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Zaporizhzhia nuclear plant: History, control and key developments

(CNN) "The day has come," Rafael Grossi, the head of the International Atomic Energy Agency (IAEA) declared Monday, marking the beginning of his journey to the largest nuclear plant in Europe that sits on the fire line between the Russian occupiers and Ukrainian forces.

On Thursday, a group of 14 inspectors led by Grossi arrived at the Zaporizhzhia nuclear power plant (NPP) in southern Ukraine, despite concerns about constant shelling in the area.

Since early March, when Russia captured the plant, international and local experts have voiced grave warnings, not only for the safety of the plant's workers, but also for fear of a nuclear disaster that could affect thousands of people in the surrounding area.

Here's a closer look at the perilous situation at the plant:

The significance of the plant

Ukraine relies heavily on nuclear power -- about half of its electricity comes from 15 nuclear reactors at four plants across the country, according to the World Nuclear Association.

Zaporizhzhia NPP, with six reactors, is the largest nuclear power station in Europe. It was mostly built in the Soviet era and became Ukrainian property after its declaration of independence from the Soviet Union in 1991.

Until recently, only two reactors were connected to Ukraine's national grid and providing power, though the units have been taken offline at various points -- and for various reasons -- since the invasion.

Where is it and who controls it?

Zaporizhzhia NPP is located on the eastern bank of the Dnipro river in Ukraine. The area, and the nuclear complex, has been under Russian control since the beginning of the war, but the plant is still mostly operated by Ukrainian workers.

At the start of the invasion, Ukrainian forces stopped Russian forces from capturing a second nuclear facility -- the South Ukraine Nuclear Power Plant -- and forced them to retreat to Dnipro, according to Petro Kotin, president of Energoatom, which runs nuclear power plants in Ukraine. The frontline hasn't moved much in months.

Each of Zaporizhzhia's reactors would cost $7 billion to replace, making the plant a target for Russians to capture undamaged, with hopes of serving its own electricity market, according to analysis by defense and security intelligence firm Janes. Should Russia keep it, Ukraine would lose 20% of its domestic electricity generating capacity.

What does its position on the frontline mean?

Shelling in the surrounding towns as well as near the power plant is common, according to local reports.

Ukraine has accused Russian forces of storing weaponry and launching attacks from the plant, knowing that Ukraine can't return fire without risking hitting the nuclear facility. Russia in turn claims Ukrainian forces are targeting the site.

The international community has been on high alert about nuclear safety, yet experts believe a Chernobyl-style disaster is unlikely. The plant is equipped with modern security systems, meaning even if there was neglect to its upkeep, or major military action caused serious damage, the result would be most comparable to the nuclear disaster in Fukushima -- which was contained locally, according to Janes and Energoatom.

Yet risks remain, one of which is potential damage to nuclear waste stored openly on site -- in ponds of water and in casks, according to Kotin from Energoatom.

Kotin has also warned that Russian attempts to switch the plant from the Ukrainian to the Russian power grid would require disconnecting all the reactors from power for a certain time, relying on emergency power generation never failing -- a "very dangerous" prospect, he told CNN in an August 22 interview.

Which parts of the plant have been affected by the conflict?

The plant's main exclusion security zone, where the reactors and nuclear fuel are located, is surrounded by Dnipro waters to the northwest and Enerhodar town to the east.

The below satellite image highlights the plant's facilities, which are vital to the accompanying timeline of events since the war began. They show just how narrowly Zaporizhzhia NPP has avoided a nuclear disaster.


Reporting and writing: CNN Staff and Henrik Pettersson

Digital design and graphics: Natalie Croker and Byron Manley

Photo editor: Clint Alwahab

Editors: Anna Brand, Nick Thompson and Eve Bower