A map of the Zaporizhzhia region shows a close-up view of the frontline in the Ukraine war. At the top of the map is the areas controlled by Ukraine, at the bottom is Russian controlled areas and in the middle is the Zaporizhzhia Nuclear Power Plant.
On the edge of the frontline in eastern Ukraine, Europe’s largest nuclear power station, the Zaporizhzhia Nuclear Power Plant, has been caught in a crossfire.
Both Russia and Ukraine have accused each other of shelling dangerously close to the plant. The damage to critical infrastructure around the facility has been significant, and there are fears more damage could lead to a radiation disaster in the country that still manages the cleanup of the Chornobyl nuclear disaster.
Experts from the International Atomic Energy Agency (IAEA) arrived at the plant on Thursday for an independent inspection after they were delayed by yet more shelling.
Russian forces captured the Zaporizhzhia nuclear plant in early March as part of what Moscow calls its “special military operation” in Ukraine. The plant is still operated by Ukrainian technicians working under “extremely stressful conditions,” according to the IAEA.
For weeks now, Ukraine and Russia have accused each other of endangering the plant's safety with artillery or drone strikes. Ukraine also accuses Russia of using it as a shield to launch attacks on Ukrainian-held territory, which Moscow denies.
Images released by U.S.-based Maxar Technologies on Aug. 30, show smoke in the surroundings of the plant, armoured personnel carriers near reactors and holes in the roof of the plant’s so-called “special buildings”, which house water treatment and waste management facilities and equipment repair shops. They are located in close proximity to the plant’s reactors.
Satellite images show the facilities of the Zaporizhzhia Nuclear Power Plant. Images show a plume of smoke near the nuclear plant, armoured personnel carries near reactor 5 and holes in the roof of a building.
The Zaporizhzhia nuclear power plant has six Soviet-designed VVER-1000 V-320 water-cooled and water-moderated reactors containing Uranium 235.
One of the biggest risks to the plant is a drop in the water supply to the reactors. Pressurised water is used to transfer heat away from the reactor and maintain control of the nuclear fission of the Uranium. If the water were cut or auxiliary systems such as diesel generators failed to pump water keeping the reactor cool, the nuclear reaction would slow and the reactor would heat up very swiftly.
At such high temperatures, hydrogen could be released from the zirconium cladding and the reactor could start to melt down.
A diagram show how the Zaporizhzhia nuclear power plant works. The water in the core is heated by nuclear fission and then pumped into tubes inside a heat exchanger. Those tubes heat a separate water source to create steam. The steam then turns an electric generator to produce electricity. The pumps that cool the reactor core and spent fuel pools need electricity to function. Therefore, it’s crucial they are powered permanently.
Besides the reactors, there is also a dry spent fuel storage facility at the site for used nuclear fuel assemblies as well as spent fuel pools which are used to cool down used nuclear fuel.
An emission of hydrogen from a spent fuel pool caused an explosion at reactor 4 in Japan’s Fukushima nuclear disaster in 2011.
However experts say the building housing the reactors and spent fuel pools is designed to contain radiation and withstand major impacts, meaning the risk of a major leak there is still limited.
The pumps that cool the reactor core and spent fuel pools need constant electricity. The prospect that electricity lines to the plant could be severed is a constant fear, a technician at the plant has said. There are back-up diesel generators but it is not clear how much diesel fuel is on site to continue to run them.
There are four regular, 750-kilovolt (kV) power lines designed to supply Zaporizhzhia but three of them “were lost earlier during the conflict,” the International Atomic Energy Agency said. On Aug. 25, Ukraine informed the agency that the fourth line was cut at least twice but was later restored. It was the first time all four regular lines had been down, forcing technicians to disconnect from the grid the two reactors that were still operating at the plant.
A map describes a series of incidents registered at the Zaporizhzhia Nuclear Power Plant. Since the beginning of the war damage has been caused to some buildings and the power lines that connect the plant to the grid.
Sources: International Atomic Energy Agency, OpenStreetMap, Open Infrastructure Map
Ukraine's state nuclear company, Energoatom, said fires in the ash pits of a coal power station near the Zaporizhzhia reactor complex interfered with the power supply to the station's two last working reactors, disconnecting them from the network.
Energoatom said that despite the incident the nuclear plant was still being supplied with the power it needs for cooling by the nearby thermal plant.
A satellite image show burnt areas along the corridors used by the transmission lines that connect the nuclear plant to the grid.
Images captured by satellite in the days following the disconnection show burnt areas in the surroundings of the plant, near or overlapping the corridors used by the regular transmission lines.
Images captured by satellite show recently burnt areas in the surroundings of the plant.
Despite these incidents, all safety systems remained operational and there had been no increase in radiation levels at the plant, IAEA’s Director General Rafael Mariano Grossi said.
With its six reactors, the Zaporizhzhia plant is the largest nuclear facility in Europe, with a total capacity of 5.7 Gigawatts. Before Moscow’s invasion, the plant supplied about 20% of Ukraine's total electricity.
The plant also plays into a larger shift in Ukraine’s energy policy away from Russia and toward the European Union.
After the invasion, Ukraine said it would disconnect its power grid from Belarus and other former soviet states, connecting it to the European Union. In July, Ukraine began exporting electricity to the European Union using an interconnection with Romania, starting with 100 megawatts. Ukrainian President Volodymyr Zelenskiy said the power transmissions to Romania was the start of a process that could help its European allies further reduce their dependence on Russian oil and gas.
A map of Ukraine shows its electricity grid and where all Ukrainian nuclear plants are located.
Sources: World Nuclear Association, Energydata.info, Natural Earth
The location of the plant on the Dnipro River and just 200 km (125 miles) from Crimea, which Russia annexed in 2014, also makes it a strategic target for Russian interests in the region.
Ukraine's nuclear power operator said on Aug. 19, it suspected Moscow was planning to switch the Zaporizhzhia plant over to Russia's own power grid, a complex operation Kyiv says could cause a disaster.
Maps show schematic representation of rough locations
International Atomic Energy Agency, World Nuclear Association, Energoatom, Energy.gov, Zaporizhzhia Nuclear Power Plant, Institute for the Study of War and AEI's Critical Threats Project, Maxar Technologies, Copernicus Sentinel-2, Openstreetmap.org, Openinframap.org, Natural Earth, Energydata.info, REUTERS
Jon McClure, Peter M. Graff
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