A Nebraska environmental group wants federal regulators to keep the Fort Calhoun nuclear plant shut down because it would be inundated by flood waters in the unlikely event of a dam failing upstream.

The Clean Nebraska group says the Nuclear Regulatory Commission's own assessment of the flood threat at the plant about 20 miles north of Omaha predicts all major equipment at Fort Calhoun would be flooded if the Oahe dam failed.

The NRC said in its memo that this flooding issue at Fort Calhoun did not represent an immediate safety concern and could be addressed later.

Fort Calhoun initially shut down for routine maintenance in 2011, but last summer's flooding along the Missouri River and several regulatory violations forced it to remain offline.