The cooling system of the spent-fuel pool in reactor 4 at the Fukushima No. 1 plant automatically suspended operations Saturday and the water temperature is starting to rise, Tokyo Electric Power Co. said.
The utility has been unable to activate a backup cooling system for the pool since operations halted at around 6.25 a.m., and is looking into the causes, Tepco officials said later in the day.
The pool’s water temperature stood at around 31 degrees Celsius when the cooling system ceased functioning and was increasing by 0.26 degree per hour late Saturday afternoon, according to the officials.
If Tepco remains unable to start up the system or its backup, the temperature could reach 65 degrees by Tuesday morning — the maximum limit specified by safety regulations.
No leakage of contaminated water from the reactor has been detected so far, Tepco said.
The No. 4 reactor’s cooling system previously shut down June 4.