In Unit 1, the fuel and the metal cladding that forms the outer jacket of the fuel rods melted, then re-solidified as fuel debris. To reduce the risk from this fuel debris, preparations are under way for retrieving it from the reactors.

Unit 1 Status

  • unit 1 status

    Survey inside containment vessel

    —Survey using robots, etc.—

    The containment vessel cannot be accessed readily by people because of the high radiation levels. Information inside the containment vessel is therefore being gathered using robots and other equipment that can be operated remotely. The surveys to date have obtained video and other images inside the containment vessel (inside the pedestal).

    —Measurement by muon tomography—

    Muons are cosmic rays that do not easily penetrate objects with large mass. They are thus used to identify the location of fuel debris, for example, from outside the reactor building.

Efforts to Date

Surveys already conducted inside containment vessel

Time Investigation Release
October 2012 (1st)

Gather information inside the Primary Containment Vessel (outside of the pedestal)

Collect sample of the stagnant water

April 2015 (2nd)

Gather information inside the Primary Containment Vessel (basement level 1)

April 2015

March 2017 (3rd)

Gather information inside the Primary Containment Vessel (basement level 1)

Collect sample of the stagnant water

March 2017

July 2017

The status of progress on the mid- to long-term roadmap (decommissioning and contaminated water measures team meetings/secretariat conferences) is updated in monthly progress reports and other materials.
See the material here for details.

Sampling

To decide the optimal method of retrieving fuel debris in each case, it is important to determine the state of the debris. Sampling is being used to study how best to retrieve, transport, and store the fuel debris. By conducting sediment sampling inside the containment vessel from March to April 2017, the elements originally inside the containment vessel were confirmed.

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