The two reactors that make up Duke Energy's Brunswick nuclear power plant in coastal North Carolina will be shutting down in anticipation of strong winds and flooding from Hurricane Florence.

The North Carolina-based utility made the announcement as it prepared for as many as 3 million residents in the hurricane impact zone to lose electricity in the next few days.

The Brunswick plant is more than 40 years old and can supply electric power to 1 million households. It was issued a license extension recently by the federal government to continue running for another 20 years.

[More: Trump faces big test on Hurricane Florence]

The power plant sits on 1,200 acres adjacent to the Cape Fear River. Hurricane damage is a concern, but reactors are hardened against both manmade and natural disasters, the company points out.

Multiple, robust safety barriers are in place, while each reactor has a concrete containment building and a steel chamber surrounding the part of the reactor that contains the nuclear fuel, according to Duke Energy.

In addition, each unit reactor has a safety system to continue cooling the core, such as multiple pumps and backup electrical supply systems.

"Nuclear stations are built to withstand a variety of external forces, including hurricanes, tornadoes, fires, floods and earthquakes," according to a company fact sheet on the plant. "Duke Energy works closely with the Nuclear Regulatory Commission (NRC), various federal agencies, state agencies and local governments to maintain emergency response plans that ensure close coordination with these groups."

The Associated Press pointed out that the power plant is the same design as the Japanese reactor that suffered multiple reactor core meltdowns in 2011 after a tsunami in Fukushima, Japan.

A federal safety review of all U.S. nuclear power plants of the same design was conducted after the 2011 disaster. Washington directed plant operators to make changes if plant vulnerabilities were found. The Nuclear Regulatory Commission's most recent status report showed that the Brunswick plant has implemented all upgrades as ordered by the federal agency, with its last upgrade to be complete in the spring of 2019.

The Fukushima plant did not have the same number of redundant safety features as the same model of reactor used in the U.S., according to experts.

As Duke Energy announced the shutdown, the Nuclear Regulatory Commission, which oversees power plant safety in the U.S., ramped up its hurricane watch center in Atlanta.

"The Nuclear Regulatory Commission will staff its incident response center in Atlanta around the clock beginning this evening as it expands its monitoring of Hurricane Florence and its effects on nuclear power plants and other NRC-licensed facilities," the NRC announced Thursday.

NRC staff members will monitor the path of Hurricane Florence on a 24-hour basis, while remaining in contact with plant operators, the commission's on-site inspectors stationed at the power plants, the NRC’s headquarters operations center, and state emergency officials, the commission explained.

"Duke Energy notified the NRC that the company is shutting down both units at the Brunswick nuclear plant south of Wilmington, N.C., as that site is facing hurricane-force winds, major storm surges, and heavy rain," the agency said.

Federal inspectors are on site at the Brunswick plant and will remain there through the storm.

The GE-Hitachi nuclear fuel processing plant near Wilmington, N.C., has also notified the federal commission that the plant will also be shutting down operations, the agency said.

"Other nuclear plants in the projected storm path have prepared for high winds and heavy rainfall," the commission explained. NRC inspectors will be at all those sites, as well.

The Energy Department's Energy Information Administration is tracking the storm's threat to energy infrastructure in real time, which the public is free to review online.

The Energy Department's analysis arm will be monitoring the effects of the storm on power outages and other energy supply disruptions. As of Thursday, the agency showed that 2 of the 11 nuclear power plants in the hurricane impact zone — Georgia, North Carolina, South Carolina, and Virginia — were operating at slightly reduced levels.

On Thursday morning, the agency showed that one reactor at the Brunswick plant was operating at 88 percent, compared with another reactor of the McGuire plant that was functioning at 99 percent of its total electricity output. Both plants are in North Carolina. In 2017, nuclear power provided 36 percent of the electricity generated in those four southern states.