## 4 Discussion  
The sensitivity parameters and assigned values were calculated with PRCC based on various site-specific input parameters listed in Table 1 in Appendix A. For preliminary calculation of the timing for site release for unrestricted reuse after NPP decommissioning, the total exposure dose was derived by assuming the concentration in the contaminated soil of various radionuclides to 0.037 Bq\(\cdot\)g\({}^{-1}\) (1 pCi\(\cdot\)g\({}^{-1}\)), the same initial condition employed in the previous works [13,32], and is presented in Figure 2. Consequently, the timing when the regulatory limit of 0.1 mSv\(\cdot\)year\({}^{-1}\) (allowing unrestricted reuse of the site after decommissioning the NPP in South Korea according to Article 4 of the Nuclear Safety and Security Commission Notification No. 2016-33) is satisfied was derived to be 4.07 years after the NPP decommissioning and a final investigation of the site condition. \begin{table}
\begin{tabular}{c c c c c c c} \hline
**Cases** & **CY\({}^{\bullet}\)[28]** & **Yankee Rowe [29]** & **Zion [30]** & **Kori-1 [13]** & **IAEA [31]** & **Wolsong (p.w)** \\ \hline
**Methods** & **RESRAD v6.2** & **RESRAD v6.2** & **RESRAD v7.0** & **RESRAD v7.2** &
\begin{tabular}{c} **IAEA** \\ **Standard** \\ \end{tabular} & **RESRAD v7.2** \\ \hline \({}^{134}\)Cs & \(1.70\times 10^{-1}\) & \(1.85\times 10^{-1}\) & \(2.78\times 10^{-1}\) & \(3.60\times 10^{-1}\) & \(2.50\times 10^{0}\) & \(2.93\times 10^{-1}\) \\ \({}^{137}\)Cs & \(2.90\times 10^{-1}\) & \(3.18\times 10^{-1}\) & \(5.81\times 10^{-1}\) & \(8.20\times 10^{-1}\) & \(2.50\times 10^{0}\) & \(6.65\times 10^{-1}\) \\ \({}^{93}\)Fe & \(1.01\times 10^{3}\) & \(1.07\times 10^{3}\) & - & - & \(2.50\times 10^{4}\) & \(1.47\times 10^{3}\) \\ \({}^{93m}\)I & \(1.52\times 10^{-1}\) & \(1.37\times 10^{1}\) & - & - & \(2.50\times 10^{2}\) & \(1.88\times 10^{2}\) \\ \({}^{93m}\)Nb & - & - & - & - & \(2.50\times 10^{2}\) & \(5.63\times 10^{3}\) \\ \({}^{94}\)Nb & \(2.60\times 10^{-1}\) & \(2.74\times 10^{-1}\) & - & - & \(2.50\times 10^{0}\) & \(2.62\times 10^{-1}\) \\ \({}^{63}\)Ni & \(2.68\times 10^{1}\) & \(3.00\times 10^{1}\) & \(1.48\times 10^{2}\) & \(5.47\times 10^{2}\) & \(2.50\times 10^{3}\) & \(5.03\times 10^{2}\) \\ \({}^{125}\)Sb & - & \(1.18\times 10^{0}\) & - & - & \(2.50\times 10^{0}\) & \(1.21\times 10^{0}\) \\ \({}^{121}\)ZnSn & - & - & - & - & - & \(6.01\times 10^{2}\) \\ \({}^{90}\)Sr & \(6.00\times 10^{-2}\) & \(6.29\times 10^{-2}\) & \(5.29\times 10^{-1}\) & \(1.75\times 10^{0}\) & \(2.50\times 10^{1}\) & \(8.42\times 10^{-1}\) \\ \({}^{93}\)Zr & - & - & - & - & \(2.50\times 10^{2}\) & \(6.75\times 10^{1}\) \\ \hline \end{tabular}  
\({}^{\bullet}\): Connecticut Yankee.  
\end{table} 
Table 5: _Cont._In addition, this study evaluated the effect of a change of input parameters on the final exposure dose result by using the sensitivity analysis feature of the RESRAD-ONSITE code. To that end, the sensitivity parameters for the 14 radionuclides were identified by applying the PRCC. Consequently, eight representative sensitivity parameters were derived as listed in Table 6. The sensitivity parameter that yielded the highest PRCC was the external gamma shielding factor, followed by the density of the contaminated zone, runoff coefficient, distribution coefficient (Kd), and evapotranspiration coefficient. Moreover, all the eight sensitivity parameters had positive correlations, and the deterministic values corresponding to the 75% quartile were derived accordingly. Furthermore, an analysis to evaluate the relative effect of changes in individual sensitivity parameters on the unrestricted site reuse criteria was also performed. To that end, the change of the site reuse criteria according to the change of input parameters was evaluated while increasing and decreasing the values of each sensitivity parameter by a factor of two. However, the input values for runoff coefficient and evapotranspiration coefficient among the sensitivity parameters were limited to the range of 0 and 1.