Colloid and colloid-borne radionuclide migration in groundwaters
- Autores: Claude Pauline Delos Anne
- Directores de la Tesis: Jesús Carrera Ramírez (dir. tes.), Jordi Guimera Sola (dir. tes.)
- Lectura: En la Universitat Politècnica de Catalunya (UPC) ( España ) en 2007
- Idioma: inglés
- Tribunal Calificador de la Tesis: Scott Altmann (presid.), Marco Dentz (secret.), Carlos Ayora Ibáñez (voc.), Daniel M. Tartakovsky (voc.), Thorsten Schäfer (voc.)
- Materias:
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- Resumen
Colloids, particles in the 1nm to 1ìm size range, are ubiquituous in groundwaters. They are characterised by their large surface area, on which cantaminants may be sorbed. Colloids travel faster than the conservative tracer, and may therefore enhance the transport of contaminants sorbed on their surface. The role of Colloid-Facilitated Transport (CFT) in solute transport is often overlooked because of the relatively small concentration of colloids in groundwater. However, this may be crucial for solutes that are hazardous at very low concentrations. Thus, CFT is of concern for nuclear waste management. This work mainly deals with two aspects of the transport of colloid-borne radionuclides infractured media: (i) the reasons for a faster colloid transport with respect to the conservative tracer; and (ii) the reversibility of actinide-colloid association. The methodology consists in an experimental laboratory work using well defined systems and radionuclide/colloid cocktails to study the transport of colloids and colloid-borne radionuclides. The experiments were carried out in different columns and repeated under different flow rates. The colloid characterization methods employed in this work included standard methods such as PCS and newly developed techniques such as s-curve analysis of LIBD data. The transport of monodisperse/polydisperse colloids and conservative/active tracers were compared. Thereafter, a formulation was developed and applied to simulate the experimental results.
In the two column types, colloids always have access to a fraction of the matrix pore space. As expected, their access increased with matrix pore size and decreasing flow rate. However, the best enhancement of microspheres was observed for an optimum flow velocity, when colloids are excluded from the matrix and the conservative tracer diffuses into the matrix.
