Following a major earthquake, a 15-metre tsunami disabled the power supply and cooling of three Fukushima Daiichi reactors, causing a nuclear accident beginning on 11 March 2011. All three cores largely melted in the first three days.
This flooding caused the failure of the emergency generators and loss of power to the circulating pumps. The resultant loss of reactor core cooling led to three nuclear meltdowns, three hydrogen explosions, and the release of radioactive contamination in Units 1, 2 and 3 between 12 and 15 March.
Nuclear Power Plant Explosions at Fukushima-Daiichi☆
The Great East Japan Earthquake on March 11, 2011 generated a series of large tsunami waves. The tsunami waves reached area deep within the units at Fukushima Daiichi nuclear power plant.
The Chernobyl accident in 1986 was the result of a flawed reactor design that was operated with inadequately trained personnel. The resulting steam explosion and fires released at least 5% of the radioactive reactor core into the environment, with the deposition of radioactive materials in many parts of Europe.
Chernobyl had a higher death toll than Fukushima
While evaluating the human cost of a nuclear disaster is a difficult task, the scientific consensus is that Chernobyl outranks its counterparts as the most damaging nuclear accident the world has ever seen.
“Fukushima will never return to being totally habitable—pockets have been taken out forever, or at least for the imaginable future.”
The government decided in April to start discharging the water, after further treatment and dilution, into the Pacific Ocean in spring 2023 under safety standards set by regulators.
The hot fuel particles reacted with water and caused a steam explosion, which lifted the 1,000-metric-ton cover off the top of the reactor, rupturing the rest of the 1,660 pressure tubes, causing a second explosion and exposing the reactor core to the environment.
1. What caused the Chernobyl accident? On April 26, 1986, the Number Four RBMK reactor at the nuclear power plant at Chernobyl, Ukraine, went out of control during a test at low-power, leading to an explosion and fire that demolished the reactor building and released large amounts of radiation into the atmosphere.
Chernobyl reactor 4 is no longer burning. The reactor was originally covered after the disaster, but it resulted in a leak of nuclear waste and needed to be replaced. The systems for a new cover for the reactor were being tested in 2020 and is sometimes referred to as a "sarcophagus."
Nobody died as a direct result of the Fukushima nuclear disaster. However, in 2018 one worker in charge of measuring radiation at the plant died of lung cancer caused by radiation exposure. In addition, there have been more than 2,000 disaster-related deaths.
Fukushima is the most radioactive place on Earth. A tsunami led to reactors melting at the Fukushima nuclear power plant. Even though it's been nine years, it doesn't mean the disaster is behind us.
Workers rushed to restore power, but in the days that followed the nuclear fuel in three of the reactors overheated and partly melted the cores - something known as a nuclear meltdown. The plant also suffered a number of chemical explosions which badly damaged the buildings.
Tiny amounts of radiation have continued leaking into the sea and elsewhere through underground passages, though the amount today is small and fish caught off the coast are safe to eat, scientists say.
With no working reactors, there is no risk of a meltdown. But the ruins from the 1986 disaster still pose considerable dangers.
A second, more powerful explosion occurred about two or three seconds after the first; this explosion dispersed the damaged core and effectively terminated the nuclear chain reaction. This explosion also compromised more of the reactor containment vessel and ejected hot lumps of graphite moderator.
When fuel rods are spent after generating power, they still have lots of internal radioactivity and are still hot. Internal radioactive decay gives off heat and remains in the fuel rods for tens of thousands of years, so they can get hotter unless something is done to cool them, Regan said.
On 4 May 1986, just a few days after the initial disaster, mechanical engineer Alexei Ananenko, senior engineer Valeri Bespalov and shift supervisor Boris Baranov stepped forward to undertake a mission that many considered to be suicide.
Nevertheless, the trial began on 6 July in the town of Chernobyl. All 6 defendants were found guilty and Bryukhanov was given a full 10-year sentence, which he served at a penal colony in Donetsk. Viktor Bruykhanov, alongside Anatoly Dyatlov and Nikolai Fomin at their trial in Chernobyl, 1986.
All water in the reactor flash-boiled to steam as the core became up to 2000°C hot. This caused huge pressure in the entire core, and a massive steam explosion took place.
“They have huge volumes of water so they cannot evaporate it like they did at Three Mile Island,” Klein said. “If they did it would likely be evaporated, go out over the ocean, condense and fall back as rainwater. There's no safety enhancement.”
A large area around the Fukushima nuclear power plant will be uninhabitable for at least 100 years.
The Japanese utility giant Tepco is planning to release more than 1 million cubic meters of treated radioactive water -- enough to fill 500 Olympic-size swimming pools -- from the wrecked Fukushima Dai-Ichi nuclear power plant into the Pacific Ocean, part of its nearly $200 billion effort to clean up the worst atomic ...
Japan's industry ministry and the IAEA have agreed to compile an interim report on the water discharge plan in 2022. Officials say it is now safe to live in most areas around the plant except for its immediate surroundings after extensive decontamination work.