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  • Author: Jiří Matějíček x
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Jiří Matějíček, Barbara Nevrlá, Monika Vilémová and Hanna Boldyryeva

Abstract

Tungsten is a prime candidate material for the plasma-facing components in future fusion devices, e.g. ITER and DEMO. Because of the harsh and complex loading conditions and the differences in material properties, joining of the tungsten armor to the underlying construction and/or cooling parts is a complicated issue. To alleviate the thermal stresses at the joint, a sharp interface may be replaced by a gradual one with a smoothly varying composition. In this paper, several techniques for the formation of tungsten-steel composites and graded layers are reviewed. These include plasma spraying, laser cladding, hot pressing and spark plasma sintering. Structure, composition and selected thermal and mechanical properties of representative layers produced by each of these techniques are presented. A summary of advantages and disadvantages of the techniques and an assessment of their suitability for the production of plasma-facing components is provided.

Open access

Monika Vilémová, Jiří Matějíček, Barbara Nevrlá, Maryna Chernyshova, Pawel Gasior, Ewa Kowalska-Strzeciwilk and Aleš Jäger

Abstract

Tungsten is a prime choice for armor material in future nuclear fusion devices. For the realization of fusion, it is necessary to address issues related to the plasma–armor interactions. In this work, several types of tungsten material were studied, i.e. tungsten prepared by spark plasma sintering (SPS) and by water stabilized plasma spraying (WSP) technique. An intended surface porosity was created in the samples to model hydrogen/helium bubbles. The samples were subjected to a laser heat loading and a radiation loading of deuterium plasma to simulate edge plasma conditions of a nuclear fusion device (power density of 108 W/cm2 and 107 W/cm2, respectively, in the pulse intervals up to 200 ns). Thermally induced changes in the morphology and the damage to the studied surfaces are described. Possible consequences for the fusion device operation are pointed out.

Open access

Petr Zahradník, Josef Frýdl, Vít Šrámek, Bohumír Lomský, František Havránek, Marian Slodičák, Antonín Jurásek, František Šach, Vladimír Černohous, Jindřich Neruda, Jiří Matějíček and Ivo Kupka

Abstract

The Forestry and Game Management Research Institute (Czechia) was founded on 31st October 1921 with the establishment of the Forest Protection Department. In the era before and after the World War II, several more institutes were founded, and they underwent a number of reorganizations during the 1950s and finally took the form more or less corresponding with the current one. The institute went through further major changes in the early 1990s. In the 1950s, the forestry research saw dynamic development, partially also caused by a significant increase in the number of experts and finalization of the original concept of the institutional structure which covered almost all fields of forestry. Research focused on topical issues of the forest management, covering forest protection, silviculture, forest ecology, biology ad breeding of forest trees, seed growing, forest economy, forestry mechanization, forest management planning and game management. Results were provided to the forestry practice, and there also were numerous monographs and both scientific and expert articles which helped disseminate new findings. Many of these findings have been applied up to now and others built the basis for further research that has been followed on by the current generation of researchers.