LEARNING MORE FROM FUKUSHIMA DAI-ICHI

A tsunami caused by the magnitude 9.0 Tohoku Earthquake of 11 March 2011 on the northeast coast of Japan drowned the emergency diesel generators of three boiling-water reactors at Fukushima Dai-ichi, resulting in station blackout and the meltdown of the three reactor cores. Although emergency injection of seawater was improvised to remove the decay heat from the reactors, it was too late to avoid boiling off of much of the water in the reactor pressure vessels and the reaction with steam of the zirconium alloy "clad" of the fuel rods in the reactor with the evolution of hydrogen, which in turn over pressurized the massive concrete containment of the reactor and compelled venting of the hydrogen and some of the radioactive material from the reactor. This paper reports the course of events, the resulting contamination of the environment and the evacuation of 180,000 inhabitants, the efforts to prevent further damage to the reactors and spent fuel pools, and how the world can learn to prevent such accidents and to better alert and inform the public of the hazards and how they can protect themselves. On March 11, 2011, an intense earthquake off the northeast coast of Japan, ranked as magnitude 9.0, severely tested Japan's earthquake code and discipline. The country and its buildings passed with flying colors. Some 16 nuclear reactors shut down instantly, as planned, as the earthquake strong motion exceeded on the order of 0.5 g, as measured by strong-motion seismometers within the buildings themselves. The reactors, including three operating reactors at Fukushima Dai-ichi (1F), Units 1, 2, and 3, automatically inserted their control rods into the reactor core, terminating the neutron chain reaction, and reducing the thermal power output to that of the "decay heat" of the fission products themselves. With so much power generation suddenly off line, transmission line power to the 1F site was lost, and emergency diesel generators (EDG) took over.(1)