Investigation of in-vessel fusion materials

This Master thesis is about investigation of in-vessel fusion materials such as Steel, CuCrZr and Tungsten.

The work will include: (i) mechanical testing, (ii) fracture surface analysis; (iii) finite element modelling.

In-vessel fusion materials are crucial components for the favourable outcome of fusion reactors. These materials are meticulously designed to withstand the harshest operating conditions marked by high heat flux and intense neutron irradiation, while also maintaining plasma purity and facilitating the extraction of power from conductive/convective heat flux in the scrape-off layer and radiation, as well as at the same time contributing to neutron shielding for the vacuum vessel and superconducting magnets. The divertor area of these reactors plays a pivotal role, as it directly manages plasma exhaust and heat dissipation, making it a primary focus for material selection and study.

Within the divertor, three baseline materials for the reactors mentioned before have been identified which are classified as in-vessel: Cu(CrZr), tungsten (W), and Eurofer97 steel. These materials have been selected for its high thermal conductivity and its ionizing radiation resilience at a high-energy environment.

The selection and characterization of these materials for the divertor area of ITER and DEMO are critical steps toward ensuring the reliability, efficiency, and safety of fusion energy production at a commercial scale.

Objective of this Master thesis is to contribute to characterization of mechanical properties of the in-vessel materials by means of mechanical testing (tensile properties) and microstructural investigation (scanning electron microscopy). By conducting these tests and analyses, a deeper understanding of the materials' behaviour under various loading conditions and operational environments can be attained.

Furthermore, mechanical properties obtained from the experimental test will be codified, meaning that results will be translated into a language of design code for fusion reactors. This will be carried out using FEM tool (Ansys).

As a result of the research, the constitutive law that describes the material behaviour (true stress-true strain) for the plastic deformation, as a function of temperature and strain, will be derived, for the optimization of divertor design.

Tentative schedule is as follows:

August 2024: detailed planning for test matrix, focusing on the following key aspects:

• Choice of the test material.
• Test temperature.
• Heat treatment conditions.

September/October 2024: start of the research exchange. The timeline will adjust to the following plan:

Training (1 month):

• Basic training: how to operate equipment will be learn
• FEM instructions will be given.

Experimental work (4-5 months):

• Mechanical test experiments
• SEM analysis
• FEM fit

Scientific training and work (continuous process that will start once results from test are generated):

• Summary of results
• Analysis of the gaps/faults which require repletion of experiment.
• Update of the summary of results.
• Conclusions.

Dissemination of results and learning how to make scientific paper. From this part of the plan the Master’s thesis will be completed and a publication will be prepared:

• Introduction: 2 weeks.
• Describe the used methods: 2 weeks.
• Describe results: 4 weeks.

May/June 2025: End