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Mitsui, Seiichiro
no journal, ,
In geological disposal of high-level radioactive waste, vitrified waste will function as the first engineered component of a multi-barrier system. The glass is expected to retain radionuclides for long time periods by limiting radionuclide release from its own structure. A more realistic understanding and modeling of the glass corrosion processes can improve reliability of the radionuclide migration analyses. Therefore, we need to develop practical performance assessment models of the glass corrosion coupled with various near-field processes to be applied to an open system relevant for disposal conditions. This presentation summarizes performance assessment studies of vitrified waste.
Okamoto, Yoshihiro; Nagai, Takayuki; Kobayashi, Hidekazu; Oyama, Koichi; Sasage, Kenichi; Shiwaku, Hideaki; Inose, Takehiko*; Sato, Seiichi*
no journal, ,
The local structures around some elements in newly developed nuclear waste glass simulation samples using phosphorus-doped borosilicate glass and iron phosphate glass as frit were investigated by synchrotron radiation based XAFS analysis. It was found that the addition of phosphorus to borosilicate glass changes the glass to a significant reduction state and counteract oxidation effects induced by increasing waste loading. In iron phosphate glass with a composition of 30% Fe
O
-PO
, the XAFS analysis results showed that the solubility of ruthenium could reach 0.5-1.0%.
Nagai, Takayuki; Kobayashi, Hidekazu; Sasage, Kenichi; Oyama, Koichi; Sato, Seiichi*; Inose, Takehiko*; Hatakeyama, Kiyoshi*
no journal, ,
We estimated the long chemical stability of simulated waste borosilicate glass samples reacting with water in a closed case by the immersion test in alkaline solution and confirmed the effect which restrains the elution of molybdenum to the solution from the glass samples made with the frit including phosphorus. After cooling the simulated waste glass samples from melt condition, the crystallization behavior in the glass samples made with the frit including phosphorus was confirmed similar to that of the sample made with a present frit composition.
Igarashi, Hiroshi
no journal, ,
The literature overseas was reviewed on the increase in the surface area of HLLW vitrified products due to cooling during glass pouring process and mechanical impact, from the perspective of a parameter of modeling the radionuclide release rate from glass in performance assessment of geological isolation. The investigation was focused on the experimental work to evaluate an increase in surface area, and how the parameters on surface area were set based on those experimental results. The surface area obtained from the experiments executed in Japan were also discussed in comparison with the overseas studies. While surface area increase factor and the management on its uncertainty in the modeling varied according to the country, the factor set in the modeling reported from Japan was within the range from overseas. The surface area increase factors from the experiment in Japan which were evaluated in the same manner as overseas, were comparable with those overseas.