Title:	Mechanical, fracture and termodynamic modelling of reactor materials
DNr:	SNIC 2022/5-497
Project Type:	SNIC Medium Compute
Principal Investigator:	Pär Olsson <par.olsson@mau.se>
Affiliation:	Malmö universitet
Duration:	2022-11-01 – 2023-11-30
Classification:	10304
Keywords:

Abstract

The purpose of this project is to investigate (i) the impact of impurities and transmutation products on the mechanical and fracture mechanical properties fusion reactor materials and (ii) the vibrational and thermodynamic properties of uranium, titanium, yttrium and zirconium hydrides. For the first project, we aim to use classical and quantum mechanical modelling to probe the effects of transmutation elements on the grain boundary strength of tungsten alloys. To this end we aim to fit empirical potentials to describe the cohesion in W-Re and W-Os alloys. They will be designed using the force-matching method, as implemented in the potfit software, in which forces and energies from DFT configurations are used to train the empirical potential. The generated potentials will be also used to investigate the impact of Re and Os impurities grain boundary decohesion. Such data will be generated to train a scale-bridging machine-learning surrogate that describes the mechanical properties of interfaces and can be used in continuum modelling to investigate the fracture of grain boundaries. We further aim to investigate the interaction between dislocations and transmuted precipitates, to quantify the hardening in fusion materials due to irradiation-induced coherent, semi-coherent and incoherent precipitates. This aims to provide data to parameterize the Bacon-Kochs-Scattergood (BKS) relation that will be used for macroscopic modelling to quantify the precipitate hardening effect. For the final part of the project, we will compute the phonon spectra of zirconium, titanium, yttrium and uranium hydrides. This serves two purposes: (i) to support experimental activities associated to devising a new method to use ultra-cold neutrons for characterizing the hydrogen content in hydride phases and (ii)) to generate thermal scattering laws (TSLs) for neutron interaction. The experimental activities will be performed under the supervision of Dr. Takeyasu Ito at the Neutron Science Center at Los Alamos Science Lab, while the researchers in Lund and Malmö will support the experimental activities with first-principles DFT data regarding phonon and thermodynamic properties. Owing to their relevance in nuclear reactor and light weight material applications, we are particularly interested in probing the vibrational properties of uranium hydrides (UHx), yttrium (YHx), titanium (TiHx) and zirconium hydrides (ZrHx). Owing to the difficulty to reproduce experimental hydrogen phonon spectra using conventional force-constant methods, we need to use ab initio molecular dynamics (AIMD) modelling to probe the dynamics of the system. For postprocessing purposes we will rely mainly on the TDEP package, which enables the extraction of finite temperature phonon data, including anharmonic effects, and has proven reliable to extract hydrogen phonon density of states. For the TSL generation, we have established a collaboration with another research group at Los Alamos, which we will support by providing additional thermodynamic and vibrational data associated with hydrides.