Inverse identification of tungsten static recrystallization kinetics under high thermal flux

Understanding of recrystallization phenomenon is essential to apprehend damage process of tungsten armored plasma facing components and to optimize their use in tokamak environment. In ITER, plasma facing components will reach extreme surface temperature value up to 2000 degrees C. Up to now, recrystallization kinetics of ITER tungsten grade were investigated from 1150 degrees C to 1350 degrees C. In order to understand tungsten recrystallization process on the wider relevant temperature range, kinetics have to be investigated at higher temperature and on several tungsten grades. Usually, kinetics are investigated by performing successive isothermal annealings on tungsten samples. Due to number of ITER tungsten grades and large temperature range (from 500 degrees C to 2000 degrees C), an important amount of tungsten samples have to be prepared to investigate recrystallization kinetics on ITER representative conditions. In this paper, an innovative way is proposed to obtain recrystallization kinetics of ITER tungsten grade based on the use of small-scale plasma facing component tested under high heat flux. Thanks to the use of this inverse method, tungsten recrystallization kinetics are identified at 1348 degrees C (+/-)( 29), 1480 degrees C (+/-)( 29), 1586 degrees C (+/- )(28) and 1696 degrees C (+/- 27) by using experimental measurements and Johnson-Mehl-Avrami-Kolmogorov model. Then, obtained kinetics are used as input data in numerical post-treatments to obtain tungsten recrystallization gradients after 500 thermal cycles at 20 MW/m(2).