By Sudarshan Varadhan, Joyce Lee and Heekyong Yang
SINGAPORE/SEOUL, August 18 (Reuters) -South Korea’s nuclear power output is racing ahead of official targets due to fewer maintenance outages, a new plant coming online and reactors running at full tilt, helping to rein in generation costs and pushing down coal usage.
Generation from nuclear plants grew 8.7% year-over-year in the six months through June – three times official plans for 2.9% annual growth – while coal-fired output plunged 16%, data from state-run utility Korea Electric Power Corp (KEPCO) showed.
“The basic principle of generator operation in the power market is minimization of generation costs. Nuclear power generally has lower fuel costs than other generation sources such as coal and liquefied natural gas (LNG),” a Korea Power Exchange (KPX) spokesperson said in a statement to Reuters.
“If nuclear and renewable facilities continue to be additionally expanded in the future, generation from gas and coal is likely to continue to decrease,” the spokesperson said.
A 29% annual decline in maintenance outage times and a 6% increase in installed nuclear capacity in the first half of 2025 also boosted output, KPX said. The 1.4 GW Shin Hanul #2 plant southeast of Seoul came online in April 2024.
South Korea is Asia’s No.2 nuclear power generator after China. It is ramping up nuclear generation as policy resistance to the technology is waning, with Japan restarting idled plants and new reactors beginning commercial operations in India.
The country of 51 million people operates 26 nuclear reactors with 26.05 GW of capacity and is building four more, including two units totalling 2.8 GW expected online in 2026.
Tighter safety checks and maintenance shutdowns after the 2011 Fukushima disaster in Japan curbed nuclear output in South Korea last decade, lifting coal and LNG use.
However, nuclear output has risen 6.1% annually since power consumption stabilised in 2022, and President Lee Jae Myung, who took office in June, has pledged continued support.
Nuclear’s share of power generation rose to 31.7% in 2024 from 25.9% in 2019, KEPCO data showed, offsetting most of coal’s decline to 28.1% from 40.4% across the same years.
That helped South Korea cut its energy import costs, with overseas coal volumes falling 8% annually on average from 2022 levels, according to customs data, and the coal import bill falling 23% over that period to $15.4 billion last year.
TRANSMISSION CONSTRAINTS
The growth in nuclear power is crowding out coal-fired power on transmission lines in South Korea.
“Plenty of coal plants are sitting idle not by choice, but because there’s no spare capacity on the transmission lines to carry more power,” said Seunghoon Yoo, professor in the energy department in the Seoul National University of Science and Technology.
Transmission constraints have also capped renewables, which along with hydropower provide just over a tenth of annual power generation, compared with a global average of 30%, according to the Institute for Energy Economics and Financial Analysis (IEEFA).
Power demand has mainly been driven by higher cooling requirements since 2022, KEPCO data showed, as industrial demand declines.
Slow power demand growth has also discouraged operation of expensive gas-fired plants through the day despite the proximity of most of those facilities to Seoul. Gas is increasingly used to manage volatility, KPX said.
“There has been an increasing pattern of gas plants operating during the morning peak hours, stopping around midday when demand is at its minimum, and restarting for the evening peak,” the power exchange said.
Electricity use by semiconductor manufacturers and data centres is rising but has not impacted fuel procurement, South Korea’s energy ministry said.
(Reporting by Sudarshan Varadhan in Singapore, Heekyong Yang and Joyce Lee in Seoul; Editing by Tony Munroe and Tom Hogue)
