LONDON: The Zaporizhzhia nuclear power plant in southern Ukraine has been bombed in recent days, raising the possibility of a serious accident just 500 km (about 300 miles) from the site of the world’s worst nuclear accident, the Chernobyl disaster in 1986.
On Thursday, United Nations Secretary-General Antonio Guterres called on Russia and Ukraine to cease all fighting near the plant after further shelling that day.
The Zaporizhzhia nuclear power plant has six Soviet-designed water-cooled and water-moderated VVER-1000 V-320 reactors containing uranium-235, which has a half-life of more than 700 million years .
It is the largest nuclear power plant in Europe and one of the largest in the world. Construction began in 1980 and its sixth reactor was connected to the grid in 1995.
As of July 22, only two of its reactors were operating, according to the Nuclear Energy Agency (NEA).
The greatest risk to reactors comes from a decline in water supply.
The pressurized water is used to evacuate the heat from the reactor and to slow down the neutrons in order to allow the Uranium 235 to continue its chain reaction.
If the water was shut off and auxiliary systems such as diesel generators failed to cool the reactor due to an attack, the nuclear reaction would slow down although the reactor would heat up very quickly.
At such high temperatures, hydrogen could be released from the zirconium sheath and the reactor could begin to melt.
However, experts say the building housing the reactors is designed to contain radiation and withstand major impacts, meaning the risk of a major leak is still limited there.
“I do not believe there would be a high probability of a breach in the containment building even if it were accidentally hit by an explosive shell and even less likely that the reactor itself could be damaged by such. This means that the radioactive material is well protected,” said Mark WenmanReader in Nuclear Materials at Nuclear Energy Futures, Imperial College London.
In addition to the reactors, there is also a dry spent fuel storage facility on site for spent nuclear fuel assemblies and spent fuel pools at each reactor site which are used to cool spent nuclear fuel.
“Spent fuel ponds are just big pools of uranium fuel rods in them – they get really hot depending on how long they’ve been there,” said Kate Brown, an environmental historian at the Massachusetts Institute of Technology whose book “Manual for Survival” documents the full extent of the Chernobyl disaster.
“If fresh water is not introduced, the water evaporates. Once the water evaporates, the zirconium coating heats up and can catch fire, then we have a bad situation – a fire. irradiated uranium which looks a lot like Chernobyl, releasing a whole complex of radioactive isotopes.”
A hydrogen emission from a spent fuel pool caused an explosion at Reactor 4 during Japan’s Fukushima nuclear disaster in 2011.
According to a 2017 Ukrainian submission to the IAEA, there were 3,354 spent fuel assemblies in the dry spent fuel facility and about 1,984 spent fuel assemblies in the pools.
That is a total of more than 2,200 tons of non-reactor nuclear material, according to the document.
After invading Ukraine on February 24, Russian forces took control of the plant in early March.
Ukrainian personnel continue to operate it, but special Russian military units guard the facility and Russian nuclear specialists provide advice. The International Atomic Energy Authority (IAEA) has warned that staff are working under extremely stressful conditions.
If there was a nuclear accident, it’s unclear who would deal with it during a war, Brown said.
“We don’t know what happens in wartime when we have a nuclear emergency,” Brown said. “In 1986, everything was working as well as in the Soviet Union so they could mobilize tens of thousands of people, equipment and emergency vehicles to the site.”
“Who would be in charge of this operation right now?
The plant was hit in March but there was no radioactive leak and the reactors were intact. Russia and Ukraine blamed each other for the strike.
In July, Russia said Ukraine had repeatedly struck the factory’s territory with drones and missiles. Pro-Ukrainian social media said “suicide drones” struck Russian forces near the plant.
Reuters was unable to immediately verify the battlefield accounts of either side.
– August 5: The factory was bombed twice. Power lines were damaged. An area near the reactors was hit.
Russia said the Ukrainian 45th Artillery Brigade also hit the territory of the factory with 152mm shells across the Dnipro River. Ukraine’s nuclear energy company, Energoatom, said Russia fired at the plant with rocket-propelled grenades.
– August 6: shelling again, perhaps twice. An area next to the dry spent nuclear fuel storage facility was hit.
Energoatom said Russia fired rockets at the plant. Russian forces said that Ukraine hit him with an 220-mm Hurricane rocket launcher.
– August 7: bombarded again
Russia said Ukraine’s 44th Artillery Brigade hit the plant, damaging a high-voltage line. The Russian Defense Ministry said the power of reactors 5 and 6 had been reduced to 500 megawatts.
– August 11: bombarded again.
Ukraine’s Energoatom said it was hit five times, Russian-appointed officials said it was hit twice during a shift change.

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