4:15 PM - 5:30 PM
[HRE31-P01] Use of sodium polytungstate as an X-ray contrast agent to reduce beam hardening in hydrogeological experiments
Keywords:beam hardening, contrast agent, Darcy flow, porous media, multi-phase flow, relative permeability
Iodine is conventionally used as a contrast agent in hydrogeological experiments using polychromatic X-ray computed tomography (CT) to monitor multi-phase Darcy flow in porous geological media. Undesirable beam hardening artifacts, however, make the quantitative analysis of the obtained CT images difficult. CT imaging of porous sand packs saturated with iodine and tungsten-bearing aqueous solutions, respectively, was performed using a medical CT scanner. The result (Fig. 1) shows that sodium polytungstate (Na6H2W12O40) significantly reduced the beam hardening compared with potassium iodide (KI). This result is due to the location of the K absorption edge of tungsten, which is nearer to the peak of the polychromatic X-ray source spectrum than that of iodine. As sodium polytungstate is chemically stable and less toxic than other heavy element bearing compounds, we recommend it as a promising contrast agent for hydrogeological CT experiments.Acknowledgements: The medical CT experiment was performed under the cooperative research program of Center for Advanced Marine Core Research (CMCR), Kochi University (13B034) with the support of JAMSTEC.References:Nakashima, Y. and Nakano, T. (2012) Analytical Sciences, 28, 1133-1138. http://dx.doi.org/10.2116/analsci.28.1133 Nakashima, Y. (2013) Journal of Hydrology and Hydromechanics, 61, 347-351. http://dx.doi.org/10.2478/johh-2013-0043Nakashima, Y. and Nakano, T. (2014) Journal of X-Ray Science and Technology, 22, 91-103. http://dx.doi.org/10.3233/XST-130411