Seven emergency diesel generators kept six shut-down reactors cool when Europe’s largest nuclear plant lost its last power line, but crews ended up running just two of them to stretch the fuel over 18

Key Points:

• The Zaporizhzhia Nuclear Power Plant in Ukraine, occupied by Russian forces, lost its last working grid connection on August 20 and relied on diesel generators until repairs were completed on September 7 under an IAEA-negotiated ceasefire.
• The plant’s six reactors are shut down, but continuous power is crucial to run cooling pumps that prevent overheating of radioactive fuel and spent fuel pools; with only one external power line operational, diesel generators are the backup.
• Zaporizhzhia has 20 diesel generators, but fuel shortages have forced it to reduce generator use from seven to two and operate cooling pumps intermittently to conserve diesel, raising concerns from the IAEA about plant safety.
• A total loss of power (station blackout) poses risks similar to Fukushima, though the plant’s long shutdown means residual heat is lower, providing more time before damage could occur; however, backup generator reliability is a growing concern due to extended use and potential common cause failures.
• Fuel deliveries face challenges due to ongoing conflict, with reports of attacks on diesel convoys, complicating resupply efforts; the plant has taken measures such as raising water levels in spent fuel pools and bringing in mobile generators to mitigate risks amid continued power instability.