The International Atomic Energy Agency (IAEA) team has this week been observing operational tests of diesel generators at the Zaporizhzhya Nuclear Power Plant (ZNPP) as part of ongoing efforts to help prevent a nuclear accident during the military conflict in Ukraine, where the off-site power situation remains challenging, Director General Rafael Mariano Grossi said.
The ZNPP has repeatedly lost all access to external electricity during the conflict, forcing it to temporarily rely on diesel generators for the power it needs to cool its reactors and for other essential nuclear safety and security functions. The tests carried out in recent days were designed to confirm that they are fully operational.
"As the off-site power situation at ZNPP is still highly precarious, it is very important that these diesel generators can immediately start up without any issues. Our experts were this week able to confirm that the diesel generators that were tested can fulfil their function if the plant once again were to lose its external connections. Continued vigilance in this respect is necessary," Director General Grossi said.
The plant has 20 emergency diesel generators (EDGs) for its six reactors. Six mobile diesel generators (MDGs) were installed by Ukraine as part of the safety measures introduced in light of the 2011 Fukushima Daiichi accident - four of which are connected to reactor units and two of which are being used outside of the ZNPP site. Last year, the ZNPP procured three new MDGs that are located adjacent to the turbine buildings of three of the reactor units, but have yet to be connected. This week, the IAEA team based at the site witnessed the testing of one EDG and one of the new MDGs.
Separately, the IAEA is aware of a report of a purported spillage of fuel held in storage for the ZNPP's diesel generators. When asked about the report, the ZNPP told the IAEA team that it was "fake" and that no such leaks had been detected from the site's fuel tanks. In addition, the plant said it has enough fuel in storage for a minimum of ten days of operation of its diesel generators. The IAEA has requested access to the fuel tanks to independently assess the situation there first-hand.
Over the past week, the IAEA team has also continued to monitor maintenance of some of the ZNPP's safety systems and discussed emergency preparedness and response arrangements with the site. Team members conducted a walkdown of the site's waterworks facilities, and of the reactor building of unit 4, where the team observed traces of dried boric acid in some rooms as well as a defective seal on a pump.
The IAEA team was informed by the site that the 330 kilovolt (kV) switchyard of the nearby Zaporizhzhya Thermal Power Plant (ZTPP) was reconnected to the ZNPP's 750 kV switchyard last Friday, about a month and a half after the connection was cut as a result of damage to the ZTPP switchyard, which can now once again function as an alternative way of providing back-up power to the ZNPP.
Throughout the week, the IAEA team reported hearing military activities at varying distances away from the ZNPP.
The IAEA teams stationed at the other nuclear sites in Ukraine continued to monitor the status of the respective facilities - the Khmelnytskyy, Rivne and South Ukraine NPPs and the Chornobyl site.
At the Khmelnytskyy site, one 750 kV line was disconnected at the request of the grid operator on 21 March and was reconnected that same evening, while refuelling activities at one of the reactor units continues. At the Rivne NPP, one reactor unit has been shut down for planned refuelling. The IAEA team at the South Ukraine NPP was informed that the site has repaired a leaking pump and that unit 1 has since returned to nominal full power.
At the Chornobyl site, a fire caused an emergency outage of one 330 kV line that provides off-site power to the plant. It was switched back on after the Ukrainian State Emergency Service extinguished the fire.
The teams at all four sites reported hearing air raids over the past week. At Chornobyl, the IAEA team was informed that a drone was detected 3 km from the site in the evening of 21 March. At around the same time, the team heard a loud explosion and also witnessed a flying drone.
