This case describes the events and conditions surrounding a critical decision that Masao Yoshida, the plant manager of Tokyo Electric Power Company's (TEPCO's) Fukushima Dai-ichi nuclear power plant, must make on March 12, 2011. A day earlier, a massive 9.0 magnitude earthquake hit the region where the power plant was located. This caused significant damage to the Fukushima Dai-ichi nuclear power plant, disabling both the regular and backup power supply. Without cooling, the nuclear reactors' temperatures would steadily rise, ultimately leading to a meltdown of the reactor core. Yoshida decides to inject fresh water into the reactors using fire engines - a procedure that has never been tried before. He soon recognises that the limited fresh water supply will run out and so decides to replace it with seawater. Less than twenty minutes after the seawater injection has started, Yoshida receives orders from senior management to stop the injection. What should he do?

This case study discusses the causes, consequences and implications of the nuclear disaster at Tokyo Electric Power Company's (TEPCO's) Fukushima Dai-ichi nuclear power plant that was triggered by a massive 9.0 magnitude earthquake and subsequent tsunami waves on March 11, 2011. There are two essential questions: First, "How could it have come so far?" Japan is rightfully considered a technologically advanced nation and is known for its diligence and high-quality products. While the combined earthquake/tsunami triggered the catastrophe, there are a number of deeper underlying causes that are described in the first section of the case. Second, "What next?" While the plant technically achieved cold shutdown with all damaged reactors reaching temperatures below 100°C, this did not mean that the Fukushima disaster was over. Instead, numerous consequences and implications extend into the future.