Since the level 2 PSA of OPR-1000 was the requirement for regulatory purposes, Cs-137 release estimation was contained as the Nuclear Safety Act of ROK in which the Cs-137 release frequency exceeding 100 TBq was determined to happen less than 1.0E-6 per year after the Fukushima Daiichi Accident. However, Cs-137 release estimation from the conventional level 2 PSA of OPR-1000 provided uncertainty due to dominant accident sequence consideration. Thus, this study aimed to develop systematic methods through the overall framework to quantify realistic uncertainty concerns of radioactive material release using sensitivity and uncertainty analysis methods and apply them to OPR-1000. This framework helped to quantify confidential value for the Cs-137 release under the BEPU approach using both parametric and non-parametric methods to cover both realistic and conservative points. Uncertainty propagation analysis showed the unexpected uncertainty increase of Cs-137 release exceeding 100 TBq. The non-parametric uncertainty analysis provided higher conservative concerns for safety than the realistic concerns in terms of economics when compared with the parametric uncertainty analysis. Wilks’ uncertainty analysis showed the importance to consider conservative Cs-137 release in order to reach the higher safety need. Sensitivity analysis showed reasonable relationships between engineering safety parameters with the Cs-137 release.

中文翻译：

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核电厂事故期间放射性释放到环境中分布的现实估计框架

由于 OPR-1000 的 2 级 PSA 是出于监管目的的要求，因此韩国《核安全法》中包含了 Cs-137 释放估算，其中确定超过 100 TBq 的 Cs-137 释放频率发生在小于 1.0E-福岛第一核电站事故后每年 6 起。然而，由于主要的事故顺序考虑，根据 OPR-1000 的常规 2 级 PSA 进行的 Cs-137 释放估算提供了不确定性。因此，本研究旨在通过总体框架开发系统方法，使用灵敏度和不确定性分析方法量化放射性物质释放的现实不确定性问题，并将其应用于 OPR-1000。该框架有助于量化 BEPU 方法下 Cs-137 释放的机密价值，使用参数和非参数方法来涵盖现实和保守点。不确定性传播分析显示，Cs-137 释放的不确定性意外增加超过 100 TBq。与参数不确定性分析相比，非参数不确定性分析对安全性的保守担忧高于经济上的现实担忧。 Wilks 的不确定性分析表明，为了达到更高的安全需求，考虑保守的 Cs-137 释放非常重要。敏感性分析表明工程安全参数与Cs-137释放之间存在合理的关系。