(CNN) -- Federal officials expressed confidence the six nuclear power plants in Hurricane Florence's path are safe, but some experts aren't so sure, warning that flooding and torrential rains could overwhelm their defenses.
The six nuclear power plants in North and South Carolina sit directly in the storm's projected path, according to Mary Catherine Green, spokeswoman for Duke Energy, which owns all six.
Duke's Brunswick Nuclear Plant and its Shearon Harris Nuclear Plant near Raleigh, both in North Carolina, are the closest to where the hurricane is forecast to make landfall, Green said.
In a press briefing, Jeff Byard, associate administrator for the FEMA Office of Response and Recovery, said the agency was not concerned about the power plants in the storm's path "at this time."
"Those power plants are, one, obviously hardened. Two, they have backup generators for power and we will rapidly assess any impacts to a nuclear power plant post-storm," Byard said in a call with media. "Obviously, it's something that we track and monitor but at this time we're not concerned with any issues pertaining to the nuclear power plants."
However, The Union of Concerned Scientists, a science-oriented public policy organization, is concerned about the Brunswick plant's ability to withstand the storm, because of what the group says is a lack of publicly available information about the plant's readiness.
According to the group, the Nuclear Regulatory Commission has not released public information validating that the plant has been properly updated to protect against flooding.
In 2012, Duke Energy reported to the NRC that there were hundreds of "missing or degraded flood barriers" at the plant. The follow-up report sent to the NRC by Duke Energy in 2015 was not made publicly available, according to The Union of Concerned Scientists.
NRC spokesman Roger Hannah said if the report wasn't made public it may have been because the report contained security-related information, but he wasn't aware of the 2015 report's status. Hannah said the Brunswick plant was up to code ahead of the storm.
"We have inspected their storm protections. We have looked at their preparations," Hannah said. "We're satisfied they met current NRC requirements."
Flooding at nuclear plants became more of a concern after a 2011 earthquake and subsequent tsunami in Japan caused one of the worst nuclear disasters since the 1986 Chernobyl incident.
Three nuclear reactors melted down at Japan's Fukushima Daiichi nuclear power plant, releasing dangerous radiation into the surrounding area.
Since the 2011 incident, the Nuclear Regulatory Commission has updated its requirements for nuclear power plants regarding natural disasters, according to former NRC chairman and managing director of the ND2 group Nils Diaz.
"These are 5-foot, 6-foot thick containment buildings," Diaz said. "Everything is put up high to prevent intrusion of a normal hurricane, but beyond that they have additional protections that are provided."
Diaz said he did not think there would be issues with the power plants in the upcoming storms.
NRC spokesman Scott Burnell said the Brunswick plant is properly fortified to withstand hurricanes of Florence's strength, and there are plans in place to shut down if necessary.
"The [Brunswick] plant already has procedures in place both to shut down well in advance of hurricane effects actually occurring on site," Burnell said. "The plant also has procedures in place to reinforce what are already robust defenses against flooding to ensure that it will remain safe as the storm passes by."
Burnell said the NRC has inspectors on site at Brunswick to monitor the plant as the staff go through their storm procedures, which he said is standard practice for the agency.
He said each plant has resident inspectors on site, and one or two additional inspectors at sites that are expected to be more directly impacted by the storm.
"We have staff at every site on the Carolinas for these plants where there's the expectation of significant effects from the storm," Burnell said.
Emergency planners have contemplated the risks of a hurricane-related nuclear power plant issue on the East Coast.
A hurricane simulation exercise conducted by FEMA and the Energy Department this spring considered how to respond to damage at a nuclear power plant, according to The Associated Press, which first reported the exercise.
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