Transmutation Effects in Fusion Reactor Materials: Critical Challenges & Path Forward: Experiments & Multiscale Modeling of Solid-state Transmutation
Sponsored by: TMS Structural Materials Division, TMS: Nuclear Materials Committee
Program Organizers: Arunodaya Bhattacharya, Oak Ridge National Laboratory; Steven Zinkle, University of Tennessee; Philip Edmondson, The University Of Manchester; Aurelie Gentils, Université Paris-Saclay; David Sprouster, Stony Brook University; Takashi Nozawa, National Institutes for Quantum and Radiological Science and Technology (QST); Martin Freer, University of Birmingham
Monday 2:00 PM
March 20, 2023
Room: 27B
Location: SDCC
Session Chair: David Sprouster, Stony Brook University; Sergei Dudarev, UK Atomic Energy Authority
2:00 PM Invited
The Effect of Chemical Element Inventory Evolution on Recoil Production and Its Effect on Defect Cluster Evolution in Tungsten: Jaime Marian1; Mark Gilbert2; 1University of California, Los Angeles; 2UKAEA
Calculations of irradiation damage in materials up to reactor-relevant doses presents several challenges, which often leads to restrictive assumptions in the formulation and construction of the models. One such challenge is accounting for changes in chemical inventory and isotopic buildup due to transmutation as the neutron dose increases with time. Here we present results of full chemical inventory calculations and their coupling to the stochastic cluster dynamics technique to carry out calculation of damage accumulation in a model system representing fusion first-wall materials. Our model considers both changes in the damage source function as a function of dose as well as in the number and type of chemical species whose kinetic evolution is tracked with dose. The results can serve to predict the impact of transmutation species on the overall kinetic evolution of tungsten and iron-based alloys.
2:40 PM
Analytical TEM Examination of Re and Os Segregation in Neutron Irradiated Tungsten: Michael Klimenkov1; Ute Jäntsch1; Michael Dürrschnabel1; Michael Rieth1; Dmitry Terentyev2; Wouter Van Renterghem2; 1Karlsruhe Institute of Technology; 2Belgian Nuclear Research Centre
Tungsten is the prime candidate material for plasma-facing components in future fusion reactors due to its several advantageous properties such as a high melting point, high sputtering resistance and low coefficient of thermal expansion. The transmission electron microscopic examination tungsten irradiated in BR2 reactor at various temperatures and damage neutron irradiated tungsten is of high importance for assessing possible limits of operation conditions and life-time of plasma facing components.This work focuses on the analysis of temperature- and dose-dependent rhenium (Re) and osmium (Os) segregation at voids, dislocation loops and grain boundaries. Segregation processes lead to a local Re and Os enrichment under certain conditions formation of σ-W(ReOs)2 and χ-W(ReOs)3 precipitates. The results contribute not only to the understanding of radiation hardening and embrittlement, which significantly limit the lifetime of W devices, but also to the verification and improvement of theoretical models for radiation-induced Re and Os diffusion in W.
3:00 PM
Co-Segregation of Transmuted Re and Os in Neutron Irradiated Tungsten: First-principles Prediction and Experimental Validation: Duc Nguyen-Manh1; Matthew Lloyds2; Jan Wrobel3; Michael Klimenkov4; Luca Messina5; Enrique Martinez6; Mark Gilbert1; 1UK Atomic Energy Authority; 2Singapore University of Technology and Design; 3Warsaw University of Technology; 4Karsruhe Institute of Technology; 5CEA; 6Clemson University
Understanding how the properties of materials change due to nuclear transmutations initiated by exposure to neutrons is a major challenge for the structural components of a fusion power plant. In this study, the multiscale modelling approach based on first-principles calculations has been employed to investigate the co-segregation effect of transmutation-generated solutes in neutron irradiated tungsten over a broad range of Re, Os, Ta and vacancy -defect concentrations. Our Monte-Carlo simulations shows that voids are decorated by Re and Os, but there is no decoration by tantalum (Ta). In the W-Re-Os-Vac system containing 1.5% Re and 0.1% Os, the chemical short-range order parameter between Re-Os is predicted to be negative for the vacancy concentration between 0.05%-0.5%. The modelling results are in an agreement with the APT and STEM experimental observations of transmutation-induced precipitation for both Re and Os in neutron irradiated W exposed at 1200K in High Flux Reactor in Petten.
