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Probe shows challenges posed by melted fuel at Fukushima plant

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

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

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

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

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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

Debris Removal at Reactor # 3 Delayed, but Arrival of the First Elements of the New Building for its Spent Fuel Removal

Transportation of the supporting part of a new roof for the Unit 3 fuel removal at Fukushima Daiichi Nuclear Power Station


The clearing of debris from reactor # 3 is delayed, delaying the construction of the new building to remove spent fuel from the pool. The debris removal was to be done in order to build a new workshop to remove the fuels from the pool.
The removal of the spent fuel should have started in January 2018. In the beginning, TEPCo was to start in 2015. We do not know their new schedule yet.


On the other hand, TEPCO communicated on the arrival of the first elements of the new building, with photos and video.

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The dose rates on the site are here. There is up to 2.6 mSv / h in the vicinity of reactor No.3.

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Links from TEPCO:
Photos of the new building
http://www.tepco.co.jp/en/nu/fukushima-np/handouts/2016/images/handouts_161220_01-e.pdf
Video
http://photo.tepco.co.jp/en/date/2016/201612-e/161220-01e.html
Dose rates in Reactor 3 vicinity
http://www.tepco.co.jp/en/nu/fukushima-np/f1/surveymap/images/f1-sv-20161219-e.pdf

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