Transport and sorption of 85Sr and 125I in crushed crystalline rocks under dynamic flow conditions

Modeling of transport of radionuclides in beds of crushed crystalline rocks under equilibrium non-linear sorption isotherm conditions

“…Details of the laboratory flow experiments with 137 Cs and 85 Sr transport by synthetic groundwater (SGW) in columns filled with crushed crystalline rocks of five various granitoides (diorite-I, diorite-II, gabbro, granite and tonalite) are described in our earlier papers [12,13], therefore only the most important information is presented here. For the selected 0.25-0.80 mm homogenized fraction, the most important hydraulic parameters were determined: dry grain bulk density (ρ), calculated porosity (θ c ), experimental porosity (θ e ) and pore volume as the average of both porosities.…”

“…(4)) can be obtained by rearranging Eq. (3), with reference to the facts that the time parameter is a function of the number of pore volumes running through the column (n PV = ut/L) and the C may be replaced by A (volume activity) (analogous equations can be found in publications [12][13][14]):…”

“…(4) and on the relation R exp ≈ n PVmax [12][13][14]. Its evaluation procedure consists of the fitting of experimental data by a trial and error method (i.e., by so called "by eye method"), in the course of which the values of three parameters, namely, R cal , Pe, and k int are sought.…”

“…Generally, two basic groups of such models can be used: (1) the first one, involving in particular the systems characterized by *Author for correspondence (E-mail: karel.stamberg@fjfi.cvut.cz). a linear isotherm, follows the explicit formulation of the c = f(t) [1][2][3][4][5][6][7][8][9][10][11][12][13][14], (2) the second one, applicable to rather complicated cases in the contaminant sorption (e.g., two site concept -considering equilibrium and kinetic aspects, two-region concept -considering mobile and immobile liquid phase, non-linear sorption isotherm, etc. ), solves the concentration vs. time dependence implicitly, using to advantage (iterative) numerical methods, supported by computers [15][16][17][18][19][20][21][22][23][24].…”

“…One of the simplest methods was derived in our earlier papers, where the radionuclide concentration dependence on time is analytically expressed [12][13][14]. This method, designed as linear sorption approach, is based on the integrated form of the basic differential advection-dispersion equation (1-D ADE) derived with several simplifying assumptions [25][26][27][28][29][30][31], such as the attainment of real sorption equilibrium, the linearity of the sorption isotherm, and the very low radionuclide concentration.…”