Damage to the interior of a support structure at the Fukushima No. 1 nuclear power plant may extend around its entire perimeter, raising concern that the extent of the damage may be greater than previously thought.
Tokyo Electric Power Company Holdings, Inc. on Tuesday released video taken by an underwater robot from inside the pedestal, a cylindrical reinforced concrete base supporting the reactor pressure vessel. After analyzing the data, TEPCO believes that the concrete of the pedestal's inner wall may be damaged all the way around, prompting the nuclear operator to apply the findings to future seismic evaluations.
The video taken of the pedestal's inner wall shows that concrete at the bottom -- from the floor to a height of about 1 meter -- was missing throughout more than half of its circumference, exposing the rebar.
The probe was conducted March 28-31.
A rod-shaped object that may have fallen from the reactor can be seen, and sediment that appears to be nuclear fuel debris that melted during core meltdown and then hardened.
The International Research Institute for Nuclear Decommissioning (IRID), which is in charge of developing decommissioning technologies for the plant, has determined that the earthquake-resistance strength would be adequate even if the concrete and rebar were completely destroyed around one-quarter of the pedestal's circumference.
TEPCO said that while the results confirmed no major damage to the concrete and rebar on the pedestal's external wall, regarding the inner wall, "[because video was unable to be taken] it's possible that the other half of the circumference is gone." TEPCO suspects the extent of the damage to the interior wall may exceed IRID's assumptions.
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