Lethal radiation detected at Fukushima plant reactor 2

 

The operator of the crippled Fukushima Daiichi nuclear power plant has released the results of its latest probe of the site.
A remote-controlled inspection of the Unit 2 reactor containment vessel last month detected a maximum of 8 sieverts per hour of radiation.
Experts say exposure to such radiation for about an hour would be fatal.
Officials from Tokyo Electric Power Company, or TEPCO, released the results on Thursday.
They said the radiation reading was taken near what appeared to be fuel debris, the term used to describe a mixture of molten fuel and broken interior parts.
The finding shows that nearly 7 years after the meltdowns, radiation levels remain so high that they present a major challenge to decommissioning work.
During the probe, 42 sieverts per hour of radiation was also detected outside the foundations of the reactor.
But officials said they have doubts about the accuracy of the reading because a cover had not been removed from the measuring instrument at the time.
They added that they don’t know why radiation levels were lower near the suspected fuel debris than around the foundations.
They gave a number of possible reasons, such as that cooling water may have washed radioactive materials off the debris.
TEPCO’s Chief Decommissioning Officer, Naohiro Masuda, says the company will develop debris-removal technology based on the outcome of the investigation.
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The corium of reactor 2 of Fukushima Daiichi is clearly visible

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Fukushima Blog by Pierre Fetet
Translation Hervé Courtois
 
It has been almost seven years since this deadly magma was created thanks to the imbecility of men. 7 years that we talk about it without ever really seeing it. And now Tepco, in January 2018, unveils, for the first time and in a very discreet manner, some very telling images of the corium of Fukushima Daiichi’s reactor 2.
 
Above illustration: screenshot made from a Tepco video
 
At first, all the media published again the photos provided by Tepco, where one sees for example a piece of a fuel assembly’s handle. It was deduced that the rest had melted but nothing more could be said.
 
In a second time, 3 days later, Tepco added a video of 3 minutes 34 that shows a selection of footage filmed inside the containment. In this video, we see very precisely corium flows that have solidified on metal structures under the reactor vessel.
 
The camera that filmed this hyper-radioactive material was designed to support 1000 Sieverts. But this device can not hide the ionizing radiation that forms many random clear points on the film.
 
The men who manipulated the probe outside the containment were certainly irradiated because the dose rate is still very high in the reactor. But Tepco has not yet released this information.
 
To summarize in images what happened in March 2011, the corium of reactor 2 passed through the reactor vessel, then made a 1 m wide large hole in the platform just below the reactor vessel:
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Source Tepco
Then it continued on its way encountering obstacles, forming stalactites in various places:
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Screenshots of the Tepco video
Finally, it spread to the bottom of the containment by cutting into the concrete. And there, we lose track because the investigations could not go further.
 
Has it gone far off the ground plate ? Did it join the toric pool by the pipes connecting the enclosure and the pool?
Let’s not forget that an explosion was heard by technicians on March 15, 2011 at 6:10 from reactor 2. Steam explosion?
Do not forget that the water that is injected continuously to cool the corium does not fill the enclosure because it is no longer intact.The water is permanently contaminated by the corium, before reaching the bottom of the plant and the groundwater. Let’s not forget that this moving groundwater flows into the Pacific, despite the ice wall, which is not perfectly watertight.
 
It will be observed that Tepco has not yet dared to provide a picture of the hole in the reactor vessel. It’s like the explosion of reactor 4, there are things that are better not to be disclosed because they tarnish the image of civil nuclear.
 
In the same manner, the people in charge of communication preferred to broadcast uncertain images on the 19th of January rather than these very interesting images which I extracted from the video.
 
Certainly, robotics in a radioactive environment has made real progress, but that hides the reality: we have not yet invented the machines that can dismantle the Fukushima Daiichi nuclear plant. And the forty years promise to complete this dismantling will certainly be insufficient.
 
Let’s not forget that there are all in all 3 coriums to recover and 3 swimming pools full of fuel to empty.
 
While Tepco “amuses” us with its technique, Tepco hopes to release 1 million tons of radioactive water in the Pacific that it has collected on the site, as if this ocean had not already suffered enough. It also makes it possible to forget the thousands of people suffering from thyroid disorders or other various pathologies due to radioactivity and the tens of thousands of displaced people who are being forced to return to contaminated territories.
 
