Abstract
Structural materials which face a thermonuclear plasma are subjected to thermal shock and cyclic loading under service conditions, since tokamak devices are usually operated as pulsed-type fusion reactors.
In order to investigate the thermal fatigue behavior of the structural materials for pulsed-type fusion reactors, a new testing apparatus was developed. The testing apparatus was composed of a closed loop fatigue testing unit, an ultra-high vacuum system and a quick heating system.
As the first testing example, thermal fatigue tests were conducted on molybdenum at cyclic temperatures between 500 and 1600°C under complete restraint conditions. Molybdenum materials are to be used as the first wall of the vacuum chamber, fixed limiters and magnetic limiters of JT-60 (JAERI tokama device).
The features of the new testing apparatus and the preliminary result of the thermal fatigue behavior of molybdenum materials are described. The thermal fatigue tests were successfully performed as expectedly. It is noted that molybdenum materials showed a remarkable buldging at the center of all the specimens manufactured from three forming methods, namely sintering, electron-beam melting and vacuum-arc melting.
