Source: NZHerald
Following the tragic earthquake and tsunami that struck Japan on March 11, nuclear reactors at the Daiichi site in Fukushima shut down, as they were designed to do. However, the natural disasters took out the power for the cooling systems, meaning that the nuclear cores at the reactors remained hot. Since then, there have been explosions at reactor units 1 and 3.
Carnegie’s James Acton explained to the Associated Press that the developments at reactor units 2 and 4 since March 15 are of greater concern. An explosion inside the containment structure at reactor unit 2 is especially worrisome – the explosion may have damaged the containment structure itself, making it even more difficult to prevent leakage of radiation. A fire in the spent fuel pool near reactor unit 4 is also a distressing development.
Acton said that Japanese regulators are very serious about safety. The earthquake that struck Japan, however, was larger than what the reactors were prepared to survive. A similar event occurred in 2007, with far less devastating results. The Kashiwazaki-Kariwa nuclear power plant automatically shut down in response to a 2007 earthquake, which was also of greater magnitude than the reactor was designed to survive. In both instances, nuclear power plants faced greater natural disasters than anticipated. As a result, Acton said, nuclear regulators must reconsider whether plants are designed to withstand the full range of catastrophes they might face.