MIAMI — The last time a major hurricane hit the Turkey Point nuclear power plant, it caused $90 million in damage but left the nuclear reactors along southern Biscayne Bay unscathed.

In anticipation of powerful Hurricane Irma, which projections Wednesday showed headed straight for South Florida, Florida Power & Light’s two nuclear plants were finalizing staffing plans and cleaning up the grounds. But neither Turkey Point nor the St. Lucie plant farther up the coast had made the call yet to shut down the plants.

Peter Robbins, spokesman for FPL, said shutting down a reactor is a gradual process, and the decision will be made “well in advance” of the storm making landfall.

FPL has long defended the safety of its nuclear power plants, which both sit along the coast, where they are potentially exposed to the strongest winds and storm surge of hurricanes. And Turkey Point weathered a Category 5 strike from Hurricane Andrew in 1992.

Robbins said the plant’s reactors are encased in six feet of steel-reinforced concrete and sit 20 feet above sea level. Turkey Point has backup generators, extra fuel and, as a “backup to the backup,” replacement parts and materials can be flown in from Tennessee.

The St. Lucie nuclear power plant is equally protected, Robbins said, and can withstand severe flooding from storm surges. St. Lucie’s nuclear plant survived Hurricanes Frances and Jeanne in 2005 and Wilma the year after.

When the eye of Andrew passed over Turkey Point, some facilities around the reactor buildings took a beating. Ultimately, the state’s oldest nuclear plant suffered $90 million in damages, including to systems that were supposed to be hurricane-proof.

One of the 400-foot smokestacks for the old oil-burning power plant was cracked in half, even though it was rated to survive 235-mph winds. Andrew blew down all but six of the 41 warning sirens within 10 miles of the plant. The storm left the plant running on backup generators for more than a week to cool the shut-down reactor. A main access road was blocked by debris.

“It handled Andrew as it was designed to,” Robbins said. “It’s one of the safest and most robust structures in the state, if not the country.”