## 5 Results
To further understand the effect of porosity change caused by dehydration on radionuclide migration, we selected I-129, Ni-59, Sr-90 and Cs137 to compare the release concentration of radionuclides at point H in Figure 11 through the buffer material with and without porosity correction. The literature suggests that the porosity of the buffer material is between 0.41 and 0.46. When the saturated density of the buffer material is 2000 kg/m\({}^{3}\), the porosity is 0.435 (i.e., the average value of 0.41-0.46) [50]. Since the value of 0.435 is often used for porosity in safety evaluations, the unmodified porosity was also set to 0.435 in this study. Using the hydration state developed in this study to select the modified porosity, we found that it is affected by decay heat in the region of 0-0.01 M, so the temperature will be greater than 90 \({}^{\circ}\)C in 3-10 years, and the porosity is 0.435 in 3-10 years. Other time periods are shown in Figure 14, and the porosity of 0.321 is seen in both time periods of 1-2 years and 11-20,000 years. At the region of 0.01-0.35 m, the porosity is 0.321 between 1 and 20,000 years. Figure 15 shows the concentration breakthrough curves with and without porosity correction of I-129, Ni-59, Sr-90 and Cs137, respectively. We found that the simulated radionuclide release concentration with modified porosity was greater than the simulation result using the traditional porosity value of 0.435. The results showed that the safety assessment and analysis of radionuclide migration using unmodified porosity may underestimate the concentration of radionuclides released from EBS. This study also showed that the porosity correction model may be an approach to the real situation of radionuclide release concentration. \begin{table}
\begin{tabular}{c c c} \hline
**Dehydration Stage** & **T** (\({}^{\circ}\)**C**) & **Dehydration Time (sec)** \\ \hline
2W\(-\)1W & 35 & 3661 \\
1W\(-\)0W & 90 & 24,799 \\ \hline \end{tabular}
\end{table} 
Table 6: Dehydration times for 2W–1W and 1W–0W transitions. \begin{table}
\begin{tabular}{c c c c c} \hline
**Time (Years)** & **Hydrous State** & \(\boldsymbol{\phi_{\alpha}}\) & \(\boldsymbol{\Delta\phi}\) & **Buffer Volume (cm\({}^{3}\))** & **Radial Compression (cm)** \\ \hline
0 & 2W & 0.177 & - & 6,301,465 & - \\
1–2 & 1W & 0.321 & 0.144 & 5,394,054 & 2.427 \\
3–10 & 0W & 0.435 & 0.258 & 5,373,529 & 2.485 \\
11–20,000 & 1W & 0.321 & \(-\)0.114 * & 5,394,054 & 2.427 \\ \hline \end{tabular}
\end{table} 
Table 7: Variations with time of the buffer volume and compression amount. Figure 10: Temperature profile at six years for the simulation region. Figure 9: Canister power as a function of time. Figure 11: Points for temperature calculation within the buffer, each gap of points is 5 cm. Figure 12: Temperature and modified porosity distribution at points A–H. Figure 13: Average temperature evolution and the modified porosity as a function of time within the buffer material. Figure 14: Schematic illustration of modified porosity setting in radionuclide transport model: (**A**) the temperature in relation to distance for the simulation from 1 year to 11 years; (**B**) schematic diagram of the buffer zone divided into two areas; (**C**) transient modified porosity distribution in buffer materials.