The International Atomic Energy Agency (IAEA) says the impact of the damage to the dam on cooling water supplies to the Zaporizhzhia nuclear power plant is being monitored but alternative sources of water on-site should provide sufficient water for cooling "for some months" and means "our current assessment is that there is no immediate risk to the safety of the plant".

Water is essential for cooling functions. This picture was taken in March during an IAEA visit to the plant (Image: IAEA)

In an update to the IAEA board of governors on Tuesday morning, Director General Rafael Mariano Grossi said the damage to the Nova Kakhovka dam - which Ukraine says was caused by the Russian shelling, and Russia blames on Ukraine - had led to a "significant reduction in the level of the reservoir used to supply cooling water" to Zaporizhzhia nuclear power plant.

The cooling water system at the plant is used for residual heat removal from the reactors (used or partially used fuel there), residual heat removal from the used fuel ponds and cooling of emergency diesel generators if and when they are running.

"Absence of cooling water in the essential cooling water systems for an extended period of time would cause fuel melt and inoperability of the emergency diesel generators," Grossi said.

IAEA staff at the plant have been told that at the moment there is a 5cm per hour reduction in the height of the reservoir, "the main line of cooling water is fed from the reservoir and pumped up through channels near the thermal power plant to the site. It is estimated that the water through this route should last for a few days".

The water level in the reservoir was about 16.4 metres at 08:00 local time - with the IAEA saying that if the level drops below 12.7 metres it can no longer be pumped. The damaged dam itself is about 140km downstream of the nuclear power plant.

There are also alternative sources of water, Grossi said: "A main one is the large cooling pond next to the site that by design is kept above the height of the reservoir. As the reactors have been shut down for many months it is estimated that this pond will be sufficient to provide water for cooling for some months. The agency will confirm this very shortly. It is therefore vital that this cooling pond remains intact. Nothing must be done to potentially undermine its integrity.
"I call on all sides to ensure nothing is done to undermine that."

The IAEA team at the site say that the nuclear power plant is "making all efforts to pump as much water into its cooling channels and related systems as possible" and non-essential consumption of water stopped.

He said that he already planned to visit the Zaporizhzhia nuclear power plant next week "and now it is essential. I will go".

The damage to the dam, which is in a Russian-controlled region, has led to severe flooding and mass evacuations. According to the Russian Tass news agency as of 09:30 GMT on Tuesday, "14 settlements with a population of 22,000 people have come within the flooding area ... and a total of about 80 villages may be inundated". According to Ukrinform, at 14:00 local time (12:00 GMT) the water level in the reservoir had dropped by 1.5 metres.

The Zaporizhzhia nuclear power plant is the largest in Ukraine, and Europe, with six reactors. It has been under Russian military control since early March 2022. Five of its six reactors are in cold shutdown and one in warm shutdown - which allows it to provide heat for the plant and the nearby city of Energodar. As it is upstream of the reservoir it is not in the areas at risk of flooding.

A failure of the Nova Kakhovka dam caused by an earthquake was a scenario examined in post-Fukushima Daiichi safety checks of the Zaporizhzhia plant, in particular the possibility of water loss in the cooling pond, and concluded that "owing to the significant width of the cooling pond levee ... water losses because of filtering will remain actually unchanged in comparison with the design-basis conditions".

Sama Bilbao y León, director general of World Nuclear Association, welcomed the fact the nuclear power plant "remains in a safe, stable situation" despite the damage to the dam, adding: "The analysis and planning done in preparing the plant’s safety case, including revisions carried out as part of the plant’s stress tests, have ensured the plant is both robust and prepared to handle challenges, such as those resulting from the rupture of the Kakhovka hydroelectric dam.

"I condemn outright the deliberate attack on the dam. Beyond the disruption to operations at Zaporizhzhia, the attack has caused a threat to life for the thousands of residents downstream of the dam, as well as the destruction of property and farmland, and environmental damage."

Researched and written by World Nuclear News