Session: 04-01 High-Level Waste Glass & Packaging

Paper Number: 111101

111101 - Tailoring Nuclear Waste Glass Properties for Joule Heated Ceramic Melter Technique With Bottom Drain Glass Pouring 

The authors describe recent advances in the development of waste glasses for vitrification of HLLW by Joule heated ceramic-lined waste glass melters with bottom drain glass pouring. Glass development in former projects (PAMELA, VEK, VPC) have shown that the waste glass must be tailor-made not only for the waste composition but also for the applied technology. For new projects the focus now was directed to a high waste glass loading and particularly to a low waste glass crystallization tendency in addition to the primary waste glass properties of chemical durability and rheological and electrical properties.

The low waste glass crystallization in the glass pouring channel is required to assure for the bottom pouring operation that the glass viscosity vs. temperature characteristic of the waste glass is maintained for safe and smooth glass pouring. A low crystallization tendency is of particular importance because glass pouring from the 1150 °C hot glass pool is performed batchwise, whereas the LFCM technology operates with continuous HLLW feeding and waste glass production. The glass pouring into stainless steel canisters takes place discontinuously every approx. 10 hours when about a quarter of the glass pool capacity of the melter is poured out. The glass in the pouring channel of the melter is heated to pouring temperatures of 1000 – 1100 °C by mean frequency and Joule heating.

In times without pouring the glass in the pouring channel assumes temperatures in a range of 600 – 1000 °C where the waste glass can be sensitive to crystallization processes, and could increase glass viscosity depending on the waste glass composition. Crystallization impacts the glass flow rate and can in the worst case cause blockage of the bottom drain. For this purpose, the glass development must consider waste glass compositions which are limited in forming crystalline phases under the described temperature conditions. In the lab scale work, it is necessary to investigate the formation and concentration of crystalline phases in the waste glass under different temperature levels and times, and also their impact on glass viscosity.

The task of quantitative determination of the crystalline content in the waste glass was performed by the used Quantitative Phase Analysis (QPA) according to the Rietveld method. It required X-ray diffraction measurements of waste glass samples between 2Q = 5 to 80° and a crystallographically known oxide mixed as standard added to the powdered sample. For the task to determine the impact of the crystalline phases on waste glass viscosity in situ crystallized glasses in viscometer measurements were conducted. The results of the investigations will be presented and discussed. The applied methods will be outlined, and conclusions will be drawn for future waste glass developments with low crystallization tendency and reliable control methods for this property.

Presenting Author: Martin Weiser Kraftanlagen Heidelberg GmbH

Presenting Author Biography: Martin Weiser studied chemistry at the Karlsruhe Institute of Technology and received his PhD in 2016. He has been working at Kraftanlagen Heidelberg since 2017 in the field of vitrification technology with a focus on process and glass chemistry including the development of tailor-made base glasses for different kinds of high-level liquid wastes. His in-depth research of glass melt properties is conducted in close cooperation with the Institute of Nuclear Waste Disposal at the Karlsruhe Institute of Technology where the German vitrification technology was developed over the last 40 years.