Let’s wait for the big communication from TEPCO: the athletes of 2020 (Tokyo Olympics) must be amazed by the Japanese hyper-technicality so as to forget the basic dangers of ambient radioactivity.
 

Fukushima Unit 2 in the News Again

From Majia’s Blog

TEPCO tells us they have identified the remains of “part of a nuclear fuel assembly” scattered at the bottom of unit 2’s containment vessel:

CHIKAKO KAWAHARA January 20, 2018 Melted nuclear fuel seen inside No. 2 reactor or at Fukushima plant. The Asahi Shimbun http://www.asahi.com/ajw/articles/AJ201801200017.html

A remote-controlled camera captured what appears to be melted fuel inside a reactor of the stricken Fukushima No. 1 nuclear power plant, operator Tokyo Electric Power Co. said. The released footage showed pebble-like nuclear fuel debris and part of a nuclear fuel assembly scattered at the bottom of a containment vessel, located just below the pressure vessel.

Where is the rest of the fuel?

Fukushima’s reactor 2 held quite a bit more than a single fuel assembly. According to a November 16 report by TEPCO titled, ‘Integrity Inspection of Dry Storage Casks and Spent Fuel at Fukushima Daiichi Nuclear Power Station,’ as of March 2010 the Daini site held 1,060 tons of spent uranium fuel. The total spent uranium fuel inventory at Daiichi in March 2010 was reported as 1,760 tons. The 2010 report asserts that approximately 700 spent fuel assemblies are generated every year. The report specifies that Daiichi’s 3,450 assemblies are stored in each of the six reactor’s spent fuel pools. The common spent fuel pool contains 6291 assemblies.

Unit 2 has been in the news. Last February, Akio Matsumura described a potential catastrophe at Unit 2:

Akio Matsumura (2017, February 11). The Potential Catastrophe of Reactor 2 at Fukushima Daiichi: What Effect for the Pacific and the US? Finding the Missing Link, http://akiomatsumura.com/2017/02/the-potential-catastrophe-of-reactor-2-at-fukushima-daiichi.html, accessed November 20, 2017

It can hardly be said that the Fukushima accident is heading toward a solution. The problem of Unit 2, where a large volume of nuclear fuels remain, is particularly crucial. Reactor Unit 2 started its commercial operation in July 1974. It held out severe circumstances of high temperature and high pressure emanating from the March 11, 2011, accident without being destroyed. However, years long use of the pressure vessel must have brought about its weakening due to irradiation. If it should encounter a big earth tremor, it will be destroyed and scatter the remaining nuclear fuel and its debris, making the Tokyo metropolitan area uninhabitable.

Unit 2 has been in the news because of persistent high radiation levels. In Feb 2017, TEPCO reported measuring radiation levels of 530 SIEVERTS AN HOUR (10 will kill you) and described a 2-meter hole in the grating beneath unit 2’s reactor pressure vessel (1 meter-square hole found in grating):

Radiation level at Fukushima reactor highest since 2011 disaster; grating hole found. The Mainichi, February 2, 2017, http://mainichi.jp/english/articles/20170202/p2g/00m/0dm/087000c

TOKYO (Kyodo) — The radiation level inside the containment vessel of the No. 2 reactor at the crippled Fukushima Daiichi nuclear complex stood at 530 sieverts per hour at a maximum, the highest since the 2011 disaster, the plant operator said Thursday.

Tokyo Electric Power Company Holdings Inc. also announced that based on image analysis, a hole measuring 2 meters in diameter has been found on a metal grating beneath the pressure vessel inside the containment vessel and a portion of the grating was distorted.

…The hole could have been caused by nuclear fuel that penetrated the reactor vessel as it overheated and melted due to the loss of reactor cooling functions in the days after a powerful earthquake and tsunami on March 11, 2011 hit northeastern Japan.

According to the image analysis, about 1 square meter of the grating was missing.

This extraordinarily high radiation in unit 2 was reported by the Japanese media in January 2017 as presenting a barrier to the decommissioning timeline:

MASANOBU HIGASHIYAMA (January 31, 2017) Images indicate bigger challenge for TEPCO at Fukushima plant. The Asahi Shimbun, http://www.asahi.com/ajw/articles/AJ201701310073.html

If confirmed, the first images of melted nuclear fuel at the Fukushima No. 1 nuclear plant show that Tokyo Electric Power Co. will have a much more difficult time decommissioning the battered facility.

