Abstract: The new French dam safety regulation classifies each dam in 4 classes depending on its height and the volume of water it stores. The first two classes require each owner to establish a safety report for an authority review. A main objective of this report is to demonstrate that all hazardous scenarios have been taken into account by the dam owner in assessing the risk level and also that sufficient safety measures have been specified to reach a global risk as low as reasonably possible. First, considering all existing data and characteristics of the dam, the owner has to carry out a risk analysis to identify all failure modes that may occur on dam structure and hydraulic equipment. Every potential accident is then characterized in terms of severity of consequences and annual occurrence probability. The severity level is assessed quantitatively or qualitatively, using a combination of maps representing the effects of the flood waves and the Population At Risks. The probability is assessed using a semi-quantitative method analyzing all scenarios and safety measures involved in prevention and protection: the bow-tie approach. This cross analysis implements an iterative approach to highlight complementary measures and recommendations and therefore enhance global safety level.

Key words: major accident, risk analysis, severity, probability, risk acceptability

摘要： 根据大坝高度和其水库蓄水库容，新的法国大坝安全管理条例将大坝分为4类。前2类要求业主完成安全报告供当局复核。该安全报告的主要目的是表明所有风险情况都已被业主纳入了风险等级评估的考虑范围，并且为实现将整体风险降低到合理可行的最低水平，已根据每座坝的具体情况采取了充分的安全措施。首先，结合目前现有的数据和大坝特性，业主需开展风险分析，以确定可能发生在大坝建筑结构和水力设备上的所有失效模式。然后就后果严重性和年发生概率对每种潜在事故进行特性分析。使用可显示洪波影响作用和风险人口的综合地图对严重性等级进行定量或定性评估。采用半定量方法分析所有情况和预防止保护安全措施，该方法即蝴蝶结法，以此方法来评估概率。综合分析采用了迭代方法来强调互补的措施和建议，以提高整体安全等级。

关键词: 主要事故, 风险分析, 严重性, 概率, 风险接受