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Concrete melted off ‘pedestal’ for damaged reactor in Fukushima

Rebars in the pedestal, which are normally covered with concrete, are seen exposed inside the No. 1 reactor at the Fukushima No. 1 nuclear power plant. (Provided by the International Research Institute for Nuclear Decommissioning and Hitachi-GE Nuclear Energy Ltd.)

November 30, 2022

The concrete support foundation for a reactor whose core melted down at the Fukushima No. 1 nuclear power plant has deteriorated so much that reinforcing bars (rebars) are now exposed.

Masao Uchibori, governor of Fukushima Prefecture, has expressed concerns about the earthquake resistance of the “pedestal” for the No. 1 reactor at the crippled plant operated by Tokyo Electric Power Co. (TEPCO).

Strong quakes struck off the coast of the prefecture in 2021 and 2022.

“There have been events that caused anxieties among residents of our prefecture, including damage to the foundation supporting the No. 1 reactor’s pressure vessel,” Uchibori told a prefectural assembly session in September. “We will check up on TEPCO’s efforts so the decommissioning work will proceed safely and steadily.”

The cylindrical pedestal, whose wall is 1.2 meters thick, is 6 meters in diameter. It supports the reactor’s 440-ton pressure vessel.

The interior of the No. 1 reactor’s containment vessel was inspected in May for TEPCO’s eventual plans to retrieve the melted nuclear fuel that dropped to the bottom of the vessel during the 2011 nuclear disaster.

The study found that the normally concrete-encased rebars were bare and the upper parts were covered in sediment that could be nuclear fuel debris.

The concrete likely melted off under the high temperature of the debris.

The International Research Institute for Nuclear Decommissioning (IRID), an entity set up by power utilities and nuclear reactor manufacturers, conducted a simulation in fiscal 2016.

IRID said seismic resistance would remain uncompromised even if about one-quarter of the pedestal was damaged.

However, only a part of the pedestal was inspected during the May study, and only from the outside.

The pedestal’s inside remains a mystery.

“The pedestal’s soundness is of foremost concern,” said Kiyoshi Takasaka, a former engineer with Toshiba Corp. who is now an adviser to the Fukushima prefectural government on nuclear safety issues. “It is important to first inspect the pedestal from the inside.”

TEPCO has prepared six types of robots to detect the fuel debris and perform other tasks in a series of inspections at the No. 1 reactor.

An internal study of the pedestal is planned toward the March end of the fiscal year as the final mission during the inspections. The task carries the risk of the robot hitting the sediment or other obstacles and being unable to return.

“We understand people’s concerns very well,” Akira Ono, president of TEPCO’s Fukushima Daiichi Decontamination & Decommissioning Engineering Co., told a news conference in October. “We hope to finish studies inside the pedestal by the end of this fiscal year.”

He said his company will scrutinize whether the previous assessment of seismic resistance is still applicable.

Haruo Morishige, who has been studying the Fukushima nuclear disaster, called for immediate emergency safety measures, such infusing concrete to reinforce the pedestal.

“There is a critical defect in terms of quake resistance,” said Morishige, based on a photo showing the interior of the No. 1 reactor. 

Morishige studied aseismic structural design for nuclear reactors when he worked for Mitsubishi Heavy Industries Ltd.

He also served as an on-site manager for the No. 3 reactor at the Ikata nuclear plant operated by Shikoku Electric Power Co., including when the reactor was being built.

The photo, released following the May inspection, shows how concrete covering the cylindrical “inner skirt” of the pedestal had melted off, laying bare part of the steel frame and rebars from the bottom to the top.

The inner skirt’s functions connect the reactor pressure vessel with the containment vessel. But the melting of the concrete has separated the pressure vessel from the containment vessel, and weakened the structure’s quake resistance, Morishige said.

The loss of concrete has also decoupled the pedetal’s walls from the floor, making it more prone to sway during seismic events, he added.

Morishige said that all concrete around the rebars inside the pedestal has likely melted away.

He also said fuel debris that flowed out from an aperture likely melted concrete around rebars over about a quarter of the outside circumference of the pedestal.

His simulation has shown that the support capability of the pedestal is now about three-eighths of the original level.

“In such a state, the reactor could topple over in an earthquake of upper 6 on the Japanese seismic intensity scale (of 7),” Morishige said.

He added that repeated exposure to seismic shocks could cause cracks in the remaining concrete, further undermining quake resistance.

“The very fact there are chances of the reactor toppling is unacceptable,” he said. “Officials should proceed with safety measures and inspections at the same time.”

