Post DNB Heat Transfer Characteristics of PWR Fuel Assemblies and their Evaluation

Abstract

In the thermal-hydraulic design of Pressurized Water Reactor, the departure from nucleate boiling (DNB) under the anticipated transients is not allowed. However, it is recognized that DNB dose not cause the fuel rod failure if the fuel rod temperature after DNB is not so high and the film boiling duration time is not so long. To establish the evaluation method of the heat transfer behavior after DNB, the post-DNB heat transfer experiments for PWR fuel assemblies were performed under the sponsorship of Ministry of Economy, Trade and Industry (METI). Based on the obtained experimental data, the post-DNB heat-transfer correlation, the model of the axial propagation of the film-boiling region after DNB and the model of the rewet front progress were investigated.