Borosilicate glass leaching

This present paper discusses in more detail three separate nuclear-related studies where surface analysis has been used extensively borosilicate glass leaching, surface chloride contamination, and gas phase oxidation of some nickel alloys. 

Analysis of Borosilicate Glass Leaching Using Secondary Ion... 

Figure 6.8 Na (by RBS) and H (by ERD) depth profiles of the surfaces of a sodium borosilicate glass leached in a pH 8 aqueous solution at 70 °C for various times. (From Reference 25.)...

Environmental water samples to be analyzed for metals are best stored in quartz or Teflon containers. However, because these containers are expensive, polypropylene containers are often used. Borosilicate glass may also be used, but soft glass should be avoided because it can leach traces of metals into the water. If silver is to be determined, the containers should be light absorbing (dark colored). Samples should be preserved by adding concentrated nitric acid so that the pH of the water is less than two. The iron in well water samples, for example, will precipitate as iron oxide upon exposure to air and would be lost to the analysis if not for this acidification. 

One disadvantage of borosilicate glass is the low solubility of sulphates, molybdates, chromates, and halogenides, which may cause separation of metastable phases (Fig. 1) at relatively low contents of these components (1-3 wt%, dependent on glass composition Camara et al. 1980 Kawamoto et al. 1981 Stefanovsky 1989 Stefanovsky Lifanov 1989). At higher concentrations, yellow phase formation may occur (Morris Chidley 1976 Stefanovsky Lifanov 1988 Lutze 1988). The yellow phase, consisting of alkali and alkaline earth molybdates, sulphates, chromates, and halogenides, concentrates Cs and Sr radionuclides, and its presence increases leach rates of these radionuclides. 

Malow, G., Lutze, W. Ewing, R. C. 1984. Alteration effects and leach rates of basaltic glasses implications for the long-term stability of nuclear waste form borosilicate glasses. Journal of Non-Crystalline Solids, 67, 305-321. 

This report describes the preparation and leach testing of fully radioactive zinc borosilicate glass, prepared from power reactor waste. Leach tests were conducted on this fully radioactive waste glass to ... 

Leaching of Sintered Granules. The initial studies in this work(J3) were done in granules consisting of 80% PW-4b spray-calcined simulated waste, 10% silica, and 10% borosilicate glass frit sintered at 1100 C. The granules were about 0.6 cm in diameter and weighed about 370 mg each. The surface area, based on the assumption of an impervious hard") spherical shape,... 

The attack of water is related to the leaching mechanism described for acids. Table 4 rates glasses based on their resistance to water attack. Low alkali, high alumina, or borosilicate glasses generally have high water durability. 

Figure 2. SIMS depth profiles for a sodium borosilicate glass blank sample, air-exposed only (a), and sample exposed to aqueous leaching at 25°C for 30 min (b).

Figure 3. Comparison of SIMS depth profiles of aqueous leaching of a sodium borosilicate glass, for 30 min (a). Key ----------, 0°C and--------, 25°C. Error func-...

Figure 4. SIMS depth profiles for a borosilicate glass exposed to 0°C aqueous leaching for periods of 5 (-----------------------) and 30 (------) min.

Figure 2 shows the predicted, normalized cumulative mass losses based on the behaviors of silicon and sodium for three different values of the leachant renewal frequency. The physical parameters used refer to the leaching of PNL 76 68 borosilicate glass in deionized water at 90°C, (4) and reference is made to the geometric surface area, SA, of the sample. In particular, the curves corresponding to silicon and sodium tend to have the same, constant slope with increasing flow rate. In particular, the curves corresponding to = 1 day 1 practically coincide, indicative of network dissolution control. 

Leach behavior of borosilicate glass containing actual radioactive SRP high-level waste is similar to glass containing nonradio<-active simulated waste. 

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