Study On Composition-dependent Mechanical Property Changes In Irradiated Borosilicate Glass

With the development of technology in the field of nuclear energy and the widespread use of nuclear power plants,the vitrification of high-level nuclear waste（HLW）is one of the highest public acceptance of a disposal method.Borosilicate glass is a glass composed mainly of silicon dioxide,boron oxide and sodium oxide,which has excellent properties and has been widely used in many fields,and is also suitable for solidifying as HLW generated by spent fuel reprocessing.However,in the long-term geological disposal environment,borosilicate glass will inevitably suffer from various irradiation damage from radionuclides and fission fragments in high-level radioactive waste.Therefore,to study the irradiation damage behavior and composition dependence of borosilicate glass are extremely crucial for evaluating the radiation stability of such a waste form in its long-term service and improving its radiation resistance.Since actual HLW-glass are applied in mutual complex radiation fields,the study of multi-particle irradiation can better simulate the actual irradiation situations of glass and provide new insights into the mechanism of mechanical property changes in glasses.In this paper,different types and doses of ions as well as electrons were selected and divided into mono and two-particle sequential irradiation of three different composition borosilicate glasses to further study the behavior of glasses under mixed irradiation.The irradiated particles included 8 Me V Au³⁺ions,0.5 Me V He²⁺ions,and 1.2 Me V electrons.After irradiation,nanoindentation and infrared spectroscopic tests were performed on different composition borosilicate glasses to study the evolution of microstructure and mechanical properties of the glasses before and after irradiation,and the following conclusions were obtained:1.In this paper,the changes of mechanical properties of three NBS glasses under irradiation were analyzed by nanoindentation tests.The results showed that the hardness of all three glasses decreased and tended to saturation after mono He-ion irradiation and no significant composition dependence can be observed.The modulus of NBS1 and NBS2 glasses decreased slightly,while that of NBS3 glass remained unchanged.2.The three NBS glasses did not show self-recovery effects in the case of mono He-ion irradiation.On the contrary,this self-recovery effect was observed in the case of mono Au-ion irradiation.This is mainly attributed to the fact that the ballistic collisions of He-ion are much less intense than Au-ion and cannot lead to larger cascade displacement densities,and the effect on temperature and irradiation damage is also less intense than the Au-ion irradiation.3.In the dual-ion sequential irradiation scenario,the He-ion induced partial recovery did affect further changes in the mechanical properties of three NBS glasses under sequential irradiation and its saturation damage level.For different borosilicate glasses with increasing ion fluence,the sequential irradiation lead the mechanical property recovered to the saturated damage level.4.For the electron-ion sequential irradiated three NBS glasses,the microstructures and mechanical properties changes were related to the glass composition.In electron pre-irradiated NBS1 and NBS2 specimens,the hardness and modulus changes exhibited damage promotion after He-ion sequential irradiation.In contrast,an obvious recovery effect was observed in the NBS3 glass.This difference in mechanical property changes under sequential irradiation was related to the composition of NBS3 glass and its phase separation.Moreover,the electron irradiation induced pre-existing responses may cause more drastic synergistic effects in the sequential irradiation of borosilicate glasses and change the final equilibrium level of modulus changes.