HEAT AND MASS TRANSFERS IN A CONCRETE WALL WITHCOMPOSITE LINER UNDER ACCIDENTAL CONDITIONS

摘要

The aim of this work was to study the behaviour of a concrete wall, covered with a composite liner andrnexposed to accidental conditions leading to high temperatures and pressures on a face of the material. In thernlaboratory, two practical levels of accidental situations (beyond design) have been considered. Firstly, the "SCI"rnscenario (accidental conditions) consisted of a rise from ambient conditions to a saturation point of 160℃, and arnpressure of 0.75 MPa in 12 hours, using the maximum increase possible with the apparatus. This rise was thenrnfollowed by cooling, leading to 0.22 MPa and 120℃ in 24 hours. These conditions were maintained for several days.rnSecondly, a "SC2" scenario (severe accident conditions) consisted of a rise to a saturation point of 173℃ and arnpressure of 1 MPa, these conditions were maintained for 24 hours before cooling.rnA cylindrical specimen of 1.3 m of thickness was used. Thermocouples, pressure taps and moisture gaugesrnwere implemented before concreting. These devices provided local information, and were mostly distributed in thernfirst 0.30 m of the concrete. The concrete composition (high performance concrete) was the same as that used for thernconstruction of the CIVAUX 2 nuclear power station.rnTypical experimental results for the evolution of temperature, pressure and water content as functions of timernare shown for the two test conditions. The concrete attached to the back of the composite dried, and a mass transferrnwas induced towards colder zones in the centre of the specimen. The liner acted as a heat insulator and the pressurernacting on the back of the composite remained lower than that applied on the composite. The residual adhesion of thernliner to the concrete was measured. Finally, the overall results allowed the comparison of situations where the wallrnwas lined and unlined, during exposure to SC 1 and SC2 conditions.