CINEMA 코드를 이용한 OPR1000 대형 배관 파단 사고 불확실도 분석

Abstract

Severe accidents in nuclear power plants are commonly simulated with integral system codes such as MAAP, MELCOR, and CINEMA. This study proposes a methodology for the uncertainty analysis applied to OPR1000, a large-scale nuclear power plant, under a severe accident scenario. The scope of this paper is narrowed down to a specific severe accident case: LBLOCA (large break loss of coolant accident). The objective of quantifying uncertainties in severe accident analysis is to address limitations in phenomenological models, operator action and mechanical system behavior. Since single-point predictions are insufficient to capture the range of possible outcomes, severe accident evaluations must be accompanied by uncertainty analysis of both the codes and the underlying phenomena. For this purpose, this study adopts CINEMA (Code for INtegration of severe accident Evaluation and MAnagement), a system code dedicated to severe accident analysis. The key FOMs (Figure of Merits) adopted in this study are SAMG (Severe Accident Management Guidelines) entry timing, CsI (cesium-iodine) release fraction, reactor vessel failure timing, the relocation to lower plenum timing, and the total mass of hydrogen generation. By designating these FOMs, the study identifies the relationship between the input variables and outcomes, elucidating the underlying sources of uncertainty, and suggest methodological apporacahes to reduce the uncertainty for the target FOMs. The result demonstrates that the outputs remain within acceptable envelopes across the sampled input space, indicating numerically stable performance and credible predictive capability of CINEMA. The results show that CINEMA can support safety assessments and emergency-strategy optimization for LBLOCA scenarios.