## 5 Results  
This study adopted the chemical kinetic model of smectite dehydration to calculate the amount of water expelled from smectite clay minerals because of higher temperatures of waste decay heat. The results were as follows:  
The heat-generating spent fuel was contained in the canister. The canister heat decay in less than 20,000 years was calculated using Equation (2) and initial canister power of 1200 W, as shown in Figure 9. In the calculation, we used the COMSOL model to calculate heat transport through the EBS to the host rock during a 20,000-year period. The parameters for the heat transport simulation are tabulated in Table 2. The highest temperature of the buffer material occurred in the sixth year; Figure 10 shows the temperature profile of that year. We selected eight points, A, B, C, D, E, F, G and H, with 5 cm between each, as the represented points for temperature calculation within the buffer (Figure 11). The temperature distribution for the eight points during the 20,000-year-period is shown in Figure 12. Figure 13 shows the average temperature evolution within the buffer material. Notably, the temperature peak occurs before 10 years. After approximately 20,000 years, the thermal caused by the release of the canister had dispersed and the temperature had reduced to nearly geothermal background level. The smectite dehydration times for 2 W-1 W and 1 W-0 W transitions are shown in Table 6. Note worthily, the dehydration times were relatively fast with values of 3661 s (2 W-1 W) and 24,799 s (1 W-0 W) at 35 \({}^{\circ}\)  
Figure 8: Schematic illustration for the Q1 transport path of radionuclide. \begin{table}
\begin{tabular}{c c c c c c} \hline \hline
**Parameter** & **Value of I-129** & **Value of Ni-59** & **Value of Sr-90** & **Value of Cs-137** & **Units** & **Source** \\ \hline Diffusion coefficient & 3.2184 \(\times\) 10\({}^{-10}\) & 3.2184 \(\times\) 10\({}^{-10}\) & 3.2184 \(\times\) 10\({}^{-10}\) & 3.2184 \(\times\) 10\({}^{-10}\) & m\({}^{2}\)/s & [50] \\ Porosity & 0.435 & 0.435 & 0.435 & 0.435 & - & [50] \\ Decay constant & 4.415 \(\times\) 10\({}^{-8}\) & 6.8628 \(\times\) 10\({}^{-6}\) & 0.024076 & 0.022977 & 1/yr & [46] \\ Half-life & 1.57 \(\times\) 10\({}^{7}\) & 1.01 \(\times\) 10\({}^{5}\) & 28.79 & 30.17 & yr & [46] \\ Distribution coefficient & - & 3 \(\times\) 10\({}^{-1}\) & 4.5 \(\times\) 10\({}^{-3}\) & 9.3 \(\times\) 10\({}^{-2}\) & m\({}^{3}\)/kg & [50] \\ Liquid density & 1000 & 1000 & 1000 & 1000 & kg/m\({}^{3}\) & - \\ Solid density & 2000 & 2000 & 2000 & 2000 & kg/m\({}^{3}\) & [50] \\ IRF & 2.9 \(\times\) 10\({}^{-2}\) & 1.2 \(\times\) 10\({}^{-2}\) & 2.5 \(\times\) 10\({}^{-3}\) & 2.9 \(\times\) 10\({}^{-2}\) & - & [46] \\ Degradation rate & 10\({}^{-7}\) & 10\({}^{-7}\) & 10\({}^{-7}\) & 10\({}^{-7}\) & yr\({}^{-1}\) & [46] \\ Solubility limit & - & 3 \(\times\) 10\({}^{-1}\) & 3.7 & - & mol/m\({}^{3}\) & [46] \\ Nucleide inventory & 3.92 & 639 & 6.94 & 11.5 & mol/canister & [51] \\ \hline \hline \end{tabular}
\end{table} 
Table 5: Parameter values of radionuclides for simulation in transient diffusion. and 90 \({}^{\circ}\)C, respectively. The hydrous state porosity due to the temperature evolution was equal to 0.177 at 0 years and 0.321 at 1-20,000 years, as shown in Figure 13. Figure 14 shows the buffer zone of 0-0.01 m near the canister during the 3-10-year-period while the temperature exceeds 90 \({}^{\circ}\)C, which means that the porosity in this state is equal to 0.435 and the hydrous state of the smectite is 0 W. In the buffer zone of 0.01-0.35 m away from the canister, the porosity is equal to 0.321 (1-20,000 years) with a hydrous state of 1 W. Table 7 shows the buffer volume and compression amount caused by dehydration and rehydration. In the 0 W state, the radial compression value is 2.485 cm. During the period of 10-20,000 years, the decay heat temperature will maintain the bentonite in the 1 W state and cause a 2.427-cm radial compression. Temperature can cause smectite dehydration and promote porosity changes.