Evolutions On Microstructure, Surface Morphology And Mechanical Properties Of Borosilicate Glasses Induced By Charged Particles

Due to the urgency of energy demand, our country will develop nuclear power positively in the next decades, and large amount of high-level nuclear wastes will be produced inevitably in this process. In order to protect the natural environment, lives and property of the people, we should dispose these hazardous wastes permanently, on the other hand, it also related to the sustainable development of nuclear energy. In our country, the treatment scheme of high-level nuclear wastes was confirmed as follows: the wastes should be immobilized in glass waste forms firstly and then it would be disposed permanently in a geologic repository. In the process of deep geological disposal, irradiation from alpha decay and beta decay can greatly affect the microstructure of the glasses, such as the variation of bond angles between elements in glasses, the production of bubbles, the appearance of point defects, etc. Meanwhile, irradiation field would lead to macroscopic changes of high-level nuclear waste glasses, such as volume changes, mechanical changes, leaching rate changes and so on.In developed countries, researching on radiation effects of glass waste forms lasts decades, but in our country, few researches in this area have been carried out due to the limitation of experimental conditions, national policies and many other factors. The studies which have been carried out just mainly focused on the effects of gamma irradiation, and the research direction also just dominated the glass leaching rate. This situation is extremely unfavorable to the safety of high-level nuclear wastes disposal, and it is also bad for long-term development of nuclear energy. For the healthy development of the national nuclear industry, the establishment of security evaluation system with independent intellectual property rights of high-level nuclear waste glasses radiation resistivity is urgent. This paper briefly describes the generation,classification, treatment and disposal of radioactive wastes, more systematically and comprehensively describes of the research status about radiation effects of the glass waste forms,and finally analyzes and discusses the main contents of this work in detail: evolutions on microstructure,surface morphology and mechanical properties of borosilicate glasses induced by charged particles. Conclusions in this work were obtained mainly as follows:1). Alterations of the glass structure induced by various particles radiation: Si-O-Si peak shifted to higher Raman shift and the D2 defect peak was found in Raman spectrum. Both of them were major caused by nuclear energy deposition, while electronic energy deposition seemed to have less effects on them. After radiation, variations of polymerization of the borosilicate glasses network showed that nuclear energy deposition of the particles in the glass lead to the decrease of matrix polymerization. The appearance of O2 molecules depended on the migration of alkali metal ions. Large amount of defect were found in the glass irradiated by electrons.2). Variations of the glass surface morphologies caused by various particles radiation:tremendous changes on glass surface were found after long time irradiation by heavy ions,leading to a lot of micro-bumps forming. These bumps, measured by AFM, were approximate several micro meters in bottom radius and 100-300 run height. There are big differences in both morphology and size of micro-bumps after different kinds of particles radiation. The threshold value of fluence to cause this effect is varied for different glasses after a kind of particle irradiation as well.3). Mechanical properties of the glasses caused by various particles radiation: nuclear energy deposition seemed to have greater effect on mechanical properties of glass comparing with electronic energy deposition. After ions irradiation,the magnitude of glass hardness decrease depended on the particles energy. If the nuclear energy deposition is the same, the hardness decreases greater with the particle energy increase. As to electron irradiation, the glass hardness decrease depended on fluence rate. The heavier density, the more apparent decrease of the glass hardness when the electronic energy deposition is the same. After various particles irradiation, the mechanical properties were enhanced for all borosilicate glasses.The results and conclusions get from our work have great importance on the establishment of security evaluation system with independent intellectual property rights of high-level nuclear waste glasses radiation resistivity.