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

Paper Number: 111102

111102 - History and Advances in German High-Level Liquid Waste Vitrification Technology With Joule Heated Liquid Fed Ceramic Melter 

This paper describes the history and advances in the past decades with the German HLLW vitrification technology using Joule-heated Liquid Fed Ceramic Melter. The development of the technology started at Karlsruhe Research Centre (now KIT) in 1976.  The melter technique has been first time applied radioactively by the Belgium PAMELA plant (1985 – 1991), followed by the German VEK facility (2009 – 2010), and is currently used in the Chinese VPC plant since 2020. Essential progress has been achieved in these decades in large-scale melter design.

The long-term operation of the PAMELA facility had shown that the flat-bottomed PAMELA melter design urgently required modification for processing noble metals containing HLLW (Ru, Rh, Pd). They are practically undissolvable in borosilicate glass and segregate towards the melter bottom where they accumulate as highly viscous and highly el. conductive noble metals sludge. This disturbs both Joule heating of the glass pool and glass pouring. After the PAMELA experiences new melter designs were carried out with sloped bottom and reducing the two redundant glass pouring systems to one bottom pouring system. The noble metal sludge is, due to the sloped walls, directed to accumulate on the small melter bottom area and is automatically discharged with every glass pouring operation to avoid sludge accumulation. Such melters were inactively tested in 1:1 scale to study the formation, behavior and outflow characteristic with periodic routine bottom drain glass pouring (e.g. large scale BVPM melter 1993-2001). The modified melter technique was used in the VEK/Germany project at former WAK reprocessing plant to vitrify the high noble metals containing HLLW stored at the site (2009-2010). Simultaneously the melter design for the Chinese VPC project was started using the sloped bottom design and other improvements including air bubbling of the upper part of the glass pool, optimized power electrode arrangement and melter start up technique, new glass level detection device and remote connection/disconnections of melter to hot cell. Simultaneously, the waste glass for the VPC project was developed with the constrain that phase separations (e.g. sodium sulfate) had to be excluded. The VPC melter started commissioning operation in 2019/2020 and active operation in 2021.

The paper will highlight these development phases of the German LFCM technology from 1976 to 2020 in more detail including dealing with remaining points like lifetime extension possibilities of individual melter components (Inconel 690 thermowell, Inconel 690 glass level detection device, optimized melter feeding control, requirements concerning waste glass properties like crystallization tendency).

Presenting Author: Siegfried Weisenburger Karlsruhe Institute of Technology

Presenting Author Biography: S. Weisenburger received a doctorate degree from Karlsruhe University, Karlsruhe, Germany, in 1975. At the Institut für Chemische Technik, Karlsruhe University, he was as Research Assistant working on high temperature X-ray measurements up to 3000 K of the lattice structure of disordered carbon and graphite materials. Since 1977 until 2006, he has been the head of the Chemical Engineering Department, Institut für Nukleare Entsorgung, Karlsruhe Institute for Technology (KIT). From 2006-2015 he worked with KIT on further development of the HLLW vitrification technology for the VPC project/China. Since 2016, the focus is on DIWOPU project. He provided primary melter and process design as well as glass developments for the radioactive vitrification plants PAMELA/Belgium, VEK/Germany, and VPC/China.