Probabilistic assessments allow the uncertainties present in reactor design and operation to be understood and reflected in the quantification of reliability. Increased awareness of the limitations of deterministic structural integrity assessments have highlighted that the unquantified margins do not provide an adequate measure of component risk.

The R5 procedure is a “UK nuclear power industry standard, frequently used in safety cases for structural integrity assessments of Advanced Gas-Cooled Reactor components operating in the creep range” [Assessment Procedure R5, EDF Energy Nuclear Generation Ltd.]. Within this procedure, Volume 2/3 covers creep-fatigue crack initiation in defect-free structures and a drafted appendix provides guidance on the application of probabilistic approaches.

A review of probabilistic approaches using the R5 procedure has been conducted, including a wider review of probabilistic assessments to ascertain general good practice. The review identifies a lack of consistency in the reporting of probabilistic assessments, particularly for correlations and convergence of outputs. Providing a structured method for reporting probabilistic assessments would be valuable to ensure consistent application and enable reproducibility of results.

概率评估使反应堆设计和运行中存在的不确定性得以理解，并反映在可靠性量化中。人们对确定性结构完整性评估的局限性的认识不断提高，这突显了未量化的边距不能提供足够的组件风险度量。

R5程序是“英国核电行业标准，在安全案例中经常用于对在蠕变范围内运行的先进气冷堆的部件进行结构完整性评估” [EDF能源核能有限公司，评估程序R5]。在该程序中，第2/3卷涵盖了无缺陷结构中的蠕变疲劳裂纹萌生，并且起草的附录为概率方法的应用提供了指导。

已经使用R5程序对概率方法进行了审查，包括对概率评估进行更广泛的审查，以确定一般的良好实践。审查发现，概率评估的报告缺乏一致性，特别是在产出的相关性和趋同性方面。提供用于报告概率评估的结构化方法对于确保一致地应用和实现结果的可重复性将是有价值的。