nuclear-news

The News That Matters about the Nuclear Industry Fukushima Chernobyl Mayak Three Mile Island Atomic Testing Radiation Isotope

Probe shows challenges posed by melted fuel at Fukushima plant

jhhll.jpg
The rod-like probe outfitted with a tong-like pinching device that was used to touch melted nuclear fuel debris at the bottom of the No. 2 reactor at the Fukushima No. 1 nuclear plant
February 18, 2019
A specially designed, remotely controlled probe touched melted nuclear fuel debris at the bottom of a ruined reactor at the Fukushima No. 1 nuclear power plant in the first successful operation to inspect radioactive debris through direct contact.
The plant’s operator, Tokyo Electric Power Co. (TEPCO), lowered the rod-like probe outfitted with a tong-like pinching device into the primary containment vessel of the No. 2 reactor at the crippled plant and used the machine to successfully lift pieces of the debris several centimeters.
The removal of the fuel debris is the biggest challenge in the long process of decommissioning the reactors, which will take at least three to four decades. The lifting of debris is a ray of hope in the grim battle to overcome the formidable challenge.
But the success was tempered by the fact that there were large chunks with slick surfaces the robot’s pinchers were unable to grab. The probe found that deposits in various conditions lie scattered about the bottom of the vessel. Some pieces are apparently entangled in the surrounding equipment.
Tasks in and around the No. 1 to No. 3 reactors at the nuclear plant cannot be carried out by humans because of dangerously high radiation levels. Nuclear fuel in the core of these reactors overheated and melted down after towering tsunami triggered by an epic earthquake knocked out vital cooling systems on March 11, 2011.
Read more:
Advertisements

February 23, 2019 Posted by | fukushima 2019 | , , , | Leave a comment

TEPCO finds some debris in Fukushima N°2 reactor could be removed

safe_image.php.jpg
February 14, 2019
TOKYO (Kyodo) — The operator of the disaster-hit Fukushima Daiichi nuclear power plant said Wednesday its latest probe has found that debris inside one of the reactors can be lifted, raising hopes for progress in its bid to remove melted fuel and decommission the complex.
During the around eight-hour examination on Wednesday, TEPCO inserted the probe, equipped with a camera, radiation meter and tong-like grips to hold objects, through a penetration hole that provides access to the primary containment vessel.
Of the six locations that were surveyed, the probe, which is 30 centimeters tall and 10 cm wide, successfully moved gravel and a stick-like structure in deposits in five areas. The tong-like grips were able to lift up to 5 cm of some of the deposits, according to TEPCO.
In the remaining area that resembled clay, however, the probe could not pick up any of the deposited material, indicating it was relatively hard.
“As we have found that we can move (the deposits), we proved that extracting fuel debris is possible. But for objects that cannot be grasped, we need to develop new equipment,”
Read more:

February 23, 2019 Posted by | fukushima 2019 | , , | Leave a comment

Fukushima Daiichi: probe touched suspected fuel debris in reactor#2

Images have been released of the reddish-brown amorphous mass. But its level of radioactivity is still unknown, which means that TEPCO has not even reached the earliest stage of its reactor decommissioning process.
I am acutely reminded again of the magnitude of this irreversible mess.
The technology we are left with is an out-of-control monster. And so long as nuclear power plants remain in operation, there is no guarantee that the same nightmare will not recur–even as we speak.

TEPCO: Probe touched suspected fuel debris
February 13, 2019
The operator of the damaged Fukushima Daiichi nuclear plant says a probe made direct contact with substances believed to be fuel debris at one of the plant’s reactors.
Tokyo Electric Power Company, or TEPCO, conducted its first contact survey of suspected fuel debris at the Number 2 reactor on Wednesday.
TEPCO has already confirmed the existence of deposits believed to be a mixture of molten nuclear fuel and structural parts at the bottom of the reactor’s containment vessel.
In Wednesday’s survey, a pole that can extend to 15 meters was sent under the reactor, and the probe was lowered from the end of the pole.
TEPCO plans to take out a small amount of the deposits with a different device in the latter half of the next fiscal year to use them as samples for study.
Officials say the probe was able to touch the deposits without any major trouble.
This is a key survey for devising a way to remove radioactive deposits.
They say they looked into the deposits’ hardness and whether they can be moved.
 
