Abstract
In-Vessel Retention (IVR) strategy is one of the most important severe accidents mitigation strategies. The Critical Heat Flux (CHF) is an important key element in the assessment of IVR efficiency. How to increase the CHF is a significant method to make sure the IVR success. Heating surface characteristics in an important factor to increase CHF of downward facing boiling surface. This paper aims to study the influence of the different roughness, surface coating, and surface aging on CHF through the mechanism experiments. An experiment facility combining both pool boiling and flow boiling operating modes was designed and taken to carry out series of CHF tests for downward facing surface. It was found that the CHF nearly maintain the same when the roughness Ra achieved a certain value (∼2.0μm), however the CHF with the roughness Ra below this value, the result showed that the nanoparticle deposited surface will enhance the CHF than the smooth surface. The influence of the different surface characteristics had different enhancement, and all surface process enhanced the CHF than smooth surface. It will be helpful to process the surface of the lower head wall when design the IVR management.