The condition of what is believed to be melted fuel inside the No. 2 reactor at the plant appears far worse than previously thought.

…High radiation levels have prevented workers from entering the No. 2 reactor, as well as the No. 1 and No. 3 reactors at the plant.

UNIT 2 HISTORY

Looking back at testimony by Masao Yoshida, Fukushima’s plant manager, and media coverage of that testimony, I see that unit 2 was identified as posing the greatest immediate risk, although the explosion at unit 3 was clearly larger (this discrepancy is perplexing).  Here is an excerpt of the testimony published by the Asahi Shimbun:

Yoshida feared nuclear ‘annihilation’ of eastern Japan, testimony shows. (September 12, 2014) THE ASAHI SHIMBUN http://ajw.asahi.com/article/0311disaster/fukushima/AJ201409120034

Plant manager Masao Yoshida envisioned catastrophe for eastern Japan in the days following the outbreak of the Fukushima nuclear disaster, according to his testimony, one of 19 released by the government on Sept. 11. . . .

. . . In his testimony, Yoshida described the condition of the No. 2 reactor at the Fukushima plant between the evening of March 14, 2011, and the next morning: “Despite the nuclear fuel being completely exposed, we’re unable to reduce pressure. Water can’t get in either.”

Yoshida recalled the severity of the situation. “If we continue to be unable to get water in, all of the nuclear fuel will melt and escape from the containment vessel, and radioactive substances from the fuel will spread to the outside,” he said. Fearing a worst-case scenario at the time, Yoshida said, “What we envisioned was that the entire eastern part of Japan would be annihilated.”

You can read more excerpts from the 400-pages of testimony published by the Asahi Shimbun, which both applauds and critiques the panel investigation of the disaster that produced the testimonies:

The Yoshida Testimony: The Fukushima Nuclear Accident as Told by Plant Manager Masao Yoshida The Asahi Shimbun http://www.asahi.com/special/yoshida_report/en/

Although the panel interviewed as many as 772 individuals involved, it failed to dig deep into essential aspects of the disaster because it made it a stated policy that it would not pursue the responsibility of individuals.

What is true about unit 2? Yoshida provides this account from the article cited immediately above:

At around 6:15 a.m. on March 15, 2011, four days after the Great East Japan Earthquake and tsunami, a round table presided by Yoshida in an emergency response room on the second floor of the Fukushima No. 1 nuclear plant’s quake-proof control center building heard two important reports, almost simultaneously, from front-line workers.

One said that pressure in the suppression chamber, or the lower part of the containment vessel for the No. 2 reactor, had vanished. The other said an explosive sound had been heard.

Question: Well, this is not necessarily in the No. 2 reactor, but sometime around 6 a.m. or 6:10 a.m. on March 15, pressure in the No. 2 reactor’s suppression chamber, for one thing, fell suddenly to zero. And around the same time, something …

Yoshida: An explosive sound.

http://majiasblog.blogspot.fr/2018/01/fukushima-unit-2-in-news-again.html

Fukushima Daiichi Reactor 2: new investigation

Tepco has just released the results of an investigation made in the containment of reactor 2. Nothing really new, apart from a found assembly element, we are waiting for radioactivity measurements now.
20 janvier 2018
A new 10-hour investigation was conducted in the Fukuishima Daiichi reactor 2 containment enclosure, according to a report released by Tepco on January 19, 2018. However, Tepco does not indicate the date of the operation. The images and measurements were taken using a 13 meter probe with a camera. TEPCO will only broadcast the radioactivity measurements later.
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Photo: an assembly element was found
According to this document, TEPCO gives two main informations:
– The entire bottom of the base of the reactor base is covered with deposits of sandy and clay.
– Some fuel assembly components have fallen to the base of the reactor base and are considered fuel debris.
As usual, Tepco does not use the word “corium”. It does not speak more about the radioactive environment of the place which is lethal (a last year made measure at this place was 530 Sieverts) but promises to return soon. I will update this page when the information falls.
The deposit of sandy and clay types is what is at the bottom of the enclosure and which had already been spotted last year around the pedestal. This vase prevents a clear view of the bottom of the enclosure because the slightest movement of the camera, the water is troubled.
For the first time, Tepco discloses a diagram showing the inside of the reactor pedestal. We see :
– an upper platform, which was already known, which allows access to control rods located just below the reactor vessel. This, according to the February 2017 report, is pierced with a hole 1 meter in diameter. It is the mass of the corium coming from the tank during the meltdown that made this hole.
– an intermediate platform that Tepco claims has not been piereced (but the diagram does not show it in full)
– An annular lower platform bordering the wall of the pedestal, which Tepco also claims that it has no hole. But, same remark, the diagram shows only half.
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The piece of assembly that emerges very clearly from a pile of various materials is an upper tie plate. It is surmounted by a bar (“bail handle”), a kind of handle for moving the assembly using an articulated arm. This photo makes it possible to deduce that at least one whole assembly has passed through the tank, which implies that the tank has a hole of at least the width of an assembly (approximately 50 cm). The probe has certainly taken pictures of this hole but Tepco do not release them.
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Type of assembly element found on the lower platform of the No. 2 reactor pedestal.
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This element is the upper part that we see for example in these assemblies of the reactor pool
Toshiba’s probe, during its presentation in Yokohama, December 22, 2017. The telescopic arm carries a panoramic camera.
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Here are the photos of the interior of the BR2 containment building released by Tepco on January 19, 2018:
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Here are some pages from the report on the same date:
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Tepco’s full report of 19 January 2018