1st contact made with melted nuclear fuel at Fukushima plant
February 14, 2019
“The probe lifted pebble-like nuclear fuel debris and structural parts up to 8 cm in diameter at five spots in the 2,500-square-cm area that was investigated. It failed to pick up debris at one spot.
TEPCO said the probe could not lift clay-like debris likely because it had adhered to the bottom of the containment vessel.
The probe also touched nuclear fuel debris lying at several spots on the lattice-shaped scaffold for workers directly below the reactor’s pressure vessel.
The previous investigation of the No. 2 reactor in 2017 located melted fuel debris on the scaffold. But a robot deployed for a further investigation broke down on its way to the debris.
In a survey last year, the utility used the rod-like probe to take images of the inside of the reactor.
TEPCO is expected to remove a small amount of nuclear fuel debris in the second half of fiscal 2019 as part of preparations for full-scale retrieval.”

February 18, 2019 Posted by | fukushima 2019 | , , , | Leave a comment

Fukushima Unit 2 Refueling Floor Work Poses Risks

Work has begun on the unit 2 refueling floor at Fukushima Daiichi. Previously, TEPCO installed a controlled building on the side of unit 2. This building provides filtered ventilation and a staging area. It will allow workers to send equipment into the reactor building refueling floor. The wall between the two buildings was opened earlier this spring.
After the initial disaster it that unit 2 was creating the most significant radiation releases to the environment.  The highest of the three units that melted down. In 2012 an obvious steam leak from the reactor well was discovered via TEPCO images.
7746043936_6baa72182e_b.jpg
TEPCO eventually put a filtration system on the building. This prevented radiation releases to the environment. The future plans for this unit include removing the entire refueling floor level. The roof and walls down to the refueling floor deck are to be removed. Then a new cover building with replacement systems will be installed. Workers are still unable to enter the refueling floor area. High radiation levels prevent human entry. Only robots have entered. TEPCO has not addressed this radiation risk during the demolition and construction phase. Earlier reporting mentioned the planned use of dust suppressants during the demolition work. There is no management plan for potential radiation releases from the reactor well.
TEPCO’s schedule shows they may begin removing equipment from inside unit 2’s refueling floor as early as mid-July. The building demolition and spent fuel removal schedule is still somewhat vague. This is dependent on other work completion.

August 1, 2018 Posted by | Fukushima 2018 | , , , | Leave a comment

Gov’t, TEPCO consider starting removal of debris from 2nd reactor at Fukushima nuke plant

reactor2 25 july 2018.jpg
The inside of the containment vessel of the No. 2 reactor at the Fukushima No. 1 nuclear plant is seen in this frame grab from video provided by the International Research Institute for Nuclear Decommissioning (IRID).
TOKYO — The government and Tokyo Electric Power Co. (TEPCO) are considering starting the removal of molten nuclear fuel from the No. 2 reactor of the Fukushima No. 1 Nuclear Power Plant, people familiar with the matter have told the Mainichi Shimbun.
Three of the four reactors at the plant in the northern Japanese prefecture of Fukushima suffered core meltdowns after the reactors’ cooling systems shut down due to tsunami triggered by the Great East Japan Earthquake of March 2011.
According to the sources, an on-site inspection of molten fuel debris inside the reactor’s containment vessel using remote control equipment will be conducted this fiscal year. Data from the test, such as the hardness of the debris and whether it is movable, will be used to develop equipment to remove and store the highly radioactive materials.
Under the road map for decommissioning the power plant revised in September last year, the government and TEPCO are to decide on a reactor on which to start debris removal and determine how to carry out the procedure by March 2020, the end of next fiscal year. Actual removal is scheduled to begin in 2021.
In January of this year, the government and TEPCO managed to insert a pipe with a camera into the No. 2 reactor’s containment vessel and captured the image of gravel- or clay-like deposits believed to be fuel debris on the floor.
According to the people familiar with the matter, the government and TEPCO have judged that it is necessary to further examine the conditions of the No. 2 reactor as a possible starting point for fuel debris removal, since inspections needed for such an operation have progressed further on the No. 2 unit more than on the other two reactors that suffered core meltdowns in 2011.
The government and TEPCO will carry out the new probe in the fall or later of this year by inserting a camera-equipped pipe attached with a device capable of directly touching the debris, which will gather data on the reactor’s current conditions. The debris is not taken out of the containment vessel at any point of this survey. In the next fiscal year starting April 2019, they will consider examining wider areas inside the containment vessel and recovering a small sample of molten fuel for analysis ahead of full-fledged extraction in 2021.
As for the other reactors, the No. 3 unit has water inside the containment vessel, the removal of which is difficult, although images of what appeared to be fuel debris were captured inside the reactor in July 2017. The No. 1 reactor, meanwhile, will receive another probe to determine the existence of molten fuel inside because an inspection carried out in March last year failed to spot any debris.
TEPCO will shortly submit a plan for the examination of the No. 1 and No. 2 reactors’ interior for fiscal 2019 and later to the Nuclear Regulation Authority.
(Japanese original by Toshiyuki Suzuki and Ei Okada, Science & Environment News Department)

