NUCLEAR energy is going through an odd patch. It refuses to die, but it does not prosper.

This is how modest the nuclear industry’s prospects now look: Senator Lamar Alexander, a Tennessee Republican who has called for building 100 reactors in the next few years, told a conference of industry specialists in late March that the long-ballyhooed “nuclear renaissance” did not really exist anymore. Now, he said, it is an “awakening to the awareness of nuclear.”

But it is an awakening with a price of $30 billion or more. Mr. Alexander was speaking to a conference convened on the 33rd anniversary of the Three Mile Island accident, a few weeks after the Nuclear Regulatory Commission gave permission to build a power reactor for the first time in more than 30 years, for the twin Vogtle reactors near Augusta, Ga.

Those will cost $14 billion, if all goes well, and more if it does not. A few days after he spoke, the commission approved a license for another pair of reactors in South Carolina, which will cost about the same. Several other companies are laying out hundreds of millions of dollars in planning for reactors that may or may not get to the groundbreaking stage.

The industry’s three great recent stumbling blocks, the Fukushima accident of March 2011, the exceptionally low price of natural gas and a recession that has stunted demand for power, mock the idea that dozens of new reactors are waiting in the wings. But in an era of worry over global warming, support is plentiful for at least keeping a toe in the water.