ATLANTA — Just as the nuclear industry is starting to build reactors after a 30-year drought, it faces another dry spell.

The industry thought it had what it needed for its rebirth: federal loan guarantees; a uniform reactor design; a streamlined licensing process. The nightmares from the 1979 partial meltdown at Three Mile Island, 1,000 new safety regulations and cost overruns would be left in the past, industry officials believed.

But what never came together was a long-term plan for how to store the used radioactive fuel. As a result, judges and regulators have slammed the brakes on new reactor projects — with two exceptions.

“Waste is an environmental concern, it’s a public health concern and it’s become a security concern because we live in a different world now,” said Sara Barczak, the high-risk energy director for the Southern Alliance for Clean Energy.

Industry officials say there is time — more than 100 years even — until the nation’s power plants run out of room to store the radioactive waste on site. But a federal appeals court ruled in June that the U.S. Nuclear Regulatory Commission — the agency charged with making sure utilities build and operate nuclear reactors safely — could no longer say it had reasonable assurance that a long-term waste-management solution would be created. Because of this, the NRC said it will not approve any new projects for now.

This leaves Atlanta-based Southern Co. and South Carolina’s SCANA with the only utilities to win approval to build nuclear reactors from scratch after an almost 30-year gap. Other utilities that have nuclear projects but are further behind in the approval process may face an additional delay of a year or more.

SCANA is building two new reactors at the V.C. Summer nuclear power site in Fairfield County with state-owned utility Santee Cooper at a cost of about $10 billion.

Georgia Power, one of Southern’s utilities in the company’s four-state territory, is building two new reactors at Plant Vogtle with a group of municipal and cooperative electric companies for $14 billion.

Efforts were made to find, research and prepare a permanent central repository during the 30-year nuclear hiatus. The federal government planned to start moving used fuel from nuclear plants to Yucca Mountain in Nevada — which scientists had been researching since the 1970s.

The government signed contracts with utilities to haul the waste there when the repository was supposed to open in 1998. A protracted approval process, environmental questions, lawsuits and mounting political pressure ground the project to a halt in 2010.

President Barack Obama appointed a bipartisan Blue Ribbon Commission to find alternative plans to Yucca Mountain. The commission supported a central repository but suggested the government secure approval from local communities to prevent the same type of backlash that Yucca Mountain received.

“Scientifically, it was a perfectly good site, but politics caught up to it,” said Steven Kraft, a senior director with the Nuclear Energy Institute, a Washington-based policy group for the nuclear industry.

For now, the utilities that own and operate the nation’s 104 reactors house the high-level spent radioactive fuel at the power plants. The rods are first cooled in water and then moved to hardened casks made from massive steel and concrete.

“It’s kind of like the deficit. Eventually you are going to have to deal with it,” said Glenn Sjoden, a nuclear and radiological engineering professor at Georgia Tech. “It’s not something you can just let sit in your backyard.”

But that’s where the used fuel will sit, in the “backyard” of nuclear plants, likely for several years, because of the federal court ruling.