August 1, 2018 Posted by | Fukushima 2018 | , , | Leave a comment

TEPCO to gauge radiation in reactor building

 

June 21, 2018
The operator of the crippled Fukushima Daiichi nuclear power plant intends to send a robot into the No.2 reactor building as early as next week to measure interior radiation levels in detail.
 
It is a key step toward removing all 615 nuclear fuel rod units that remain in a storage pool in the building, and eventually decommissioning the reactor.
 
The pool is located on the top floor of the building. The No.2 reactor experienced a meltdown after the major earthquake and tsunami that hit eastern Japan in 2011.
 
Tokyo Electric Power Company, or TEPCO, plans to transfer the fuel units to reduce the risks posed by possible earthquakes and other factors.
 
TEPCO needs to map radiation levels and other detailed conditions inside the building before retrieving the fuel units.
 
The utility on Thursday finished breaching a wall of the building to allow entry to a robot and heavy machinery. Work on the 5-meter wide and 7-meter high hole started last month.
 
TEPCO plans to send a robot fitted with a camera and a radiation measurement device through the opening as early as next week.
 
And TEPCO could start removing the fuel around fiscal 2023 based upon the survey results.
 
TEPCO also seeks to begin retrieving nuclear fuel from the No.1 reactor around fiscal 2023 and from the No.3 reactor as soon as this autumn. Both reactors had a meltdown following the natural disaster.

 

June 26, 2018 Posted by | Fukushima 2018 | , , | 1 Comment

TEPCO prepares to remove fuel from damaged reactor

 

May 28, 2018
The operator of the damaged Fukushima Daiichi nuclear power plant has started laying the groundwork to retrieve fuel from one of the plant’s reactor buildings. It’s a crucial step toward scrapping the complex.
 
Tokyo Electric Power Company began the work on Monday to move 615 fuel rod units from a storage pool on the top floor of the No. 2 reactor to a more secure location.
 
The No. 2 reactor is one of 3 at the plant that melted down in the 2011 accident. Radiation levels inside the reactor building remain high.
 
TEPCO will open a hole measuring 5 by 7 meters in the building’s wall and send a robot through it to measure radiation levels inside.
 
A section of the wall will be divided into 29 blocks, each with a handle to facilitate its removal.
 
From a control room some distance from the reactor building, TEPCO officials will remotely operate a machine to remove the blocks.
 
The work is expected to continue until mid-June.
 
The plant operator will measure radiation levels before deciding how to retrieve the fuel rods. The company plans to start retrieving the fuel in fiscal 2023.
 
TEPCO official Hiroshi Noda says that although the decommissioning work for the No. 2 reactor has just started, it’s a major step forward.
 
He says the company will make sure that the work will have no impact on the environment.

 

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

New Data for Unit 2’s Missing Fuel

u2_pedestal_web.jpg
TEPCO published a Roadmap document right before leaving for Golden Week vacation. In this document is a 30+ page section of new data for unit 2’s missing fuel.
 
TEPCO has given varying explanations for unit 2’s meltdown and fuel location. Two muon scans have been completed for unit 2. The first found no fuel remaining in the RPV. A second scan by TEPCO claimed to have found some fuel in the bottom of the RPV, our analysis of the scan found otherwise. It is likely that all of the fuel inside the reactor vessel melted and all of it except for some residues is no longer in the RPV.
 
Fuel debris volume:
The volume of fuel debris inside unit 2 is difficult to calculate due to a number of factors. The debris is spread between multiple areas including the floor grate level, the pedestal floor and whatever debris may have burned down into the pedestal floor. The total volume of the fuel core is known for unit 2 but the exact size of the pedestal diameter is not known.
 
A fuel debris volume estimate was made for unit 1 based on known data and meltdown events at that reactor. Unit 1 is smaller than unit 2 in both fuel core size and size of the reactor structures. The general reactor building sizes and the fuel core sizes should be something that could roughly scale up for unit 2. Unit 1 estimate showed a fuel volume of all of the fuel and related melted structural materials as 60-100 cm deep.
 
