Experimental investigations on penetration failure by tube ejection for an APR1400 ICI nozzle during a severe accident

•Tube ejection experiments were performed for an APR1400 ICI nozzle.•We used ZrO2 and UO2-ZrO2 melts and pressurized the ICI nozzle up to 1.3–3.2 bar.•No tube ejection occurred in all the tests despite the tube weld failure.•Non-tube ejection experimental results were not estimated by the existing criteria.•Tube ejection was prevented by ERVC with maintaining the integrity of tube weld. This paper describes experimental investigations on the penetration failure by tube ejection for an APR1400 in-core instrumentation nozzle during a severe accident. The penetration tube specimens interacted with around 2500 °C ZrO2 and UO2-ZrO2 melts and pressurized up to 1.3–3.2 barg. The ERVC (external reactor vessel cooling) effect on the tube ejection was investigated under the maximum heat removal of 466 kW/m2 by water flow at 2.5 m3/hr. ERVC was found to be an effective means to prevent tube ejection by maintaining the structural integrity of the penetration tube weld. However, contrary to the predictions by existing criteria, no tube ejection occurred in all non-ERVC tests despite the penetration tube weld failure. In order to validate the existing criteria, it is still needed to realize the tube ejection using the penetration tube specimen with a freely expanded RV lower head under higher in-vessel heat flux and pressure conditions.