(This article was written by Keitaro Fukuchi and Tetsuya Kasai.)

https://www.asahi.com/ajw/articles/14767569

December 4, 2022 Posted by | Fuk 2022 | , , , | Leave a comment

New Discovery At Fukushima Unit 3 Provides Clues To Meltdown Severity, Environmental Releases

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May 3, 2019
TEPCO recently published a video of the work to remove spent fuel from the unit 3 fuel pool. In this video was an unexpected finding with serious implications.
In the video of the fuel assembly removal from a fuel rack inside the spent fuel pool, was a tell tale sign of something significant. Prior to the effort to remove fuel from the pool, the pool underwent significant cleaning work. This included removing most of the debris that fell into the pool along with use of a vacuum to remove small pieces of broken concrete and dust.
What remains adhered to the side of the fuel rack appears to be the same thick white substances found inside the reactor containment of unit 3 and in the pedestal below the reactor vessel. These substances also have the same appearance as those inside containment. They are stuck to both vertical and horizontal surfaces as if they splattered then stuck to where they landed. What these may be and how they managed to end up on the fuel racks is explained further in this report.
Read more:
Simply Info

New Discovery At Fukushima Unit 3 Provides Clues To Meltdown Severity, Environmental Releases

May 8, 2019 Posted by | fukushima 2019 | , , | Leave a comment

NHK’s new documentary, Meltdown: Cooling Water Crisis provides new insight into a series of less known events in the Fukushima disaster.

June 5, 2018 Posted by | Fukushima 2018 | , , | Leave a comment

TEPCO president gave order not to call 2011 crisis a ‘meltdown’

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NIIGATA–An investigation committee is leveling the blame for the failure to use the word “meltdown” following the Fukushima nuclear accident in March 2011 at Tokyo Electric Power Co. President Masataka Shimizu.
Shimizu instructed TEPCO employees not to use the term on his own and was not following orders from the prime minister’s office, the committee’s report said on Dec. 26.
TEPCO did not publicly confirm that a meltdown had occurred until May 2011.
“There were no instructions (to TEPCO) from the prime minister’s office on whether to use the word ‘meltdown’ or not,” the panel said as to why the announcement was delayed for two months.
The committee was jointly set up by the Niigata prefectural government and TEPCO to investigate the cause of the accident at the Fukushima No. 1 nuclear power plant due to the Great East Japan Earthquake and tsunami of March 11, 2011.
The investigation is a prerequisite for the prefectural government starting discussions on whether to agree to the restart of the Kashiwazaki-Kariwa nuclear power plant, also operated by TEPCO, in the prefecture.
The description of the investigation committee’s report contrasted sharply with a report released in June 2016 by a third-party investigation committee set up by TEPCO.
According to the third-party committee’s report, Shimizu instructed then Vice President Sakae Muto through a TEPCO employee “not to use the word ‘meltdown’ at the direction of the prime minister’s office” when Muto held a news conference on March 14, 2011, three days after the nuclear accident ensued.
As Shimizu’s memory had faded, the third-party committee was unable to confirm details of the “instruction” from the prime minister’s office, but assumed that there was a directive from the prime minister’s office.
Whether an order had been issued by the prime minister’s office became a focus of the investigation of the Niigata prefectural government and TEPCO committee.
According to the joint panel’s report, Shimizu met with then Prime Minister Naoto Kan and then Chief Cabinet Secretary Yukio Edano of the Democratic Party of Japan-led government at the prime minister’s office on March 13, 2011, a day before Muto’s news conference.
In that meeting, Shimizu received instructions from Kan and Edano on sharing information.
Shimizu thought that since the definition of a “meltdown” is vague, an announcement that one had occurred could cause a panic unless the release of such news was made after reaching a consensus with the prime minister’s office.
Based on this reasoning, Shimizu instructed TEPCO’s employees “not to use the word ‘meltdown,’” on his own, he was quoted by the report as telling members of the investigation committee.

December 28, 2017 Posted by | Fukushima 2017 | , , , | Leave a comment

HELEN CALDICOTT: The Fukushima nuclear meltdown continues unabated

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Dr Helen Caldicott, explains recent robot photos taken of Fukushima’s Daiichi nuclear reactors: radiation levels have not peaked, but have continued to spill toxic waste into the Pacific Ocean — but it’s only now the damage has been photographed.

RECENT reporting of a huge radiation measurement at Unit 2 in the Fukushima Daichi reactor complex does not signify that there is a peak in radiation in the reactor building.

All that it indicates is that, for the first time, the Japanese have been able to measure the intense radiation given off by the molten fuel, as each previous attempt has led to failure because the radiation is so intense the robotic parts were functionally destroyed.

The radiation measurement was 530 sieverts, or 53,000 rems (Roentgen Equivalent for Man). The dose at which half an exposed population would die is 250 to 500 rems, so this is a massive measurement. It is quite likely had the robot been able to penetrate deeper into the inner cavern containing the molten corium, the measurement would have been much greater.

