Runaway electron beam formation, vertical motion, termination and wall loads in EU-DEMO

TL;DR

This study uses advanced simulations to predict runaway electron behavior, vertical motion, and wall loads in the EU-DEMO tokamak, providing insights into mitigation strategies for future fusion reactors.

Contribution

It offers the first comprehensive predictive analysis of runaway electron dynamics, including formation, vertical motion, termination, and wall impact in a realistic DEMO scenario.

Findings

Runaway electron beams can form under plausible DEMO conditions.

Vertical motion of the beam can occur due to loss of control.

Wall loads from runaway electrons can be significant, informing protection strategies.

Abstract

Runaway electron loads onto material structures are a major concern for future large tokamaks due to the efficient avalanching at high plasma currents. Here, we perform predictive studies using the JOREK code for a plausible plasma configuration in the European DEMO fusion power plant with focus on a pessimistic scenario in which a multi mega-ampere runaway electron beam is formed. The work first comprises axisymmetric predictions of runaway electron beam formation in a mitigated scenario and of the simultaneous vertical motion of the beam due to loss of position control. The subsequent runaway electron beam termination triggered by a burst of MHD activity during the course of the vertical motion is then simulated in 3D with the runaway electron fluid self-consistently coupled to the MHD modes. Finally, the resulting deposition pattern of the runaway electrons onto wall structures is calculated with a relativistic test particle approach. This way, the suitability of a possible sacrificial limiter concept for the protection of first wall components is assessed.