Thermal treatment of plutonium contaminated material (PCM) waste
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Thermal treatment of plutonium contaminated material (PCM) waste Luke Boast1 M.C.Stennett1 and Neil C. Hyatt1 1 Department of Materials Science & Engineering, the University of Sheffield, Mappin Street, Sheffield S1 3JD, UK ABSTRACT Key drivers for the application of thermal treatment processes include the reduced volume, improved passive safety, and superior long term stability of the vitrified wasteform products. These advantages have led to a renewed interest in thermally treating various UK ILW streams. To support the increased investment in thermal treatment technologies a fundamental understanding of the processes and the impact of waste inventory needs to be established. The research described in this report aims to provide the evidence necessary to support a major investment in thermal treatment of Plutonium Contaminated Materials (PCM). The report describes the use of laboratory scale waste simulants to develop an understanding of the waste and matrix interactions during thermal treatment of PCM waste. The report includes the thermal treatment process and characterization of the vitrified product. INTRODUCTION Plutonium Contaminated Materials (PCM) waste is a subcategory of intermediate level waste, which is generated as a result of the handling of plutonium during nuclear fuel processing and other related activities. The amount of PCM waste in the UK is estimated to be over 31,000m³, with 70% of PCM waste stored at the Sellafield site [1]. The PCM waste, which can incorporate masonry, metal, organic or a mixture of each, are double bagged in heat sealed PVC linings before being stored in 200 L mild steel drums. The heterogeneous nature of the waste material presents a considerable materials science and engineering challenge for PCM waste immobilization. A process is already in place at the Sellafield site for the treatment of some categories of PCM waste, centered on the Waste Treatment Centre (WTC). The general method of the WTC is compression of the 200 L drums containing the PCM waste, and the resulting crushed drums are grouted in cement and stored within 500 L steel storage containers [2]. There are however concerns regarding the reliability of the supercompaction and subsequent grouting process to deliver a consistent wasteform suitable for long-term storage and eventual disposal [3]. Thermal treatment is the main alternative technology available for the treatment of PCM waste. Key drivers for the application of thermal treatment processes include the reduced volume, improved passive safety, and superior long term stability, of the vitrified wasteform products. Proof of concept studies by the University of Sheffield, have demonstrated PCM compatibility with currently available thermal treatment technology platforms [4]. In this study [4] the authors successfully vitrified simulant PCM waste. Using ground granulated blast furnace slag (GGBS) which enabled a mixed slag/metal wasteform for high metal waste feeds. However, GGBS has a wide range of applications, combined with low levels of production in t
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