The incident occurred when a worker was moving through a narrow aisle where the switch panel is located, accidentally bumping the switch that controls the water injection pump for reactor No. 3. The cooling system was off for about an hour, according to Tokyo Electric Power Company (TEPCO).
CTV News is reporting that the No. 3 reactor, one of three that melted down following the March 2011 earthquake and tsunami, was out for nearly an hour before a backup pump was activated.
At a news conference, TEPCO spokesman Yuichi Okamura said there was enough water left in the reactor and there was no temperature increase or radiation leak associated with the incident.
Japan Today points out that while there was no injuries, radiation leak or increase in temperature in the core of the reactor, the decommissioning work on the crippled power plant is being done on a very fragile system.
We are reminded that for the first two or three years following the 2011 meltdown, TEPCO was using makeshift pipes, wiring and other equipment. There have been a series of minor blackouts, rat-chewed cables, cooling stoppages and other problems.
Even though TEPCO says conditions at the plant have stabilized, it is the unforeseen incidents like what happened today that highlight the fragility of the decommissioning work which is expected to last for decades.
The incident occurred when a worker in a full-face mask and HazMat suit was “passing through a dimly lit aisle that was only 85 centimeters (2.8 feet) wide, flanked by tall switch panels on both sides,” Okamura said. While carrying equipment, the worker lost his balance, jamming the switch with his elbow.
The safety cover was torn off and the lever for the water injection pump was inadvertently turned off, stopping the water from entering the reactor. The pump had been pouring 4.2 tons of water per hour into the reactor. When the water injection pump was reactivated, TEPCO increased the inflow of water to 4.4 tons per hour.
TEPCO also said it suspended the cooling system for a shared spent fuel storage pool for reactors one through three after they found that an air removal valve was left open, possibly due to human error, reports the Japan Times. After no other problems were found, the cooling system was reactivated six-and-a-half hours later.