South Korea has decided to suspend operations at two more nuclear reactors over the use of unauthorized parts.
The Nuclear Safety and Security Commission also delayed the start of operations at two other reactors, but said there was no public safety threat.
Two reactors were suspended in late 2012, amid a scandal over parts with fake safety certificates.
South Korea has 23 nuclear reactors which supply about a third of its electricity needs.
The suspension of two reactors raised questions about power supply over the summer, local media said.
The two reactors to be suspended pending replacement of the unauthorized parts are the Shin Kori Reactor 2 and Shin Wolsong Reactor 1, the commission said.
South Korea has suspended operations at two more nuclear reactors over the use of unauthorized parts
Shin Kori Reactor 1, which is currently undergoing maintenance, and Shin Wolsong Reactor 2, a new reactor, will also not operate until parts are replaced.
All components used in South Korean nuclear reactors require specific certification.
But last year a minister revealed that some parts used in two reactors at the Yeonggwang nuclear plant had not been properly vetted.
Knowledge Economy Minister Hong Suk-woo said these were “non-core” parts that included fuses, cooling fans and power switches – items which could be used in other industries but needed international certification for nuclear power plant usage.
Earlier this month, six nuclear power engineers and suppliers were jailed in connection with the supply of components with forged safety certificates mainly to the Yeonggwang complex.
At least 30 people have been killed and other 800 have been injured after a 6.3 magnitude earthquake struck Bushehr province in south-west Iran, officials say.
Rescue teams have been sent to the affected area, but darkness is hampering rescue operations.
The quake struck 90 km (60 miles) south of Iran’s only nuclear power station in Bushehr, the US Geological Survey (USGS) says.
At least 30 people have been killed and other 800 have been injured after a 6.3 magnitude earthquake struck Bushehr province in south-west Iran
However, the nuclear plant has not been affected and is working normally, officials have said.
The quake was felt across the Gulf in Dubai, Abu Dhabi and Bahrain.
Some 10,000 people are thought to live in the affected area in more than 50 villages, two of which have reportedly been completely leveled.
The governor’s office has sent generators to the area so rescue operation can continue overnight.
Seismologists said the quake struck at 16:22 local time at a depth of 10 km (6.2 miles) near the town of Kaki, south of Bushehr – a Gulf port city that is home to Iran’s first and only nuclear power plant.
Iran’s seismological centre in Bushehr province, linked to Tehran University, registered the quake at a magnitude of 6.1.
Tens of aftershocks – the strongest measuring a magnitude of 5.4 – struck within an hour, sending many people into the streets for safety.
One resident in Bushehr told Reuters news agency that they could “clearly feel the earthquake” but there was no damage.
State media reported that phone lines had been brought down by the quake and its aftershocks.
The earthquake shook buildings across the Gulf.
The governor of Bushehr, Fereydoun Hassanvand, told Iranian state TV that the nuclear plant was not damaged.
An official with the Russian firm Atomstroyexport told Russian media that the quake “in no way affected the normal situation at the reactor”.
“Personnel continue to work in the normal regime and radiation levels are fully within the norm,” the official was quoted by Russian state news agency Ria as saying.
Iran’s nuclear programme has roused concern among major powers that Tehran wants to build nuclear weapons – a charge Iran strongly denies.
Iran straddles a major geological fault line, making it prone to seismic activity. In 2003, an earthquake in the city of Bam left more than 25,000 people dead.
A Japanese parliamentary panel has said in a report the crisis at the Fukushima nuclear plant was “a profoundly man-made disaster”.
The disaster “could and should have been foreseen and prevented” and its effects “mitigated by a more effective human response”, it said.
The report catalogued serious deficiencies in both the government and plant operator Tepco’s response.
It also blamed cultural conventions and a reluctance to question authority.
The six-reactor Fukushima Daiichi nuclear plant was badly damaged after the 11 March 2011 earthquake and tsunami knocked out cooling systems to reactors, leading to meltdowns and the release of radioactivity.
Tens of thousands of residents were evacuated from an exclusion zone around the plant as workers battled to bring reactors under control. Tepco declared the reactors stable in December 2011.
Members of the Fukushima Nuclear Accident Independent Investigation Commission were appointed to examine the handling of the crisis and make recommendations.
The investigation included 900 hours of hearings and interviews with more than 1,000 people.
A Japanese parliamentary panel has said in a report the crisis at the Fukushima nuclear plant was "a profoundly man-made disaster
In the panel’s final report, its chairman said a multitude of errors and willful negligence had left the plant unprepared for the earthquake and tsunami.
“Although triggered by these cataclysmic events, the subsequent accident at the Fukushima Daiichi Nuclear Power Plant cannot be regarded as a natural disaster,” it said.
“It was a profoundly man-made disaster – that could and should have been foreseen and prevented.”
After six months of investigation, the panel concluded that the disaster “was the result of collusion between the government, the regulators and Tepco” founded in the failure of regulatory systems.
It said that the situation at the plant worsened in the aftermath of the earthquake because government agencies “did not function correctly”, with key roles left ambiguous.
It also highlighted communication failures between Tepco and the office of then Prime Minister Naoto Kan, whose visit to the site in the immediate aftermath of the earthquake “diverted” staff.
The report said regulators should “go through an essential transformation process” to ensure nuclear safety in Japan.
“Japan’s regulators need to shed the insular attitude of ignoring international safety standards and transform themselves into a globally trusted entity,” it said.
The report made several recommendations including:
• Permanent parliamentary monitoring of the nuclear regulatory body
• Reforming the crisis management system, with more government responsibility for public welfare
• Reforming nuclear energy laws to meet global safety standards
• Monitoring nuclear operators and developing a system for independent investigative bodies
All of Japan’s nuclear plants were shut down in the wake of the disaster. But on Sunday the first reactor was restarted in the town of Ohi in Fukui prefecture.
The restart sparked large protests in Tokyo but Prime Minister Yoshihiko Noda urged support for the move, saying a return to nuclear power was essential for the economy.
The government is continuing to assess whether other nuclear plants are safe to be restarted.