SEOUL (Reuters) - South Korean nuclear regulators have discovered nearly a thousand more parts supplied for nuclear power plants with fake quality certificates, they said on Tuesday, adding that this would not lead to further reactor shutdowns.
Revelations that fake certificates were supplied by eight firms forced the shutdown of two of the country's 23 reactors this month, raising the risk of winter power shortages.
A third reactor was subjected to an extended maintenance period after microscopic cracks were found in tunnels that guide control rods. Nuclear normally accounts for a third of South Korea's power supplies.
The Nuclear Safety and Security Commission said further investigation had uncovered 919 parts of 53 items supplied by two new firms with forged quality documents. Most had been fitted in six reactors -- five of which were already affected by the earlier revelations.
"We see it as possible for now to change the parts without shutting more reactors down," a commission spokeswoman told Reuters by telephone.
Six reactors are offline now, according to government data.
Authorities in Asia's fourth-largest economy, heavily dependent on oil and gas imports, have said they may have to introduce rolling blackouts this winter as the grid will have less than a third of normal reserve capacity.
The country's sole power transmitter and distributor, Korea Electric Power Corp (KEPCO), said it would hold a drill on Wednesday to check for stable power supply and gauge the chances of outages this winter.
Authorities have stressed that the parts - such as fuses, switches and heat sensors - are not crucial to the nuclear process and there is no safety risk.
The Korean government has been criticized for a lack of transparency over safety in its nuclear program and for the dual supervisory and promotion roles of its regulators.
Public opinion is traditionally pro-nuclear, although an opposition lawmaker has pressed the government to resume publishing polls on nuclear safety after a loss of confidence in the sector following last year's Fukushima disaster in Japan.
The International Energy Agency (IEA), which advises industrialized nations and represents 28 oil importing countries, said last week that South Korea needed to rebuild public trust in nuclear power by boosting transparency and improving regulation.
In the first revelations this month, eight firms were found to have submitted 60 false certificates to cover more than 7,000 parts mostly used in the two reactors that were shut. That sparked an inspection in all 23 reactors as well as five under construction.
(Reporting by Eunhye Shin and Meeyoung Cho; Editing by Ron Popeski)