## 3 Methodology  
This study sought to develop a process for evaluating the structural and job risks involved in the nuclear decommissioning process using the fuzzy theory proposed by [PERSON] (1965). For this purpose, we divided the research into three stages, namely (1) risk identification, (2) data collection, and (3) conduct measurement (Figure 1).  
Figure 1: Flow of research methodology.  
The case study for the risk assessment methodology developed from the results of this study is the Kori-1 nuclear power plant. This is the Korea's first commercial nuclear power plant and type is pressurized-water reactor type. The facility was shut down on June 19, 2017, after 39 years of commercial operation, and decommissioning is currently in progress.  
For this study, a risk assessment was carried out for the shield concrete structure as this suffers the greatest number of structural and job-related accidents within the entire nuclear power plant decontamination and decommissioning process. The technological methods utilized to perform concrete decommissioning generally include cutting and crushing; in this case, a diamond wire saw was used for cutting up the concrete, to alleviate public concerns.  
Step 1. Risk identification:  
Figure 2 shows a flow chart of the structural and job risks associated with each process using a matching process based on similarities between construction and decontamination and decommissioning operations. The risk list was created by considering the characteristics of construction and decontamination and decommissioning, and the risks matched for each process based on those potentially encountered during the decontamination and decommissioning of a nuclear reactor concrete structure. These were identified in previous studies, including a case study that described the decommissioning and demolition of a research nuclear reactor and the development of a work breakdown structure (WBS) for reactor decommissioning and demolition [28].  
Step 1.1. Preparation Phase:  
Unlike existing risk assessment methods, this study classified the risks for each process in terms of the work type, structural risks, and job risks (Tables 2 and 3). The risk list was created based on the construction risks identified in the OSHA standard, which is widely used in the construction industry [29]. In addition, to account for the special characteristics of the decontamination and decommissioning process for nuclear facilities, we consolidated/added/deleted risk items by considering the risks presented by the IAEA to create the final risk list [30].  
\begin{table}
\begin{tabular}{c c} \hline \hline
**Classification** & **Hazards** \\ \hline Potential hazards for construction workers [29] & Falls, trench collapse, scaffold collapse, electric shock and arc flash/arc blast, failure to use proper personal protective equipment, repetitive motion injuries Fire, explosion, flooding, toxic and hazardous materials, electrical hazards, physical hazards, human and organizational initiating events \\ \hline \hline \end{tabular}
\end{table}
Table 2: Work hazards.  
Figure 2: Risk identification step process.  
We derived the most problematic structural and job risks in order to use the developed risk assessment methodology to establish a decommissioning process plan in accordance with the ALARA principle (As Low As Reasonably Achievable) [31]. Here, structural risks refer to potential damage to the structure itself due to various hazards encountered during decontamination and decommissioning, as well as damage to temporary structures or the heavy equipment used in decommissioning, while job risks refer to direct physical injuries experienced by workers on the site due to disasters and accidents.