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Fukushima earthquake: How big is the risk of a nuclear catastrophe?

Eleven years after the Fukushima nuclear disaster, the north-east coast of Japan is again shaken by a severe earthquake. How big is the danger today?

Fukushima – A severe earthquake off the coast of Japan on Wednesday (March 16, 2022) suddenly brought back memories of the reactor disaster at the Fukushima Daiichi nuclear power plant in 2011. The 7.4 magnitude earthquake shook the coastal region and large parts of Japan almost exactly eleven years to the day after the nuclear disaster. With a magnitude of 9.0, the devastating earthquake that triggered the massive tsunami and thus triggered the catastrophe was significantly more powerful than it was this year.

Nevertheless, the current shock, which could be felt as far as Tokyo 250 kilometers away, put the Japanese authorities on alert again. However, a tsunami warning was withdrawn by the weather authority after just a few hours. Eleven years ago, the tidal wave killed around 18,500 people and triggered the worst-case scenario in the Fukushima Daiichi nuclear power plant*. Over 100,000 people had to leave their homes, and many have not been able to return to the ghost town next to the nuclear power plant to this day*.

The power plant operator Tepco announced on Thursday night (03/17/2022, local time) that it wanted to investigate irregularities or problems in Fukushima Daiichi. And nuclear engineer Toshio Kimura warned last year that there could well be another nuclear catastrophe in Japan* – because the nuclear power operators are unreliable and safety standards are neglected. But how big is the danger really today?

Major earthquake in Japan: Incidents at the Fukushima Daiichi nuclear power plant

On the morning after the violent earthquake, the Japanese authorities initially gave the all-clear – there had been no major irregularities in the nuclear power plant. And this despite the fact that the consequences of the quake gradually became more visible in large parts of the country on Thursday. Cracks appeared in highways and streets, goods fell from the shelves in shops, the furnishings in apartments collapsed and numerous houses were damaged, as pictures from the Japanese television station NHK showed.

Eine Grafik-Karte verortet das Erdbeben der Stärke 7,4 vom 16. März 2022 in der Nähe von Fukushima.

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A graphic map locates the 7.4 magnitude earthquake of March 16, 2022 near Fukushima.

In the meantime, the power went out in more than 2.2 million households in the country as a result of the earthquake – which can quickly become a danger, especially in nuclear power plants, as Professor Clemens Walther from the University of Hanover said in an interview with Der Spiegel. Walther is the executive director of the Institute for Radioecology and Radiation Protection in Hanover. When the power fails in nuclear power plants, cooling of the reactor core also fails as a result. And that allows for a meltdown with devastating consequences.

Earthquake in Fukushima: Fuel elements produce significantly less heat

However, Clemens Walther also emphasized in the Spiegel interview that the situation in Fukushima is very different today than it was eleven years ago. The decisive difference: none of the six reactors is in operation anymore. Reactors 3 and 4 have already been completely emptied. In the other reactors there are still fuel elements that still need to be cooled, “but not as much as there was after the accident eleven years ago,” said Walther.

In fact, as a result of the severe tremors, the cooling system for the spent fuel pools in reactors 2 and 5 stopped temporarily, as reported by local media, citing the power plant operator Tepco. According to Walther, however, the radioactive material only produces around 0.4 percent of the heat that it produced immediately after the reactors were switched off. He therefore considers it impossible that there will be another meltdown here.

Danger of a nuclear catastrophe in Fukushima: power plant operator Tepco has increased

According to the expert, in addition to the situation in the reactors, the situation at the plant has also changed compared to 2011. Although the Fukushima Daiichi nuclear power plant is almost at sea level, the protective barrier and quay wall in the harbor could still fend off powerful waves. Tepco had the outer quay wall raised to a total height of eleven meters with an L-shaped concrete wall in 2020.

However, on Wednesday (03/16/2022) there was no danger at all from the sea. After the earthquake, the Japanese authorities warned of a tsunami wave about one meter high – and withdrawn the warning just a few hours later. The 2011 tsunami that devastated the power plant and everything around it was 14 meters high.

Ein Foto aus einem Flugzeug von Kyodo News zeigt das Kernkraftwerk Fukushima Daiichi: Infolge eines schweren Erdbebens am 16. März 2022 kam es in der Atomruine Fukushima zu einer Panne.

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As a result of a severe earthquake on March 16, 2022, there was a breakdown in the Fukushima nuclear ruins – but the catastrophe like eleven years ago did not happen.

Major earthquake in Fukushima: what happens when a nuclear reactor collapses

In the case of a level 7.4 earthquake, houses are often destroyed in the vicinity of the epicenter and entire buildings collapse like a house of cards. Numerous houses were also destroyed in the Fukushima region on Wednesday. According to expert Clemens Walther, the reactors in Fukushima are designed to withstand level 8 earthquakes, and in 2011 they even withstood level 9.

Nevertheless, since the disaster eleven years ago, the reactors have not been as stable as before, explains Walther. If they were to collapse as a result of the current severe earthquake, radioactivity could well be released. According to Walther, that would be “very ugly”, especially for the people in the area and the workers in the nuclear ruins, but it is really not likely at the moment. The extent to which the renewed quake actually affected stability must be investigated on site.

Fukushima Daiichi nuclear power plant: What happens when contaminated material ends up in the sea?

Japan lies in what is known as the “Ring of Fire,” a region around much of the rim of the Pacific Ocean where volcanic eruptions and earthquakes are very common. Especially in nuclear power plants, special safety precautions should therefore be taken with a view to possible natural disasters.

But not only the acute dangers are cause for concern: Since 2011, the nuclear power operator and the authorities have been fighting for years to dispose of gigantic amounts of radioactive water, dangerous filter residues and millions of tons of contaminated earth* from the area around Fukushima Daiichi. If there is another tidal wave, there is also a risk that the contaminated substances will be washed into the sea, for example, and cause damage there or spread further.

After the earthquake in Fukushima: Contaminated substances rather harmless

The nuclear expert Clemens Walter noted in the Spiegel interview that in Japan, for example, hundreds of thousands of black sacks with contaminated soil are stored close to the coast. They could be destroyed and swept away by a tsunami. However, the waste is only slightly radioactive and it is not a question of quantities “that we could prove here in Germany or that would cause serious damage locally,” says Walther.

The situation is similar with the contaminated water from Fukushima*, which has been the subject of dispute in Japan and its neighboring countries for years. Clemens Walther considers it unlikely that the water can be washed out of the tanks in a tidal wave. The only thing that cannot be ruled out is that a strong earthquake like the one that hit Fukushima on Wednesday could damage and crack the containers. And here too: “This is rather low-level radioactive waste. […] The amount is harmless from a radio-ecological point of view due to the massive dilution in the sea,” explains the expert.

Fukushima: Pressure drop in reactor 1 of the nuclear ruins – “No increased radiation”

As a result of the severe earthquake, the pressure in the containment of reactor block 1 in the nuclear ruins initially rose and then dropped to below the level before the earthquake, the Japanese broadcaster NHK reported. The operator group Tepco is currently still in the process of determining the cause of the pressure drop. Reactor 1 is one of the three reactor blocks that were severely damaged in the 2011 Fukushima nuclear disaster. However, the measuring stations on the site did not show any increased radiation values, citing Tepco.

A robot was originally supposed to be used on Thursday to track down the fuel in the reactor that melted eleven years ago. The use had to be postponed because of the investigations into the pressure drop, it said. (iwe) *fr.de is an offer from IPPEN.MEDIA.

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