NUMERICAL SIMULATION OF SURFACE TENSION DRIVEN FLOWS AND BORON CONCENTRATIONS AROUND A VAPOR BUBBLE DURING SUB-COOLED POOL BOILING IN BORIC ACID SOLUTION

摘要

In this study, the previously developed hemispherical bubble model has been extended to a full spherical bubble, in which the bubble contact angle can range from 0° to 90°. The surface tension driven flow and boron concentration distributions around the bubble under sub-cooled boiling are simulated with constant wall temperature. Bubble contact angle and sub-cooling level are studied on their effects on boron concentration distribution. Boron precipitation under these circumstances is discussed. This is of possible concern in precipitation of boron from the solution at the triple interface during sub-cooled boiling. The deposition of porous compounds on fuel cladding provides one of the possible hideout mechanisms for Boron, which may eventually result in Axial Offset Anomaly (AOA) in PWRs.