A Preliminary Development of the K-DEMO Divertor Concept

Abstract

A preconceptual design study for the Korean fusion demonstration tokamak reactor (K-DEMO) has been started in 2012. The results of the preliminary concept study on the K-DEMO divertor are summarized in this paper. An up–down symmetric double-null configuration is selected as a primary choice for study with high elongation of 2 and the triangularity of 0.625. For the vertical maintenance of the K-DEMO in-vessel components, upper and lower divertors are subdivided into 32 toroidal modules, respectively. With maintaining its functionality, the poloidal coverage of divertor is restricted to maximize the breeding area of blanket. The plasma radiation from the core and the edge plasma and the fusion neutron wall loading onto the first walls of the in-vessel components were calculated as heat sources to the structures of the in-vessel components. The divertor targets are tilted at $\sim 10^{\circ }$ against separatrix field line to handle the conceived engineering limit of steady 10 MW/ $\text{m}^{2}$ of peak heat flux with $\sim 50$ % of core plasma radiation and $\sim 85$ % of divertor plasma radiation. Divertor adopts tungsten monoblock targets, reduced activation steel-based structures carrying the pressurized water coolant. Also, the preliminary electromagnetic force extrapolated from the ITER disruption events was considered as a mechanical load to the structures in addition to the coolant pressure. The developed concept on the target and structure is supported by preliminary thermohydraulic and structural analyses using ANSYS, which show that the temperature and the stresses are within their allowables.