On the history and status of reactor pressure vessel steel ductile to brittle transition temperature shift prediction models

[摘要] This paper melds an overview of the history of Reactor Pressure Vessel (RPV) embrittlement research, focusing on predicting ductile-to-brittle transition temperature shifts (Delta T), along with an assessment of the current status of these efforts, especially for extended life operation. The 60-year history of RPV research reveals remarkable progress on a very complex and challenging problem that has, for several decades, been a paradigm for a 'science in service of engineering' approach to a critical technological challenge. This research has laid the foundation for properly analyzing modestly accelerated materials test reactor (MTR) data to make robust Delta T predictions beyond the current low flux (phi) power reactor surveillance database. We show that most current models, that are accurate at lower fluence (phi t), systematically and significantly underpredict Delta T at high phi t, largely owing to the currently unaccounted for contribution of late blooming MnNiSi precipitates (MNSPs). We propose a simple empirical approach to predicting Delta T between phi t approximate to 4 x 10(23) n/m(2) (the currently reliable Delta T model limit) and 14 x 10(23) n/m(2) (for extended life). The method is shown to be empirically robust, and is supported by a microstructurally informed physical model. In addition to quantifying the role of MNSPs, important observations include approximately linear Delta T dependence at high phi t (versus the previous approximate to root phi t trend at lower phi t), and a diminution of the effect of phi. The decreased phi effect at high phi t has very important implications for the use of accelerated MTR data to predict service relevant DT. (C) 2019 Elsevier B.V. All rights reserved.

[发布日期] 2019-12-01

[关键词] RPV embrittlement;Charpy shifts;Copper rich precipitates;Manganese-nickel-silicon precipitates;Radiation-enhanced diffusion;Avrami models;Irradiation hardening