Glass - Back to the Future!

Presenting Author:
Tetsuji Yano

article posted 23 March 2016

Tetsuji Yano 1995 Doctor of Engineering from Tokyo Institute of Technology. After the assistant professor and associate professor of Tokyo Institute of Technology, Professor of the department of chemistry and Materials Science, Tokyo Institute of Technology at the present. The structural studies of glass, melt and the materials in vitrification have been conducted using high-temperature Raman spectroscopy, high-temperature X-ray computed tomography etc. Investigation field covers from the basic science to the engineering of glass melting in industry.

Development of the aluminoborosilicate glass system with high-loading capacity of HLW using a new combinatorial approach

Tetsuji Yano1*, Kodai Mori1, Shinya Ohashi1, Tetsuo Kishi1, Kenji Takeshita1, Yoshiyuki Miura2, Norio Kanehira2
1Tokyo Institute of Technology, Tokyo 152-8550, Japan 2Japan Nuclear Fuel Limited (JNFL), Aomori 039-3212, Japan

High-loading capacity of high-level radioactive nuclear wastes (HLW) into glass has been strongly desired to improve the management of the geological disposal of HLW wastes. An aluminoborosilicate glass system has been developed to encapsulate more than 20 mass% of HLW oxides from the reprocessing procedure at Rokkasho, and the active vitrification operation is planned using Liquid-Fed Joule-heating Ceramic Melter(LFCM) by JNFL. For the reduction of the number of canisters, the immobilization of larger amount of HLW in glass is desirable, and suitable glass system has to be developed promptly. The basic research programs for the next generation virification technology commissioned by the Ministry of Economy, Trade and Industry of Japan started from 2014, and the development of new glass composition with high loading capacity of HLW is one of the quite important missions in this program. Our group has developed a new combinatorial approach in this program, and applied to the investigation of the glass compositions in aluminoborosilicate glass system, which are expected to include more than 30 mass% of HLW in oxide form accompanying high chemical durability. The developed combinatorial method prepares the glass specimens with composition gradients controlled by the robotic dispenser system. This enables us to accelerate the speed of the glass sample preparation, and also the judgement of vitirification. Figure 1 shows the set up of the dispenser system. A couple of slurries with different compositions are loaded and dispensed on the substrate with the controlled mixing ratio. After dried, the specimens are heated in the electric furnace up to 1200 oC and kept for 1 h to complete vitirification. The heated sample is transferred to the annealing furnace and cooled to the room temperature. Figure 2 shows the examples of the specimen with B2O3/Al2O3 composition gradient and 30 mass% HLW. From the X-ray diffraction and X-ray fluorescence analyses, the vitrification degree of the sample glasses on the substrate are investigated to pick up the glass compositions which have high-loading capacity of HLW.

Figure 1. Appearance of the robotic dispenser system used for the combinatorial approach to prepare the glass specimens with a composition gradient.

Figure 2. Top view of an example of the platelet glass specimen on the substrate prepared by the developed combinatorial method. The sample size is 3x3 cm.