Characterisation of Plasma Vitrified Simulant Plutonium Contaminated Material Waste
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0985-NN10-06
Characterisation of Plasma Vitrified Simulant Plutonium Contaminated Material Waste Neil C. Hyatt1, Suzy Morgan1, Martin C. Stennett1, Charlie R. Scales2, and David Deegan3 1 Immobilisation Science Laboratory, Department of Engineering Materials, The University of Sheffield, Mappin Street, Sheffield, S1 3JD, United Kingdom 2 Nexia Solutions Ltd., Sellafield, Seascale, Cumbria, CA20 1PG, United Kingdom 3 Tetronics Ltd., 5, Lechlade Road, Faringdon, Oxfordshire, SN7 8AL, United Kingdom ABSTRACT The potential of plasma vitrification for the treatment of a simulant Plutonium Contaminated Material (PCM) was investigated. It was demonstrated that the PuO2 simulant, CeO2, could be vitrified in the amorphous calcium iron aluminosilicate component of the product slag with simultaneous destruction of the organic and polymer waste fractions. Product Consistency Tests conducted at 90∫C in deionised water and buffered pH 11 solution show the PCM slag product to be durable with respect to release of Ce. INTRODUCTION Plutonium Contaminated Materials (PCMs) arise from operational and decommissioning activities involving contact with plutonium isotopes. PCM waste is heterogeneous, comprising a mixture of masonry, metallic, polymer and organic materials. Typically, PCM materials are packaged in polythene and stored in standard 200 litre waste drums. It is estimated that only 5% of the existing PCM inventory (volume: 13445 m3) has been conditioned to a form suitable for long term passive storage [1]. The present ìconditioningî process involves ìsuper-compactionî of 200 litre waste drums with the compacted ìpucksî re-packaged in 500 litre drums. Although super-compaction achieves a degree of volume reduction, there is no guarantee that the supercompacted waste material will be accepted for eventual repository disposal due to the residual organic (cellulose-based) and polymeric fractions. Destruction of this organic waste component by high temperature oxidation would potentially afford a greater degree of volume reduction and result in a conditioned waste-form more acceptable for repository disposal. We have, therefore, explored the potential of using a remotely coupled cold crucible plasma vitrification furnace for suitable conditioning of PCM wastes. The plasma melting coverter had a refractory lined, water-cooled roof and sidewalls, and a hemispherical, water-cooled, copper crucible for skull melting. Ancillary equipment included: water supply, distribution and monitoring manifold, argon gas supply, feeding equipment, offgas handling equipment, DC plasma power supply and integrated programmable logic controller (PLC) and supervisory control and data acquisition (SCADA) systems. The converter was designed to allow material to be fed at up to 50 kg/hr, with plasma power delivery of up to 250 kW. The theoretical energy requirement (T.E.R) for material treatment was approximately 0.55 kWh/kg. The vitrified product was intermittently tapped from the furnace into pre-heated cast iron moulds. The equipment and tapping process
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