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A Method for Combination of Top-down and Bottom-up Approaches for Scenario Development
- 언어ENG
- URLhttps://db.koreascholar.com/Article/Detail/430856
p.230
To prove the long-term safety of deep geological repository, the safety assessment is needed to ensure that the expected performance of repository satisfies the regulatory standards. Scenario development is process of analyzing events and evolutions that can directly or indirectly affect the performance of a disposal system and is a pre-step for quantitative safety assessment. Scenarios are used to identify and define cases to be assessed by numerical modeling, and cases are mainly divided into normal (also called the ‘reference’ and ‘expected evolution’) and abnormal scenarios. Mainly two approaches have been used to set up scenarios. One is a bottom-up approach that starts with features, events and processes (FEPs). This approach can analyze the evolution and events related to the performance of the disposal system in an inductive manner. The other is top-down approach that analyzes the events and evolution of disposal system, focusing on situations that may affect the safety function of the components. This approach starts with a set of intuitively predefined expected failures of safety function. Combining the two approaches is more effective in demonstrating comprehensiveness which is a main challenge of scenario analysis, and almost national radioactive waste management institutions combine top-down and bottom-up approaches for development of scenarios. An approach combining the two approaches is called a hybrid approach, and the detailed method differs from each institution and has not been determined. In this study, some work for constructing the scenario using hybrid approach was performed. Firstly, defining each component’s safety function and screening FEPs according to several rules were performed for a generic repository. Secondly, we extracted performance factors that are considered likely to affect safety functions. And lastly, we integrated FEPs correlated with performance factor to simplify the analysis. These results will be material to construct the scenario using hybrid approach.