[pdf] HANDOUTS_180119_01-E

Source : http://www.fukushima-blog.com/2018/01/reacteur-2-de-fukushima-daiichi-nouvelle-investigation.html

Special thanks to Pierre Fetet of the Fukushima Blog

Translation Hervé Courtois (Dun Renard)

TEPCO claims to have found ‘fuel debris’ in No. 2 reactor

reactor 2 melted fuel spotted 2018-01-19.png
TEPCO finds ‘fuel debris’ in No. 2 reactor
 
The operator of the damaged Fukushima Daiichi nuclear power plant says it has found what looks like fuel debris in the plant’s No. 2 reactor.
The nuclear accident occurred in March, 2011.
 
Tokyo Electric Power Company, or TEPCO, on Friday looked inside the containment vessel of the No. 2 reactor.
 
TEPCO confirmed, for the first time, the existence of chunks that are believed to be a mixture of melted nuclear fuel and parts of bindings.
 
The company plans to determine how to remove the debris based on the results of the investigation.
 

Tepco to resume attempt to probe damaged reactor at Fukushima No. 1 plant

Reactor 2.jpg
Tepco to resume attempt to probe damaged reactor at Fukushima No. 1 plant
The operator of the Fukushima No. 1 nuclear power plant has said it will resume late this week a survey of the crippled No. 2 reactor using a telescopic arm, hoping to obtain images of melted nuclear fuel.
In Friday’s survey, Tokyo Electric Power Company Holdings Inc. aims to investigate the area beneath the reactor’s pressure vessel, through which nuclear fuel is believed to have melted. The step is needed to help develop a plan for removing the fuel for the ultimate decommissioning of the plant.
Tepco, in announcing the move on Monday, said it will insert a 13-meter long pipe at the bottom of the pressure vessel and then deploy a camera at the tip of the pipe to film the bottom of the outer primary containment vessel, where fuel is believed to have accumulated.
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The device will also measure the temperature and radioactivity levels in the area. The survey is expected to take one day.
In January last year, an inserted camera with a limited view captured possible melted fuel in the interior of the No. 2 reactor.
The following month, Tepco attempted a survey using a scorpion-shaped robot inside the unit, but the effort ended in failure due to a technical flaw.
Nearly seven years after the March 2011 earthquake and tsunami that wrecked the plant, details of the damage to the reactors remain largely unknown due to high levels of radiation.
Reactors 1, 2 and 3 at the four-reactor plant suffered core meltdowns due to a loss of cooling water in the world’s worst nuclear crisis since the 1986 Chernobyl disaster.

Fukushima Unit 2 Radiation Readings Revised

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TEPCO revised unit 2’s containment inspection radiation readings done earlier in 2017, claiming a set of instrument and calibration errors caused the inaccurate readings.

TEPCO claims that their camera based radiation estimates were too high due to an oversight where they forgot to reset the sensitivity threshold on the equipment that was reading camera interference.

The final claim made in the report for downgrading the radiation readings was that one of the 4 sensors was reading considerably higher than the other 3. When they took that sensor out of the readings the other 3 sensors read considerably lower.

Source : Tepco’s handout

http://www.tepco.co.jp/en/nu/fukushima-np/handouts/2017/images/handouts_170727_03-e.pdf