3:20 PM
Ab Initio Study of Tungsten-based Alloys Under Fusion Power-plant Conditions: Yichen Qian1; Mark Gilbert2; Lucile Dezerald3; Duc Nguyen-Manh2; David Cereceda1; 1Villanova University; 2Culham Centre For fusion Energy; 3Universite de Lorraine
Tungsten is considered a leading candidate for plasma-facing materials (PFMs) in future fusion energy devices. The most attractive properties of tungsten for magnetic and inertial fusion energy reactors are its high melting point, high thermal conductivity, low sputtering yield, and low long-term disposal radioactive footprint. However, tungsten also presents a very low fracture toughness, limiting applications. Given their proximity to the plasma, it is crucial to understand how the exposure of candidate tungsten-based PFMs to the neutron fluxes expected in fusion reactors impacts their material behavior over time.In this work, we present a computational approach that combines inventory codes and first-principles DFT electronic structure calculations to understand the behavior of transmuting tungsten-based PFMs. In particular, we calculate the changes in the chemical composition, the elastic and plastic properties, and the density of states for five tungsten-based PFMs when exposed to EU-DEMO fusion conditions for ten years.
3:40 PM Break
4:00 PM Invited
Experimental Validation of Simulated Transmutation Predictions for Fusion Materials: Mark Gilbert1; Arunodaya Bhattacharya2; Philip Edmondson3; Jean-Christophe Sublet4; 1Ukaea; 2ORNL; 3University of Manchester; 4IAEA
No dedicated fusion facility to study the transmutation effects in prospective fusion reactor materials exists. Therefore, the engineers and scientists designing the fusion reactors that will be constructed in the next two decades must rely on simulations of transmutation response to inform material performance predictions. The reliability of transmutation predictions must be tested in creative ways until fusion reactor operation data becomes available. In this paper we will describe some recent work to test the direct transmutation output from inventory simulation codes, which are the tools able to predict the evolution in material composition (transmutation) under neutron irradiation. Successes include the use of atom probe tomography (APT) to measure transmutation, where inventory codes also help to improve the APT methodology.We also highlight more indirect validation of transmutation predictions via comparison of simulations with radiological measurements, that can be successfully obtained even from low flux fusion neutron sources.
4:40 PM
Ab Initio and Classical Molecular Dynamics Study of Re Transport in W: Osetsky Yury1; German Samolyuk1; 1Oak Ridge National Laboratory
Experiments observed intensive Re clustering and precipitate formation under irradiation conditions. The current assumption is that Re is transported by a non-dissociative low energy interstitial-mediated mechanism that is incorporated into kinetic Monte Carlo modeling parameterized using defect energies derived by ab initio calculations. Here we demonstrate that the fast diffusion path, combining several configurations with similar energies and low-energy transition states between them, may not be realized under the truly dynamic conditions necessary for thermally activated diffusion. Using ab initio molecular dynamics modeling (AIMD), we determined that Re transport is very slow and occurs via a dissociative mechanism. Larger scale classical MD estimated diffusion coefficients and demonstrated that the activation energy for Re transport is controlled by the dissociation energy of the Re-contained interstitial. The overall diffusivity by interstitial migration in W-Re system is decreased by two orders in magnitude compared to pure W.
5:00 PM
Modelling of Re/Os Transmutation Product Segregation in Irradiated W Using Atomistic Kinetic Monte Carlo: Matthew Lloyd1; Robert Simpson1; Enrique Martinez2; Duc Nguyen-Manh3; 1Singapore University of Technology and Design; 2Clemson University; 3United Kingdom Atomic Energy Authority
Precipitation of Re and Os transmutation products is a key contributor to thermal/mechanical property degradation in W under neutron irradiation. A combination of nanoscale voids, precipitates and dislocation loops all lead to embrittlement, and an increase in the ductile to brittle transition temperature. Experimental evidence suggests that the respective population of these defects depends strongly on the dose rate, irradiation temperature, transmutation rate and concentration of transmutation products (which depends on the neutron energy spectrum). In this study we investigate the role of different parameters on the segregation of Re and Os in irradiated W using a solute and defect concentration dependant Ising model. Atomistic Kinetic Monte-Carlo (AKMC) simulations have been carried out at different temperatures and dose rates and compared with experimental data obtained using Atom Probe Tomography (APT) of neutron and heavy-ion implanted W.