Technological Processes for Steel Applications in Nuclear Fusion

Abstract

Plasma facing components for energy conversion in future nuclear fusion reactors require a broad variety of different fabrication processes. We present, along a series of studies, the general effects and the mutual impact of these processes on the properties of the EUROFER97 steel. We also consider robust fabrication routes, which fit the demands for industrial environments. This includes heat treatment, fusion welding, machining, and solid-state bonding. Introducing and following a new design strategy, we apply the results to the fabrication of a first-wall mock-up, using the same production steps and processes as for real components. Finally, we perform high heat flux tests in the Helium Loop Karlsruhe, applying a few hundred short pulses, in which the maximum operating temperature of 550 °C for EUROFER97 is finally exceeded by 100 K. Microstructure analyses do not reveal critical defects or recognizable damage. A distinct ferrite zone at the EUROFER/ODS steel interface is detected. The main conclusions are that future breeding blankets can be successfully fabricated by available industrial processes. The use of ODS steel could make a decisive difference in the performance of breeding blankets, and the first wall should be completely fabricated from ODS steel or plated by an ODS carbon steel.

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“…Oxide Dispersion-Strengthened (ODS) steel can both widen and raise the operating temperature window, which would result in a more efficient fusion reactor [19]. Furthermore, recent advances in fabrication and machining mean that ODS steel could be used in flat blanket first walls [20]. Vanadium alloys, considered a less mature technology [21], can also offer improved high temperature performance relative to RAFM steels [19] but also suffer from high levels of tritium retention and are susceptible to lowtemperature irradiation embrittlement [22].…”

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“…Steamless piping, gorging, casting, bolting, plate, pressure vessels, piping, and feedwater lines; internal stainless steel cladding; steam generator channel heads [30,31] Advanced Nuclear Energy *Fusion RAFM steel (Eurofer97 [180][181][182][183], CLAM [31], Infrafm [31], FB2h [31]; Rusfer [31]; 9Cr-2WVTa [31]) Ferritic steel [31] First wall at reactor, blanket, shield, vacuum vessel, and divertor [30,31] Advanced Nuclear Energy Fusion ODS alloy [31] ODS ferritic alloy [31] Advanced Nuclear Energy…”