“This was one of the most significant safety events in US nuclear history and yet it was not significantly dangerous to the public,” said Stein. “That speaks to the robustness of these plants.”

NRC licensing requires reactor buildings to be built to withstand “tornado missiles,” or large objects colliding at high speeds, Stein added. “They are literally designed to withstand these kinds of events safely,” he said.

Still, NextEra plans to increase weather-related safety measures at the reopened Duane Arnold plant.

“We do look at those events and try to garner lessons learned and ask, what could make the plant even safer than it is?” said NextEra consultant Michael Davis at a public information meeting held in Cedar Rapids by the Iowa Utilities Commission on Nov. 13.

The company is considering installing a third diesel generator to provide additional backup power, and will also design Duane Arnold’s replacement water-cooling towers with a higher wind resistance threshold, said Davis.

Google representatives did not respond to questions about whether the damage incurred at Duane Arnold during the 2020 derecho raised any concerns for nuclear safety during severe weather events.

The NRC safety requirements mandate that applicants “consider the most severe meteorologic and seismic conditions known in the proposed area,” when selecting reactor sites, an NRC representative wrote in a statement to Inside Climate News.

“It’s important to understand that nuclear plants are built to withstand extreme environmental hazards and that the NRC requires plants to maintain redundant systems, components and programs to be able to mitigate loss of off-site power events,” the NRC added.

Lokenvitz, the former Duane Arnold engineer, views the plant’s reopening as a sort of resurrection. If the facility hadn’t already been slated for decommissioning when the derecho struck, Duane Arnold would have been rebuilt and continued to produce power, she said.

“That plant operated exactly as designed. It was just the perfect storm.”