Advances in a Bioprocess for the Treatment of Nuclear Waste: Spent Ionic Exchange Resins
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Advances in a Bioprocess for the Treatment of Nuclear Waste: Spent Ionic Exchange Resins León Mosquera Rodríguez1,2 and Ramón A. Pizarro2 Programa Nacional de Gestión de Residuos Radiactivos, Comisión Nacional de Energía Atómica, Av. del Libertador 8250 (C1429BNP), Ciudad Autónoma de Buenos Aires, Argentina. 2 División Radiomicrobiología, Unidad de Actividad Radiobiología, Centro Atómico Constituyentes, Comisión Nacional de Energía Atómica, Av. Gral. Paz 1499 (B1650KNA), San Martín, Prov. de Buenos Aires, Argentina.
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ABSTRACT Development of a bioprocess intended to achieve a volume reduction of spent resins (either from research and power reactors) is the main purpose of this research project. Search is constrained to microorganisms that exhibit radioresistance, and which can be cultured in a heavy metal environment with additives of nuclear reactor waters such as boron, lithium and gadolinium compounds. Bacteria adapted to a radioactive environment were obtained by treating a RA-3 Reactor spent ionic exchange resin sample (kept at Área de Gestión Ezeiza: AGE) with sterile water; microorganisms suspended were isolated, subject to purity controls and characterized. Experiments performed with these strains include: -Culture in a mineral-broth having polystyrene as source of both carbon and energy. The strain RMB 1200 gave the highest number of viable cells, then being tested with some aromatic compounds, and with some additives of nuclear reactor waters and other elements found in spent resins. -An anionic exchange resin sample was heated, yielding a chemical environment resembling to that of radiolysed resins, and then RMB 1200 strain was cultured with this solid. -A technique to stain polymers was developed in order to find morphological changes caused by microbiological activity. Microscopic examination of cultured polymer samples has been performed. Results obtained with RMB 1200 include metabolic capabilities to use aromatic carbon sources (benzoate, polyphenols), its growth with polystyrene and resin, and short-term tolerance to several xenobiotics assayed at higher concentration levels than the ones of spent resins. INTRODUCTION A large volume of spent resins from nuclear industry needs to be managed after several decades of nuclear power plants activity. Furthermore, world's energy demand increases and several nuclear power plants are currently planned and under construction, suggesting the rise of new challenge to be faced: nuclear waste management improvements are critical to ensure a reasonable development of nuclear industry for the next years. Alternatives to manage spent resins typically include their cementation, polymer matrix immobilization and pyrolysis, and every option has its advantages as well as some difficulties [13]. A relatively recent work [4] has shown that biodegradation of ionic exchange resins is
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feasible, and the design and development of a bioprocess intended to achieve a volume reduction of this nuclear waste is the main objective of this research project. Bacteria adapted to
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