the estimation of transition temperature shift the based on the use of the ASTM PLOTTER database to train and validate a number of Machine Learning regression models. These results outperform the prediction ability of existing embrittlement trend curves. In addition, the Permutation Importance algorithm was used to identify the most relevant features on the shift and the Partial Dependence Plots were used to estimate the individual influence of each of the features. This work received partial financial support in the frame of the Euratom research and training programme 2019-2020 under grant agreement No 900018 (ENTENTE project)
8:40 AM
Next Steps for Improved Defect Production and Mixing Parameters: Beyond NRT DPA, ARC-DPA and RPA: Steven Zinkle1; 1University of Tennessee
Quantitatively accurate model predictions of radiation effects processes in materials requires knowledge of several defect production and mixing parameters. The international benchmark for defect production (NRT dpa) was developed in the mid 1970s based on relatively simplistic binary collision approximation simulations, and was shown to be inaccurate for energetic displacement cascades within two years of its publication. Two improved parameters known as athermal recombination corrected (ARC-DPA) and replacements per atom (RPA) have recently been recommended to account for in-cascade recombination and mixing in energetic displacement cascades. However, these parameters are only valid for temperatures near absolute zero. Consideration of correlated recombination effects leads to additional modifications of the NRT dpa value for all irradiation sources. This presentation will summarize experimental and modeling studies that indicate the correlated recombination-corrected defect production (CORR-DPA) at elevated temperatures is ~20-30% of the NRT dpa for energetic cascades and electron irradiations, respectively.
9:00 AM
Comparison of Temperature-dependent Swelling Behavior in FCC Compositionally Complex Alloys and 316H Stainless Steel under Heavy-ion Irradiation: Calvin Parkin1; Michael Moorehead1; Mohamed Elbakhshwan1; Kumar Sridharan1; Lingfeng He2; Adrien Couet1; 1University of Wisconsin-Madison; 2Idaho National Laboratory
In-core structural materials for advanced reactor designs are expected to demonstrate superior resistance to environmental degradation to currently-licensed stainless steels and ferritic-martensitic steels. Compositionally complex alloys (CCAs), which have already shown reduced void swelling compared to less complex binary and ternary alloys, present the opportunity to advance fundamental understanding of matrix composition as a design parameter for irradiation resistance, opening novel alloy design pathways for advanced reactor applications. To compare their swelling behavior to conventional structural materials, two FCC CCA compositions were irradiated to 100 dpa alongside 316H stainless steel at the UW Ion Beam Laboratory using 4MeV Ni ions at multiple temperatures. TEM characterization of irradiated samples is performed to determine the swelling as function of temperature as well as void size and elemental distribution as function of depth. The swelling-temperature bell shape curves are used to assess the void swelling resistance of CCAs relative to more conventional alloys.
9:20 AM
Free Surface Impact on Radiation Damage in Pure Nickel by In-situ Self-ion Irradiation: Can It be Avoided?: Kan Ma1; Brigitte Décamps2; Thomas Jourdan1; Frédéric Prima3; Marie Loyer-Prost1; 1Cea; 2CNRS/ Université Paris-Saclay; 3PSL Research University, Chimie ParisTech-CNRS
In-situ irradiation in a Transmission Electron Microscope (TEM) is a powerful tool to study microstructural evolution, and obtain an insight into dynamic mechanisms of fundamental radiation damage. Howerver, a major issue of these studies is the influence of free surfaces, acting as a strong sink for radiation-induced defects.In this work, in-situ irradiation experiments are combined with a calculation model to get a better understanding of the so-called surface effect and determine in which conditions it could be avoided. Nickel is chosen for the high mobility of its self-interstitials. Ultra-high purity Ni thin foils are in-situ irradiated by 2 MeV Ni2+ ions at high temperatures (400-700°C) using the JANNuS-Orsay facility. Microstructural evolution and dislocation loop characteristics are finely analyzed in function of specimen thickness.
9:40 AM
Pushing towards the Limits in Characterization of Radiation Damage: Joven Lim1; Eric Prestat2; Andrea Sand3; Daniel Mason1; Aslak Fellman4; Quentin Ramasse5; Grace Burke2; 1UKAEA/CCFE; 2University of Manchester; 3University of Aalto; 4University of Helsinki; 5University of Leeds
Being able to image and characterize the nature and characteristics of irradiation-induced defects (ID) at various damage levels in nuclear material is crucial for physics understanding, performance prediction and next-generation materials development. No characterization technique yet exists to provide detailed analysis of ID from less than 1 nm and at atomic level. According to Molecular Dynamics (MD) estimates, ID clusters that are less than 2 nm in size may contribute to ~97% of the overall defect population at low DPA, and these ‘invisible’ ID will have a significant contribution to the hardening effects on the irradiated material. AtomCRaD is a EUROfusion funded project to develop modern advanced Scanning Transmission Electron Microscopy (STEM) technique that couple with STEM image simulation and outputs from MD simulations to characterize small ID, < 2nm in diameter, in crystalline materials. In this talk, we will present the outcomes of AtomCRaD and limitations of this technique.
10:00 AM Break