Study of plasma off-gas treatment from spent ion exchange resin pyrolysis.
Polystyrene divinylbenzene-based ion exchange resins are employed extensively within nuclear power plants (NPPs) and research reactors for purification and chemical control of the cooling water system. To maintain the highest possible water quality, the resins are regularly replaced as they become contaminated with a range of isotopes derived from compromised fuel elements as well as corrosion and activation products including14C,60Co,90Sr,129I, and137Cs. Such spent resins constitute a major proportion (in volume terms) of the solid radioactive waste generated by the nuclear industry. Several treatment and conditioning techniques have been developed with a view toward reducing the spent resin volume and generating a stable waste product suitable for long-term storage and disposal. Between them, pyrolysis emerges as an attractive option. Previous work of our group suggests that the pyrolysis treatment of the resins at low temperatures between 300 and 350 °C resulted in a stable waste product with a significant volume reduction (>50%) and characteristics suitable for long-term storage and/or disposal. However, another important issue to take into account is the complexity of the off-gas generated during the process and the different technical alternatives for its conditioning. Ongoing work addresses the characterization of the ion exchange resin treatment's off-gas. Additionally, the application of plasma technology for the treatment of the off-gas current was studied as an alternative to more conventional processes utilizing oil- or gas-fired post-combustion chambers operating at temperatures in excess of 1000 °C. A laboratory-scale flow reactor, using inductively coupled plasma, operating under sub-atmospheric conditions was developed. Fundamental experiments using model compounds have been performed, demonstrating a high destruction and removal ratio (>99.99%) for different reaction media, at low reactor temperatures and moderate power consumption. The role of H2O as an important participant of the oxidation mechanisms in plasma conditions was established. The combination of both processes could represent a simple, safe, and effective alternative for treating spent ion exchange resins with a large reduction of generated gaseous byproducts in fuel cycle facilities where processes that utilize open flames are undesirable.
Programa Nacional de Gestión de Residuos Radiactivos, Comisión Nacional de Energía Atómica, Centro Atómico Constituyentes, Av. General Paz 1499, 1650, San Martín, Buenos Aires, Argentina.|Escuela de Ciencia y Tecnología, Universidad Nacional de General San Martín, Campus Miguelete, Martín de Irigoyen 3100, 1650, San Martín, Argentina.
Hernán Ariel
HA
Castro
Programa Nacional de Gestión de Residuos Radiactivos, Comisión Nacional de Energía Atómica, Centro Atómico Constituyentes, Av. General Paz 1499, 1650, San Martín, Buenos Aires, Argentina.
Vittorio
V
Luca
Escuela de Ciencia y Tecnología, Universidad Nacional de General San Martín, Campus Miguelete, Martín de Irigoyen 3100, 1650, San Martín, Argentina. bianchi@cnea.gov.ar.|Gerencia de Química, Comisión Nacional de Energía Atómica, Centro Atómico Constituyentes, Av. General Paz 1499, 1650, San Martín, Buenos Aires, Argentina. bianchi@cnea.gov.ar.
Hugo Luis
HL
Bianchi
D002588:Cesium Radioisotopes; D003037:Cobalt Radioisotopes; D005740:Gases / Q000032:analysis*; D007457:Iodine Radioisotopes; D007474:Ion Exchange; D007475:Ion Exchange Resins / Q000737:chemistry*; D055848:Nuclear Power Plants; D010084:Oxidation-Reduction; D058626:Plasma Gases; D000077319:Pyrolysis; D011850:Radioactive Waste; D013326:Strontium Radioisotopes; D018505:Waste Management / Q000379:methods*; D014866:Waste Products / Q000032:analysis
D002588:Cesium Radioisotopes; D003037:Cobalt Radioisotopes; D005740:Gases; D007457:Iodine Radioisotopes; C000614963:Iodine-129; D007475:Ion Exchange Resins; D058626:Plasma Gases; D011850:Radioactive Waste; D013326:Strontium Radioisotopes; D014866:Waste Products; C000614989:Cesium-137; C000615395:Cobalt-60; C000615490:Strontium-90
Nuclear waste; Off-gas treatment; Plasma; Pyrolysis; Spent ion exchange resins