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IAEA needs to clarify significant discrepancy between high measurement of reservoir height, Director General says

Experts of the International Atomic Energy Agency (IAEA) need access to a location near Ukraine’s Zaporizhzhia Nuclear Power Plant (NPP) to clarify the reason for a significant discrepancy between different measurements of the height of the reservoir that is supplying water to cool the facility’s six reactors and spent fuel storage, Director General Rafael Mariano Grossi said yesterday (11 June).

The level of the Kakhovka reservoir has been dropping rapidly since the downstream dam was severely damaged five days ago. However, the power plant reported over the weekend that it had been stable for about a day as measured at the inlet of the Zaporizhzhia Thermal Power Plant (ZTPP) where water is pumped into a channel for use at the nearby nuclear power plant.

By 9 am local time on Sunday, the water level by the Zaporizhzhia NPP was estimated at 11.27 metres, down from nearly 17 metres before the dam was breached, according to data received by the IAEA experts at the nuclear 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, IAEA said. The height of 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 nuclear power plant, the water pumps continue to be operable. At present, however, they are not continuously being operated as both the Zaporizhzia channel and the large cooling pond near the nuclear power plant are full, holding sufficient water reserves for several months of cooling requirements, IAEA said.

The Zaporizhzia NPP cooling pond and the facility’s discharge channel are both integral to continuing to supply cooling water and the Director General stressed again that maintaining their integrity is vital for the safety of the plant.

“The thermal power plant plays a key role in 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 Zaporizhzia Nuclear Power Plant,” Mr Grossi added.

The Director General, who will travel to Kyiv and the Zaporizhzia NPP next week, reiterated that the IAEA also requires access to the electrical switchyard of the nuclear power plant.

The facility’s switchyard has in the past been used to provide backup power to the Zaporizhzia NPP, but its last 330 kilowatt (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 Zaporizhzia NPP 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, IAEA said.

At the nuclear power plant 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 plant is considering the possibility of installing an independent steam boiler that would allow also unit 5 to be put in cold shutdown while still meeting the need for steam supply to the site, IAEA noted.

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