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首页> 外文会议>ASME(American Society of Mechanical Engineers) Pressure Vessels and Piping Conference: Design and Analysis of Ressure Vessels and Piping: Implementation of ASME B31, Fatigue, ASME Section VIII, and Buckling Analyses; 20030720-20030724; Cleveland,OH; US >THE SENSITIVITY OF PRESSURIZED THERMAL SHOCK ANALYSIS RESULTS TO ALTERNATIVE MODELS FOR WELD FLAW DISTRIBUTIONS
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THE SENSITIVITY OF PRESSURIZED THERMAL SHOCK ANALYSIS RESULTS TO ALTERNATIVE MODELS FOR WELD FLAW DISTRIBUTIONS

机译：焊接缺陷的交替模型对热冲击分析结果的敏感性

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The United States Nuclear Regulatory Commission (USNRC) initiated a comprehensive project in 1999 to determine if improved technologies can provide a technical basis to reduce the conservatism in the current regulations for pressurized thermal shock (PTS) while continuing to provide reasonable assurance of adequate protection to public health and safety. A relaxation of PTS regulations could have profound implications for plant license renewal considerations. During the PTS re-evaluation study, an improved risk-informed computational methodology was developed that provides a more realistic characterization of PTS risk. This updated methodology was recently applied to three commercial PWRs. The results of this study provide encouragement that a technical basis can be established to support a relaxation of current PTS regulations. One significant model improvement applied in the PTS re-evaluation study was the development of flaw databases derived from the non-destructive and destructive examinations of material from cancelled reactor pressure vessels (RPV). Empirically-based statistical distributions derived from these databases and expert illicitation were used to postulate the number, size, and location of flaws in welded and base metal (plate and forging) regions of an RPV during probabilistic fracture mechanics (PFM) analyses of RPVs subjected to transient loading conditions such as PTS. However, limitations in the available flaw data have required assumptions to be made to complete the risk-based flaw models. Sensitivity analyses were performed to evaluate the impact of four flaw-related assumptions. Analyses addressed: 1) truncations of distributions to exclude flaws of extreme depth dimensions, 2) vessel-to-vessel differences in flaw data, 3) large flaws observed in weld repair regions, and 4) the basis for estimating the number of surface breaking flaws. None of the four alternate weld flaw models significantly impacted calculated vessel failure frequencies or invalidated the tentative conclusions derived from the USNRC PTS re-evaluation study.
机译：美国核监管委员会（USNRC）于1999年发起了一个综合项目，以确定改进的技术是否可以提供技术基础，以减少现行的加压热冲击（PTS）法规中的保守性，同时继续为以下方面提供充分的保护：公共卫生与安全。放宽PTS法规可能对工厂许可证续签的考虑产生深远影响。在PTS重新评估研究期间，开发了一种改进的风险知情计算方法，该方法可更真实地描述PTS风险。最近将这种更新的方法应用于三个商业PWR。这项研究的结果令人鼓舞，可以建立技术基础来支持放宽当前的PTS法规。在PTS重新评估研究中应用的一项重大模型改进是开发了缺陷数据库，该缺陷数据库源自对已取消反应堆压力容器（RPV）的材料进行的非破坏性检查和破坏性检查。从这些数据库中获得的基于经验的统计分布和专家的启发被用于假设RPV的概率断裂力学（PFM）分析过程中RPV的焊接和母材（板和锻件）区域的缺陷的数量，大小和位置到瞬态负载条件（例如PTS）。但是，可用缺陷数据的局限性要求进行假设以完成基于风险的缺陷模型。进行了敏感性分析，以评估四个缺陷相关假设的影响。分析涉及：1）截短分布以排除极深尺寸的缺陷； 2）缺陷数据的容器间差异； 3）在焊缝修复区域观察到的大缺陷；以及4）估计表面破裂次数的基础缺陷。四个替代焊缝缺陷模型均未显着影响计算的容器故障频率或使从USNRC PTS重新评估研究得出的初步结论无效。

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