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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.”

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February 18, 2019 Posted by | fukushima 2019 | , , , | 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.
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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)

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

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

TEPCO to look inside Fukushima reactor 3

TOKYO (Jiji Press) — Tokyo Electric Power Company Holdings Inc. will probe the inside of the containment vessel of the No. 3 reactor at its disaster-stricken Fukushima No. 1 nuclear power plant this summer, company officials said Monday.
 
The aim of the move is to confirm the expected presence of melted nuclear fuel debris in the containment vessel.
 
TEPCO explained the plan at a Nuclear Regulation Authority meeting on the decommissioning process of the Fukushima plant, which suffered a triple meltdown due to damage from the March 2011 earthquake and tsunami.
 
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May 24, 2017 Posted by | Fukushima 2017 | , , | Leave a comment

New robot built to study inside of No. 1 reactor at Fukushima plant

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A new investigative robot, equipped with a censoring unit hanging through metal grating, is scheduled to be send into the No. 1 reactor at the Fukushima No. 1 nuclear power plant in the coming months. (Kohei Tomida)

 

HITACHI, Ibaraki Prefecture–Another robot has been developed for the elusive goal of locating melted fuel and surveying the interior of the No. 1 reactor at the Fukushima No. 1 nuclear plant.

A team of engineers and researchers from Hitachi-GE Nuclear Energy Ltd. and the International Research Institute for Nuclear Decommissioning revealed the robot on Feb. 3.

Tokyo Electric Power Co., operator of the plant, plans to deploy the robot into the No. 1 reactor before the end of March.

The robot will be fitted with a censoring unit mounted with a camera, dosimeter and lighting. Its purpose is to give TEPCO an idea of the location and condition of the melted nuclear fuel in the reactor.

Most of the melted fuel is believed to have fallen through the reactor’s pressure vessel, landed on the bottom of the surrounding containment vessel, and is soaking in cooling water about 2 meters deep.

The new robot will maneuver around metal grating originally set up for maintenance work about 3.5 meters above the bottom of the containment vessel.

At each of five survey points, the robot will lower the censoring unit through the grating. The unit can operate in water.

In April 2015, TEPCO sent two robots into the No. 1 reactor, but they could not locate the melted fuel.

One of them became stuck, and high radiation levels disabled the camera on the other. TEPCO abandoned the machines in the reactor.

On Jan. 30, a remote controlled video camera sent into the No. 2 reactor took what are believed to be the first images of melted fuel at the plant.

http://www.asahi.com/ajw/articles/AJ201702060040.html

February 6, 2017 Posted by | Fukushima 2017 | , , , | Leave a comment

TEPCO to probe Fukushima reactor again to confirm nuclear debris

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An executive of the operator of the crippled Fukushima Daiichi nuclear complex said Friday the company plans to probe inside the plant’s No. 2 reactor by the end of February to confirm whether the black mass spotted in a recent survey was nuclear debris.

Naohiro Masuda, the chief decommissioning officer at Tokyo Electric Power Company Holdings Inc. told Kyodo News it is “possible” to conduct the probe using a robot, the day after the operator announced it had detected extraordinarily high radiation levels inside the reactor.

The operator will be able to tell whether the deposits are nuclear debris from the March 2011 meltdown if new images and data such as the radiation levels and temperatures are obtained in the upcoming robot survey, he said.

http://english.kyodonews.jp/news/2017/02/456944.html

February 3, 2017 Posted by | Fukushima 2017 | , , , | Leave a comment