TFTR materials issues and problems during design and construction

TFTR as well as its contemporaries, T15, JT60 and JET, have important contributions to make towards our understanding of plasma conditions In the thermonuclear regime. One of the main objectives of TFTR is to produce fusion power densities approaching those in a fusion reactor, ∼1 Wcm−3, at Q∼1 − 2. TFTR will be the first tokamak to routinely use deuterium tritium, and produce ∼1019 fusion neutrons per pulse. With startup of TFTR on December 24, 1982, the demonstration of physics feasibility of “breakeven” is close at hand. Since TFTR performance will be reactor relevant, the capability of materials/components to withstand the hostile effects of a plasma environment will be presented. It is Intended that designers of future fusion devices benefit from the materials technology developments and applications on TFTR. In an attempt to comply with this mandate, this paper will describe TFTR issues on materials, their developments, selections, problems and solutions. Special emphasis will be given, in particular, to the impurity control devices in TFTR, namely, the limiter and surface pumping system located inside the vacuum vessel. The plasma will interact with these components and they will be subjected to disruptions, a vacuum of 10−6 to 10−8 torr and a nominal temperatures of <250°C. “Painful” materials development problems encountered will be reviewed, as well as important “lessons learned.” A briefing on the materials of construction will be given, with some comments on the problems that developed and their solutions.