Steffen Antusch

Materials for DEMO and reactor applications-boundary conditions and new concepts

DEMO is the name for the first stage prototype fusion reactor considered to be the next step after ITER towards realizing fusion. For the realization of fusion energy especially, materials questions pose a significant challenge already today. Heat, particle and neutron loads are a significant problem to material lifetime when extrapolating to DEMO. For many of the issues faced, advanced materials solutions are under discussion or already under development. In particular, components such as the first wall and the divertor of the reactor can benefit from introducing new approaches such as composites or new alloys into the discussion. Cracking, oxidation as well as fuel management are driving issues when deciding for new materials. Here composites as well as strengthened CuCrZr components together with oxidation resilient tungsten alloys allow the step towards a fusion reactor. In addition, neutron induced effects such as transmutation, embrittlement and after-heat and activation are essential. Therefore, when designing a component an approach taking into account all aspects is required.

Two-Component Tungsten Powder Injection Molding for Mass Production of He-Cooled DEMO Divertor Parts

Abstract Fusion technology as a possible and promising alternative energy source for the future is intensively investigated at Karlsruhe Institute of Technology (KIT). The KIT divertor design for the future DEMO fusion power plant is based on a modular concept of He-cooling finger units. More than 250,000 single parts are needed for the whole divertor system, where the most promising divertor material, tungsten, must withstand steady-state heat loads of up to 10 MW/m2. Powder injection molding (PIM) as a mass-oriented manufacturing method of parts with high near-net-shape precision has been adapted and developed at KIT for producing tungsten parts, which provides a cost-saving alternative compared to conventional machining. While manufactured tungsten parts are normally composed of only one material, two-component PIM applied in this work allows the joining of two different materials, e.g., tungsten with a tungsten alloy, without brazing. The complete technological process of two-component tungsten PIM of samples, including the subsequent heat-treatment process, is outlined. Characterization results of the finished samples, e.g., microstructure, hardness, density, and joining zone quality, are discussed.

Manufacturing and characterization of PIM-W materials as plasma facing materials

Powder injection molding (PIM) was used to produce pure and particle reinforced W materials to be qualified for the use as plasma facing material. As alloying elements La2O3, Y2O3, TiC, and TaC were chosen with a particle size between 50 nm and 2.5 μm, depending on the alloying element. The fabrication of alloyed materials was done for different compositions using powder mixtures. Final sintering was performed in H2 atmosphere at 2400 °C resulting in plates of 55 × 22 × 4 mm3 with ~98% theoretical density. The qualification of the materials was done via high heat flux testing in the electron beam facility JUDITH-1. Thereby, ELM-like 1000 thermal shock loads of 0.38 GW m−2 for 1 ms and 100 disruption like loads of 1.13 GW m−2 for 1 ms at a base temperature of 1000 °C were applied. The obtained damage characteristics, i.e. surface roughening and crack formation, were qualified versus an industrially manufactured pure reference tungsten material and linked to the materials microstructure and mechanical properties.

Assessment of copper based materials for the Water-Cooled Divertor concept of the DEMO European Fusion reactor

High Heat Flux component fabrication for the DEMO European Fusion reactor requires the development of structural materials that exhibit high thermal conductivity, strength and radiation resistance. Depending on the cooling concept used (Water or Helium), several different materials are typical candidates for the divertor structural application, such as Tungsten alloys, Copper alloys, or Reduced Activation Ferritic Martensitic (RAFM) steels. This paper focuses on the use of Copper materials for Water-Cooled Divertor concepts. In this work, several possible solutions based on alternative copper material development were investigated. Reinforcement routes based on alloying, dispersion strengthening and composite material were studied. Material production was performed by several conventional melting processes on a laboratory scale. The produced materials were then characterized and compared using metallography, mechanical and thermal properties.

Newly developed innovative manufacturing technologies for He-cooled DEMO divertor

A modular He-cooled divertor concept for DEMO has been developed at Karlsruhe Institute of Technology (KIT). The design goal is to achieve a DEMO-relevant high heat flux of 10 MW/m2. The reference design HEMJ (He-cooled modular divertor with multiple-jet cooling) uses small tungsten-based cooling finger modules. The divertor parts are connected by brazing. They are cooled by helium impinging jets. After the performance and functionality of design has been confirmed through numerous high heat flux (HFF) tests, the current R&D focuses on the manufacturing technology in order to arrive at a robust design and a mass-production of parts. In this paper, newly developed innovative technologies for manufacturing tungsten-based divertor modules (e.g. deep drawing, powder injection molding) as well as for joining the components of different materials shall be presented.

He-cooled divertor for DEMO: Technological studies and experimental verification of the design

A modular He-cooled divertor concept for DEMO is being investigated at Forschungszentrum Karlsruhe (FZK) within the framework of the EU power plant conceptual study. The design goal is to reach a heat flux of at least 10 MW/m2. The reference divertor design is based on the use of a tungsten tile which is brazed to a thimble made of W-1wt%La2O3 cooled by helium impingement jets. The current divertor work programme focuses on manufacture and high-heat-flux tests of prototypical tungsten mock-ups to demonstrate the manufacturability and the performance of the design. Till now three high-heat-flux test series on 1-finger mock-ups were successfully performed in a combined helium loop and TSEFEY facility at Efremov. Technological study on fabrication of a 9-finger module of stain less steel was carried out. First gas flow tests showed uniform mass flow rate distribution which agrees well with calculation results. These initial test results confirm the performance of this concept and serve as a strong basis for further development of the material and concept and more integrated testing.