A wind plant only gets energy when the wind blows.

A solar panel only absorbs energy when the sun shines.

A nuclear power plant, though, runs nearly all the time.

That gives nuclear power the highest operating rate and is one of the reasons it's undergoing a renaissance.

In a world concerned about global warming, nuclear power is cleaner than gas or coal, and much safer than it was in 1979 at the time of the Three Mile Island accident, said John J. Hirt, who is seeking an MBA in finance and is participating in the University of Wisconsin-Madison business school's Applied Security Analysis Program.

The U.S. is behind the rest of the world in the amount of nuclear power it generates.

But that may be changing.

The Department of Energy's Energy Information Administration estimates between 250 and 500 baseload plants -- those that run all the time -- will be needed in the U.S. by 2030. The U.S. Nuclear Regulatory Commission has received applications over the last few years for 25 new reactors to complement the 104 plants currently in use.

"I think we're finally starting to take this seriously," Hirt said.

There are risks, of course. No one knows for sure how much it will cost to build a nuclear power plant in the U.S., but once it's up and running, "it's about as cheap as you can get," Hirt said.

There are also concerns about the safe disposal of spent nuclear fuel, but all the spent fuel created in the last 40 years would fit on a football field stacked seven yards high, and much of it can be stored at the plant site, according to the Nuclear Energy Institute.

Investors who believe the U.S. will move toward using more nuclear power might want to consider some of the stocks Hirt is analyzing:

Japan Steel Works Ltd. (JPSWY, $52), Tokyo, makes products from casts, forged steel and plastics. The company is the only major producer of large, steel-forged radiation shields for nuclear power plants, Hirt said.

Japan Steel Works' stock doesn't trade very much, but its customers are putting down $100 million deposits just to hold a place in line for the radiation containment forgings, Hirt said.

"They have a big, first-mover advantage. For the competition to come in and get up to speed would take three to five years," he said.

Cameco Corp. (CCJ, $16.22), Saskatoon, Saskatchewan, Canada, produces uranium and has a gold mine in Kyrgyzstan in central Asia.

Cameco is the world's largest producer of uranium, a critical component in producing nuclear reactions. Uranium prices have been coming down, but if there is a significant build-out of nuclear power plants, they'll go higher again, Hirt said.