Inside unit 2 about 50% of the pedestal floor was found to be covered with 70 cm of fuel debris. Additional fuel debris in an unknown volume is on the floor grate level. An unknown amount is burned down into the pedestal concrete basemat. Further fuel debris may be in lower reactor piping systems or the outer drywell floor. Unit 2’s fuel debris volume would also be reduced as the control rod drive array and bottom head of the reactor vessel are still intact. That large amount of metal structural material is known to not be part of the melted fuel debris in unit 2.
 
What has been found on inspection may be all of the fuel debris for unit 2 if a portion of the material is burned down into the pedestal basemat concrete. In most meltdown scenarios that is a given assumption unless the containment structure was heavily and repeatedly flooded with water at the time the fuel first dropped into the pedestal. With unit 2 that is an unlikely scenario.
 
There is an alternative possibility that a large amount of the radioactive materials in the fuel vaporized during the meltdown and escaped containment. This concept requires more investigation to confirm vaporization but this possibility for unit 2 is not completely ruled out. Fused microparticles containing nuclear fuel and other meltdown related materials have been found over a wide swath of Fukushima and beyond. Unit 2’s refueling floor blow out panel and reactor well containment gasket are one escape path for micro materials, steam and other gasses. Unit 2’s venting attempts are another concern. TEPCO has claimed the direct drywell venting of unit 2 didn’t work and the rupture disc for this system did not break as intended. TEPCO has provided no conclusive proof of this claim such as photos, video or other tangible evidence for this claim. Due to this, there is still the possibility that unit 2’s venting released some of these fused microparticles of fuel.
 
Radiation levels:
The radiation levels found in unit 2’s pedestal including a reading close to the fuel debris pile were between 7-8 Sieverts/hour. The high reading found along the CRD rail in 2017 was between 200-300 Sieverts/hour. These pedestal readings are drastically lower than what would be expected near an unshielded large pile of fuel debris.
By comparison, radiation levels along the outer containment wall in 2012 were within a similar range of the lower readings found on the CRD rail in 2017.
 
The elephant’s foot at Chernobyl, measured within the first year of the disaster, converted to Sieverts was 100 Sievert/hour.
 
Underwater readings in unit 1’s torus room near what is suspected fuel debris, taken in 2012 were 100,000 to 1 million Sieverts/hour.
 
Radiation levels near the fuel debris indicate that the top layers of debris may be mostly metallic materials with little fuel.
 
Radiation levels indicate that fuel bearing debris is not in the visible layer in the pedestal. (other possible locations – vaporized/vented, beneath the metallic layer, sml amounts in piping).

Roadmap document, section on unit 2:
http://www.tepco.co.jp/nu/fukushima-np/roadmap/2018/images1/d180426_08-j.pdf#page=3

TEPCO photo page for unit 2 findings:
http://photo.tepco.co.jp/date/2018/201804-j/180426-01j.html

May 10, 2018 Posted by | Fukushima 2018 | , , | Leave a comment

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.
 
jhjjkkllmm.jpg

 

February 1, 2018 Posted by | Fukushima 2018 | , , | Leave a comment

The corium of reactor 2 of Fukushima Daiichi is clearly visible

1
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 3min34 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:
2
Source Tepco
Then it continued on its way encountering obstacles, forming stalactites in various places:
3
5
5
4
8
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 its 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.
 

January 28, 2018 Posted by | Fukushima 2018 | , , | 1 Comment

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

January 27, 2018 Posted by | Fukushima 2018 | , , | Leave a comment

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.
1.JPG
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.
2.JPG
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.

3.jpg

4.jpg
Type of assembly element found on the lower platform of the No. 2 reactor pedestal.
5.jpg
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.
6.JPG
7.JPG
Here are the photos of the interior of the BR2 containment building released by Tepco on January 19, 2018:
10.jpg
11
12
13.jpg
14.jpg
15.jpg
16.jpg
17.jpg
18
19
20.JPG
Here are some pages from the report on the same date:
x.JPG
y
z
o

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)

January 21, 2018 Posted by | Fukushima 2018 | , , , | 2 Comments

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.
 

January 19, 2018 Posted by | Fukushima 2018 | , , | Leave a comment

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

Reactor 2.jpg
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.
u2_pedestal_composite_web.jpg
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.

January 18, 2018 Posted by | Fukushima 2018 | , , | Leave a comment

Fukushima Unit 2 Radiation Readings Revised

jhjklmmù.jpg

 

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

 

 

July 31, 2017 Posted by | Fukushima 2017 | , , , | Leave a comment