Unsolved issues related to thermal-hydraulics in the suppression chamber during Fukushima Daiichi accident progressions

Abstract

On 11 March 2011, the Great East Japan Earthquake and Tsunami hit the Fukushima Daiichi Nuclear Power Station. The Fukushima Daiichi Units 1–3 lost all DC and AC power supplies, which set in motion a chain of events that led to releases of radioactivity to the environment. Since then, TEPCO has made many efforts to investigate the accident progressions and the status of the reactors and containment vessels. However, there still exist several tens of unsolved issues to be investigated for the fully understanding of the accident. In this paper, we introduce the unsolved issues related to thermal-hydraulics in the suppression chamber during the Fukushima Daiichi accident progressions. Especially, in Units 2 and 3, there are possibilities that thermal stratification inside their suppression chambers played an important role. It is important that these phenomena are addressed following both theoretical and experimental approaches as support to severe accident simulations.