Cooling water injections into the No. 3 reactor of the Fukushima No. 1 nuclear power plant in northeastern Japan were halted for about an hour Monday morning, according to operator Tokyo Electric Power Company Holdings Inc.
During the suspension, Tepco was unable to inject a sufficient amount of water for cooling the No. 3 reactor, which suffered a nuclear fuel meltdown when the plant was damaged in the March 2011 earthquake and tsunami.
According to Tepco, a regular water injection pump for the reactor stopped operations shortly after 10 a.m. A secondary pump was activated about an hour later.
There was no major change in radiation levels at the plant, the firm said.
Tepco believes the pump went offline after a worker’s elbow hit the cover of a switch, damaging it and causing the switch to turn off, during regular maintenance.
Before the suspension, Tepco was pouring 4.2 tons of water per hour into the reactor. After the resumption, it increased the hourly amount to 4.4 tons.
The firm also said that it suspended the cooling system for a shared spent fuel storage pool for reactors 1 through 3 after finding that an air removal valve was left open, possibly due to human error.
After confirming no other problems, it reactivated the cooling system about 6½ hours later.