Onagawa, the Nuclear Power Plant that Survived a Catastrophic Meltdown

by Pavas B5 years ago
Picture Onagawa, the Nuclear Power Plant that Survived a Catastrophic Meltdown

On March 11, 2011, Japan was hit with the biggest earthquake ever recorded in the country’s history. What followed was the Tohoku Tsunami which led to the infamous Fukushima Daiichi Nuclear Disaster. Even though the disaster seemed like an inevitable result of some catastrophic natural calamity, it was later found out that it could have been easily prevented. Onagawa Nuclear Power Plant, a similar nuclear plant, shared the same disaster conditions, and despite being closer to the epicenter, it survived the tsunami and the earthquake. The difference was the adamant belief of one man regarding the safety protocols of the plant.

There were three nuclear plants in the region affected, Fukushima Daiichi, Fukushima Danini, and Onagawa, with Onagawa being the closest to the proximity of the earthquake, about 60 kilometers nearer to the epicenter than Fukushima Daiichi. All of them shared the same catastrophic conditions, yet their fates were very different.

Nuclear power plants
Image showing locations of the Nuclear Power Plants. Image credits: Maximilian Dörrbecker, Connormah, W.Rebel /Wikimedia

Onagawa Nuclear Power Plant is situated in the Miyagi Prefecture in the northeast region of Tohoku in Japan. The construction of the plant began in 1980, and it is known as the most quickly constructed nuclear power plant in the world. The plant was managed by the Tohoku Electric Power Company. Fukushima Daiichi and Fukushima Danini power plants were constructed about 12 kilometers apart and were managed by Tokyo Electric Power Company. While Fukushima Daiichi and Daini suffered major damages during the earthquake, Onagawa remained unharmed.

On March 11, 2011, an earthquake of magnitude 9.1 hit the northeast region of Japan and was followed by a Tsunami which reached a height of 30 meters in some areas. The height of the tsunami waves was more at the Onagawa plant, at 14.3 meters, compared to 13.1 meters at Fukushima Daiichi.

Image credits: ChiefHira/Wikipedia

When the earthquake hit the nuclear plants, the reactors automatically shut down, but it was the tsunami after the earthquake that flooded Fukushima Daiichi.

Image credits: Sadatsugu Tomizawa/NASA

One of the key safety details in the construction of the Onagawa plant that helped withstand the tsunami was the 14.8-meter-high tsunami wall. On the contrary, Tokyo Electric Power Company that operated and constructed Fukushima Daiichi Power Plant lowered the height of a 35-meter seawall by 25 meters in order to save the running cost of seawater pumps.

The construction of the Onagawa Nuclear Power Plant was so impeccable that hundreds of residents who lost their homes in the tsunami took refuge in the plant as there was no other safer place in the region.

Onagawa nuclear power plant
Onagawa Nuclear Power Plant. Image credits: Nuclear News

Immediately after the earthquake, reactors at the Fukushima Daiichi plant automatically stopped, but the tsunami flooded the generators that were providing power to the cooling pumps. The loss of coolant caused hydrogen explosions, three nuclear meltdowns, and the release of radioactive material. The release of radioactive material triggered the establishment of a 30-kilometer evacuation zone around the plant. Even though it has been eight years since the disaster, radioactive water continues to leak to this day. It was the most significant nuclear disaster after the Chernobyl Nuclear Disaster in 1986 and was rated 7 on the INES scale.


Fukushima disaster
Image credits: Chernobylguide

Conditions were similar at the Fukushima Daini plant; all the units automatically shut down after the earthquake. The tsunami caused the generators to fail, but because of the heroic efforts of the staff, they were able to cool down and stabilize the reactors. On the other hand, the nuclear plant at Onagawa remained unscathed by the tsunami as the 14.8-meter-high walls were tall and firm enough to prevent any flooding. The power-plant was the only safe place in the region, and about two to three hundred residents of the town who lost their homes took shelter in the power plant’s gymnasium.

According to the colleagues of Hirai Yanosuke, a 12-meter wall would have been sufficient, but he insisted that Tohoku Electric spend extra money on the construction of a larger Tsunami wall.

Yanosuke Hirai
Yanosuke Hirai. Image credits: Zsefvgyj,/Wikipedia, IAEA/Wikipedia

Hirai Yanosuke was the vice president of Tohoku Electric Company from 1960 to1975. It was due to his beliefs regarding safety that the company developed a strong safety culture. The company conducted various surveys and simulations to predict the tsunamis before the construction began in 1980. After the construction, Tohoku Electric also conducted periodic safety checkups to ensure the safety of the plant and the people. As a part of the safety culture, every employee was given thorough disaster-management training.

Tokyo Electric Power Company was warned time and again about the flaws in their construction design. The construction of the plant was based on the studies that were considered old, and even though new data and knowledge of seismic activities in the region had been presented, no firm action was taken by the plant authorities. In fact, in the year 2002, the Tokyo Electric Power Company revised the height of the 10-meter seawall to 5.7 meters. A number of man-made factors contributed to the disaster at the Fukushima Daiichi power plant. Despite being given several warnings, the plant managed overlooked them every time.


After the earthquake and Tsunami of 2011, all three power plants were shut down and remain inoperable since.

Power plants
Image credits: Abasaa/Wikipedia

According to inspection reports by the International Atomic Energy Agency, the nuclear plant at Onagawa was “remarkably undamaged.” As of 2018, the company decided to decommission the oldest unit, Unit 1, of the power plant.

The nuclear disaster at the Fukushima Daiichi plant is the most expensive disaster and will cost as much as $192.5 billion. While the efforts of decommissioning the plant are ongoing, it will take up to 40 years to complete the process.  Following the disaster, Tokyo Electric scrapped all their plans for building any new units.

One of the reports by the NAIIC stated that Tepco “…resorted to delaying tactics, such as presenting alternative scientific studies and lobbying.”  According to Dr. Kiyoshi Kurokawa, the former chairman of NAIIC, “The earthquake and tsunami of March 11, 2011, were natural disasters of a magnitude that shocked the entire world. Although triggered by these cataclysmic events, the subsequent accident at the Fukushima Daiichi Nuclear Power Plant cannot be regarded as a natural disaster. It was a profoundly man-made disaster that could and should have been foreseen and prevented.”

[sources:1, 2, 3, 4, 5]

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