Will Duke Energy’s Brunswick nuclear plant’s flood barriers stop Hurricane Florence?

Will Duke Energy’s Brunswick nuclear plant’s flood barriers stop Hurricane Florence? BY JOHN MURAWSKI, Sep 12, 2018, newsobserver.com
Hurricane Florence is shaping up to be the most powerful storm to ever
threaten Duke Energy’s 1970s-era Brunswick nuclear plant, a 1,200-acre energy complex sitting in the path of the monster storm.
And it will be the first major test of the safeguards installed at the dual-reactor plant, about 30 miles south of Wilmington, since the 2011 nuclear disaster at the Fukushima Daiichi plant in Japan, which is the same generation and design as the Brunswick plant.
Seven years ago, a tsunami swamped Fukushima’s emergency backup generators, cutting off power that was needed to pump water to constantly cool the facility’s radioactive nuclear fuel. The loss of power caused nuclear fuel to overheat in three reactor cores, triggering hydrogen explosions and spewing radioactivity into the atmosphere.
Brunswick is one of about two dozen U.S. reactors that relies on General Electric nuclear technology that dates back to the 1960s, designed at a time when engineers underestimated the vulnerability of nuclear facilities during natural disasters.
The nuclear industry has learned about the limitations of its early optimism the hard way: at Three Mile Island, at Chernobyl, at Fukushima; and also during periodic forced shutdowns in this country when nuclear plants were repeatedly fined by regulators for falling short of safety standards and posing unacceptable risks to the public.
The Fukushima disaster raised questions about the Brunswick plant’s capability to withstand massive flooding, and caused the U.S. Nuclear Regulatory Commission to determine that is not fully safe without modifications. As a result, Brunswick’s emergency plan now calls for installing nine temporary flood barriers in advance of a hurricane, to compensate for deficiencies in the original design.
“The good news is, because of Fukushima, the plant is better prepared,” said Dave Lochbaum, director of the nuclear safety project for the Union of Concerned Scientists, a watchdog group. “If it hadn’t been for Fukushima, that vulnerability would not have been identified.”
Nuclear plants have consistently proven hardy against hurricanes. Hurricane Andrew, a Category 5 storm, passed directly over the Turkey Point plant in Florida in 1992, causing extensive damage to communications systems and the fire protection system, but the nuclear safety infrastructure remained intact, according to the Union of Concerned Scientists. Several storms have passed close to Brunswick, including Hurricane Fran in 1996, which made landfall as a Category 3 hurricane.
During Hurricane Matthew in 2016, wind speeds never reached hurricane force at the Brunswick site and there was no flooding, said Duke spokeswoman Karen Williams.
A modern fortress guarded by armed security, the Brunswick plant is touted by Duke as one of the most robust type of structures standing in the Unites States. But a year after the Fukushima incident, Duke Energy discovered scores of potential areas of leakage and water penetration at Brunswick that had to be fixed. Duke identified the problems as missing seals, missing or corroded bolts, broken links or pressure plates, corrosion, open terminal boxes, gaps in weather stripping on doors and inadequate repairs for previous leakage.
Brunswick is built at an elevation of 20 feet above sea level and designed to withstand a storm surge of 22 feet, which would leave the plant’s emergency generators high and dry. Brunswick, which is four miles inland, can withstand maximum sustained winds over 200 miles per hour of a Category 5 hurricane, Williams said.
Florence is expected to make landfall as a Category 4, which ranges from 130 mph to 156 mph; but Galen Smith, the plant’s on-site resident inspector with the Nuclear Regulatory Commission, said flooding poses the greater threat to the facility.
As far as wind damage goes, Smith said that the structures containing Brunswick’s twin nuclear reactors are virtually impenetrable, enclosed in walls several feet thick that are cast from concrete and rebar.
Emergency generators are a nuclear plant’s artificial life support, fired up when a nuclear facility is put in mandatory shutdown mode during a hurricane that can knock out the power grid, which would be the plant’s normal source of juice. The generators operate the pumps that supply the water needed to cool the reactor core and keep radioactive fuel rods from overheating and triggering a runaway nuclear reaction.
“We have verified the capability to withstand a total loss of electric power to our plants,” Williams said. “We have verified our capability to withstand flooding and the impact of floods on systems inside and outside the plant.”
At least two NRC inspectors will ride out the storm inside the plant, Smith said, and they have been making rounds daily to monitor the progress as plant operators prepare for the storm. Smith said Brunswick has five on-site diesel generators that are backed up by two additional generators installed at elevated levels to stay dry if high waters defy all estimates.
“They have everything they need to operate the plant safely,” Smith said. “It’s just a matter of executing at this point. Even if the storm is bad, they should do fine.”
The temporary flood barriers, called “cliff edge barriers,” hint at the remote potential for catastrophe inherent to the business of splitting atoms to make electricity. In nuclear parlance, a “cliff edge” effect refers to a small variation in plant conditions that can trigger an abrupt change, pushing a nuclear plant over the cliff, from normal functioning to a critical state.
Brunswick’s “cliff edge” barriers will be installed to prevent sea water from gushing through doorways that protect safety equipment and sensitive areas of the plant. The barriers are designed to repel a storm surge of 26 feet, said NRC spokesman Scott Burnell, citing documentation submitted by Duke Energy.
Each barrier consists of an aluminum plate fasted to the wall with stainless steel anchors and backed by a rubber strip to create an waterproof seal. They will be installed at nine doors in the diesel generator building, control building and in the reactor building’s airlock doors. It takes workmen up to 2 1/2 hours to install each barrier, and Duke begins setting up the barriers as soon as a hurricane watch is issued.
The cliff edge barriers are not considered some crude patch job, but a high-tech upgrade. Burnell characterized them as part of Brunswick’s long-term strategy for “dealing with events that might exceed the plant’s original design basis.”
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