Balancing Cost and Risk by Optimizing the High-Level Waste and Low-Activity Waste Vitrification
In the currently used melters, the waste loading for nearly all high-level waste (HLW) is limited by crystallization. Above a certain level of waste loading, precipitation, settling, and accumulation of crystalline phases can cause severe processing problems and shorten the melter lifetime. To decrease the cost without putting the vitrification process at an unreasonable risk, several options, such as developing melters that operate above the liquidus temperature of glass, can be considered. Alternatively, if the melter is stirred, either mechanically, by bubbling, or by temperature gradients in induction heating, the melt can contain a substantial fraction of a crystalline phase that would not settle because it would be removed from the melter with glass. In addition, an induction melter can be nearly completely drained. For current melters that operate at a fixed temperature of 1150C, optimized glass formulation within currently accepted constaints has been developed. This approach is based on mathematically formulated relationships between glass properties and glass composition. Finally, re-evaluating the liquidus-temperature constraint, which may be unnecessarily restrictive for some HLWs, has recently been investigated. An attempt is being made to assess the rate of settling of crystalline phases in the melter and evaluate the risk for melter operation. Based on a reliable estimate of such a risk, waste loading could be increased, and a substantial saving can accrue. For low-activity waste (LAW), the waste loading in glass is limited either by the product quality or by segregation of sulfate during melting. The formulation of constraints on LAW glass in terms of relevant properties has not been completed, and no property-composition relationships have been established so far for this type of waste glass.
- Research Organization:
- Pacific Northwest National Lab. (PNNL), Richland, WA (United States)
- Sponsoring Organization:
- USDOE
- DOE Contract Number:
- AC05-76RL01830
- OSTI ID:
- 944915
- Report Number(s):
- PNNL-SA-32749; KP1301020; TRN: US0900730
- Resource Relation:
- Conference: WM 2K proceedings Feb. 27-Mar 2, 2000 Tucson Arizona
- Country of Publication:
- United States
- Language:
- English
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