When the tsunami caused the Fukushima breakdown
Although all the working units of the nuclear reactor were shut down following the Tohoku earthquake, the question of how Fukushima-I exploded has baffled many observers.
The answer to this, according to Dr. Noritaka Yusa of Tohuku University, is fairly simple. Following the Tohuku earthquake of 11 March 2011, all nuclear reactors were shut down. Additionally, diesel generators were switched on to ensure an adequate supply of water to the nuclear plant. However, when the 14-metre tsunami hit Fukushima, the diesel generators were destroyed and the sea water pumps were damaged. This implied that sufficient water was not available for the proper functioning of the cooling system resulting in overheating of the fuel rods overheating and ultimate meltdown.
Dr. Noritaka of Department of Quantum Science and Energy Engineering, Graduate School of Engineering, Tohoku University, who was at AIT on 23 February 2016, elaborated on how the lack of external power resulted in the disaster. Fukushima-I did not have electricity, and it died; while some of the other units at Fukushima, which had external power to provide the cooling water survived, he remarked.
Explaining the historic background to the reliance of nuclear power in Japan, Dr. Noritaka stated that Japan has extremely limited quantities of coal and gas, and no oil reserves. Further, since the land mass is not physically connected to any other country which makes transmission of power extremely difficult. These factors contributed to Japan’s reliance on nuclear energy.
He also spoke about the lessons learnt from the Fukushima disaster, stating that both tsunami countermeasures and accident management systems under severe disasters were insufficient. He remarked that while the slogan that nuclear energy was 100 percent safe is an easy way to communicate with lay audiences; but from an engineering viewpoint, a 100 per cent safety impedes scope for improvements.
Dr. Noritake was introduced to AIT by Dr. Weerakorn Ongsakul of the Energy Field of Study from AIT’s School of Environment, Resources and Development (SERD).