Experimental investigation on heat transfer in transient boiling

Overview & Synopsis

During reactivity initiated accidents in a core of a nuclear reactor, a power excursion occurs on some fuel rods. The consequent rapid boiling is a matter of study for the nuclear power plants safety evaluation, because of the risk for rod-clad failure. In order to better understand the influence of power excursions and to characterise the phases of the rapid boiling phenomenon, an experimental set-up has been built at IMFT. The test section is a semi annulus. The inner half cylinder is made of a stainless steel foil, heated by Joule effect. Its temperature is measured by an infrared camera filming the backside of the foil, coupled with a high-speed camera for the visualisation of the phenomena. Measurements were made for two types of tests: when a square current signal is applied to the foil and when the current output follows a triangular shape. These measurements showed the influence of both shape and value of the supplied power and of the temperature increase rate on the wall temperature during boiling.