Following the explosion at the Kakhovka dam and hydro plant in southern Ukraine, which flooded a huge area and displaced thousands of people, and what seems to be the beginning of the anticipated military counter offensive by the Ukrainian army, the International Atomic Energy Agency issued a statement in Update 165 on 11 June about the threat to the nearby Zaporizhzhya nuclear power plant. “Experts of the IAEA need access to a location near Ukraine’s Zaporizhzhya NPP to clarify the reason for a significant discrepancy between measurements of the height of the reservoir that is supplying water to cool the facility’s six reactors and spent fuel storage” said director general Rafael Mariano Grossi.
The level of the Kakhovka reservoir has been dropping rapidly since the downstream dam was breached on 6 June, but the ZNPP reported shortly afterwards that it had been stable for about a day as measured at the inlet of the Zaporizhzhya thermal power plant (ZTPP) where water is pumped into a channel for use at the nearby nuclear power plant.
By 9am local time on 11 June, the water level by the ZTPP was estimated at 11.27 metres, down from nearly 17 metres before the dam was breached, according to data received by IAEA personnel at the ZNPP site.
However, the height is reportedly continuing to fall elsewhere in the huge reservoir, causing a possible difference of about two metres compared with the level reported by the ZTPP. The water level is a key parameter for the continued operability of the water pumps.
“It is possible that this discrepancy in the measured levels is caused by an isolated body of water separated from the larger body of the reservoir. But we will only be able to know when we gain access to the thermal power plant,” director general Grossi said.
At the current height of the reservoir by the ZTPP, the water pumps continue to be operable. At the moment, however, they are not continuously being operated as both the ZTPP channel and the large cooling pond near the ZNPP are full, holding sufficient water reserves for several months of cooling requirements.
The ZNPP cooling pond and the ZTPP discharge channel are both essential to continuation of the cooling water supply and the director general stressed that maintaining their integrity is vital for the safety of the plant.
“The thermal power plant plays a key role for the safety and security of the nuclear power plant a few kilometres away. I fully expect that our experts will be able to go there very soon to independently assess the situation. I will also personally raise this important matter with the Zaporizhzhya NPP,” he added, and he reiterated that the IAEA also requires access to the electrical switchyard of the ZTPP.
The ZTPP switchyard has in the past been used to provide back-up power to the ZNPP, but its last 330 kV line is still not available after being disconnected more than three months ago. Europe’s largest nuclear power plant now relies entirely on its sole remaining 750 kV power line for off-site electricity, which has been cut repeatedly since the military conflict began in February 2022.
Even though the ZNPP has not been producing electricity for several months now, it still needs access to water and power for cooling and other essential safety and security functions and to avoid the risk of a potential fuel meltdown and release of radioactive material.
At the ZNPP itself, five reactors are in cold shutdown, while the sixth – unit 5 – remains in hot shutdown to produce steam to support processes that contribute to safety on the site.
The safety of Ukraine's Zaporizhzhya nuclear power plant (pictured) could be at risk from the drop in water levels at Kakhovka reservoir – which supplies cooling water to the plant – following the recent explosion at the Kakhovka dam and hydro plant