Design details of bottom shape for the 3rd glass melter in TVF

Asahi, Yoshimitsu; Shimamura, Keisuke*; Kobayashi, Hidekazu; Kodaka, Akira

JAEA-Technology 2021-026, 50 Pages, 2022/03

JAEA-Technology-2021-026.pdf:6.29MB

In Tokai Reprocessing Plant, the highly active liquid waste derived from a spent fuel reprocessing is vitrified with a Liquid-Fed Ceramic Melter (LFCM) embedded in Tokai Vitrification Facility (TVF). For an LFCM, the viscosity of melted glass is increased by the deposition of oxidation products of platinum group elements (PGE) and the PGE-containing glass tends to settle to the melter's bottom basin even after draining glass out. Removal of the PGE-containing glass is needed to avoid the Joule heating current from being affected by the glass, it requires time-consuming work to remove. For the early accomplishment of vitrifying the waste, Japan Atomic Energy Agency is planning to replace the current melter with the new one in which the amount of PGE sediments would be reduced. In the past design activities for the next melter, several kinds of shapes in regard to the furnace bottom and the strainer were drawn. Among these designs, the one in which the discharge ratio of PGE-containing glass would be as much as or greater than the current melter and which be able to perform similar operational sequences done in the current melter is selected here. Firstly, an operational sequence to produce one canister of vitrified waste is simulated for three melter designs with a furnace bottom shape, using 3D thermal-hydraulic calculations. The computed temperature distribution and its changes are compared among the candidate structures. After discussions about the technical and structural feasibilities of each design, a cone shape with a 45 slope was selected as the bottom shape of the next melter. Secondly, five strainer designs that fit the bottom shape above mentioned are drawn. For each design, the fluid drag and the discharge ratio of relatively high viscosity fluid resting near the bottom are estimated, using steady or unsteady CFD simulation. By draining silicone oil from acrylic furnace models, it was confirmed experimentally that there are no vortices