None of these failures has threatened the public. But the diesel generators serve the crucial function of supplying electricity to cooling systems that prevent a nuclear plant's hot, radioactive fuel from overheating, melting and potentially releasing radiation into the environment.
That worst-case scenario happened this year when the Fukushima Dai-ichi nuclear plant in Japan lost all backup power for its cooling systems after an earthquake and tsunami.
Experts say the failures generally are not cause for alarm. But they have prompted federal regulators to increase scrutiny at plants where the problems happen.
Published 09 October 2011, 15:45 IST