Nuclear power has been around the block. Once viewed as the savior for an increasingly energy hungry world and then turned into the energy industry’s goat, its players uniquely know the fortunes of fame and costs of calumny. 

But nuclear is making a comeback–a quiet, cautious and almost polite comeback.

On the environmental side, many experts worry that we’re pumping way too much carbon into the atmosphere, causing a greenhouse effect, which over the long term will make the world more inhospitable than any fallout from nuclear power.

In light of this view, advocates for nuclear power our finding a receptive audience. It’s clean, cheap power on a massive scale and would be able to allow industrial and developing nations to take some of their older, dirtier power plants offline. These folks would prefer carbon sequestration, but that’s about as elusive as the Yeti. And time is of the essence.

The power industry would be more than happy to erect new nuclear power facilities, but the last such build-out in the US was a fiasco at best. And this time around they want guarantees and funding from the federal government that will lessen the financial risk.

In the ensuing years since Three Mile Island and Diablo Canyon sealed the fate of the US nuclear power industry, nuclear power plant production has been rationalized and globalized. Back in the 1970s and ’80s, there were almost a dozen different plant designs; each time a new plant in a new location with a new design came before the Nuclear Regulatory Commission (NRC), each piece of the proposal had to be addressed separately. It took large amounts of time and money just to get through the regulatory hurdles before ground was ever broken.

And because almost every project involved a new design, it meant construction was a bear; no company had any particular expertise in all the designs. These challenges left a bad taste in everyone’s mouth regarding nuclear power in the US.

But current exigencies–fossil fuel issues, environmental issues, resource demand issues, domestic security issues–have brought nuclear back to center stage–or at least front stage right. Also, bear in mind that nuclear power accounts 16 percent of electricity generated worldwide and eliminates about 2.5 billion tons of carbon-dioxide emissions annually.

And this isn’t your father’s nuclear industry. Today, there are only a handful of major plant designs, and they’ve been built around the world. Toshiba (Japan: 6502; OTC: TOSBF), which owns the former Westinghouse’s nuclear division, and Siemens (NYSE: SI) are two of the leading players and are doing a lion’s share of the work in China and Asia. GE (NYSE: GE) produces a light water reactor that makes up about 33 percent of the US nuclear power plants and is developing a new generation of the old model.

It’s this new generation of reactors that’s firing enthusiasm inside industry, the markets and energy-hungry customers. We’re working on a bigger piece with our favorites on the old and new side of nuclear power for Portfolio 2020; this article will focus on a dark horse with a lot of closing speed: thorium.

Thorium is a neighbor of uranium in the periodic table, in the actinide series. Basically that means it’s a really heavy rare earth metal (REM) that’s ideal for nuclear fission.

Thorium is readily available and burns more efficiently than uranium, leaving less waste. It also has fewer and less hazardous peripheral waste products, and its half life is measured in centuries, not millenia. And there’s plenty of Thorium in the US.

Why haven’t we used Thorium the whole time?  The answer traces back to the Cold War. Uranium is refined into plutonium, which can be used to make nuclear weapons. Thorium, unfortunately, is no help in building an arsenal of nuclear weapons; when push came to shove for the early development of civilian nuclear energy, the powers that be backed uranium.

But this approach is being reevaluated for a number of pragmatic reasons. If you’re building new reactors, why not build them to run on a different fuel? And there’s already been decades of study on Thorium-based reactors, so researchers aren’t starting cold.

Thorium also enjoys significant support on Capitol Hill. Senate Majority Leader Harry Reid (D-NV) is a big proponent of Thorium reactors. He has joined forces with fellow power Senator Orin Hatch (R-UT) to draft the Thorium Independence and Security Act with the specific purpose of getting Thorium reactors up and running. The bill sets out to establish an office in the NRC specifically for Thorium production and use.

Not surprisingly, Nevada and Utah hold the lion’s share of Thorium reserves in the US. Also, a shift to Thorium would slow any movement on the Yucca Mountain nuclear waste facility boondoggle that Reid deeply opposes in his home state. The bill is sitting in committee, likely because it was introduced just before the financial markets unraveled, and there hasn’t been the time to make this a priority. But that time is nigh.

Here’s an excerpt from a joint statement they issued when introducing the bill:

Using thorium for nuclear power has a number of potential benefits over conventional uranium. As a resource, thorium is abundant in the U.S. and throughout the world. A thorium fuel rod would remain in the reactor about three times as long as conventional nuclear fuel, cutting the volume of spent nuclear fuel by as much as two-thirds. Also, thorium nuclear fuel would significantly reduce the possibility that weapons-grade material would result from the process. Finally, a thorium fuel cycle could be used to dispose of existing plutonium stockpiles, which is the national security goal.

At this point, there’s only one real player in the Thorium space that’s publicly traded, Lightbridge Corp (NSDQ: LTBR). And it debuted in October 2009. I can’t gauge how Lightbridge will shape up as time passes; right now it’s a hot story, but it’s going to have to demonstrate some staying power. The pending legislation will be a boon to this company, but it doesn’t look like it’s getting through committee anytime soon. That means Lightbridge is going to have to have the legs to get it through adoption of the technology on the industrial side and by Congress on the legislative side.

For now, I’d stick to the established players in nuclear power and the big construction and consulting firms that develop, design and maintain the facilities. But keep an ear to the ground on Thorium reactors.

GS Early is associate editor of Portfolio 2020.