The troubled Fort Calhoun nuclear power plant in Nebraska is gradually moving closer to restart, but officials say significant work remains.

Omaha Public Power District officials provided an update Tuesday to the Nuclear Regulatory Commission on the plant 20 miles north of Omaha that has been shut down since April 2011.

OPPD CEO Gary Gates says the plant is on the right path and the utility is improving its oversight.

And he says Exelon, the company hired four months ago to run Fort Calhoun, is strengthening the safety culture of the plant.

But officials still have to test a number of systems that haven't been used in nearly two years and complete other upgrades to the plant.

Regulators say they won't let the plant restart until they're sure it's safe.