## 4 Discussion  
The ability to demonstrate that properly disposed radioactive waste radionuclides will not expose an average member of the critical group to radiation doses greater than 0.1 mSv per year is a key safety element of engineered designed barriers at near-surface radioactive waste disposal sites [2; 3]. This safety measure acknowledges that radionuclides will migrate from the disposal site into the surrounding ecosystem due to a variety of factors, but the \begin{table}
\begin{tabular}{c c c c c c c c c} \hline \hline  & \multicolumn{2}{c}{\({}^{14}\)C} & \multicolumn{2}{c}{\({}^{137}\)Cs} & \multicolumn{2}{c}{\({}^{90}\)Sr} & \multicolumn{2}{c}{\({}^{99}\)Tc} \\ \cline{2-9}
**Year** & **Upper:** & **Lower:** & **Upper:** & **Lower:** & **Upper:** & **Lower:** & **Upper:** & **Lower:** \\  & **10,000** & **2500** & **200** & **2** & **300** & **3** & **30,000** & **300** \\ \hline
300 & \(2.9\times 10^{-17}\) & \(5.8\times 10^{-17}\) & \(6.1\times 10^{-17}\) & \(1.7\times 10^{-16}\) & \(6.8\times 10^{-18}\) & \(2.2\times 10^{-17}\) & \(3.0\times 10^{-15}\) & \(2.8\times 10^{-14}\) \\
500 & \(1.8\times 10^{-15}\) & \(3.7\times 10^{-15}\) & \(8.2\times 10^{-16}\) & \(2.3\times 10^{-15}\) & \(8.5\times 10^{-17}\) & \(2.8\times 10^{-16}\) & \(1.9\times 10^{-13}\) & \(1.8\times 10^{-12}\) \\
1000 & \(2.5\times 10^{-14}\) & \(4.9\times 10^{-14}\) & \(8.6\times 10^{-20}\) & \(2.4\times 10^{-19}\) & \(5.1\times 10^{-21}\) & \(1.7\times 10^{-20}\) & \(2.7\times 10^{-12}\) & \(2.6\times 10^{-11}\) \\
5000 & \(8.8\times 10^{-14}\) & \(1.8\times 10^{-13}\) & 0 & 0 & 0 & 0 & \(1.5\times 10^{-11}\) & \(1.4\times 10^{-10}\) \\
10,000 & \(7.1\times 10^{-14}\) & \(1.4\times 10^{-13}\) & 0 & 0 & 0 & 0 & \(2.2\times 10^{-11}\) & \(2.1\times 10^{-10}\) \\
50,000 & \(1.3\times 10^{-15}\) & \(2.5\times 10^{-15}\) & 0 & 0 & 0 & 0 & \(4.5\times 10^{-11}\) & \(4.1\times 10^{-10}\) \\
100,000 & \(4.1\times 10^{-18}\) & \(8.2\times 10^{-18}\) & 0 & 0 & 0 & 0 & \(5.4\times 10^{-11}\) & \(4.8\times 10^{-10}\) \\ \hline \hline \end{tabular}
\end{table} 
Table 4: Radionuclide Concentration in Well water (\(\text{Bq}/\text{L}\)) with sensitivity on distribution coefficient. \begin{table}
\begin{tabular}{c c c c c c c c c} \hline \hline  & \multicolumn{2}{c}{\({}^{14}\)C} & \multicolumn{2}{c}{\({}^{137}\)Cs} & \multicolumn{2}{c}{\({}^{90}\)Sr} & \multicolumn{2}{c}{\({}^{99}\)Tc} \\ \cline{2-9}
**Year** & **Upper:** & **Lower:** & **Upper:** & **Lower:** & **Upper:** & **Lower:** & **Upper:** & **Lower:** \\  & **1 \(\times\) 10\({}^{-11}\)** & **1 \(\times\) 10\({}^{-13}\)** & **5 \(\times\) 10\({}^{-69}\)** & **5 \(\times\) 10\({}^{-11}\)** & **5 \(\times\) 10\({}^{-10}\)** & **5 \(\one of interest in this study is concrete degradation. Thus, the aim of this study was to determine whether radionuclide migration caused by concrete degradation can result in significant radiation exposure to the public. This effect of radionuclide migration due to concrete deterioration is assessed in terms of the exposure dose from four radionuclides (\({}^{14}\)C, \({}^{137}\)Cs, \({}^{90}\)Sr, and \({}^{99}\)Tc) via RESRAD-offseting ground water pathways, assuming drinking water will be fetched from a well located 300 m from the disposal site. The four radionuclides were chosen based on their long half-lives (more than 20 years) and the availability of sorption data. By restricting the half-life to at least 20 years, the specified radionuclides can be expected to be present in the disposal site after 300 years of regulatory control. Previous studies have shown that concrete will deteriorate in four phases over its lifetime, with each stage defined by a decreasing pH and C/S ratio in concrete pore water. Sorption data in the form of distribution coefficients and diffusion coefficients have been published on the behavior of numerous radionuclides during the four stages of degradation. The results of this study show that when concrete deteriorates, the amount of radiation released reflect changes in radionuclide sorption properties.