FINAL RESULTS FROM THE IN SITU VITRIFICATION TREATMENT AT MARALINGA

Geosafe Australia Pty. Ltd. (Geosafe) and AMEC Engineering Pty. Ltd. (AMEC) are working together in Australia to use the GeoMelt vitrification process to treat hazardous wastes and remediate contaminated sites. The GeoMelt process represents a group of vitrification technologies that can be arranged in various ways to meet a wide range of site remediation and waste treatment requirements. All of the GeoMelt technologies involve the electric melting of contaminated soils and wastes to result in the destruction, removal or permanent immobilisation of contaminants. The original GeoMelt technology is GeoMelt In Situ Vitrification (ISV) wherein contaminated soils and wastes are treated in place, in the ground. This base technology has been developed into other configurations that allow a wider range of treatment applications. Adaptations of the process include melting wastes above ground in refractory lined vessels. Geosafe and AMEC recently completed a multi-year program involving the GeoMelt-ISV technology for the Australian Commonwealth Government at the Maralinga Site in South Australia. The Maralinga Site became contaminated as a result of above-ground nuclear weapons tests and safety trials conducted by the UK in the late 1950's and early 1960's. Geosafe's and AMEC's role in the clean-up project was to use the GeoMelt-ISV process to treat a group of burial pits containing mixed transuranic buried waste at the Taranaki area. A total of 11 pits were treated with the process. A lack of pit characterisation data and inaccurate historical records resulted in a number of challenges to the project. The total estimated volume of the 11 pits treated was on the order of 800% larger than that specified in the historical records. The GeoMelt-ISV process was successful in achieving its main role of converting the loose, friable, radioactive contamination in the pits into dense, hard, intrusion-resistant vitrified masses to eliminate the long-term hazards associated with subsidence or human intrusion. This paper summarises the final results from the project.