There was no radiation leak has occurred and the problem will not have a bad impact on the environment, according to the Nuclear and Industrial Safety Agency of Japan.
Pressure in the accumulator in the emergency reactor core cooling system while down on Friday night, sounding the alarm. Accumulator coolant will be injected into the reactor in an emergency, Kyodo News said.
The pressure has stabilized since then, but the use of the reactor was stopped Saturday night to find out what is causing the problem.
The reactor had undergone the procedure before the final adjustment of commercial operations for a very long period of about four months. 1.18 million kilowatt reactor was equivalent to about four percent of total output power to Kansai Electric.
Kansai Electric Company President, Makoto Yagi issued a statement, saying, "We will make best efforts to secure additional supply capacity in order to prevent situations that lead to the extinction."
Usage is expected to ask for more power-saving measures from the public and the industry as a result of the accident, while securing the supply of other utilities, analysts said.
Ohi reactor, one of 19 who are still active in Japan after the devastating earthquake and tsunami in March that pushed the world's worst nuclear crisis in two decades, operated at full capacity for phase adjustment, including when the accident happened Friday night.