New reactors should not come first in climate policy.

Reactors often run at high annual availability. They are not immune to common failures. In 2022, stress-corrosion inspections, repairs and a maintenance backlog cut average availability across France’s fleet to 54%, down from 73% in 2015–2019.

Heat brought a different shared constraint in June and July 2026. Rules on river warming and thermal discharges caused total or partial unavailability at French riverside reactors. RTE measured an effective availability loss of up to about 8 GW in late June and about 9 GW around mid-July.

Power systems keep fast reserves for their largest credible sudden loss. In its 2013 supporting document, ENTSO-E based Continental Europe’s 3,000 MW reference incident on two 1,500 MW nuclear units. A 2025 British study found that Hinkley Point C can create a contingency of up to 1.8 GW, compared with 1.32 GW for Sizewell B.

An NREL review found that cooling design can matter more than fuel type. Once-through systems withdraw 10 to 100 times more water per unit of electricity than recirculating systems, while recirculating systems consume at least twice as much. The U.S. EPA says intake structures can kill or injure fish, shellfish and their eggs.

A reactor does not need a gas pipeline, but it still needs uranium and services for conversion, enrichment and fuel fabrication. In 2025, Russia supplied about 16% of uranium, 24% of conversion services and 23% of enrichment services delivered to EU utilities.

The IAEA says uranium tailings can retain up to 85% of the ore’s initial radioactivity and also contain heavy metals and other potentially harmful compounds. A pooled study of uranium miners in North America and Europe found elevated lung-cancer mortality, with a smaller excess among workers hired in 1965 or later.

War can damage power lines, interrupt access to electricity and cooling, restrict maintenance and put staff under severe pressure. In February 2026, the IAEA reported two more total losses of off-site power at Zaporizhzhia. Enrichment and reprocessing raise a separate concern because both are proliferation-sensitive.

UNSCEAR recorded about 118 thousand evacuees after Fukushima, including people evacuated for reasons other than the nuclear emergency. The WHO reports no acute radiation injuries or deaths from radiation exposure, while evacuation and relocation caused broad social, economic and public-health harm.

The revised Paris Convention sets operator liability at a minimum of €700 million. Under the Brussels system, public funds complement the available compensation to at least €1.5 billion. Germany’s current rules require financial security of up to €2.5 billion.

The IAEA reported in 2024 that no geological repository for high-level waste or spent fuel was operating. In March 2026, Finland’s Posiva facilities at Olkiluoto were still under operating-licence review.

For three EU decommissioning programmes involving older, early-closed reactors, the European Court of Auditors found that cost estimates rose 40% from €4.1 billion in 2010 to €5.7 billion in 2015, leaving a €1.7 billion funding gap before final disposal.

SMRs already operate in Russia and China. What is missing is a track record of repeatable, competitively priced deployment. The promised savings depend on standard designs, factory production and a large order book, while smaller reactors lose some economies of scale.