Plastic Scintillation microspheres for radioactivity determination: synthesis, characterization and production
Plastic scintillation microspheres (PSm) are a solid dispersion of one or more fluorescent solutes encapsulated within a polymeric matrix. PSm appear as an alternative to the use of liquid scintillation cocktails for radioactivity determination with the advantage of avoiding the mixed waste, for the...
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| Tipo de recurso: | tesis doctoral |
| Estado: | Versión publicada |
| Fecha de publicación: | 2015 |
| País: | España |
| Institución: | CBUC, CESCA |
| Repositorio: | TDR. Tesis Doctorales en Red |
| OAI Identifier: | oai:www.tdx.cat:10803/380546 |
| Acceso en línea: | http://hdl.handle.net/10803/380546 |
| Access Level: | acceso abierto |
| Palabra clave: | Química analítica Analytical chemistry Radioquímica Radiochemistry Ciències Experimentals i Matemàtiques 543 |
| Sumario: | Plastic scintillation microspheres (PSm) are a solid dispersion of one or more fluorescent solutes encapsulated within a polymeric matrix. PSm appear as an alternative to the use of liquid scintillation cocktails for radioactivity determination with the advantage of avoiding the mixed waste, for the measurement of salty samples, for performing measurements in continuous, or for employing them as a medium to join the measurement and separation steps. However, PSm are not completely available in the market, since only a few providers supply them at a high cost and with a limited range of sizes and compositions. This thesis has been focused in two main objectives. The first one has been the evaluation of the feasibility of different methodologies to produce PSm, starting at laboratory scale and addressing their production at a higher scale. The second one has been to increase the knowledge about the energy transfer mechanism through the evaluation of different quenching agents and different organic scintillators. The production of PSm was successfully performed through organic solvent extraction/evaporation methodology (E/E). Other techniques based on drying, the Spray Drying (SD) and the supercritical antisolvent (SAS) were also evaluated. The E/E allowed the production of PSm at laboratory and at large scale with features and radiometric performances comparable to those of the commercial ones, and also producing PSm with the ability for alpha/beta discrimination. On the other hand, SD and SAS proved to produce PSm and polystyrene based submicron particles, respectively, which enabled the measurement of radioactivity but involving a high associated operational cost and a low production yield. Finally, the evaluation of the energy transfer mechanism was performed by conducting a systematic study of the interference of several quenching agents when different organic scintillators were employed. Moreover, the wide range of PSm diameters obtained allowed the study of the relationship between the size and the radiometric capacities, resulting in a better understanding of the energy transfer mechanism through the evaluation of the particle and optical quenching. |
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