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JAEA Reports

Structural investigation of simulated waste glass surface drained in operation confirmation test of 3rd TVF glass melter

Nagai, Takayuki; Hasegawa, Takehiko*

JAEA-Research 2023-008, 41 Pages, 2023/12

JAEA-Research-2023-008.pdf:7.52MB

To reduce the risks posed by stored the high-level radioactive liquid waste (HAW), Tokai Vitrification Facility (TVF) is working to produce the HAW into vitrified bodies. With the aim of steady vitrification of HAW in TVF, the vitrification technology section has manufactured a new 3rd melter with an improved bottom structure and is working to verify the performance of this melter. In this study, solidified glass samples were taken from simulated vitrified bodies produced by flowing molten glass during the bottom drain-out test in the operation confirmation of the TVF 3rd melter. And the properties of the surface layer and fracture surface of the vitrified bodies were evaluated by using Raman spectroscopy, synchrotron radiation XAFS measurement, and laser ablation inductively coupled plasma atomic emission spectroscopy (LA ICP-AES) analysis. As a result of measuring the surface layer and fracture surface of the solidified samples produced on an actual scale, a slight difference was confirmed between the properties of the surface layer and those of the fracture surface. Since the chemical composition of these simulated vitrified bodies does not contain platinum group elements, it is expected that the glass structure of solidified glass samples is different from that of the actual vitrified body. However, this sample measuring was a valuable opportunity to evaluate samples produced by using the direct energized joule heating method. The properties of cullet used the operation confirmation of the TVF 3rd melter and the cullet of another production lot were measured and analyzed in the same manner under the measuring conditions of solidified glass samples. As a result, it was confirmed that cullet with different producing histories have different glass structures even with the same chemical composition, and that differences in glass structures remain in the glass samples after melting these cullet.

JAEA Reports

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 $^{circ}$ 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