## 6 Conclusions and Discussion  
In this study, we proposed a framework that can quantitatively present subjective judgments or evaluations of ambiguous and qualitative experts about the safe degree of decommissioning work of bio-shield structure in nuclear power plant. First of all, we derived the risks for each decontamination and decommissioning process via the matching process based on the construction industry hazard profile and the decontamination and decommissioning processes. Subsequently, an assessment model was developed and the safety performance of risks elicited was conducted measurement. Existing risk assessments for the decontamination and decommissioning of nuclear facilities have generally focused on the radiological factors involved. In addition, if risk scores must be consolidated based on an unclear correlation between radiological, non-radiological, and structural risks, there is a limitation that it becomes far more difficult to control the consolidation method for each factor or any fluctuations in the risk score after consolidation. This paper highlights the problems caused by these existing deterministic risk assessment methods and suggests a risk assessment methodology that incorporates fuzzy functions as a viable alternative approach. The following results were obtained through the risk assessment case study of cutting work performed as part of the decontamination and decommissioning of the Kori-1 nuclear power plant by applying the proposed assessment methodology. First, using the fuzzy analysis model, we proposed a methodology in which the function is configured so that the assessor can respond to a range of risks even while knowing only the approximate opinion of the nuclear power plant decontamination and decommissioning experts rather than precise information, thereby enabling the assessor to develop a better understanding of the important decision-making characteristics. Second, we classified the risks for each process in terms of work type, structural risk, and job risk, and developed a risk classification system that analyzes and compares alternatives through a multidimensional approach. While the previous deterministic studies were difficult to reflect the structural characteristics of each bio-shield structure in a uniform risk assessment method, the risk assessment model developed in this study reflects the characteristics of nuclear power plant decontamination and dismantling work, so it is possible to assess the risks according to the situation. Third, we proposed a fuzzy number weighted average analysis model, which was then employed to develop a methodology to relatively assess risks that are difficult to compare directly. Existing risk assessment methods have limitations in establishing a specific safety plan because there is no distinction between detailed tasks. On the other hand, the risk assessment method developed in this study is based on suggesting strategies such as safety behavior rules through analysis of changes in relative risk when applying alternatives. The fuzzy based risk assessment model proposed in this study can reduce the risk of prediction failure compared to the results of the existing deterministic risk assessment model. This will enable personnel to assess various risks of decontamination and decommissioning work of nuclear power plant structures that cannot be quantitatively assessed owing to the lack of data. Further, the proposed fuzzy based risk assessment model can be extended to cover risk assessment exercises in other engineering fields that are dependent on the judgment of experts and also suffer from a lack of available statistical data and the difficultly of relatively assessing factors. In future work, we plan to move on to develop an overall risk assessment process and step-by-step comparative analysis model for decontamination and decommissioning by extending the risk assessment to the pre- and post-operation phases of cutting based on the proposed fuzzy based risk assessment model.