## 3 Methodology
### Matching Phase:  
Decontamination and decommissioning of the shield structure of the nuclear power plant can be considered a specific type of decommissioning and demolition operation within the construction process, hence the same standards can be applied. We therefore matched the main work tasks and their characteristics based on the similarities between decontamination and decommissioning and construction to derive the risks. This type of risk derivation and assessment system that takes into account site characteristics can be utilized as a tool for preliminary inspections of actual sites [32,33]. First, in order to identify and specify appropriate risks for the decontamination and decommissioning processes for the concrete shield structure of the nuclear power plant, we listed the decontamination and decommissioning processes involved and their possible risks by work type. This consisted of three levels: work type (Level 1), work content (Level 2), and work details (Level 3). Level 1 includes the main tasks that are performed for each step, Level 2 describes the types of risks associated with each of these main tasks, and Level 3 provides detailed descriptions of the tasks performed (work location/work object/work equipment) for each item listed in Level 2. According to a report by the US Department of Energy (DOE, 1998), structural risk management is vital in the decontamination and decommissioning of nuclear power plants, as the activities involved have similar characteristics to the original construction process. Therefore, possible structural and job risks were derived for each process based on the similarities between construction and decontamination and decommissioning for this study, focusing on the structural and decommissioning job risks that may arise during the direct decommissioning of shield structures. The example shown in Table 4 presents details of the cutting processes involved in: (1) the site preparation; (2) the decontamination process; (3) the various drilling and cutting demolition activities; and (4) the equipment transportation and the removal of the decontamination and decommissioning products, based on the decommissioning work breakdown structure of the TRIGA Mark-III reactor, which was decommissioned in 2005 following the guidelines provided in the IAEA's nuclear power plant decommissioning package (IAEA, 1999). The process is divided into wire saw installation, cutting, and residual concrete removal, which are further divided into four tasks. \begin{table}
\begin{tabular}{c c l} \hline \hline
**Risk** & **Item** & **Description** \\ \hline \multirow{4}{*}{Structural risks} & Collapse & Structures or temporary objects (equipment, machines, scaffolds, etc.) fall over or collapse \\  & Drop & Decommissioned or temporary objects (equipment, machines, scaffolds, etc.) drop from a high platform to a low platform \\ \hline \multirow{4}{*}{Job risks} & Eye attack & Victim’s eyes are exposed to dust and similar materials \\  & Fall & Worker falls from a high platform such as a structure, \\ \cline{1-1}  & Jam & Worker is caught between moving objects, or twisted or \\ \cline{1-1}  & Electric shock & Direct by a rolling body or protrusion \\ \cline{1-1} \cline{2-3}  & & Current flows through a worker’s body \\ \hline \hline \end{tabular}
\end{table} 
Table 3: Structural and job risks associated with decommissioning a bio-shield structure. We derived the risks for each decontamination and decommissioning process via the matching process described above (the Matching Phase in Figure 2) based on the construction industry hazard profile and the decontamination and decommissioning processes required by nuclear power plant shield concrete structures, configured above.