War in Ukraine: differences between nuclear power plants in Zaporizhzhia and Chernobyl

The International Atomic Energy Agency has warned of damage to some buildings, systems and equipment at the Russian-occupied Ukrainian power station.

In recent days, facilities at Zaporizhzhia, Europe’s largest nuclear power plant in southeastern Ukraine, which has been under Russian control since the beginning of the occupation, have been shaken by several explosions.

Russia and Ukraine made mutual accusations about the bombing.

The International Atomic Energy Agency (IAEA) has repeatedly expressed its concerns about attacks on the plant and has proposed establishing a nuclear safety buffer zone around the plant.

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Olli Heinonen, former deputy director general of the IAEA, told the BBC that bombing the nuclear power plant was like playing “Russian roulette”.

“A single bullet fired in the wrong place at the wrong time will have far-reaching consequences,” warned the former UN nuclear watchdog official.

But he also explained that a single bullet is unlikely to damage the reactor itself, which is protected by meters of concrete and metal.

The risk, he said, was that the bombing would have disrupted the electricity supply to the cooling system, meaning the reactor or spent fuel would get too hot, causing the fuel to melt and release radioactivity.

Added to this is the fact that if employees can work, they can “make mistakes” because of the pressure they are under.

“This is a dangerous game and it has to end,” Heinonen added.

“The news from our team is extremely worrying,” said IAEA chief Rafael Grossi, whose field team reported damage to some of the facility’s buildings, systems and equipment.

“There have been explosions at the nuclear power plant, this is absolutely unacceptable. Whoever is behind this should stop immediately. As I have said many times, they are playing with fire.”

But after all, what does this plant look like and what are its risks?

Europe’s largest

The Zaporizhzhia nuclear power plant, built between 1984 and 1995, is the largest nuclear power plant in Europe and the ninth largest in the world.

It has six reactors, each generating 950 MW, with a total output of 5,700 MW, producing enough energy to power around 4 million homes.

According to the IAEA, in normal times the plant produces about 20% of Ukraine’s electricity and almost half of the energy produced by the country’s nuclear facilities.

The resort is located in Enerhodar, in the southeast of Ukraine, on the banks of the Kakhovka reservoir on the Dnieper River. It lies approximately 200 km from the disputed Donbas region and 550 km southeast of the capital, Kiev.

The importance of the facility led Russia to occupy it in March, at the beginning of the war. Since then, both sides have accused the other of repeatedly bombing the facility.

The Russians hired Ukrainian technicians to operate the plant.

In August, the plant was temporarily disconnected from the Ukrainian power grid for the first time in its history, when a fire knocked down the last remaining 750 kilovolt power transmission line twice.

UN nuclear experts conducted the first inspection of the facility in September, accompanied by Russian soldiers, and found that the integrity of the facility had been “compromised multiple times”.

Differences from Chernobyl

Some analysts say the Zaporizhia plant is different and safer than the one in Chernobyl in 1986, the scene of the world’s worst nuclear disaster.

The six reactors in Zaporizhzhia, unlike Chernobyl, are pressurized water reactors (PWR) and have containment structures around them to prevent any radiation release.

“Zaporizhzhia was built in the 1980s, so it’s relatively modern,” says Mark Wenman, director of the Doctoral Training Center for the Future of Nuclear Energy.

“There is a solid containment building. 1.75 m thick, heavily reinforced concrete on the earthquake bed. [para resistir a terremotos]…and it takes a lot of time to break it.”

It denies comparisons to 1986’s Chernobyl or 2011’s Fukushima. He explains that Chernobyl had serious design flaws, while in Fukushima, diesel generators, which he believed would not exist in Ukraine, flooded because the generators were inside the containment building.

The Zaporizhzhia plant also does not contain graphite in its reactor. Graphite caused a major fire in Chernobyl and was the source of the radiation cloud circulating Europe.

In addition, PWR reactors are also equipped with fire protection systems.

After the attacks of September 11, 2001, nuclear power plants in the US underwent tests to detect possible attacks by large aircraft and were considered quite safe, so damage to the reactor containment building may not be the greatest danger.

supply risk

More worrying is the loss of power supply to the nuclear reactors. If this happens and the backup diesel generators fail, there will be a loss of cooling. Without electricity to power the pumps around the reactor’s hot core, the fuel begins to melt.

The plant was temporarily disconnected from the Ukrainian power grid on August 25 when a fire toppled the last remaining 750 kilovolt power transmission line twice. The other three were decommissioned during the war.

In this case, electricity was supplied via a less powerful transmission line from a nearby coal-fired power station, and diesel generators were also used, according to officials.

But Ukraine’s nuclear agency says generators are not a long-term solution, and if the last power transmission line on the national grid fails, nuclear fuel could begin to melt, leading to “release of radioactive materials” into the environment.

A pump and generator failure can result in reactor core overheating and destruction of plant facilities.

“It wouldn’t be as bad as Chernobyl, but it could still release radioactivity, and it depends on which way the wind is blowing,” says Claire Corkhill, professor of nuclear matter decay at the University of Sheffield in England. .

For him, the risk of something going wrong is real, and Russia will be as exposed as Central Europe.

But Iztok Tiselj, a professor of nuclear engineering at the University of Ljubljana in Slovenia, believes the risk of a major radioactive event is minimal, as only two of the six reactors are operational.

“There is nothing for European citizens to worry about,” he says.

Are the other four reactors idle in cold state? therefore the amount of energy required to cool the reactors is less.

human factor

Another major safety risk could come from the fuel used on Zaporizhzhia. When the fuel runs out, is the waste cooled in spent fuel tanks? and then transferred to dry storage.

“If they had been damaged, radioactivity would have been released, but that wouldn’t have been as serious as the loss of coolant,” Corkhill says.

Iztok Tiselj believes that any publication will be so small that it is meaningless.

At the heart of this crisis are its employees working under the Russian occupation and under intense stress. Two employees told the BBC about the daily risk of kidnapping.

UN Secretary-General António Guterres urged Russia to withdraw its troops and demilitarize the region with a “circle of safety”. Russia refused, arguing that it would make the facility more vulnerable.

Did the authorities warn of the disaster that would ensue if Russia tried to shut down the entire plant to cut off the supply to Ukraine? and reconnect it to the occupied Crimean peninsula.

Mark Wenman believes it is the human factor that poses the greatest risk of nuclear accidents, whether it’s chronic fatigue or stress.

“And that violates all security principles.”

If something goes wrong, they need to be at their peak and they probably aren’t, says Claire Corkhill.

In a letter signed by dozens of officials, they ask the international community to consider:

“We can control nuclear fission professionally,” they say, “but we are helpless in the face of human irresponsibility and stupidity.”

– This text was published at https://www.bbc.com/portuguese/internacional-63727896.