Every time the Earth shakes off the coast of Asia, the scenario comes back to mind. In 2011, the Fukushima power plant experienced the worst accident in nuclear history since Chernobyl, shaken by a powerful earthquake followed by a tsunami. So obviously, when an earthquake shook Taiwan on Tuesday, followed by another near Japan, worried eyes converged on the stricken power plant.
Because although the reactors are now shut down, the site remains highly sensitive. “No anomaly” was noted after the second earthquake on Thursday, reassured the operator Tepco, responsible for the decontamination and dismantling of the plant. But the operations are far from over. Since the summer of 2023, Tepco has launched four operations to discharge water from reactor cooling and treated on the site into the sea. A drop of water: in total, Japan will have to treat and discharge 1.3 million m³ of water, currently stored in more than 1,000 reservoirs on site, over a period of 30 years.
Water, mud and corium
The safety of these reservoirs therefore raises questions. Because if the objective of the treatment is to reduce the radioactivity of the water below the threshold of 1,500 becquerels per liter, Tepco reported on February 7 a leak of 5.5 tons of water loaded with 22 billion becquerels . Mixing with sea water, particularly in the event of a new tsunami, would be catastrophic. Another sensitive element, the mud resulting from the treatment is also very radioactive. Here, everything that could be put in place in terms of security was put in place. The sludge is stored in so-called “high integrity” containers (HIC), stored on a separate site surrounded by thick concrete walls. The only problem is that the maximum storage capacity could be reached as early as 2027, according to The world.
What remains is the heart of the power plant, that is to say the three reactors which melted. Now stopped and cooled, they no longer represent a risk of loss of control. But decontamination turns out to be extremely complicated. In total, nearly 880 tons of fuel melted during the disaster, irreparably damaging the reactors. At around 3,000°C, corium formed from the radioactive material and the elements surrounding it. In March 2023, a robot sent into reactor number 1 confirmed that the fuel had passed through the tank and damaged the concrete base, as reported The world.
An earthquake could complete the fracturing of this base and allow the corium to come into contact with the soil under the power plant. “The base of reactor number 1 could collapse and the reactor vessel could fall,” worried Chihiro Kamisawa, of the Citizen Nuclear Information Center. A fear that Tepco brushes aside, wanting to be reassuring about the state of the plant.