SEOUL (REUTERS) - A South Korean nuclear reactor has restarted after a month-long closure due to a control rod problem, a spokesman at state-run atomic operator Korea Hydro and Nuclear Power Co said on Thursday.

The country's nuclear watchdog said in a statement on Wednesday that it had conducted thorough checks at the 950-MW Hanul No.1 reactor in Uljin county, over 300 kilometres southeast of Seoul, and that the facility was safe.

The restart comes at the peak time for electricity demand, with households and businesses cranking up air conditioners to avoid the summer heat.

The government said last month that power supply would be stable this summer thanks to new generating capacity and fewer closed nuclear power plants.

The country was hit by a nuclear safety scandal in 2012 that prompted the closure of some reactors. It has been under pressure to lower its usage of nuclear power after the scandal and as neighbouring Japan struggles to clean up after the Fukushima disaster.