Inspections and response efforts from the February 2021 earthquake were still underway when another earthquake hit on March 20th. Due to the additional quake, inspections to look for new damage caused by the second quake were initiated.
On March 22nd TEPCO announced that the water level inside unit 1’s containment has continued to gradually drop and is now below the L2 sensor.
Unit 1’s water injection rate has been increased to compensate for the new water leak:
“As announced today (March 22nd) at 10:10 pm, due to the drop in the water level in the reactor containment vessel of Unit 1, today (March 22nd) 10:42 pm, the reactor water injection amount is as follows. I changed it as follows. <Reactor water injection amount change> Unit 1 reactor water injection amount: 3.0m3 / h → 4.0m3 / h”
As of March 23rd the water level rose slightly due to the extra water injection. By March 26, TEPCO caused the water level to fill back up to the T2 line. They consider this confirmation they can control the water level inside containment and planned to reduce the water injection rate.
New damage was found on site as inspections took place. An area outside the bunker building on the hill was found to have subsided as seen in the photo below.
A tank (tank K4) at the F tank farm near units 5-6 suffered pipe damage. The Plastic connector pipe cracked and was temporarily patched. TEPCO slated this for a future replacement. A different tank (tank N1) was found to have moved about 7mm. Ongoing inspections of the connection pipes of tanks with known slippage found displacement in the pipes did not exceed manufacturer’s tolerances so no further action was taken. These inspections are yet to be fully completed.
Additional damage was found around the bunker building as documented in this 3.26.21 report. This included ground subsidence below a steel plate that has been installed to provide solid ground for large equipment.
A radiation monitor in the unit 3 defueling building failed due to the earthquake. A fuse blew during the quake taking the monitoring station offline. Spent fuel removal work has already been completed at unit 3’s spent fuel pool but the monitor still serves a useful purpose as a radiation monitor on the refueling floor level of the building.
A follow up report was issued on the radiation alarm that was triggered soon after the initial quake at the storm drain outlet in the quay. A hot spot was found in the W2 waste container yard, upstream from the radiation monitor. Containers stored there have been in the process of being moved to indoor storage. Workers found a gel like mass with higher than normal radiation levels. The mass had a reading of 5 mSv/hr. TEPCO appears to assume it is part of whatever caused the elevated radiation levels in the storm drain system.
Inspection work on site is still ongoing. We will update as more information comes out.
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