Study On Solidification Technology Of Simulated Radioactive Nuclide In Borosilicate Glass And Glass-Ceramic Systems

In order to obtain glass suitable for vitrification of nuclear waste, to meet the requirements of high performance, we prepared borosilicate glass by melting cooling method with SiO2, Al2O3, B2O3, CaO, Na2O and TiO2as raw materials and5wt%CeO2as simulated nuclide and studied solidification treatment of simulated radioactive waste with actinides. Fourier transform infrared spectroscopy (FTIR), differential thermal analysis (DTA), Raman spectroscopy were used to characterize the glass structure. The leaching resistance property of glass was tested by inductively coupled plasma mass spectrometry (ICP-MS). The results show that:with the SiO2/B2O3mass ratio decrease, glass transition temperature (Tg) of borosilicate glass increased firstly and then decreased; B exited as [BO3]、[BO4] groups, with the increase of B2O3content, part of the [BO4] turned into [BO3].[BO3] and [BO4] in the glass matrix reached a certain balance when the B2O3content reached at17.82wt%. At this time the glass network structure became the most compact and the density of the glass got a maximum value2.58g/cm3. The normalized release rate (NR) of Ce in product conformance test (PCT) decreased first and then increased. We got the best glass anti-leaching property when the content of B2O3was17.82wt%. We also found that the addition of a small amount of TiO2had an important role to enhance the glass network structure. With the addition of TiO2, NR of Ce became much lower than parent glass. NR of Ce was the lowest when glass doped with3wt%TiO2, leaching rate (NR) of14days was5.59×10-6g/(m2·d), the main technical specifications have met the design requirement.We studied the difference of component and heat treatment temperature on the crystallization effect of YAG (Y3Al5O12) galss-ceramic with Y2O5, SiO2, Al2O3, Na2O, K2O and Li2O as raw materials,0.5wt%CeO2as simulated nuclide. The results show that:The crystal process of Y2O3-Al2O3-SiO2-K2O (YASK) system glass-ceramics was much more complex; the crystal phase including YAM (Y4Al2O9), K1+xAl1+xSi1-xO4, Y2SiO5and YAG turned out irregularly with the increase of heat treatment temperature; YAG (Y3Al5O12) crystal phase did not precipitate until the heat treatment arrived at1300℃. Compared with YASK system glass-ceramics, the crystal forming temperature of YAG in Y2O3-Al2O3-SiO2-Li2O (YASL) glass-ceramics was much lower. YAG (Y3Al5O12) crystal phase appeared when the heat treatment arrived at1000℃. With the increase of heat treatment temperature, the number of impurity phase gradually decreased. After3hours treatment at1300℃, pure phase of YAG crystal phase was obtained. As the temperature increases, YAG crystal shaped from spherical to square and its particle size became larger. As the extension of leaching time, Normal leaching rate of Ce first decreased rapidly, then remained stable; with the heat treatment temperature increased, the leaching rate of YASL glass-ceramic showed a declining trend; the best heat treatment temperature was1300℃at which YASL glass-ceramic had the best leaching resistance (3.6×10-6g/(m2·d)); NR of YASK glass-ceramics was much lower than ordinary glass and sample heat treated at850℃had the least leaching rate (4.0×10-6g/(m2·d)).