A Probabilistic Physics of Failure Approach to Prediction of Steam Generator Tube Rupture Frequency

摘要

In probabilistic safety assessments of pressurized water reactors, it is imperative to assess the potential and frequency of steam generator tube rupture failures. Estimation of frequency of steam generator tube ruptures has traditionally been based on historical occurrences, which are not applicable to new designs of steam generators with different geometries, material properties, degradation mechanisms and thermal-hydraulic behaviors. This paper presents a new probabilistic mechanistic-based approach for estimating steam generator tube rupture frequencies that is based on the principle that failure of passive systems is governed by degradation or unfavorable conditions created through the underlying operating conditions and underlying mechanical, electrical, thermal, and chemical processes. As opposed to using the historical data for reliability prediction, the developed probabilistic physics-of-failure based approach identifies, probabilistically models, and simulates potential degradations in new and existing steam generator designs to assess degradation versus time, until such degradation exceeds a known endurance limit. An example application of proposed probabilistic physics-of-failure based reliability prediction approach has been presented for a new design of steam generators consisting of helical tubes and more advanced tube material. The developed probabilistic physics-of-failure based approach when combined with probabilistic safety assessment techniques can provide an effective tool for the evaluation of safety and reliability of steam generators, particularly new steam generator designs used in advanced reactors.