Thermomechanical damage thresholds of tungsten as candidate first wall material under pulsed soft X-ray irradiations

Abstract

In a Z-Pinch driven fusion-fission hybrid reactor (Z-FFR), a thin spherical metal shell and rare Ar buffer gas are introduced to mitigate the transient X-ray bursts to prevent the first wall from fatal damages by intense X-rays, which take almost 20% of the fusion energy yield (approximately 300 MJ). Thereby soft X-rays as well as the EUVs, are believed to become the dominant threatening sources that the first wall will suffer from. Tungsten is chosen to be the prime candidate material of the Z-FFR first wall, and has been tested on ‘QG-I’ facility to determine the single-shot thermomechanical damage thresholds under pulsed soft X-ray irradiations, as well as to verify and validate the modeling and calculating code ‘FWDR1D’. Several tens of tungsten samples as well as zirconium samples were exposed to a variety of X-ray fluences in the range of 0.1 to 0.7 J/cm2 and with an account of more than 20 shots. The theoretical and experimental results meet well, and analysis of the results indicates that tungsten has specific thermomechanical damage thresholds with X-ray fluences in the range of 0.15 to 0.21 J/cm2 under single-shot soft X-ray irradiations.