One of the new nuclear reactors under trial operation here has shut down due to a technical glitch, a week after resuming a test run following a stoppage due to flaws in coolant pumps in March, officials said Monday.

The Shin (New) Wolsong 1 reactor went offline on Sunday morning after its turbine generator was automatically stopped, said officials at the Korea Hydro & Nuclear Power Co.

It did not cause any leaks of radioactive materials or other serious accidents, but raised the possibility of delaying the timing of starting its regular operation, originally set for July.

"This stoppage is not related to the safety of the reactor or any leaks of radioactive materials," said a company official in the city of Gyeongju, about 370 kilometers southeast of Seoul.

"We are figuring out the exact cause of the breakdown," the official said on the condition of anonymity.

With a capacity of one million kilowatts, the Shin Wolsong 1 is a pressurized heavy water reactor with designs based on a Canadian technology.

South Korea, Asia's fourth-largest economy, relies on 21 nuclear reactors for nearly half of its electricity needs.  (Yonhap)