Limitations for tungsten as plasma facing material in the diverse scenarios of the European inertial confinement fusion facility HiPER: Current status and new approaches

Abstract

The high-power laser energy research (HiPER) project was a European project for demonstrating the feasibility of inertial fusion energy based on using direct-drive targets in a shock ignition scheme using a drywall evacuated chamber. HiPER was intended to drive the transition from a scientific proof of principle to a demonstration power plant in Europe. The project was divided into three realistic scenarios (Experimental, Prototype, and Demo) to help identify open problems and select appropriate technologies to solve them. One of the problems identified was the lack of appropriate plasma-facing materials (PFMs) for the reaction chamber. Therefore, a major challenge was to develop radiation-resistant materials able to withstand the large thermal loads and radiation in these reactors. In this paper, we describe the main threats that coarse-grained W would face in the diverse HiPER scenarios. Based on purely thermomechanical considerations, the W lifetimes for the HiPER Prototype and Demo scenarios are limited by fatigue to 14 000 h and 28 h, respectively. The combined effects of thermal load and atomistic damage significantly reduce these lifetimes to just ∼1000 shots for the Experimental scenario and a few minutes and seconds for the Prototype and Demo scenarios, respectively. Thus, coarse-grained W is not an appropriate PFM for the Prototype or Demo scenarios. Therefore, alternatives to this material need to be identified. Here, we review some of the different approaches that are being investigated, highlight the work done to characterize these new materials, and suggest further experiments.