## 3 Results
### Simulation for Transport: HTO, Se, and Cs  
Among the models in STANMOD, the equilibrium and non-equilibrium models in CXTFIT were primarily used to evaluate the transport parameters based on the experimental data. Generally, the sum of squared residuals (\(SSQ\)) are the degree to which the experimental results (\(Ce\)) deviate from the predicted values (\(Cp\)), where the \(RMSE\) (root mean square error) is defined as:  
\[RMSE=\sqrt{\frac{\sum\bigl{(}C_{p}-C_{e}\bigr{)}^{2}}{N}}=\sqrt{\frac{\sum \bigl{(}SSQ\bigr{)}^{2}}{N}} \tag{18}\]  
The BTC data are shown in Figure 4, and the simulation results are summarized in Tables 2-4 for the equilibrium model and non-equilibrium regions and site models. The figure shows that there was no retardation phenomenon with the HTO retardation factor (\(R\approx 1\)). In addition, the results for both of the non-equilibrium regions and the two transport model sites were better than that for the equilibrium model due to the lower residuals (\(SSQ\) or \(RMSE\)). However, Tables 3 and 4 show there was an obvious difference in the BTCs of Se(IV) and Cs, with a higher retardation factor (\(R>\)1). This indicated a kinetic sorption reaction of Se(IV) and Cs on the granite, which suggests suitable fitting and explanations using the different reaction transport models (see Figure 4d-i and Table 4).  
Figure 3: The experimental breakthroughs in different lengths. (**a**) HTO; (**b**) Se(IV); (**c**) Cs; (**d**) 2 cm; (**e**) 4 cm; (**f**) 8 cm.  
Figure 4: The experimental breakthroughs and curve-fittings for HTO, Se(IV), and Cs. (**a**) 2 cm-equilibrium model; (**b**) 4 cm-equilibrium model; (**c**) 8 cm-equilibrium model; (**d**) 2 cm-physical non-equilibrium model; (**e**) 4 cm-physical non-equilibrium model; (**f**) 8 cm-physical non-equilibrium model; (**g**) 2 cm-chemical non-equilibrium model; (**h**) 4 cm-chemical non-equilibrium model; (**i**) 8 cm-chemical non-equilibrium model.  
\begin{table}
\begin{tabular}{c c c c c c c c} \hline \hline \multirow{2}{*}{**RN**} & \multirow{2}{*}{**No.**} & \multirow{2}{*}{**D**} & \multirow{2}{*}{**\(\mathbf{\theta}\)**} & \multirow{2}{*}{**\(\mathbf{\alpha}\)**} & \multirow{2}{*}{**R**} & \multirow{2}{*}{**SSQ**} & \multirow{2}{*}{**RMSE**} \\  & & **(cm2/min)** & & **(-)** & & **(cm)** & & \\ \hline \multirow{3}{*}{HTO} & Fit 1-1 & 0.1158 & 0.46 & 0.53 & 1.00 & \(2.76\times 10^{-1}\) & \(1.40\times 10^{-1}\) \\  & Fit 2-1 & 0.1173 & 0.46 & 0.53 & 1.00 & \(1.21\times 10^{0}\) & \(1.86\times 10^{-1}\) \\  & Fit 3-1 & 0.2627 & 0.46 & 1.19 & 1.00 & \(2.43\times 10^{0}\) & \(3.06\times 10^{-1}\) \\ \hline \multirow{3}{*}{Se(IV)} & Fit 4-1 & 0.4889 & 0.46 & 2.22 & 1.47 & \(2.19\times 10^{-1}\) & \(6.68\times 10^{-2}\) \\  & Fit 5-1 & 0.3296 & 0.46 & 1.50 & 1.67 & \(1.35\times 10^{-1}\) & \(5.25\times 10^{-2}\) \\  & Fit 6-1 & 1.2847 & 0.46 & 5.84 & 1.34 & \(6.88\times 10^{-2}\) & \(3.39\times 10^{-2}\) \\ \hline \multirow{3}{*}{Cs} & Fit 7-1 & 0.5641 & 0.46 & 2.56 & 4.00 & \(1.44\times 10^{0}\) & \(1.71\times 10^{-1}\) \\  & Fit 8-1 & 0.8889 & 0.46 & 4.04 & 4.00 & \(2.41\times 10^{0}\) & \(2.11\times 10^{-1}\) \\ \cline{1-1}  & Fit 9-1 & 3.0345 & 0.46 & 13.79 & 4.00 & \(2.14\times 10^{0}\) & \(2.05\times 10^{-1}\) \\ \hline \hline \end{tabular}
\end{table}
Table 2: The fitting parameters for HTO, Se(IV), and Cs using the equilibrium model.