Photo/IllutrationThe No. 3 reactor, center, of the Genkai nuclear power plant in Genkai, Saga Prefecture, where steam was found to be leaking from a pipe on March 30 (Asahi Shimbun file photo)

Kyushu Electric Power Co. suspended generation of electricity at the No. 3 reactor of its Genkai nuclear power plant in southwestern Japan early March 31, just days after bringing it back online.

The suspension was due to steam leaking from a pipe that was detected the previous day. There was no discharge of radioactive substances, the company said.

The utility restarted the No. 3 reactor at the plant in Genkai, a town in Saga Prefecture, on March 23, after a hiatus of more than seven years, and began generating and transmitting electricity two days later.

The company had gradually been raising the reactor's output, which was then at 75 percent capacity.

It said a worker spotted the leak around 7 p.m. on March 30 from a pipe sending water to a steam generator. The pipe is part of the reactor's secondary cooling system.

The utility had to gradually lower the power output from late at night to cool the area affected by the steam leakage to carry out checks.

Soon after 6 a.m. on March 31, the utility suspended power generation and transmission by shutting down the turbine. The reactor's output was lowered to 13 percent capacity.

A different glitch occurred at the No. 1 reactor of the utility's Sendai nuclear power plant in Satsuma-Sendai, Kagoshima Prefecture, in 2015, but the company did not need to suspend power generation that time. The No. 1 reactor had resumed operations just nine days earlier.