What Happens When a Nuclear Site Is Hit? | WIRED

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Into the second month of the US-Iran war, the conflict in the Gulf continues to escalate—airstrikes widening, oil markets reacting, and pressure mounting around the Strait of Hormuz. But beyond the immediate security and economic concerns, another question is quietly taking shape: What actually happens if a nuclear site is hit?

In most cases, even if a nuclear facility is hit, a large-scale radiological disaster is unlikely. Modern sites are designed with multiple safety systems that can shut down reactors and contain damage.

The risk isn’t defined by the strike itself, but by what the strike damages inside the facility. The risk becomes significantly higher, however, if those systems fail—or if an operational nuclear power plant is directly affected.

Where the Risk Begins

On February 28, when the US and Israel launched a coordinated military campaign against Iran’s leadership and military infrastructure, Iran’s nuclear and ballistic missile sites were marked as potential targets. As the conflict deepened, Iranian officials reported strikes on the Natanz nuclear facility, a primary uranium enrichment complex, located around 140 miles from Tehran.

This was followed by strikes on the Ardakan facility as well as the Khondab heavy water reactor, which was left inoperable after the attack. Earlier this week, additional heavy bunker-buster bombs were also launched in Isfahan, in close proximity to the Isfahan Nuclear Technology Center.

So far, international watchdogs have reported no radiation leaks from the targeted facilities. The International Atomic Energy Agency (IAEA) has said there is no indication of off-site contamination, even after reported strikes on sites such as Natanz and near Isfahan.

But the concern isn’t limited to the impact site.

Across the Gulf, the risks are shaped by geography and infrastructure. Much of the region depends on desalinated seawater—systems that pull directly from the sea. If radioactive material were to enter marine environments, it wouldn’t just spread through ecosystems, but through the infrastructure that supplies drinking water to millions.

The Bushehr nuclear power plant, located along Iran’s Gulf coastline, sits within close proximity to neighboring states. While it has not been directly affected, experts have repeatedly warned that any escalation involving coastal nuclear infrastructure could have cross-border consequences.

What Happens Next

Not every strike on a nuclear site leads to a dramatic mushroom cloud explosion or an immediate radiation release. What matters is where the site is hit and how much damage is done to its safety systems.

Within minutes of impact, a reactor is designed to shut down automatically. This stops the nuclear reaction, acting as the first line of defense. But shutdown doesn’t eliminate the risk.

The reactor core continues to generate heat through radioactive decay, and that heat must be controlled. The extent of the damage—whether to buildings, control systems or backup infrastructure—determines how effectively those safety mechanisms can continue to function.

In past incidents, including the Fukushima Daiichi nuclear disaster in Japan, the shutdown worked as intended. The crisis began only after a tsunami disabled critical systems in the hours that followed.

An Iranian woman walks past a view of Tehran's research reactor in Tehran.

PHOTOGRAPH: MORTEZA NIKOUBAZL/GETTY IMAGES

Without cooling, heat begins to build inside the reactor core. If cooling systems are damaged, whether through loss of power, failed pumps, or destroyed backup generators, the temperature continues to rise. In water-cooled reactors, this can lead to the accumulation of hydrogen gas, increasing the risk of explosions that can further damage the facility.

As conditions worsen, fuel rods inside the reactor begin to degrade. This is the point at which radioactive materials can be released.

These materials include different types of radioactive isotopes, such as noble gases, volatile isotopes, long-lived isotopes and fuel particles. While some, like noble gases, disperse quickly and have limited short-term impact. Others, particularly long-lived isotopes—which can remain in the environment for years or even decades—and fuel particles, can cause serious contamination if not contained.

For example, Russia’s Chernobyl disaster caused a complete fuel meltdown, releasing dangerous long-lived isotopes into the atmosphere and contaminating large parts of Europe.

How the World Responds

In the event of a nuclear incident, the IAEA’s Incident and Emergency Centre (IEC) acts as the global focal point for preparedness and response.

Amgad Shokr, director of IEC, says the process begins by verifying information with national authorities and assessing the situation and its potential impact.

Map of Iran showing nuclear sites, reactors and uranium mines.

INFOGRAPHIC: GETTY IMAGES