A brief summary of the progress on the EFDA tungsten materials program

Abstract

The long-term objective of the European Fusion Development Agreement (EFDA) fusion materials programme is to develop structural and armor materials in combination with the necessary production and fabrication technologies for reactor concepts beyond the International Thermonuclear Experimental Reactor. The programmatic roadmap is structured into four engineering research lines which comprise fabrication process development, structural material development, armor material optimization, and irradiation performance testing, which are complemented by a fundamental research programme on ''Materials Science and Modelling.'' This paper presents the current research status of the EFDA experimental and testing investigations, and gives a detailed overview of the latest results on materials research, fabrication, joining, high heat flux testing, plasticity studies, modelling, and validation experiments.Corresponding author. Michael Rieht

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“…"In general, High-Z core concentrations decrease with increasing density [43,46,47], as expected from the reduction of physical sputtering with edge temperature, and are lower (by factors of 2.5-10) in the divertor than in limiter geometries [47][48][49][50]. "…”

“…Like the protection layer of the first wall, the plasma facing divertor parts are intended to be made of tungsten or tungsten alloys. In helium cooled divertor designs tungsten materials are also considered for structural use (e.g., as pressurized pipes or thimbles) [49,50]. Since the requirements for both applications (armor or structure) are quite different, in this paper we distinguish between armor and structural materials which in both cases could be made of tungsten.…”

“…As a last option, however, the effect of titanium has still to be investigated. [49,50]" Experiments to test thermal shock and fatigues have been performed in Jülich and Garching [63][64][65] varying the power flux from 0.19 and 1.13 GW/m 2 and the temperature from 25˝C to 400˝C with a load of pulsed from 100-1000 per 1 ms concluding that "the most promising material so far is W-1 vol.%Y 2 O 3 showing as yet no crack formation, while pronounced cracking is observed in W-5 vol.%Y 2 O 3 and W-5 wt.%Ta materials under similar loadings [49,50]"…”

“…Thin films of such alloys showed a strongly reduced oxidation rate compared to pure tungsten. However, the formation of brittle tungsten silicide may be disadvantageous for the powder metallurgical production of bulk W-Cr-Si alloys if a good workability is needed [49,50]." Several oxidation tests have been made with different W-based alloys at a temperature of 1073 K for 3 hours (see Table 1 taken from [69]).…”

“…Table 1 shows good results for Tungsten-Chromium-Titanium alloys. The amour of first wall needs a certain thickness (in the order of millimeters) using the above mentioned combinations (W-Cr-Si and W-Cr-Ti) obtaining a quasi-dense material [49,50,70,71]. "So far, thin tungsten plates show the best ductility, as long as specific fabrication or machine rules are followed: (1) stress concentrators have to be avoided and (2) the anisotropic microstructure has to be aligned to the contour of the according part.…”