Xiancai Meng

Compatibility of Molybdenum, Tungsten, and 304 Stainless Steel in Static Liquid Lithium Under High Vacuum

Molybdenum (Mo), tungsten (W), and stainless steel (SS) are widely used as important structure materials and first wall materials in fusion devices, while liquid lithium (Li) limiter/divertor can provide an attractive option for withstanding high heat load and solving life-time problem of first wall. Studying the compatibility of these materials exposed to liquid Li is significant for the application in Mo, W, and SS in fusion reactors. The corrosion behaviors of Mo, W, and 304SS exposed to static liquid Li at 600 K up to 1320 h under high vacuum with pressure 10−4 Pa were investigated. After exposure to liquid Li, it was found that the weight loss of Mo, W, and 304SS increases with corrosion time, but the total amount is moderate. 304SS specimens produce a non-uniform corrosion behavior because of Cr, Ni, and carbon (C) elements selectivity depletion and formation of carbides compound near surface. Mo and W surface microstructures are unchanged. 304SS surface hardness increases with corrosion products because these particles include C element, which increases by 49 HV after exposed to liquid Li for 1320 h, while Mo and W surface hardness are unchanged by the reason of their excellent corrosion resistance.

Upgraded flowing liquid lithium limiter for improving Li coverage uniformity and erosion resistance in EAST device

We report on design and technology improvements for a flowing liquid lithium (FLiLi) limiter inserted into auxiliary heated discharges in the experimental advanced superconducting tokamak device. In order to enhance Li coverage uniformity and erosion resistance, a new liquid Li distributor with homogenous channels was implemented. In addition, two independent electromagnetic pumps and a new horizontal capillary structure contributed to an improvement in the observed Li flow uniformity (from 30% in the previous FLiLi design to >80% in this FLiLi design). To improve limiter surface erosion resistance, hot isostatic press technology was applied, which improved the thermal contact between thin stainless steel protective layers covering the Cu heat sink. The thickness of the stainless steel layer was increased from 0.1 mm to 0.5 mm, which also helped macroscopic erosion resilience. Despite the high auxiliary heating power up to 4.5 MW, no Li bursts were recorded from FLiLi, underscoring the improved performance of this new design.