The Fukushima Daiichi nuclear disaster was an energy accident at the Fukushima Daiichi Nuclear power plant in Okuma which was due to the tsunami following the Tohoku earthquake on 11 March 2011. Right after the earthquake, the active reactors were automatically shut down their sustained fission reactions. But due to the tsunami the emergency generators were disabled which are basically used to provide power to control and operate the pumps which are necessary to cool the reactors. The insufficient cooling led to three nuclear meltdowns, hydrogen-air explosions and the release of radioactive material in three units from 12 to 15 March.
On 5 July 2012, the Fukushima Nuclear Accident Independent Investigation Commission (NAIIC) found that the causes of the accident had been foreseeable and that the plant operator, Tokyo Electric Power Company (TEPCO) had failed to meet basic safety requirements such as risk assessment, preparing for containing collateral damage and developing evacuation plans.
The following reasons are the cause for the disaster, TEPCO did not follow the original layout of the piping system for the emergency cooling system. They violated the approved plan for the piping system. After the tsunami the isolation condenser should have taken over the function of the cooling pumps by considering the steam from the pressure vessel into water to be used for the cooling the reactor. However the condenser did not function properly. There were no proper safety measures taken for a possible tsunami. The generator room was flooded through a door and some holes for cables. A 2008 in-house study identified an immediate need to better protect the facility from flooding by water. The study mentioned the possibility of tsunami-waves up to 10.2 meters. Officials insisted that such a risk was unrealistic and did not take the prediction seriously. At a meeting of the G8’s Nuclear Safety and Security Group in Tokyo, an expert warned that a strong earthquake with a magnitude above 7.0 could pose a serious problem for Japan’s nuclear power stations.
Violation and misjudging any level of safety aspects will lead to major disasters especially when it’s surrounded by human lives. In this case to make the system much safer the following changes are required, the generator room should have been equipped with better ways to prevent the flood water into the room. The tsunami and earthquake warnings which were given well before the incident should have been considered and implemented in order to prevent the disaster. Better functioning of risk assessment is required in order to find out the potential failures of the system.
References
https://en.wikipedia.org/wiki/Fukushima_Daiichi_nuclear_disaster#Prior_safety_concerns