Experiment techniques in bottom reflooding of hot channels

A hypothetical loss of coolant accident (LOCA) in water cooled reactors may result in rapid heating of the fuel channels. To prevent the fuel from reaching a metallurgical prohibited temperature, safety systems are available to reflood the core by cold water. The reflooding phase of thr LOCA essentially terminates the accident and provides a long term cooling. The present paper describes a few novel experimental techniques and facilities developed for transient two-phase flow measurements during bottom reflooding of hot channels. It concentrates mainly on the detection of void fraction by gamma-ray attenuation, the instantaneous mass balance measurement of the two phase using a phase separator and on a metering device for measuring low vapor flowrate. (author)