Influences of some engineered factors on IVR-ERVC limits

Abstract

In-vessel retention (IVR) through passive external reactor vessel cooling (ERVC) has been adopted as one of the key severe accident mitigation strategies for Chinese-designed large-scale advanced passive pressurized water reactor. From the view of thermal load effectiveness, critical heat flux (CHF) of reactor pressure vessel (RPV) out wall has been taken as one of the key criteria for IVR-ERVC feasibility. In order to investigate the ERVC limits, as well as its performance during IVR-ERVC process, a campaign of CHF tests under real plant conditions is conducted on the full-height REPEC-II facility, which has been designed according to the prototypic ERVC configuration and verified following an integrated, hierarchical scaling approach. Based on the abundant results acquired in the tests, it is attempted, in this paper, to summarize and evaluate ERVC performances and trends under various practical engineered conditions. The main evaluation results includes: influences on CHF of RPV out wall with various non-uniform heat load distribution and ERVC channel configurations, effects of subcooling, heating surface conditions (prototypic surface material and its oxidization) and water chemistry on external cooling limits, etc. These are expected to help designers with reliable estimation on impact of some related engineered factors on real IVR-ERVC performance.