Old reactors, new tricks

In February 2002, during a routine inspection at Ohio´s Davis-Besse nuclear power station, inspectors found three cracks in the lid of the reactor´s pressure vessel, the mighty steel cylinder that encloses the radioactive core. One crack was in the housing of a mechanism that drives control rods into the reactor core to manage the nuclear reaction. The flaws needed to be repaired, but there was no sense of urgency-that is, until workers began fixing the crack in the control rod mechanism and they felt a wiggle. A wiggle that was all wrong.