President Vladimir Putin’s outrageous assault on Ukraine has unleashed a new horror: the specter of nuclear meltdowns as an act of war.

Russian forces took over Ukraine’s largest nuclear power plant last week, the six-reactor Zaporizhzhia facility in the southern part of the country. Before troops captured the plant, however, their tanks fired explosive shells on it, damaging part of the facility and setting buildings on fire. Firefighters attempting to get to the blaze came under fire as well.

Initial reports that a reactor building itself was burning turned out to be mistaken, but the chilling possibility of a nuclear core meltdown had already sown alarm throughout Europe. It became clear Putin would not have to use a nuclear weapon to threaten international radioactive catastrophe. He only had to send conventional ground forces to attack an operating commercial reactor or a spent fuel rods storage site. 

Even without direct damage to a reactor or its containment building, major radiation releases can result from a reactor’s cooling systems losing power. That’s because a fuel rod meltdown can take place if a cooling shutdown lasts long enough, even when the reactor has been taken offline and is not producing power. 

A similar danger can result from a power outage to the cooling systems for spent fuel rods’ storage pools. Even though these rods are no longer in use, they continue to generate heat. If power is down for a significant period of time, this heat could evaporate the water in the storage pools, crack open the pool structure itself, and spill radioactive material. 

Ironically, one of the first major facilities the invading Russians captured was the old Chernobyl plant, site of the world’s worst nuclear accident to date. Ukrainian sources report that Russians have forced the plant’s crews to stay on duty past exhaustion, risking further release of radiation there.

The risk is magnified because Ukraine is highly dependent on nuclear power, with 15 reactors at four stations producing about half of its national power supply.

The more recent Fukushima meltdown in 2011 contaminated a wide region in Japan, including adjacent marine areas. It resulted from an earthquake and tsunami damaging cooling systems in three reactors. It led to a shakeup in Japan’s energy policy, including a reduction of their dependence on nuclear power. 

Nuclear plants have long been considered dangerous potential targets for terrorism because the secondary damage from radiation release in a populated area causes far greater loss of life, health impacts, and economic damage than does an initial bomb explosion alone. The war in Ukraine should remind us of all the risks which make commercial nuclear power such an expensive and undesirable option.

Solar arrays, wind turbines, and large-scale battery storage don’t carry the risk of catastrophic radiation release. They also don’t produce waste and contamination that have to be guarded for centuries after their useful life ends. Let’s keep those factors in mind as we evaluate plans to address the climate crisis.