Divertor of the European DEMO: Engineering and technologies for power exhaust

TLDR

A fusion power plant must exhaust enormous thermal and nuclear heating power through the divertor, which must endure high heat fluxes, erosion, neutron irradiation, and provide cooling, shielding, and gas handling while maintaining structural integrity, safety, maintainability, availability, waste, and cost considerations. This paper presents an overview of the divertor load specifications, design descriptions, and highlights of technology R&D work, and outlines the further work required. It details the design approach and key technology options identified during the Pre‑Conceptual Design phase, based on seven years of R&D. The Pre‑Conceptual Design activities concluded in late 2020, establishing a baseline design and key technology options that were verified by the EUROfusion Divertor team and endorsed by the Gate Review Panel.

Abstract

In a power plant scale fusion reactor, a huge amount of thermal power produced by the fusion reaction and external heating must be exhausted through the narrow area of the divertor targets. The targets must withstand the intense bombardment of the diverted particles where high heat fluxes are generated and erosion takes place on the surface. A considerable amount of volumetric nuclear heating power must also be exhausted. To cope with such an unprecedented power exhaust challenge, a highly efficient cooling capacity is required. Furthermore, the divertor must fulfill other critical functions such as nuclear shielding and channeling (and compression) of exhaust gas for pumping. Assuring the structural integrity of the neutron-irradiated (thus embrittled) components is a crucial prerequisite for a reliable operation over the lifetime. Safety, maintainability, availability, waste and costs are another points of consideration. In late 2020, the Pre-Conceptual Design activities to develop the divertor of the European demonstration fusion reactor were officially concluded. On this occasion, the baseline design and the key technology options were identified and verified by the project team (EUROfusion Work Package Divertor) based on seven years of R&D efforts and endorsed by Gate Review Panel. In this paper, an overview of the load specifications, brief descriptions of the design and the highlights of the technology R&D work are presented together with the further work still needed.