Glass - Back to the Future!

Presenting Author:
Katsushige Komatsu

article posted 6 April 2016

Katsushige Komatsu earned his BEng from Iwate University in 2003, and joined Japan Nuclear Fuel Chemical Analysis Co. Ltd. in 2009. Since April 2014, he is also a visiting researcher of the University of Shiga Prefecture.

Search of vitrification matrix with high-loading capacity
change of chemical durability and MoO3 solubility with B2O3 and Al2O3 contents

Katsushige Komatsu*1, Akihiro Yamada1, Jun Matsuoka1,
Naomichi Shimoyama2 & Norio Kanehira2
1 University of Shiga Prefecture, Hikone, Shiga 522-8533, Japan
2 Japan Nuclear Fuel Limited, Aomori 039-3212, Japan

Development of high-level radioactive waste glass with high-loading capacity is proceeding in Japan. High-loading capacity increases the concentration of fission products in radioactive waste glass. As fission products contain molybdenum, high-loading capacity increases its concentration in glass. It is expected that the increase of molybdenum concentration may enhance the precipitation of yellow phase, which is based on CaMoO4 and Na2MoO4 crystals. However, Na2MoO4 crystalline phase has poor chemical durability. Therefore, it is important for the glass matrix development to achieve higher molybdenum solubility compared to that of presently used glass composition.
High-level radioactive waste glass used in Japan belongs among alkaline aluminoborosilicate. It is known that the precipitation of yellow phase is diminished by increasing the boron content. On the other hand, chemical durability of borosilicate glass is known to be decreased with increasing boron content. Thus, search about change of chemical durability and MoO3 solubility with B2O3 content is very important for the development of vitrification matrix with high-loading capacity. However, there are few studies about these two properties at the same time.

Figure 1. Chemical durability as a function of SiO2/B2O3 molar ratio and Al2O3 content

In this study, chemical durability and MoO3 solubility of the glasses with simplified composition for high-level radioactive waste glass were investigated with the change in SiO2/B2O3 molar ratio and also in the Al2O3 content (Figure 1,2). A suitable composition region is found in this study.

Figure 2. MoO3 solubility as a function of SiO2/B2O3 molar ratio and Al2O3 content

This study is a part of the basic research programs for the next generation vitrification technology, which are commissioned project from Ministry of Economy, Trade and Industry of Japan to IHI corporation, Japan Nuclear Fuel Limited (JNFL), Japan Atomic Energy Agency (JAEA) and Central Research Institute of Electric Power Industry (CRIEPI).