Davis-Besse started leaking boric acid in 1996. Between 1998 and 2000, the leakage began causing problems for other equipment. In 1999, FirstEnergy, the corporation that operates Davis-Besse, found traces of rust particles in the filters of radiation monitors. These filters, which sample the air inside the reactor's containment structure, are normally replaced every two to three months. When the leakage began, the filters had to be replaced every day.
"That should have been a sign that something was not right here," Lochbaum said.
FirstEnergy ignored photographic evidence documenting rust seeping from the reactor head as early as April 2000, Ryder said.
So if I'm reading this correctly, this problem was known about for 7 years!?!