The four steam generators at San Onofre — two per reactor, each with 9,727 alloy tubes — function something like a car radiator, which controls heat in the vehicle’s engine. The generator tubes circulate hot, radioactive water from the reactors, which is used to make steam to turn turbines that produce electricity.

Overall, investigators found wear from friction and vibration in 15,000 places, in varying degrees, in 3,401 tubes inside the four replacement generators.

SoCal Edison plans to permanently shut down San Onofre nuclear plant

Sounds a little more serious than a couple of tubes…