Photo/IllutrationThe Genkai nuclear power plant in Genkai, Saga Prefecture, where a steam leak was found at its No. 3 reactor on March 30 (Nami Sugiura)

Kyushu Electric Power Co. has located a 1-centimeter hole in a pipe that leaked steam last week and forced a suspension of electricity generation at a recently reactivated nuclear reactor in Saga Prefecture.

The glitch in the No. 3 reactor of the Genkai nuclear power plant was detected early in the evening of March 30, which led to reduced operations the following day.

The hole was in a pipe that forms part of a system to remove gases from water pumped to a steam generator, the utility said April 1.

The company is trying to ascertain the cause of the problem.

It remains unknown when Kyushu Electric Power can resume operations at the reactor in southwestern Japan.

It said no radioactive substances leaked.

The utility had intended to restart the facility's No. 4 reactor in May this year, but that may now be delayed, it added.

According to the utility, water and steam that do not contain radioactive substances circulate in the pipes of the secondary cooling system. A device called a deaerator removes gases from the water.

A similar problem occurred in the past.

The No. 3 reactor was brought back online March 23 after a hiatus of seven years and three months.