A survey of plasma facing materials for fusion power plants

Abstract

A future fusion power plant will confine very hot ionised gas or 'plasma' containing the hydrogen isotopes deuterium and tritium in a toroidal magnetic chamber (or 'tokamak'). The energy from the resulting fusion reactions will be released as energetic a particles and neutrons. The solid material lining of the inner wall of the chamber (the plasma facing material or 'armour') will be exposed to fluxes of particles and radiation and this armour must shield the outer mechanical structures from plasma damage. At the surface of the armour, the physical processes are complex and there will be an interchange of particles between solid and plasma. Where ions strike surfaces, they are implanted and sputtered atoms and neutrals are released into the plasma. Therefore armour and plasma form a coupled system. Projecting from current experimental knowledge, this survey gives a perspective of the conditions and behaviour of three leading candidate plasma facing materials (carbon, beryllium and tungsten) in a power plant.

Spark plasma sintering of tungsten–yttrium oxide composites from chemically synthesized nanopowders and microstructural characterization

“…Tungsten, owing to its high melting point combined with high strength at elevated temperatures, high thermal conductivity and low sputtering yield, is being considered as one of most promising candidates for plasma facing wall material in future fusion reactors [1][2][3][4]. However, a major limitation of its use is the inherently high ductile-brittle transition temperature (DBTT).…”

Chemically produced nanostructured ODS–lanthanum oxide–tungsten composites sintered by spark plasma

“…In modern fusion reactor design, an armor material must have high melting point and stable mechanical properties at elevated temperatures (strength, creep, fatigue etc. ), high thermal conductivity, low coefficient of thermal expansion and thermal shock resistance, reduced activation and high sputtering resistance [1][2][3][4][5]. To bear up the thermal conditions, carbon-carbon composites are good heat conductors but the higher erosion rates and low sputtering resistance make it unacceptable for high quality and stable plasma reaction.…”

“…The rate of materials erosion determines both the service lifetime of components and the quality of the plasma. So far, only tungsten or its alloys seem to be a better choice for longer and smooth running of high quality plasma as well as for economy and efficiency of a commercial fusion reactor [1][2][3][4][5].…”

Influence of H+ ion irradiation on the surface and microstructural changes of a nuclear graphite

“…The erosion by physical and chemical sputtering represented significant material loss contributing to not only reduction of the lifetime of carbon-based facing materials but also impurity buildup in the plasma and amorphous carbon film deposition at other vessel locations [42]. Therefore, the physical and chemical erosion processes have to be studied from the viewpoint of perspective.…”