The purpose of this paper is to provide a case study that compares the results from a consequence-based facility siting study (FSS) limited to a specified release size as the maximum credible event (MCE) versus a risk-based study with a range of release sizes and associated frequencies. The results are intended to highlight potential differences in the building siting decisions made using a consequence-based approach with a limited MCE versus those made with a risk-based approach. Most recommended practices and other FSS guidance documents advise evaluating MCEs for an FSS. However, there can be uncertainty in MCE selection and the values used in industry span a considerable range. Arguments for limiting the MCE in a consequence-based FSS to a 2-in. release include that most accidental releases (i.e., > 95%) are smaller and that a 2-in. release size is the largest that provides actionable information upon which siting decisions can be made. However, a number of well-known incidents in industry involve releases larger than 2-in., which introduces uncertainty as to a reasonable upper-bound for an MCE. The use of a risk-based FSS approach effectively eliminates the decision regarding release size since this approach aggregates the full range of operational scenarios and release sizes along with the associated likelihood of failure. Based on the MCE scenario(s) employed and the criteria selected, consequence-based and risk-based FSS evaluations for a given site may lead to very different conclusions as to which buildings are considered safe and what types of mitigation actions should be taken.

中文翻译：

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设施选址——协商“最大可信事件”的雷区

本文的目的是提供一个案例研究，将基于结果的设施选址研究 (FSS) 的结果进行比较，该研究仅限于作为最大可信事件 (MCE) 的指定释放大小与具有一系列范围的基于风险的研究释放大小和相关频率。结果旨在强调使用基于结果的方法和有限的 MCE 做出的建筑选址决策与使用基于风险的方法做出的决策的潜在差异。大多数推荐的做法和其他 FSS 指导文件都建议为 FSS 评估 MCE。然而，MCE 选择可能存在不确定性，工业中使用的值跨越相当大的范围。将基于结果的 FSS 中的 MCE 限制为 2 英寸的参数。释放包括大多数意外释放（即 > 95%）较小，并且 2 英寸。发布大小是最大的，它提供了可用于做出选址决策的可操作信息。然而，行业中许多众所周知的事件涉及大于 2 英寸的释放，这给 MCE 的合理上限带来了不确定性。使用基于风险的 FSS 方法有效地消除了关于发布规模的决定，因为该方法汇总了所有操作场景和发布规模以及相关的失败可能性。根据所采用的 MCE 情景和选择的标准，针对给定场地的基于后果和基于风险的 FSS 评估可能会得出非常不同的结论，即哪些建筑物被认为是安全的以及应该采取哪些类型的缓解措施。