South Korean nuclear reactors have been abruptly shut down 128 times over the past decade because of faulty parts, officials said Thursday, amid a scandal over forged safety certificates.

Government officials who inspected 22,000 certificates for parts used in 20 working reactors found that 277 or 1.2 percent of the documents had been forged, the Prime Minister's Office said.

A separate probe of eight other reactors, which are offline or under construction, showed that 0.9 percent of the certificates had been forged, the office said.

It did not specify whether the defective parts which caused the 128 shutdowns had been given fake certification.

South Korea has 23 reactors which are meant to meet more than 30 percent of electricity needs, and it also hopes to export its expertise.

In 2009 it won a $20.4 billion contract to build four nuclear plants in the United Arab Emirates.

But the govenment's inspection revealed widespread corruption in the nuclear industry, which is undergoing a crisis of confidence following a series of shutdowns.

Public prosecutors have charged about 100 people over the scandal involving fake safety certificates.

In a separate case of document forgery eight suppliers last year were found to have faked warranties covering thousands of items used in several reactors.

The scandal further undermined public confidence already shaken by the 2011 Fukushima nuclear disaster in Japan and its ongoing repercussions.

Despite concern over how the nuclear sector is run, the government has vowed to push ahead with plans to build an additional 16 reactors by 2030.