Ukraine's nuclear power plants are built strong, and experts say there's little chance of a Chernobyl-like disaster

• Russia took control of Ukraine's Zaporizhzhia nuclear power plant Friday.
• Ukrainian officials said fighting near reactors could lead to Chernobyl-like disasters.

Despite dire warnings from Ukrainian officials, fighting at any of Ukraine's nuclear power plants is extremely unlikely to trigger a nuclear disaster, experts said.

Shocking images on Friday showed fire breaking out at the Zaporizhzhia power plant as Russia invaded the site. The fire has now been put out and Russian forces have seized control of the plant.

Shortly after fighting broke out, Ukraine's minister of Foreign affairs published a tweet saying "If it blows up, it will be 10 times larger than Chornobyl!"

Ukraine President Volodymyr Zelensky has said in a Facebook post Friday morning: "There are 15 nuclear reactors in Ukraine. If one of them blows, that's the end for everyone, that's the end of Europe."

Neither claims stands up to scrutiny, however.

Nuclear power plants can't "blow up" like an atom bomb, and although the war in Ukraine is a catastrophe for millions of people, an attack on its nuclear facilities has no prospect of wiping out an entire continent.

Experts say that this is very unlikely to happen. Here's why.

Power plants cannot explode like a bomb

Although both use radioactive fuel as their basis, nuclear power reactors and nuclear weapons are nothing alike in how they work, as explained in this PBS feature from 2011.

The aim of nuclear power generation is to create a constant, controlled reaction that can be used to power turbines and generate electricity.

Through various different reactor designs, the idea is to keep the reaction in equilibrium indefinitely and contain the radioactive material.

Atomic bombs are instead designed to create a reaction that releases huge amount of energy in an instant, causing widespread devastation familiar from images of mushroom clouds dwarfing entire cities.

They use far more volatile nuclear fuel than electricity reactors, in a different composition. Even they are quite difficult to set off, requiring elaborate detonation mechanisms using material that does not exist inside a nuclear reactor.

To give a comparison — both a box of matches and fireworks can use phosphorus as a fuel. But there is no way that matches can explode on their own.

Modern reactors are nothing like Chernobyl's

Chernobyl's reactor, called RBMK, was extremely unstable and the staff controlling the plant were poorly trained, per the World Nuclear Association.

The reactor design had flaws which meant that the reaction could spiral out of control. These flaws do not exist in modern reactors, which are designed even in failure to prevent the nuclear reaction from escalating.

Zaporizhzhia uses pressurized water reactors which are "a lot safer" than the reactors at Chernobyl, said Tony Irwin, a professor at the Australian National University, per The Guardian.

Even at Chernobyl, the explosions were from water being superheated to steam and exploding — it was not a nuclear blast.

Chernobyl's reactor was not contained as well

US Energy Secretary Jennifer Granholm said Friday that Zaporizhzhia reactors are contained in robust containment structures.

Chernobyl's were not, per the International Atomic Energy Agency (IAEA). It was this poor containment which led to the disastrous consequences at Chernobyl, as the reactor fuel was exposed directly to the environment, poisoning the immediate area for decades, and spreading small quantities of radioactive material over vast distances.

At Zaporizhzhia, this is almost incapable of happening. Airtight containment prevents radioactive materials from leaking out, per Jeremy Gordon, a nuclear safety consultant.

Though it is not designed to specifically sustain the impact of an artillery shell, it is "very robust" and can withstand earthquakes and impacts, Robin Grimes, professor of materials physics at Imperial College London said in a statement Friday.

In spite of the fighting, Zaporizhzhia is working normally

As of early Friday, all systems are in perfect working order at Zaporizhzhia, the IAEA said in a press conference Friday. Ukrainian safety personnel is still in place monitoring the power plant.

In the confusion of the fighting, some people thought that the reactor itself had been hit. But this didn't happen.

The building which was struck and caught fire was a training building that was relatively far from the reactors, per the IAEA.

Fighting could affect cooling, but the reactor should still be fine

"Obviously, it's not a good idea if you start shooting massive missiles at reactors," Irwin said, per The Guardian.

If the reactors are not cooled down by a constant flow of water taken from a river, it risks melting, which would indeed be a problem. To keep it cool, pumps and circuits need to remain intact, Gordon said. The plant also needs power and trained staff to operate safely.

All of these could be collateral damage to the fighting. But the cooling system has backups, Irwin told The Guardian. The core is also designed to control heat and pressure even without cooling, said Gordon.

In the very unlikely worst-case scenario, the containment would keep most of the radioactive elements from leaking, which would create a situation like a meltdown in Fukushima Japan — still a disaster but by no means the end of the world.