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Decommissioning Plan of Fukushima Daiichi Nuclear Power > Plan & Action > Major Initiatives for Water Management > PCV

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Investigation inside the Reactor Primary Containment Vessel (“PCV”)

Unit 1

Over the period from April 10 to 20, 2015, a pre-investigation was conducted for the purpose of locating where melted fuels have been dropped in the PCV and identifying the condition of them including the form. In which, for the first time since the accident, robots were inserted into the damaged PCV to capture images of the internal conditions. The robot, which is a collective wisdom of Japan, worked so hard in this investigation to bring us vital information, i.e. images, radiation doses, and temperature inside the PCV. Inserting of robots into the PCV performed this time has been such an unprecedented challenge to the nuclear industry, and we believe that the fact that critical data was gained from the investigation have made a great step forward in the decommissioning operation to continue at the plant. At the same time, through piling up -one by one- each of the data obtained this time, we will get the most out of it for future decommissioning activities.

*This investigation is conducted within the site test “Investigation B1” on grating around the pedestal inside Unit 1 PCV in the “Development of a technology to investigate inside the Reactor Primary Containment Vessel (PCV)” by the International Research Institute for Nuclear Decommissioning (IRID).

[Video] 2015.05.18 An unprecedented challenge Robots obtain crucial information on conditions inside the Fukushima Reactor (4:04)

Investigation overview

  • Access route
    (Counterclockwise route)
  • Access route
    (Clockwise route)
  • Where robots remained
  • Images taken could be seen by a click
Robot used for this investigation
Robots List

Findings

Check on the access route for next investigation.

No obstructions were found around the opening to access the bottom part of the PCV. That means the opening is available to use as part of an investigation route to find the fuel debris in the future.

Grasp temperature and radiation doses

Data on temperature and radiation dose at each investigation point was obtained. The level of the measured radiation dose indicated lower values compared to the assumption. As a result, the investigation ended up being performed with a much longer time than originally planned.

No significant damages found on the facilities inside PCV

No significant damages were found on the facilities inside the primary containment vessel.Air conditioning systems (HVH), piping systems of re-circulation pump (PLR pump), pedestal wall, recirculation pump (PLR pump), and inner surface of the containment vessel.

Check on the grating (netting-type floor) at the 1st floor inside PCV

The existence of a fallen object or obstacle, and the condition of the grating were checked by investing around inside the PCV.

Other information obtained

Both robots used were determined to be left inside the PCV. Also it was confirmed that the remaining cable, which is extended from the robots will not cause trouble when conducting the upcoming investigation.

Photos and videos

Development of a technology to investigate inside the Reactor Primary Containment Vessel (PCV)

April 30, 2015
"Development of a technology to investigate inside the Reactor Primary Containment Vessel (PCV)" - Results of site test "Investigation B1" on grating around the pedestal inside Unit 1 PCV

Development of a technology to investigate inside the Reactor Primary Containment Vessel (PCV)- Results of follow up check after the site test Investigation B1on grating around the pedestal inside Unit 1 PCV - [Report for April 18 and April 19, 2015]

April 20, 2015
"Development of a technology to investigate inside the Reactor Primary Containment Vessel (PCV)"- Results of follow up check after the site test "Investigation B1"on grating around the pedestal inside Unit 1 PCV - [Report for April 18 and April 19, 2015]

(4/20 video added) Development of a technology to investigate inside the Reactor Primary Containment Vessel (PCV) - Site test Investigation B1 on grating around the pedestal inside Unit 1 PCV - [Prompt report for April 16, 2015]

April 17, 2015
(4/20 video added) "Development of a technology to investigate inside the Reactor Primary Containment Vessel (PCV)" - Site test "Investigation B1" on grating around the pedestal inside Unit 1 PCV - [Prompt report for April 16, 2015]

(4/17 video added) Development of a technology to investigate inside the Reactor Primary Containment Vessel (PCV)- Site test Investigation B1 on grating around the pedestal inside Unit 1 PCV -[Prompt report for April 15]

April 16, 2015
(4/17 video added) "Development of a technology to investigate inside the Reactor Primary Containment Vessel (PCV)" - Site test "Investigation B1" on grating around the pedestal inside Unit 1 PCV -[Prompt report for April 15]

April 10, 2015
"Development of a technology to investigate inside the Reactor Primary Containment Vessel (PCV)"‐Site test "Investigation B1" report on grating around the pedestal inside Unit 1 PCV‐(Prompt report of inspection commencement on April 10, 2015)

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