What happens when a nuclear facility is attacked? Analysis finds low risk of a large-scale radiological disaster, but cross-border implications may arise.

In the context of several Iranian nuclear facilities repeatedly subjected to attacks, experts say the probability of a large-scale radiological disaster remains generally low, according to Wired.

Iran’s facilities: reported attacks, no recorded leaks

In early March, Iran said the Natanz nuclear facility—about 140 miles from Tehran and a core center for uranium enrichment—had been attacked. More recently, bunker-busting bombs were reported to have fallen near Iran’s Isfahan Nuclear Technology Center.

Despite these incidents, international monitoring agencies have not recorded any radiological leaks in Iran, including at Natanz or in the Isfahan vicinity.

Bushehr, Iran’s only operating nuclear power plant on the Persian Gulf coast, was also struck at the end of March by a falling projectile. While no direct damage has been reported, experts warn that any incident there could have consequences beyond a single country.

Why the Gulf region raises the stakes

The drinking water of most Gulf region countries depends on desalination plants. In a worst-case scenario, radioactive material entering seawater could jeopardize regional drinking-water supply chains for millions of people.

What happens after an attack: shutdown is not the end

When a plant’s sensors detect strong ground motion—whether from an attack or an earthquake—the emergency shutdown sequence is triggered. However, shutting down is only the initial step and does not eliminate risk entirely.

Even after shutdown, the reactor core continues to generate heat from radioactive decay, requiring continuous cooling. Maintaining control depends on the integrity of the plant, the control systems, and especially the availability of backup power to support cooling.

In practice, the Fukushima disaster illustrates how procedures can be followed yet the crisis can escalate: the initial shutdown occurred as designed, but the tsunami disabled the power grid, cutting off cooling and allowing heat to accumulate.

Worst-case pathway: loss of cooling and release

When cooling water stops circulating, it boils and vaporizes, exposing fuel rods that must remain submerged. This can lead to hydrogen pressure building up, an explosion, and the release of radioactive materials to the environment.

In such a scenario, some rare gases such as Xenon and Krypton would disperse quickly and, after a short time, their concentrations would drop to safer levels. By contrast, radioactive isotopes including Cesium and Strontium have long half-lives spanning many years or decades, and could cause long-lasting contamination.

The Chernobyl disaster (April 1986) is cited as an example: it released a large amount of radioactive isotopes into the atmosphere, contaminating a significant part of Europe for a prolonged period.

How safety agencies respond

In a nuclear emergency, the International Atomic Energy Agency would activate a global response through its Incident and Emergency Centre (IEC), described as the hub for information and action.

IEC Director Amgad Shokr says the process begins with verifying information with national authorities and assessing severity to provide accurate, timely updates to member states and the public.

If radiological dispersion is detected, standard measures would be deployed, ranging from evacuations to coordinated emergency response based on the severity.

Assessment of current risk

Experts say most attacks on nuclear facilities are unlikely to lead to a large radiological disaster because modern plants are designed with multiple layers of protection. These are intended to allow shutdown and backup cooling even if parts of the facility are damaged, limiting the likelihood of radiological release.

The worst-case scenario would require essential safety systems—particularly the cooling system—to be disabled for an extended period, potentially leading to core meltdown. In that case, radioactive materials could escape into surrounding air and water, with cross-border spread depending on wind and currents.

In the Gulf region, the risk is described as more severe due to heavy reliance on desalination and the sea’s quasi-closed nature, which can prolong contamination and affect critical infrastructure and ecosystems.

At present, there have been no confirmed reports of radiological leakage beyond borders from Iran’s nuclear facilities. The risk is described as controlled, but it depends on whether key safety systems can withstand increasing pressure.