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.

-jsq