DIRECT CONTAINMENT-HEATING EXPERIMENTS FOR VANDELLOS AND ASCO NUCLEAR-POWER-PLANTS

The ongoing IPE studies for the Vandellos and ASCo nuclear power plant s require evaluation of accident phenomena that have been perceived to potentially challenge containment integrity including direct containm ent heating (DCH). Analyses and scaled experiments performed to date i ndicated that the lower containment structures play a substantial role in mitigating the extent of DCH given a high pressure melt ejection. Since the geometry is judged to be of major importance, linearly scale d experiments were conceived and conducted to evaluate the role of suc h structures in the Vandellos and ASCo specific configurations. The Va ndellos test configuration with an initally dry cavity and significant exhaust area for the instrument tunnel resulted in the dispersal of a majority of the debris from the instrument tunnel into the lower comp artment. The test of the ASCo configuration with an initially wet reac tor cavity and limited exhaust area from the instrument tunnel exhibit ed the retention of the majority of the debris within the instrument t unnel and reactor cavity. The observed pressure responses in these sca led experiments for the seal table room, lower containment vessel, and upper containment vessel were all less than the containment design ba sis pressure. These test results contribute to the existing technical basis for concluding that direct containment heating would not represe nt a challenge to the integrity of these containments.