Study On The Changes Of Macroscopic Properties And Microstructure Of The Ternary Borosilicate Glasses Induced By Gamma-ray Irradiation

Nuclear power is currently widely used as a cleanly and efficiently energy source,but the radioactive waste with strong radioactivity and long half-life produced in the process of nuclear power production has greater harm to the biosphere.Therefore,how to safely dispose of such high level radioactive waste has become a major factor restricting the development of nuclear power.At present,deep geological disposal methods are widely used internationally to store high-level radioactive waste for a long time,that is,the high-level radioactive waste is often buried under the deep ground after solidification.Borosilicate glasses have been used as the first barrier to prevent the leakage of radioactive nuclear waste.The study of the radiation effects of different components of the candidate material after radiation exposure has important guidance and reference significance for the safe geological disposal of radioactive waste.In the process of long-term geological disposal,gamma rays run through the entire process,and borosilicate glass is used as a solidified material.Therefore,it is necessary to study the effect of gamma rays on sodium borosilicate glass.In this work,gamma rays were first used to radiate borosilicate glass with different compositions（NBS2 and NBS8）,and the absorbed dose range was 0-1×10~7 Gy.Then the nanoindentation technology,ultraviolet spectroscopy（UV-Vis）,Raman spectroscopy（Raman）and fluorescence spectroscopy（PL）were used to study the radiation resistance of different components of borosilicate glasses from the changes in mechanical properties,optical properties and microstructure.The results showed that:（1）Different from the results of previous studies,we found that the mechanical properties of NBS8 glass have a slight upward trend after gamma irradiation.Through analysis and discussion,we found that the absorbed dose would affect the network forming structure of borosilicate glass after reaching a certain threshold.The structure related to mechanical properties of glass was the[BO₄]units.（2）Through ultraviolet spectrum analysis,it can be seen that the band gap of the samples became smaller and the Urbach energy increased as the absorbed dose increasing,which reflected the changed in the internal structure of the borosilicate glass after gamma-ray irradiation,resulting in defects and further increasing the short-range disorder of the glasses.In the paper,we will discuss in detail the mechanism that the band gap and Urbach energy changed.（3）Through Gaussian fitting of the fluorescence spectrum of NBS2 and NBS8glasses irradiated with gamma rays,the relationship between the concentration of non-bridging oxygen vacancy color center（NBOHC）and the absorbed dose were obtained.It was found that the concentration of the defect showed an exponential trend and began to increase rapidly after the absorbed dose reached 1.0×10~5Gy.This paper not only discussed the generation mechanism of the defect,but also concluded that the increasing in the degree of disorder within the glass that is the increase in Urbach energy.The increasing in disorder was related to the generation of NBOHC.（4）Through Raman spectroscopy,another parameter named Noise that characterizes the degree of structural disorder was obtained.It can be found that the Noise gradually increased with the absorbed dose increasing.Especially,the Noise changed exponentially with the absorbed dose when the absorbed dose reached1.0×10~5Gy.Furthermore,we also found that the Noise and the Urbach energy that represent structural disorder showed a linear trend with absorbed dose,which further reflected the increase of disorder in the glass caused by irradiation.The paper has done a certain study on the changes in the microstructure and mechanical properties of the ternary borosilicate glasses after gamma irradiation,and compared it with the changes in mechanical properties of ternary borosilicate glasses after Xe-ions irradiation.The main reason for the changes in the hardness of borosilicate glass caused by irradiation is that the network forming structure mainly refers to[BO4]units were changed.The research results of this paper have certain reference value for designing better-performing solidified glass and evaluation of some macroscopic properties in the process of deep geological disposal.