Speaker
Muyuan Li
(Max-Planck-Institut für Plasmaphysik)
Description
Maintenance of structural integrity under high-heat-flux (HHF) fatigue loads is a critical concern for assuring the reliable HHF performance of a plasma-facing divertor target component. Loss of structural integrity may lead to structural as well as functional failure of the component.
Currently, a full tungsten divertor was chosen by ITER Organization, and plenty of HHF qualification tests have been conducted. The tested prototypes showed that the tungsten monoblock armor often suffered from deep cracking, when the applied HHF load approached 20 MW/m22. The deep cracks were initiated at the armor surface and grew toward the cooling tube in the vertical direction.
The deep cracking seemed not to affect the heat removal capability of tungsten divertor, as most of the cracks were perpendicular to the loading surface. However, the inherently unstable nature of brittle cracking may likely increase the risk of structural failure. Understanding the cracking mechanism is therefore of essential importance for divertor design.
In the previous work [1], a two-stage modeling approach was employed where deep cracking was thought to be a consecutive process of crack initiation and growth, which was assumed to be caused by plastic fatigue and brittle facture, respectively. This theoretical interpretation fitted quite well with the experimental observation and revealed that the key factor for deep cracking was the plastic strain accumulation in the tungsten armor, which seemed hardly avoidable.
In this contribution, designs of tungsten divertor with different dimensions and castellation based on an ITER-like divertor are proposed to avoid deep cracking at 20 MW/m22. The mechanical and fracture behavior are assessed with the aid of finite element simulations. Plastic fatigue and brittle fracture failures in tungsten block are evaluated. The feasibility of manufacturing is also discussed.
[1] M. Li, J.-H. You / Fusion Engineering and Design 101 (2015) 1–8
Co-authors
Jeong-Ha You
(Max-Planck-Institut für Plasmaphysik, Garching, Germany)
Muyuan Li
(Max-Planck-Institut für Plasmaphysik, Garching, Germany)
