PNNL

Abstract

Grain boundary (GB) failure in tungsten under shock loading after irradiation is a key factor to estimate the performance of tungsten as a plasma facing material in nuclear fusion reactors. In this work, GB evolution after absorption of different radiation defect clusters under shock loading has been investigated at atomic scale through non-equilibrium molecular dynamics (NEMD) method. Different to the cases without radiation defects, after absorption of interstitial dislocation loops and vacancy clusters, two mechanisms have been identified for the decrease of critical shock velocity (vc) and the related GB failure. The direct void growth, from the remaining vacancy cluster which could not be annihilated by compressive stress wave, is the 1st mechanism. In the 2nd mechanism, activation of slip systems, dislocation formation and motion, and void nucleation and growth dominate the failure process. The preferred slip direction of activated system into the crystal with a higher atomic planar density but a lower atomic linear density is also explored. The higher potential energy and local stress concentration around a defect absorption region in GB are responsible for the decrease of vc and reveal the underlying physics for GB failure that is always triggered from the defect absorption region in GB. These results indicate that under a high dose of radiation damage, GB failure induced by shock loading should be considered seriously in order to estimate the lifetime of tungsten-based plasma facing materials.