Fukushima Daini

Japan Probes Nuclear Cooling System Shutdown After Earthquake

Japan is investigating why a cooling system used to store nuclear fuel rods was temporarily knocked offline at Tokyo Electric Power Co. Holdings Inc.’s shuttered Fukushima Dai-Ni atomic plant after a 7.4 magnitude earthquake struck the same region devastated by a tsunami in March 2011.

The temblor early Tuesday caused water in the pool at the plant northeast of Tokyo to move, according to the utility known as Tepco. Sensors registered the motion as a decline in water levels, triggering an automatic shutdown, the utility said.

One of at least two cooling pumps supplying water to the spent fuel pool at Dai-Ni’s No. 3 reactor was shut around 6:10 a.m. Tokyo time, according to Tepco. The utility started another pump to resume cooling the fuel rods around 7:47 a.m., it said in an e-mailed statement.

More than five years after the…