Apparently we still don’t know why this happened:
At approximately 7:50am on Sunday, March 31, 2013, a 600-ton generator stator fell onto the turbine deck and then about 30 feet to the train bay floor as was being lifted out of the Unit 1 turbine building at the Arkansas Nuclear One plant. One worker was killed and four others injured when the load fell.
Dave Lochbaum wrote for Union of Concerned Scientists 18 June 2013, Fission Stories #139: Arkansas Nuclear One Fatal Event,
The NRC reviewed U.S. nuclear plant experience with lifting loads with cranes between 1968 and 2002. The NRC reported that about two load drops per year happened during this period with ten incidents causing deaths. The NRC’s review concluded that there had been only three very heavy load drops (defined as a load weighing more than 30 tons). ANO-1 makes four.
While accidents can also happen with wind turbines or even installing solar panels on rooftops, a single solar or wind accident doesn’t take down 2,568 megwatts for 3 1/2 months. Big baseload is fragile. And ANO1 is still down:
ANO1 is run by Entergy, the same company that couldn’t keep the power on during the Super Bowl, and couldn’t keep Pilgrim 1 open during a Massachusetts snowstorm. The bigger they are, the harder they fall.