A nuclear watchdog has asked the operator of Japan’s wrecked Fukushima nuclear power plant to assess potential risks from damage found in a key supporting structure inside the worst-hit of the three melted reactors.
A robotic probe inside the Fukushima Daiichi nuclear power plant's Unit 1 primary containment chamber found its pedestal — a main supporting structure right underneath the core — was largely damaged. The thick concrete exterior was missing almost all the way around, exposing the internal steel reinforcement.
About 880 tons of highly radioactive melted nuclear fuel remain inside the plant's three reactors. Robotic probes have provided some information, but the status of the melted debris is still largely unknown.
Based on data collected from earlier probes and simulations, experts have said most of the melted fuel inside Unit 1, believed to be the worst hit, fell to the bottom of the primary containment chamber, but some might have fallen through into the concrete foundation — a situation that makes the already daunting task of decommissioning extremely difficult.
At a meeting Wednesday of the Nuclear Regulation Authority, its commissioners agreed to order operator Tokyo Electric Power Company Holdings to urgently assess the risks from the pedestal damage, including possible leaks of radioactive substances from cracks and holes caused by the meltdown. The authority also requested that TEPCO assess potential risks if, in the event of another disaster, the pedestal fails to support the reactor.
"We need to think about responses in case of an accident," watchdog commissioner Shinsuke Yamanaka told reporters. “TEPCO has a responsibility to make the risk assessment as soon as possible.”
TEPCO has said that, even though the concrete exterior is largely missing, the steel reinforcement remains intact and there is little safety risk. If the pedestal fails, its surrounding structures can prevent the reactor from collapsing. TEPCO said it planned to further analyze data and images over the next couple of months to find out the extent of the reactor’s earthquake resistance.
The images were the first to be taken from inside the pedestal since the March 11, 2011, disaster. Robots were sent in earlier attempts but were unable to reach the pedestal and take pictures. The images, captured in March by a remote-controlled underwater vehicle, show details of the damage inside the pedestal, where traces of melted fuel can most likely be found and will be key to an investigation by TEPCO and nuclear experts.
The damage is believed to be from the initial earthquake in 2011, but it's not known if it happened more recently. The images of the exposed steel reinforcement have triggered concerns among local residents about the reactor’s safety.
The Fukushima Daiichi plant's plan to release treated, but still slightly radioactive, water into the sea has also triggered concerns and protests from the local fishing community and neighboring countries, including South Korea.
A South Korean delegation of government experts visited the plant for two days earlier this week to see the facilities related to the planned water release. The team members were to meet with Japanese officials Thursday in Tokyo, where they said they planned to follow review of the International Atomic Energy Agency, which has been assisting Japan to improve transparency and credibility.
Trial removal of melted debris is expected to begin in Unit 2 later this year after a nearly two-year delay. Spent fuel removal from the Unit 1 reactor’s cooling pool is to start in 2027 after a 10-year delay. Once all the spent fuel is removed from the pools, melted debris will be taken out of the reactors starting in 2031.
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26 Comments
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Yrral
Did they consult the Chinese, Russian and North Korean
TaiwanIsNotChina
Not much point in fostering good will from declared enemies.
moonbloom
Yes of course best to foster ill will instead, that's a great approach to life and geopolitical affairs.
wallace
The situation will remain highly dangerous and critical while the melted fuel remains. The radiation levels inside the No2 reactor are 500 SIEVERTS.
It will take decades to find a solution. Another powerful earthquake and tsunami could destroy the reactors and wash them out to the sea.
Fukushima is more dangerous than Chornobyl.
1glenn
Rather than the operator assessing risk, isn't that the job of the "watchdog" at this point? The confidence of the public in the operator's ability to assess risk was destroyed when they failed to take into consideration the likelihood of a tsunami following an earthquake. Earthquakes in Japan? Never happen.
For one thing, the nuclear facility should have been located on higher ground.
1glenn
Regarding the radioactive stored water that they want to release, my understanding is that it is so little radioactive that it is safe to drink. If that is true.......
Roy Sophveason
Theoretically, yes. In practice it probably tastes horrible, what with it being industrial sea water and all.
Then what?
wallace
The structures were weakened by the powerful earthquake. The containment vessels were damaged. The reactor building structures were weakened. There is still spent fuel in the No1&2 cooling pools. The site could not withstand another powerful quake. It would crack open the reactors releasing a massive amount of radiation greater than it was in 2011.
