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information about Fukushima published in English in Japanese media info publiée en anglais dans la presse japonaise

Robot checking No.1 containment vessel

April 10, 2015

 

Robot inspects inside of Fukushima No. 1 reactor container

http://mainichi.jp/english/english/newsselect/news/20150410p2g00m0dm062000c.html

 

TOKYO (Kyodo) -- The operator of the crippled Fukushima Daiichi nuclear power plant on Friday began a remote-controlled robot survey inside the No. 1 reactor's containment vessel, a step toward grasping the condition of melted fuel debris in detail and extracting it.

It is the first time Tokyo Electric Power Co. has deployed a robot to check the interior of a reactor's primary containment vessel since the March 2011 three-reactor meltdown triggered by a huge earthquake and tsunami.

TEPCO plans to eventually inspect the lower part of the containment vessel where a chunk of fuel debris is believed to be accumulating. That, however, is currently not feasible as the robot cannot be deployed in highly radioactive water generated in the process of cooling the fuel. A water-proof version of the robot is expected to be developed by the end of next March.

During Friday's survey, TEPCO hopes to obtain data on radiation levels and temperature and footage of the upper part of the vessel. Another survey will follow Monday next week.

Developed by Hitachi-GE Nuclear Energy Ltd. and the International Research Institute for Nuclear Decommissioning, the robot is equipped with cameras, a thermometer and dosimeter. Under high levels of radiation harmful to electronics, it can function properly only for around 10 hours, the institute said.

On Friday morning, workers inserted the shape-shifting robot through a narrow pipe, operating it from a location with relatively low levels of radiation within the reactor building. The robot can expand to a U shape to crawl inside the container, according to TEPCO.

Fuel inside the Nos. 1 to 3 units is believed to have melted through the reactor pressure vessels and has been accumulating in the outer containers. But the details remain unknown more than four years after the nuclear crisis due to extremely high levels of radiation.

In October 2012, radiation levels inside the containment vessel, which workers measured by lowering a dosimeter, measured up to 11 sieverts per hour.

Last month, the utility said it has confirmed nearly all fuel in the No. 1 reactor has melted and fallen into the containment vessel, through analysis utilizing cosmic rays called muons.

April 10, 2015(Mainichi Japan)

 

 

 

See also:

 

Robot enters primary containment vessel of reactor 1 in Fukushima

http://www.japantimes.co.jp/news/2015/04/10/national/remote-controlled-robot-probe-inside-reactor-1-containment-vessel/#.VSfYmpPwmos

 

Kyodo

A robot on Friday crept into the deadly primary containment vessel of reactor 1 of the Fukushima No. 1 power plant to surveil its damaged interior, Tokyo Electric Power Co. said.[… ]

 

 

 

How robots are used at Fukushima Daiichi

http://www3.nhk.or.jp/nhkworld/english/news/20150410_12.html

 

Apr. 10, 2015 - Updated 03:16 UTC+2

The operator of the damaged Fukushima Daiichi nuclear plant has no choice but to rely on robots to determine the state of the 3 reactors that suffered meltdowns. The high radiation levels could prove fatal for humans in a short period of time.

In March of last year, Tokyo Electric Power Company deployed a robot on the top floor of the building that houses the No.2 reactor and drilled for samples from the concrete floor. The operation was aimed at assessing the level of contamination in the building.

Robots are being developed to decontaminate the reactor buildings. One of them sprays particles of dry ice onto the floors and walls to remove their surfaces.

Robots are also used to study the condition of the reactors' containment vessels.

In November of 2013, a robotic probe confirmed for the first time that radioactive water was leaking from the containment vessel of the No.1 reactor.

But there are limits to what robots can do. A number of narrow spaces and uneven surfaces inside the reactor buildings are littered with debris.

This makes it difficult for robots to move around freely, and they often become stuck and irretrievable.

Another major obstacle is the intense radiation. Images of the inside of the containment vessel of the No.2 reactor shot by an endoscopic camera are completely fogged due to the radiation.

When approaching the nuclear fuel, even robots can malfunction or fail to capture clear images.

In the latest probe, efforts are being made to avoid such glitches by minimizing the use of computer circuits and other means. Still, engineers say, the probe can operate for only 2 days.

The government and Tokyo Electric are planning to examine the inside of the containment vessel of the No.2 reactor as well. But the intense radiation from the melted fuel makes it difficult even for robots to approach.

 

 

April 9, 2015

Robot to survey damaged Fukushima reactor

http://www3.nhk.or.jp/nhkworld/english/news/20150410_06.html

 

Apr. 9, 2015 - Updated 23:08 UTC+2

The operator of the crippled Fukushima Daiichi nuclear power station will start looking inside one of the damaged reactors on Friday, with the help of a robot.

Three of the plant's reactors suffered meltdowns due to the March, 2011, earthquake and tsunami.

Since then, extremely high levels of radiation have prevented surveys on the location of molten fuel and internal damage to the reactors and their containment vessels. The vessels enclose reactor cores.

The plant's operator, Tokyo Electric Power Company, plans to put a 60-centimeter-long, snake-shaped robot into the No.1 reactor containment vessel.

The utility will operate the robot by remote control and have it negotiate obstacles.

Radiation and temperature levels will be measured and an installed camera will allow workers to study internal damage.

TEPCO also plans to run the robotic assessment on Monday.

Up until now the company has used computer simulations and scans with subatomic-particles to predict what the No.1 reactor containment vessel is like inside.

The results indicate almost all its nuclear fuel has melted and fallen to the bottom of the vessel in the basement of the reactor building.

TEPCO officials say they hope to understand the internal damage to the vessel and gain clues on how best to remove the nuclear fuel.

They will make the most of data collected to help decommission the reactors.

 

 

 

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