Wolsung Unit-1 nuclear power plant in North Gyeongsang Province broke down on Sunday at 4:51 p.m., amplifying concern over old nuclear plants.

The Korea Hydro and Nuclear Power Co. said that the plant stopped producing power as its power transformer failed, leading the power-generating turbine to grind to a halt.

The KHNP said that it would take approximately three days to replace the parts.

The accident took place amid the state assessment period of the unit’s suitability for continued operation. After 30 years of operation since 1982, the nuclear plant will reach its originally intended expiration date on Nov. 20. The KHNP is pushing for government approval of an additional 10 years’ operation of the nuclear power plant.

Wolsung Unit-1 has experienced multiple power outages, which have become more frequent since 2011. The unit halted operation as voltage-adjustment parts failed in mid-July 2011. The plant’s power production was halted when the cooling pump broke down on Jan. 12 this year.

The plant had undergone a 27-month refurbishment process and resumed operation in July 2011.

The KHNP said that the breakdown involved neither significant safety issues nor any leak of radioactivity, and said the plant would receive a stable power supply from other sources.

The company stressed that the outage had nothing to do with the unit’s core facilities, including the nuclear reactor.

Currently, Wolsung Unit-1 produces about 678,000 kilowatts of electricity, accounting for about 0.8 percent of the nation’s power consumption.

By Chung Joo-won  (joowonc@heraldcorp.com)