Phillip bear
Yes, the risks certainly go beyond those associated with the stored water.
lunatic
It took 3 months in Chernobyl to construct a sarcophage to contain the radiation.
You would think that after 50 years of technological advancement we would be more efficient.
look at us, after 10 years nothing has been done.
Phillip bear
Ironically, tritium, along with the more abundant, more stable, deuterium, are the two fuels used in a number of experimental fusion reactors currently under development. If those reactors are developed in the future, they will need to extract the tritium, which on average, is normally very dilute globally (10-16 % of hydrogen).
With a half-life of 12.32 years and potentially harmful, tritium is a double-edged sword. A half-life of 12.32 years also tells us that about half of the tritium that existed in 2011 has now become the more stable and more safer Helium-3 atom.
wallace
lunatic
Chernobyl and Fukushima cannot be compared. They are two very different types of nuclear disaster. Chernobyl was an explosion in the reactor which was built without a containment vessel. The first sarcophagus was just temporary. 31 people died building it. It took 206 days.
The more permanent sarcophagus took about 8 years to construct and suppose to last 100 years.
A leading Russian scientist has claimed that the sarcophagus entombing Chernobyl's broken nuclear reactor is dangerously degraded and he warned that its collapse could cause a catastrophe on the same scale as the original accident almost 20 years ago.
Fukushima were three reactor meltdowns.
A sarcophagus cannot be built to cover the site because the melted fuel requires constant cooling. There is the problem of the underground water becoming contaminated and reaching the ocean.
The nuclear disaster won't be resolved this side of 50 years or 2061.
It is not correct to say nothing has happened at Fukushima. A tremendous amount has been achieved to date given the difficulty of working at a plant destroyed by an earthquake and tsunami and having to often work remotely because of dangerous levels of radiation.
Roy Sophveason
In building a concrete sarchophagus? Why would we want to do that? We want to retrieve the fuel and debris, something that's quite hard to do if all of it is encased in a lump of concrete.
lunatic
Not a single core has been extracted yet.
Feels like they will just keep pumping water for an eternity.
I would feel safer if we can outsource de decommissioning to someone other than TEPCO.
Roy Sophveason
That is correct. I'm not entirely sure if they finished the cover on Unit 1 yet, but that has to be done first, they wanted to be done with that this year. The roadmap says they then want to start removing fuel beginning in 2024, and be done by 2031.
Please, by all means, step up. You seem to know everything better than the people actually working on the problem, to you they are all maliciously stupid.
wallace
lunatic
I presume you mean the corium or melted fuel. There are some fuel rods in the reactor vessels that have not melted. There are melted fuel rods still inside the reactor vessel. And then there are the melted fuel rods that eat through the base of the reactor vessel and dropped into the containment vessel and the suppression rings.
Some experts believe some escaped into the basements.
The radiation levels inside the reactors are about 500 SIEVERTS. Whatever goes in there, a camera or robot or other measuring device in a very short time its electronics are fried. There are about 800 tons of corium that need constant cooling with water and yes for eternity if it's not removed.
There are many companies involved with Fukushima not just TEPCO. Toshiba and Hitachi's nuclear divisions are also involved.
Do you have any idea how to remove the 800 tons of corium like keeping it underwater to prevent the release of very high levels of dangerous radiation?
The spent fuel from No1&2 must be removed first and the buildings made safer.
wallace
No one has the experience of resolving the Fukushima Nuclear Disaster because it never happened before.
wallace
I think the corium will not be able to be removed before 2050.
Phillip bear
Thanks for the information Wallace.
However, the following doesn't seem to add up ... Can you please clarify?
The Chernobyl event occurred on the 26th of April 1986, about 37 years ago.
wallace
Sorry, I posted that in error. He was referring to the first concrete sarcophagus now replace with a new one expected to last 100 years.
wallace
The corium will probably need to cool before any attempt is made to remove it.
Phillip bear
Thanks Wallace, Cheers
Phillip bear
My posting about tritium today at 4:08 pm
had lost its formatting ...
It should have read 10 raise to -16 power % .... that is, ...
0.0000000000000001%
RKL
But of course.
wallace
RKL
Is that all you have?
wallace
The clean-up will last more than 300 years.
https://www.asahi.com/ajw/articles/14232870
There are photos of the corium
https://simplyinfo.org/tag/corium/