In-Keun Yu

Fabrication of Li 4 SiO 4 Pebbles Using Slurry Droplet Wetting Method for Solid Breeding Material

Abstract Lithium orthosilicate (Li4SiO4) pebbles are the primary candidate breeder for the Korean Helium-Cooled Solid Breeder test blanket module because of their superior overall performance qualities such as reasonable lithium atom density, favorable tritium release behavior, low activation property, and chemical stability. The aim of this study is to develop a fabrication method for Li4SiO4 pebbles with high sphericity and stable micro-crystalline structure. Li4SiO4 slurry was prepared by mixing Li4SiO4 powder and polyvinyl alcohol (PVA) solution. The Li4SiO4 gel-spheres were made by dropping slurry mixture into hydrogen peroxide (H2O2) solution. The gel-spheres were floated up to the surface of the H2O2 solution after staying at the bottom for a while and then aged on the surface of the H2O2 solution. The gel-spheres were dried at room temperature and sintered at several temperatures for 4 hours in air atmosphere. The sintered pebbles kept the shape of spheres during the sintering process in spite of shrinkage. Furthermore, the pebbles had relatively high sphericity. Also, the effects of PVA content and sintering temperature on the properties of the Li4SiO4 pebbles were investigated.

Low Cycle Fatigue properties at elevated temperature on TIG

Since the Test Blanket Module (TBM) will be operated at the wide range of elevated temperatures under cyclic thermal loading condition, thermal fatigue is one of the key life-limiting factors. The primary candidate for the structural material of TBM is the Reduced Activation Ferritic/Martensitic (RAFM) steel. A TIG welding of RAFM steel is one of key technologies for the fabrication of the TBM. Especially, the integrity of TIG welded RAFM steel under long-term thermal load condition should be guaranteed considering the TBM operation in ITER. In the previous study, a TIG welding condition for the RAFM steel was derived and main results were published. In this study, Low Cycle Fatigue (LCF) test was performed on the base metal and TIG weldment. To confirm the reliability of the TIG welded RAFM steel, the effects of Heat Affected Zone (HAZ) on LCF properties at room temperature and 550 °C were investigated.