Comparison of the Relative Importance of Copper Precipitates and Point Defect Clusters in Reactor Pressure Vessel Embrittlement

摘要

Embrittlement of reactor pressure vessel (RPV) steels is believed to arise primarily from matrixc hardening due to the formation of radiation-induced point defect clusters (PDC) and radiation-enhanced, copper-rich precipitates (CRP). A model has been developed to investigate the relative importance of PDC and CRP in RPV embrittlement. The model has been used to determine the influence of a range of irradiation and material parameters on the predicted change in yield strength. The results indicate that there are temperature and displacement rate regimes wherein eith er CRP or PDC can domiate the material's response to irradiation. Both interstitial land vacancy type defects contribute to the PDC component. The different dependencies of the CRP and PDC on temperature and displacement rate indicate that simple data extrapolations could lead to poor predictions of RPV embrittlement. Fortunately, the yield strength changes predicted by the composite PDC/CRP model exhibit very little dependence on displacement rate below about 5 x 10-9 dpa/s. If this result is confirmed, concerns about accelerated displacement rates in power reactor surveillance programs should be minimized. The sensitivity of the model to microstructural parameters highlights the need for more detailed characterization of RPV steels.