Intrinsic effects of Cr-layered accident-tolerant fuel cladding surface on reflood heat transfer

Abstract

A transient flow quench experiment was conducted to investigate the reflood heat transfer of a Cr-layered vertical tube, which is considered to be the most promising candidate for an accident-tolerant fuel cladding application. Cr was physically deposited on a stainless-steel tube by using DC magnetron sputtering. Owing to the increased nanoscale features of the Cr coating, the surface showed an enhanced capillary wicking potential with superhydrophilic characteristics. In addition, an oxidized Cr-coated specimen was prepared to examine the effects of oxidation during normal operations and blowdown phases in a loss-of-coolant accident. After being heated to 740 °C, the specimens were subjected to a continuous flow of deionized water and heat generation with varying coolant subcooling. The temperature history during quenching was recorded, and the quench behavior was visualized using a high-speed camera. The quench performance, including the quench temperature, critical heat flux, film boiling heat transfer coefficient, and quench front velocity, was analyzed for each specimen by performing an inverse heat conduction analysis. The effects of the Cr coating and oxidation were found to have different impacts on the quench performance, depending on the coolant subcooling and boiling regimes.