Study of Media Effect on Glass Surface
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STUDY OF MEDIA EFFECT ON GLASS SURFACE LUO Shanggeng*, WU Zhaoguang* and Delu LIU** *China Institute of Atomic Energy, Beijing 102413, China "**University of Science & Technology Beijing 100083, China ABSTRACT The present work described the effects of media, such as tuff, zeolite, bentonite and Fe2 03, on the glass surface leached in deionized water or in underground water. Element depletion or enrichment differ in different media system. No crystals were found in the leached glass surfaces layer. But there are pitting corrosion and precipitates on the leached glass surfaces. The amounts, both of them, increase along with the leaching time. INTRODUCTION In the past decade, numerous studies related to leaching tests of HLW-glass form have been carried out 1'-31 . After long term disposal, there are host rock, backfilling material, corrosion product of the steel container and water surrounding the HLW glass form. Simulating this condition, the media effect was studied. The leached glass surfaces were analysed by X-ray fluorescence spectrometry (XRF), X-ray diffraction (XRD) and scanning electron microscopy with X-ray energy dispersive spectroscopy (SEM-XEDS). The experimental results of the media effects, such as element variety, crystallization, pitting corrosion and precipitation on leached glass surfaces are presented in this paper. EXPERIMENTAL The composition of borosilicate glass containing simulated HLW is given in Table I. Table I Composition of borosilicate glass Base glass High level waste Component wt% Component wt% Component SiO 2 46.2 A12 0 3 1.70 SrO B 20 3 13.4 Cr 2 0 3 0.11 TiO2 Na 2 0 4.0 Fe2 0 3 5.24 U308 A12 0 3 2.5 K2 0 0.02 ZrO 2 MgO 1.5 MnO2 0.04 mixed RE CaO 2.5 Na 2 0 5.07 TiO 2 5.0 NiO 0.08 Li 2 0 3.4 PuO 2 ' 0.01 ZrO 2 1.5 SO 3 "* 1.55 Using U 3•Os instead of PuO 2 Adding Na2SO4
wt% 0.09 0.12 4.73 0.50 0.75
The glass samples were melted at 1100 0 C for 3 h and annealed at 450 'C for 1.5 h, then slowly cooled to room temperature. The annealed glass bars were cut into thin plates, polished and cleaned using acetone or alcohol with or without ultrasonator. The leach test container is made of PTFE (see Fig.1) which has to be cleaned according to the standard procedure[4]. The static leach tests were carried out using the modified MCC-1. The mass losses have been reported in previous paper[sl.
Mat. Res. Soc. Symp. Proc. Vol. 353 01995 Materials Research Society
64
The composition of leaching media (tuff, Na-bentonite, zeolite) with particle size of 180 mesh is listed in Table II. The Fe203 has the same particle size. The composition of simulated underground water is given in Table III. The leaching system with different media is shown in Table IV.
Fig. 1. Leach test container made of PTFE
Table II
Composition of tuff, zeolite and bentonite
composition Si0 2
17.48 3.15 3.29
zeolite(%) 70.45 12.35 0.59
bentonite(%) 63.55 15.60 0.16 2.57
TiO 2
0.36
0.19
0.44
Na 2 O
1.50
1.09
2.68
K2 0
0.25
1.14
0.15
MnO MgO CaO
0.06
0.05
-
1.01 0.65
1.68 1.66
3.08 1.25
H20 P205
4.88
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