Some low-lying plants face a watery future, but the legacy of Fukushima is spurring action.

Picture of San Onofre Nuclear Generating Station

The San Onofre plant on California’s coast has shutdown, but there’s disagreement over storing its toxic waste close to the shoreline.

Just east of the Homestead-Miami Speedway, off Florida‘s Biscayne Bay, two nuclear reactors churn out enough electricity to power nearly a million homes. The Turkey Point plant is licensed to continue doing so until at least 2032.

At some point after that, if you believe the direst government projections, a good part of the low-lying site could be underwater. So could at least 13 other U.S. nuclear plants, as the world’s seas continue to rise. (See maps below.)

Their vulnerability, and that of many others, raises serious questions for the future. The new UN climate accord, reached over the weekend after two weeks of talks in Paris, prods countries to shift from fossil fuels toward energy sources that emit zero planet-warming carbon emissions.

Nuclear could be part of the solution, because it can deliver large, steady amounts of carbon-free electricity. That’s why China, the world’s largest carbon emitter, aims to expand its nuclear capacity by spending $78 billion to add six to eight nuclear reactors each year for five years.

Then again, safety concerns have stoked opposition to nuclear. Reactors can’t operate safely without uninterrupted power and vast amounts of cool water, which is why they’re often located near coastlines, rivers, and lakes. Even when a plant isn’t running, its fuel continues to generate heat that needs to be controlled to prevent explosions or radioactive leaks.

The disaster at Japan’s Fukushima Daiichi showed what can happen when a massive surge of water hits a nuclear plant. Seas of nearly 50 feet washed over it during the 2011 earthquake and tsunami, knocking out the power needed to run its cooling systems. A last-resort bank of batteries lasted only eight hours. As a result, three reactors suffered partial meltdowns and radiation leaked into the air and ocean.

The event gave nuclear a black eye, prompting countries worldwide to take a closer look at their power plants. In the United Kingdom, for example, a pair of reactors were taken offline in 2013 because of concerns that an extreme event could overwhelm its seawall, which was then improved.

Storms and Warming

The United States has 100 operational nuclear reactors, and another 17 that are being decommissioned. In the past, historical data about storms and flooding would inform the licensing requirements for a unit.

“We generally thought that backward look was sufficient,” says Dave Lochbaum, director of the Nuclear Safety Project at the nonprofit Union of Concerned Scientists. Fukushima and big storms like Hurricane Sandy in 2012 showed “that’s a tenuous assumption at best.”

The industry is now reevaluating its flood risks, and hatched a strategy it calls FLEX, where key backup equipment is stationed at multiple locations so it can be shuttled to a distressed plant. This way, instead of defining a theoretical crisis—a storm surge of a certain height, a hurricane by category—ahead of time, says Jim Riley of the industry’s Nuclear Energy Institute, “we’re saying, give us the event and we’ll deploy the equipment.”

Some think more needs to be done, faster. “The Nuclear Regulatory Commission has been slow to implement those Fukushima lessons learned,” says Matthew McKinzie, nuclear program director at the environmental group Natural Resources Defense Council. “Nuclear safety is a work in progress.”

Researchers at Stanford University echoed that concern in 2013, flagging four East Coast plants (the Salem and Hope Creek plants in New Jersey; Millstone in Connecticut; and Seabrook in New Hampshire) as especially vulnerable to storm surges and arguing for, among other measures, more and taller seawalls. A more recent analysis from the Union of Concerned Scientists found that at least four nuclear plants are vulnerable to storm surges by 2050.