The scientific objective of the project is to validate the performance of baseline and novel tungsten grades with a potential to tolerate neutron irradiation damage and to offer enhanced toughness and low swelling as matrix material for tungsten-based composites. The project will be based on:
(a) usage of experimental facilities available at LHMA for microstructural characterization, such as PALS, TEM and SEM-EBSD.
(b) exploitation/development of the computational tool on the basis of kinetic Monte-Carlo techniques to simulate microstructural damage induced by fast and thermal neutrons in BR2 conditions and specifically applied to the TUNER project.
The main technical goal is to describe the irradiation-induced microstructure evolving as a result of neutron damage in a wide temperature range (400-1200 C) as a function of initial material's microstructure and accumulated irradiation dose (0.05, 0.1, 0.5 and 1 dpa). One of the major technological concerns is the formation of voids which results in swelling, loss of thermal conductivity and raise of Ductile to Brittle Transition Temperature (DBTT). Therefore, the primary experimental information is to obtained using PALS coupled with annealing runs to clarify thermal stability of the neutron damage. Transmission electron microscopy will be used as supplementary tool.
In support of PALS/TEM measurements, the rationalization of the experimental results will be performed using physically-based modelling, for which NMS/SMM unit has long experience in applying for similar BCC metal: Iron and Fe-Cr-Carbon alloys. Main computational tool will be kinetic Monte Carlo (KMC) techniques based on the most recent developments done by Dr. Castin (who is also co-mentor for this project) to enable hybridization of object and atomistic methods. This will enable to treat simultaneously both radiation induced objects (i.e. point defects, loops, voids, etc) and transmutation induced Re/Os solutes. Treatment of the transmutation products is absolutely necessary because the high fraction of thermal neutrons in BR2 spectrum as compared to the expected fusion spectrum.
Given the success of the model, the prediction of the impact of neutron damage on the microstructure of baseline and advanced tungsten grades is to be made for expected fusion conditions. This can be done by introducing the relevant fusion spectrum and damage rate, according to available conceptual studies, in the KMC tool and modelling the microstructure in the diverter strike zone, dome and first wall armor parts. This project will therefore help to clarify up to which extend and what is the best way to use the fission irradiation to characterize impact of neutron irradiation in expected fusion conditions.