Fukushima Daiichi Unit 3 New Containment Leaks

New problems have been found related to the containment damage at unit 3 caused by the February 2021 earthquake. TEPCO previously admitted there was containment damage and a slight drop in the water level in containment. New evidence appears to have found the location of at least some of the leaks.

Containment water levels began to drop after the February earthquake and have somewhat stabilized at a level of 500mm or about 19 inches lower than normal.


On the first floor, water is leaking into the MSIV room area noted in red. Water from containment flows out of the MSIV room to a pair of floor drains on the first floor. This water then reaches two sections of the basement torus room. The northeast and southeast triangle areas were both found to have water level increases related to the new leak from containment. The southeast triangle houses a floor drain sump where some of this containment water is flowing into.

Water flowing out of the MSIV room to a first floor floor drain.


The floor drain sump in the basement experienced a fluctuation in water levels:

Unit 3 Reactor Building B1FL Sub drain
Pump stop setting TP-550mm
Maximum water level approx. TP-1,870 mm (3/10 20:47)
Before water level change Approximately TP-2,100mm (3/9 10:00)
Approximately TP-2,092mm (3/11 15:00)

A temporary pump was installed in the northeast triangle area to remove excess water on March 11th. TEPCO thinks the water flowing into the northeast triangle is due to one of the floor drains being clogged and mentioned water removal from this area may become a permanent task. Workers were able to clear the floor drain but assume it is at risk for clogging again in the future. They may consider creating a new route for this water to flow including the possibility of drilling a hole in the floor. When the water is pumped out of the triangle areas, it is transferred to the main torus room. Water there is eventually pumped out for water treatment.

Water levels in the torus room basement triangle areas are documented in the graphs below. Blue is the northeast triangle, pink is the southeast triangle. The increased activity on the pink graph indicates pumping out water more often. The blue graph shows increased water levels before a temporary pump was installed.


The leak is around the first floor area so it doesn’t risk drastically lowering the water level inside containment. It does appear to be leaking larger volumes of water through the MSIV room, carrying radioactive particles along with it.


TEPCO Documents:





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