South Korea's nuclear watchdog said on Friday, Feb 7, it will expand its investigation of reactor parts manufactured or certified by foreign companies since 2008 to see if it can find more instances of forged safety certificates, according to Reuters.

The broadened investigation may require parts replacement at some reactors via extended maintenance shutdowns that could trigger power shortages again this summer.

Asia's fourth-largest economy has been striving to avoid blackouts during peak demand seasons ever since the discovery of locally forged safety certificates for replacement parts kicked off a nuclear scandal in late 2012.

The scandal sparked an investigation of locally produced parts in January of last year that was broadened to some foreign produced parts in June.

The Nuclear Safety and Security Commission said in a statement that its investigation since mid-2013 found eight cases out of 2,075 samples of foreign manufactured reactor components that had been supplied with fake documents.

The regulator now plans to widen its investigation to all parts manufactured overseas to be installed at the country's 23 reactors since 2008, including those in storage for existing or upcoming reactors, the statement said.

The statement noted it would investigate a combined total of about 200,000 reactor components manufactured in the United States, Canada, France, Britain, Germany and other countries, along with their safety documentation.

It did not name the countries or companies involved in the eight instances of fake documents for overseas components. The nuclear safety commission also did not say how long the expanded investigation would take.

The expanded investigation is likely to lead to extended shutdowns for two nuclear plant that are already offline for scheduled maintenance. The statement said the restart of those reactors would be delayed until they are proved to have no foreign or local components with fake certificates.

South Korea's 23 reactors supply about a third of the nation's power. The plants are operated by Korea Hydro & Nuclear Power (KHNP), which is owned by state-run Korea Electric Power Corp (KEPCO).

Currently three reactors are offline, including the two down for maintenance and a third awaiting an extension of its operating license after its 30-year permit expired in November 2012.

A fourth reactor is scheduled to shut on Saturday for 53 days of maintenance through April 1, according to KHNP data.

The nuclear watchdog's statement noted that 14 nuclear plants are set to be closed this year for scheduled maintenance.

Facing public criticism over nuclear safety in the wake of its nuclear scandal and Japan's Fukushima crisis, Seoul formally adopted a lower target for nuclear power early this year.

It still plans to double its nuclear capacity over the next two decades as its state-run industry builds at least 16 new domestic reactors and pushes for sales to overseas projects.