South Korea's Nuclear Surge as Coal Use Plummets

South Korea's Nuclear Power Surge Outpaces Targets

South Korea is witnessing a significant increase in nuclear power generation, surpassing official targets due to fewer maintenance outages, the addition of a new plant, and reactors operating at full capacity. This shift is helping to reduce generation costs and decreasing reliance on coal.

In the six months ending in June, nuclear power generation increased by 8.7% year-over-year, which is three times the official target of 2.9% annual growth. Meanwhile, coal-fired power output dropped by 16%, according to data from Korea Electric Power Corp (KEPCO). The Korea Power Exchange (KPX) spokesperson highlighted that nuclear power typically has lower fuel costs compared to coal and liquefied natural gas (LNG), making it a more cost-effective option in the power market.

"If nuclear and renewable facilities continue to be expanded in the future, generation from gas and coal is likely to continue to decrease," the spokesperson added. A 29% annual reduction in maintenance outage times and a 6% increase in installed nuclear capacity during the first half of 2025 have also contributed to this growth. The 1.4 GW Shin Hanul #2 plant, located southeast of Seoul, began operations in April 2024.

South Korea ranks as Asia's second-largest nuclear power generator after China. The country is increasing its nuclear generation as policy resistance to the technology diminishes. Japan is restarting previously idled plants, and new reactors are beginning commercial operations in India. South Korea operates 26 nuclear reactors with a total capacity of 26.05 GW and is constructing four more, including two units totaling 2.8 GW expected to come online in 2026.

Impact of Safety Measures and Policy Shifts

Tighter safety checks and maintenance shutdowns following the 2011 Fukushima disaster in Japan led to a decline in nuclear output over the past decade, resulting in increased use of coal and LNG. However, nuclear output has grown by 6.1% annually since power consumption stabilized in 2022. President Lee Jae Myung, who took office in June, has pledged continued support for nuclear energy.

The share of nuclear power in South Korea’s electricity generation rose to 31.7% in 2024, up from 25.9% in 2019. This increase has offset most of the decline in coal, which fell to 28.1% from 40.4% during the same period. This shift has helped South Korea reduce its energy import costs, with overseas coal volumes decreasing by an average of 8% annually from 2022 levels. Coal import costs dropped by 23% over that period, reaching $15.4 billion last year.

Transmission Constraints and Renewable Challenges

The growth in nuclear power is leading to a reduction in coal-fired power on transmission lines in South Korea. Seunghoon Yoo, a professor at the Seoul National University of Science and Technology, noted that many coal plants are idle not by choice but due to limited transmission capacity. Transmission constraints have also hindered the expansion of renewable energy sources, which along with hydropower account for just over 10% of annual power generation, compared to a global average of 30%.

Power demand has primarily been driven by higher cooling needs since 2022, according to KEPCO data, as industrial demand declines. Slow power demand growth has discouraged the operation of expensive gas-fired plants despite their proximity to Seoul. Gas is increasingly used to manage volatility, with KPX reporting that gas plants often operate during morning peak hours, stop around midday when demand is low, and restart for evening peaks.

Electricity use by semiconductor manufacturers and data centers is rising, but this has not impacted fuel procurement, according to South Korea's energy ministry.