The commission's inspectors found that some of the shutdowns might have been preventable if the Tennessee Valley Authority's plant management had more quickly implemented safety improvements after the initial problems were discovered.
Some of the problems stemmed from the Unit 1 reactor reopening in 2007 after 22 years of being shut down. The unit had a history of safety problems before it closed in 1985.
"Based on the results of the inspection, no findings of significance were identified," said Eugene Guthrie, an NRC branch chief who oversees inspections of TVA nuclear facilities. "The NRC determined that your proposed corrective actions are appropriate to resolve the deficiencies."
TVA's own review also confirmed many of the findings. TVA provides power to almost all of Tennessee and parts of six other Southern states. It has pushed in recent years to expand its nuclear power program.
TVA has implemented many safety changes at Browns Ferry, about 110 miles south of Nashville, but it still has work to do. This spring, the facility will undergo a safety survey with employees, which inspectors and management expect to lead to additional changes and improvements.
Browns Ferry management said that, after the five shutdowns from May through October 2007, the plant brought in outside experts to help get to the root of the problem. That led to additional problems discovered and improvements at the plant, which has three nuclear reactors.
"Protecting the health and safety of the public is our number one mission, not only at Browns Ferrry, at TVA, throughout all the nuclear industry," said Rusty West, TVA's vice president in charge of the plant.
Federal inspectors said some plant technicians were failing to fill out certain problem evaluation reports. And TVA's initial review of the shutdowns didn't find all of the causes of the problems. When TVA brought in private experts later, they helped identify almost three times as many causes of the unexpected shutdowns.