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Reactor No.2: Fuel assembly likely dropped through pressure vessel

Reactor No.2: Fuel assembly likely dropped through pressure vessel

For more details, see TEPCO's handouts on







January 20, 2018


Melted nuclear fuel seen inside second Fukushima reactor



A photo provided by the International Research Institute for Nuclear Decommissioning on Jan. 19, 2018 and taken by a robotic probe shows a part of what is believed to be the handle of a fuel rod container and melted fuel in small lumps scattered on a structure below the No. 2 reactor core at the Fukushima No. 1 nuclear plant. (International Research Institute for Nuclear Decommissioning via AP)


TOKYO (AP) -- The operator of Japan's crippled Fukushima nuclear plant said Friday that a long telescopic probe successfully captured images of what is most likely melted fuel inside one of its three damaged reactors, providing limited but crucial information for its cleanup.

Tokyo Electric Power Co. said the fishing rod-like device carrying a camera went deep into the plant's Unit 2 primary containment vessel. The images indicated that at least part of the fuel had breached the core, falling to the vessel's floor, TEPCO spokesman Takahiro Kimoto said.


"There is so much that we still haven't seen," Kimoto told reporters. "But we were able to obtain important information that we need in order to determine the right method for removing the melted fuel debris."


A massive earthquake and tsunami in 2011 caused three reactors at the Fukushima plant to melt. The plant's decommissioning is expected to take decades.


Melted fuel has previously only been documented inside Unit 3, where an underwater probe captured images of large amounts of melted fuel debris that looked like molten lava mixed with broken parts of equipment and structures on the concrete floor.


During Friday's investigation, the device -- developed by Toshiba Corp. and the International Research Institute for Decommissioning, a government-funded organization of nuclear companies -- found deposits in the shape of pebbles, clay and other forms, Kimoto said.

Determining the location of the melted fuel is crucial in planning for its removal, the hardest process in the plant's decommissioning.


The government and TEPCO plan to determine the methods and start removing melted fuel from one of the three reactors in 2021. But experts say a lack of data is delaying the development of the precise type of technology and robots.


The images from Friday's probe show was what is believed to be a stainless steel handle of a case containing bundles of fuel rods sitting on a pile of pebble-shaped and clayish substances, in a sign the rods melted and breached the bottom of the core. The deposits seemed to be scattered in a wide area around the pedestal, the main structure that sits underneath the core.


Experts say they believe part of the fuel still remains inside the core of the Unit 2 reactor, while almost all of the fuel rods in Unit 1 and 3 melted and fell to the bottom of the primary containment chambers.




See also : https://www.japantimes.co.jp/news/2018/01/19/national/tepco-spots-fukushima-fuel-debris-reactor-2-says-fuel-rod-assembly-fell-reactor/#.WmMFunkiGos


Tepco spots Fukushima fuel debris in reactor 2, says fuel rod assembly ‘fell out of reactor’

by Kazuaki Nagata

Tokyo Electric on Friday said it had spotted what is almost certainly fuel debris in reactor 2 at the Fukushima No. 1 plant that shows its fuel assembly likely dropped through the pressure vessel.[...]




 January 20, 2018


Melted nuclear fuel seen inside No. 2 reactor at Fukushima plant


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.

The footage was taken Jan. 19 inside the No. 2 reactor, which went into meltdown due to the 2011 earthquake and tsunami disaster.

“From the look of things, it must be nuclear fuel debris,” said a TEPCO official.

The utility inserted an extendable rod with a span of 16 meters into the containment vessel from an opening in the side. It was positioned in an area just below the pressure vessel.

The remote-controlled camera was affixed to the tip of the rod and then lowered, along with a dosimeter to measure the amount of radiation inside.

The footage showed that a handle for a 4-meter-long nuclear fuel assembly, which had been originally located in the pressure vessel, had dropped to the bottom of the containment vessel.

The handle had been installed on the top of the nuclear fuel assembly. This led TEPCO to conclude that all of the nuclear fuel below the handle had melted.

An accumulation of pebble-like materials around the handle prompted the official to remark that the same phenomenon was observed after the Three Mile Island nuclear accident in Pennsylvania in 1979.

"(What we found this time) is apparently the same situation,” the official said.

Reactor No.2: Fuel assembly likely dropped through pressure vessel
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