Strikes to Iran’s Bushehr nuclear power plant could release long-lasting radioactive cesium 137 into the Persian Gulf, causing environmental calamity and threatening drinking-water supplies for millions

By Stephanie Pappas edited by Andrea Thompson

Just steps from the Persian Gulf in the Iranian coastal town of Bushehr sits the nation’s only nuclear power plant. Though a fragile ceasefire enacted on April 7 paused the bombing of Iran, the plant was rocked by nearby missile strikes four times during the conflict, with one strike killing a security guard and damaging an outbuilding.

Given the possibility that the war could restart, experts are concerned. Damage to the Bushehr nuclear power plant could release long-lasting radioactive cesium 137 from spent fuel holding ponds into the Persian Gulf, threatening fisheries and drinking-water supplies for millions of people. A direct strike could engender a nuclear meltdown. Such a meltdown is unlikely to create a fiery Chernobyl-style catastrophe, says Ali Alkis, a nuclear security expert and doctoral student at Hacettepe University in Türkiye, but it could lead to a slower-rolling environmental calamity.

“The most realistic pathway to a severe accident is not a Hollywood-style explosion but a loss of cooling over time,” Alkis says. “If both external power and backup systems are compromised, the reactor core could overheat, potentially leading to fuel damage or meltdown.”

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The Bushehr plant has been in operation since 2011 and possesses one operational Russian-designed VVER V-446 reactor with a net capacity of 915 megawatts of electricity, which accounts for about 2 percent of Iran’s power.

On March 22 U.S. ambassador to the United Nations Michael Waltz declined to promise that the U.S. would not target the plant, saying “all options should be on the table.” President Donald Trump had repeatedly threated to bomb all of Iran’s power plants if the country does not reopen the Strait of Hormuz to ship traffic.

The Bushehr reactor is contained in a reinforced concrete-and-steel liner and has multiple fallback cooling systems to keep the core from overheating. If it does overheat, the nuclear fuel can melt, potentially allowing radioactive materials to breach the containment system. Spent fuel is also stored in cooling ponds within the reactor, says Scott Roecker, vice president for nuclear materials security at the nonprofit Nuclear Threat Initiative. If these cooling ponds were breached, they, too, could overheat and create a cascading meltdown that could release radioactive material into the air or the Persian Gulf.

“This is basically what happened in the case of Fukushima, where they lost power and then the cooling, and they had a meltdown,” Roecker says.

Cesium 137 is one contaminant of particular concern in the spent fuel because it emits strong and dangerous gamma radiation. Cesium 137 is highly soluble in water and has a half-life of 30 years, Alkis says. The spent-fuel ponds at Bushehr have long been a concern, with a 2021 paper finding that a spent fuel fire there could spread radioactive fallout over the surrounding coastline, including the city of Ahvaz, which has a population of about 1.3 million.

Another concern is the risk of water contamination. Because many Gulf nations depend on desalination of ocean water for their drinking water, any radioactive contamination of the Persian Gulf could lead to an immediate water crisis. Qatar’s prime minister Sheikh Mohammed bin Abdulrahman bin Jassim Al Thani said in an interview last year that Qatar would run out of water in three days if a nuclear accident were to contaminate the Gulf. Cesium can be removed from water, however, with methods such as reverse osmosis. This technique was used in the cleanup after the Fukushima accident, so desalination systems might be able to adapt to handle the contamination.

Regardless of the outcome at Bushehr, protecting nuclear power plants in war is likely to become increasingly pressing as countries look to expand nuclear power to meet climate targets, Roeker says. This isn’t the first time in recent years an active nuclear plant has been caught in the crossfire: the Russian seizure of Ukraine’s Zaporizhzhia nuclear power plant in 2022 raised similar alarms of a catastrophic accident. “Unfortunately, the Ukraine precedent makes it clear that there don’t seem to be too many rules when it comes to attacking nuclear power plants in wartime,” says Edwin Lyman, director of nuclear power safety at the Union of Concerned Scientists.

Beyond the Iran conflict, he says, keeping nuclear power plants on the table as military targets is dangerous. Adversaries may try to target infrastructure around the plants to prevent them from delivering power or even to force them to shut down operations, he adds. “That kind of instability raises the risk of an accident,” Lyman says.