# Activity Evaluation Methodology for the Disposed Medical Linear Accelerators
## 5 Conclusions  
We proposed a simple methodology for evaluating radioactivity in radioactive materials generated during medical linac disposal. Using an in situ HPGe detector and survey meter, we identified the radionuclides of each component, and radioactivity was calculated. According to Japanese regulations, when the dose rates for the components are similar to the dose rate of the background, it is allowed to be self-disposed. Based on Canadian regulations, we can expect that all the components except the target, 15 MV collimator, and 15 MV filter can be cleared on the decommissioning day.  
The proposed method will be potentially beneficial as a general framework for establishing the linac radioactivity evaluation and safety management standards. Furthermore, it is expected that it can also be applied to the radiation evaluation field of linear accelerators and high-energy particle accelerators from other manufacturers.  
Conceptualization, N.H.K. and S.H.C.; Data curation, Y.J.J.; Formal analysis, Y.J.; Funding acquisition, D.W.K. and S.H.C.; Investigation, K.B.K.; Methodology, N.H.K. and J.H.Y.; Project administration, S.H.C.; Supervision, J.K. and D.W.K.; Validation, K.B.K. and J.K.; Writing--original draft, N.H.K.; Writing--review and editing, S.H.C. All authors have read and agreed to the published version of the manuscript.  
The Nuclear Safety Research Program supported this work through the Korea Foundation of Nuclear Safety (KoFONS) using financial resources granted by the Nuclear Safety and Security Commission (NSSC) of the Republic of Korea (No. 2003013, No. 20205013) and the National Research Foundation of Korea (NRF) grant funded by the Korean government (No. 2020 MZD9A3094170, RS-2022-00144201).  
Not applicable.  
\begin{table}
\begin{tabular}{l c c c c c c} \hline \hline  & \multicolumn{2}{c}{**Self-Disposal**} & \multicolumn{3}{c}{**On the Day of Disposal**} & \multicolumn{2}{c}{**Five Weeks after Disposal**} \\ \cline{2-7}
**Component** & **Reference** & **Criteria** & **Surface** & **Activity** & **Difference Rate** & **Device Rate** & **Activity** \\  & **Nuclide** & **(Bq/g)** & **(μSv/h)** & **(Bq/g)** & **(μSv/h)** & **(Bq/g)** \\ \hline Target & \({}^{196}\)Au & 0.1 & 26.856 & 1471.58 & 7.049 & 382.20 \\ Target holder & \({}^{60}\)Co & 0.1 & 0.949 & 8.77 & 0.57 & 4.85 \\ Scattering foil & \({}^{60}\)Co & 0.1 & 0.654 & 381.64 & 0.414 & 216.31 \\
15 MV primary collimator & \({}^{60}\)Co & 0.1 & 7.65 & 60.78 & 7.002 & 55.57 \\
6 MV primary collimator & \({}^{60}\)Co & 0.1 & 0.223 & 0.99 & 0.262 & 1.30 \\
15 MV flattening filter & \({}^{60}\)Co & 0.1 & 6.966 & 743.82 & 3.636 & 383.07 \\
6 MV flattening filter & \({}^{60}\)Co & 0.1 & 0.202 & 132.60 & 0.16 & 78.00 \\ Ion chamber & \({}^{60}\)Co & 0.1 & 0.208 & 7.73 & 0.118 & 1.29 \\ Y jaw & \({}^{60}\)Co & 0.1 & 0.208 & 3.40 & 0.118 & 1.42 \\ MLC & \({}^{60}\)Co & 0.1 & 0.19 & 9.96 & 0.134 & 5.24 \\ Shielding block & \({}^{124}\)Sb & 0.1 & 0.798 & 3.42 & 0.392 & 1.81 \\ \hline \hline \end{tabular}
\end{table}
Table 6: Radioactivity calculated using the Japanese radioactive waste management methodology.