International Topical Meeting on Nuclear Research Applications and Utilization of Accelerators

4-8 May 2009, Vienna

Influence of Radiation Damage Obtained Under Fast Charged Particle Irradiation on Plasma-Facing Erosion of Fusion Structural Materials

A.I. Ryazanov, A.N. Bruchanov, O.K. Chugunov, V.M. Gureev , B.I. Khripunov, V.S. Koidan, S.N. Kornienko, B.V. Kuteev, S.T. Latushkin, A.M. Muksunov, V.B. Petrov, V.P. Smirnov, V.G. Stolyarova, and V.N. Unezhev

Russian Research Center “Kurchatov Institute” (RRC KI), Moscow, Russian Federation

Corresponding Author: ryazanoff@comail.ru

Selection of the structural materials for the fusion reactor is a very actual problem. Plasma-facing materials (PFM’s) in diverter and on the first wall of a fusion reactor will be affected by high heat flux, fast particles and 14 MeV neutron irradiation. All these factors are crucial for the lifetime of the fusion structural materials. Fast neutrons produce a high-level of radiation damage (estimated value is up to hundred dpa) in first wall materials during long operation of the fusion reactor. At the same time, PFM’s will suffer radiation erosion induced by the plasma. While important data on the plasma erosion have been collected for non-irradiated materials, it is difficult to qualify PFM’s at present taking into account radiation damage effect. This paper is devoted to the experimental results concerning radiation damage effect on erosion of materials under plasma impact. To obtain a high level of radiation damage, we simulated neutron irradiation using fast ion irradiation with energy interval of 1 — 60 MeV accelerated on the cyclotron at Kurchatov Institute. Using this method we can accumulate the radiation damage equivalent to fast neutron effect at the dose of up to 10²⁶ neutron/m² in a few days operation of the cyclotron. Both carbon materials and tungsten were taken for the study as the targets: MPG-8 (Russian graphite), SEP NB-31 (ITER PFM candidate) and W (99.95% wt). Irradiation of these materials on the cyclotron has been performed with 5 MeV carbon ions (for carbon materials) and α particles 3.4 MeV for tungsten. The experiments have been performed on the materials having accumulated 0.1 — 10 dpa of radiation damage. Plasma erosion was studied on the linear plasma simulator LENTA. Irradiated samples were exposed to steady-state deuterium plasma at 100 eV (D ⁺ ions) to dose of up to 10²⁵ ion/m². The microstructure modification was studied and following comparison has been made on the damaged and non-irradiated materials. Enhancement of the erosion process was detected for the radiation-damaged materials. New experimental approach developed in this work to explore the plasma-facing materials for accounting of neutron effect and the results obtained appear to be important for the further studies of the combined plasma and neutron irradiation effect on fusion PFM’s.

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