Persistent instability in Ukraine’s electrical grid continues to challenge nuclear safety during the military conflict, at times causing disruptions in the availability of off-site power for the country’s main nuclear sites, IAEA Director General Rafael Mariano Grossi said today. 

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Early in the morning of 6 December, at 3:21am, the Zaporizhzhya Nuclear Power Plant (ZNPP) suffered yet another loss of all off-site power – its 11th during the conflict – lasting for about half an hour when both of its remaining power lines were disconnected within 20 minutes of one another. 

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At the time of the event, all available emergency diesel generators (EDGs) on site automatically started up to generate the electricity the plant needs to operate the water pumps used for reactor cooling and for other essential nuclear safety and security functions. 

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“While the emergency backup system functioned as designed, repeated loss of off-site power events increases operational stress and highlights the importance of maintaining reliable off-site power,” Director General Grossi said.

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While the 330 kilovolt (kV) Ferosplavna-1 line was reconnected to the ZNPP after just 29 minutes, the 750 kV Dniprovska main power line was restored nine hours later. Earlier in the autumn, the ZNPP went for one month without any off-site power, the longest such event during the conflict. 

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Elsewhere in Ukraine, widespread military activities last Saturday also affected the grid and external power supplies to the three operating nuclear power plants (NPPs), prompting them to reduce the output of several reactors. 

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“These disruptions have resulted in fluctuating power outputs, temporary disconnections, and forced outages at some units. In several cases, units were taken off-line or operated at reduced capacity to maintain grid balance and prevent equipment damage following sudden protection actuations,” Director General Grossi said.

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“In terms of nuclear safety and security, the fragile grid and power situation remains one of the biggest challenges. As the Seven Indispensable Pillars for ensuring nuclear safety and security during an armed conflict clearly state: there must be a secure off-site power supply from the grid for all nuclear sites. All too often, this is far from the reality that our experts see on the ground,” he said.

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On a more positive note, the operating NPPs’ nuclear safety systems have continued to function as intended, and emergency power supplies remain fully available. The IAEA teams based at Ukraine’s nuclear sites continue to monitor conditions closely and maintain communication with operators.

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As part of the IAEA’s ongoing efforts to help prevent a nuclear accident during the conflict, an IAEA team is this month visiting more than 10 electrical substations, following recent attacks targeting key energy infrastructure. The 1-12 December mission is assessing the damage, reviewing repair efforts, and identifying practical steps to strengthen the resilience of off-site power supplies to the country’s NPPs. 

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At the ZNPP on 5 December, the IAEA team observed an EDG test. At the full-load stage during the test, a smoke cloud and flames of up to a few metres high were suddenly seen shooting up from the EDG building’s exhaust chimney. The flames subsided after one-two minutes. The IAEA team was informed that the fire was caused by the ignition of accumulated soot in the exhaust system, that had been piled up during its prolonged operation during the October-November loss of off-site power event. After test completion, the team was informed by the ZNPP that it had been successful and that the EDG was put back to standby mode. The IAEA team later visited the EDG building and did not notice any issues with respect to nuclear safety. 

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As part of the IAEA’s comprehensive programme of assistance, the physical protection department of Ukraine’s Central Enterprise for Radioactive Waste Management received four all-terrain vehicles. The delivery was funded by the United Kingdom. 

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Text Courtesy, IAEA