These facts illustrate why it will be almost impossible to “decommission” units 1, 2 and 3 as no human could ever be exposed to such extreme radiation. This fact means that Fukushima Daichi will remain a diabolical blot upon Japan and the world for the rest of time, sitting as it does on active earthquake zones.

What the photos taken by the robot did reveal was that some of the structural supports of Unit 2 have been damaged. It is also true that all four buildings were structurally damaged by the original earthquake some five years ago and by the subsequent hydrogen explosions so, should there be an earthquake greater than seven on the Richter scale, it is very possible that one or more of these structures could collapse, leading to a massive release of radiation as the building fell on the molten core beneath. But units 1, 2 and 3 also contain cooling pools with very radioactive fuel rods — numbering 392 in Unit 1, 615 in Unit 2, and 566 in Unit 3; if an earthquake were to breach a pool, the gamma rays would be so intense that the site would have to be permanently evacuated. The fuel from Unit 4 and its cooling pool has been removed.

But there is more to fear.

The reactor complex was built adjacent to a mountain range and millions of gallons of water emanate from the mountains daily beneath the reactor complex, causing some of the earth below the reactor buildings to partially liquefy. As the water flows beneath the damaged reactors, it immerses the three molten cores and becomes extremely radioactive as it continues its journey into the adjacent Pacific Ocean.

Every day since the accident began, 300 to 400 tons of water has poured into the Pacific where numerous isotopes – including cesium 137, 134, strontium 90, tritium, plutonium, americium and up to 100 more – enter the ocean and bio-concentrate by orders of magnitude at each step of the food chain — algae, crustaceans, little fish, big fish then us.

Fish swim thousands of miles and tuna, salmon and other species found on the American west coast now contain some of these radioactive elements, which are tasteless, odourless and invisible. Entering the human body by ingestion they concentrate in various organs, irradiating adjacent cells for many years. The cancer cycle is initiated by a single mutation in a single regulatory gene in a single cell and the incubation time for cancer is any time from 2 to 90 years. And no cancer defines its origin.

We could be catching radioactive fish in Australia or the fish that are imported could contain radioactive isotopes, but unless they are consistently tested we will never know.

As well as the mountain water reaching the Pacific Ocean, since the accident, TEPCO has daily pumped over 300 tons of sea water into the damaged reactors to keep them cool. It becomes intensely radioactive and is pumped out again and stored in over 1,200 huge storage tanks scattered over the Daichi site. These tanks could not withstand a large earthquake and could rupture releasing their contents into the ocean.

But even if that does not happen, TEPCO is rapidly running out of storage space and is trying to convince the local fishermen that it would be okay to empty the tanks into the sea. The Bremsstrahlung radiation like x-rays given off by these tanks is quite high – measuring 10 milirems – presenting a danger to the workers. There are over 4,000 workers on site each day, many recruited by the Yakuza (the Japanese Mafia) and include men who are homeless, drug addicts and those who are mentally unstable.

There’s another problem. Because the molten cores are continuously generating hydrogen, which is explosive, TEPCO has been pumping nitrogen into the reactors to dilute the hydrogen dangers.

Vast areas of Japan are now contaminated, including some areas of Tokyo, which are so radioactive that roadside soil measuring 7,000 becquerels (bc) per kilo would qualify to be buried in a radioactive waste facility in the U.S..

As previously explained, these radioactive elements concentrate in the food chain. The Fukushima Prefecture has always been a food bowl for Japan and, although much of the rice, vegetables and fruit now grown here is radioactive, there is a big push to sell this food both in the Japanese market and overseas. Taiwan has banned the sale of Japanese food, but Australia and the U.S. have not.

Prime Minister Abe recently passed a law that any reporter who told the truth about the situation could be gaoled for ten years. In addition, doctors who tell their patients their disease could be radiation related will not be paid, so there is an immense cover-up in Japan as well as the global media.

The Prefectural Oversite Committee for Fukushima Health is only looking at thyroid cancer among the population and by June 2016, 172 people who were under the age of 18 at the time of the accident have developed, or have suspected, thyroid cancer; the normal incidence in this population is 1 to 2 per million.

However, other cancers and leukemia that are caused by radiation are not being routinely documented, nor are congenital malformations, which were, and are, still rife among the exposed Chernobyl population.

Bottom line, these reactors will never be cleaned up nor decommissioned because such a task is not humanly possible. Hence, they will continue to pour water into the Pacific for the rest of time and threaten Japan and the northern hemisphere with massive releases of radiation should there be another large earthquake.

https://independentaustralia.net/politics/politics-display/helen-caldicott-the-fukushima-nuclear-meltdown-continues-unabated,10019

February 13, 2017 Posted by | Fukushima 2017 | , , | 1 Comment