Properties of Concrete Subjected to Severe Accident Conditions at Fukushima Daiichi Nuclear Power Plant

The Fukushima Daiichi Nuclear Power Plant lost its core cooling function due to the massive tsunami generated by the 2011 off the Pacific coast of Tohoku Earthquake, which caused core meltdown, resulting in high temperature inside the containment vessel and exposing the RPV pedestal, a reinforced concrete structure, to an abnormally high temperature environment. In order to cool the molten core, water was poured into the containment vessel, and the concrete structure was gradually cooled in the process. Since it will take at least 40 years from the earthquake to remove the fuel from the core, the long-term integrity of the RPV pedestal is a major concern for the decommissioning of Fukushima Daiichi. In this study, the effects of high temperature exposure and subsequent wetting conditions on concrete properties were experimentally investigated. As a result, it was confirmed that the strength of concrete decreased by heating at high temperature, but recovered under subsequent wetting conditions.