Nuclear energy is getting more and more attention as one solution. A generation after the Three Mile Island and Chernobyl accidents, global pressures and new technology are reshaping how we think about nuclear power. President Obama is calling for tripling loan guarantees for developing new plants, from $18 billion to $54 billion. Even some environmentalists are warming up to nukes. They see them as a good way of getting power without boosting carbon output.

Here's where things stand. The U.S. gets 20% of its power from 104 nuclear reactors, in 31 states, but a new one hasn't been put online since 1996. Well, that's about to change. "energyNOW!"'s Lee Patrick Sullivan takes us on a tour of a new reactor under construction, in this "energyNOW!" Spotlight.

[SULLIVAN] If you've ever driven the back roads between Knoxville and Nashville, you may have driven right by Watts Bar units 1 and 2. Well, they just happen to be nuclear power plants. And what makes them so special is, unit 1 was the last U.S. commercial nuclear power plant to go online in the last century. Unit 2 will be the first of this century.

[DARLENE VISCUSIE] We're going up to the turbine deck.

[SULLIVAN] I met up with one of the plant's 200 engineers, Darlene Viscusie. She gave me a rare tour of the facility, including an "up close and personal" look at the plant's 1.21 gigawatt generator.

[DOC BROWN] To generate the 1.21 gigawatts...

[DOC BROWN] 1.21 gigawatts?!

[SULLIVAN] Only this massive piece of machinery would never fit in a DeLorean.

I wish we had "feel-o-vision" so you could feel this, but it's a pretty awesome feeling, isn't it?

[VISCUSIE] Yes, it is -- you can actually feel it in your chest.

[SULLIVAN] Viscusie knows nuclear power. You can say it's in her DNA. Her father was here at Watts Bar from the beginning, working as an engineer for unit 1. Now that unit 2 is under construction, Darlene will be following in her father's footsteps. For now, I'm following in her footsteps, right into the reactor containment building, something very few people ever get to see in any capacity.

Ow!

And that's why reporters wear helmets. Cameras are rarely in places like this, mostly because the buildings are radioactive during operation.

Those right there? Well, those are the control rods. They are dropped into the containment vessel to control the strength of a nuclear reaction. This time next year, I would have to be suited up like I was going to the moon to get that close to them.

So you grew up knowing that eventually one would be here. Did you ever think that you would be working on the start-up of this?

[VISCUSIE] I never had plans to work at a nuclear power plant. An opportunity happened, and here I am, and I love every day.

[SULLIVAN] As complicated as building and running a nuclear facility can be, how it makes electricity is pretty basic. Now, most power plants are all trying to do the same thing, and that is, boil water. Boiling water creates steam. Steam turns a turbine, which creates electricity. The only thing that's different is the fuel. So it could be oil, coal, nuclear -- they're all simply trying to boil water -- even natural gas like is being used here in this stove is trying to boil water -- although most natural gas power plants also have combustion and a dual cycle method, but, you know, that's another story.

What separates nuclear from fossil fuels -- there's no flame. Fuel rods packed with nuclear fuel react through fission, creating heat -- a lot of heat. So much heat, the rods are constantly submerged in water. That water heats up another set of pipes, also filled with water. Those pipes travel to more water that boils and creates steam. Why all the different sets of pipes? Well, you wouldn't want radioactive steam, would you?

Safety is also the reason a concrete containment building is built around the reactor vessel.

Now, to give you an example of how thick the walls are in the containment building, they've cut this hole to bring in equipment. This is the secondary containment wall, and this is at least 2 feet thick, and there's three of them. In total, there's more concrete in a nuclear power plant than was used in building the Pentagon, and that's the world's largest office building. There's also an enormous amount of steel. Hundreds of engineers are needed. And then there's the waste. What to do with the radioactive fuel once there's no more life left in it.

[JIM HOPSON, TVA WATTS BAR] If it's managed appropriately, nuclear waste is something that can be easily dealt with. We've done it for decades; we know how to manage it.

[SULLIVAN] But with President Obama recently slamming the door on the unfinished Yucca Mountain Nuclear Repository -- a $90 billion project designed to store nuclear waste in Nevada -- nuclear facilities still have to store their waste on site, some in water, others are cased in concrete and kept at the plant.

And safety concerns aren't limited to keeping radioactive material inside the containment building; they're also concerned with keeping terrorists out. This is the only part of the several layers of security at this plant that we were allowed to record. In the wake of 9/11, plants beefed up their security, and although we can't discuss procedure or show video, think of a prison -- but the criminals are on the outside.

[TERRY JOHNSON, TVA WATTS BAR] As you came in here today, you saw the level of security to keep people -- make sure we know who's getting here --

[SULLIVAN] If you want to know the level of security, it's making me miss the TSA. That's the level of security it took to get in here.

In fact, before we could leave, TVA security officials had to review every second that we shot, to make sure we weren't giving away any security secrets.

So, why go through all this fuss, all the concrete that's needed, the steel, the number of engineers? And then you have to deal with the waste. Why go through all that? Well, this is why. This is the size of one nuclear fuel pellet. It has the same energy density as one ton of coal or 149 gallons of oil. Oh, and there's 20 million of them in there.

There's also another benefit to nuclear power, one that has split the environmental community. On one hand, nuclear waste lasts tens of thousands of years. On the other, its only emission is steam.

[JIM HOPSON] The power that we get right now is completely green. There are no greenhouse gases, no carbon emissions associated with it.

[SULLIVAN] As for Darlene Viscusie, nuclear power's zero emissions is something that attracted her to becoming a nuclear engineer.

Your father worked on the last one to go on before the end of the century. You're working on the first one of this century. Will your grandkids work on the ones for the next century?

[VISCUSIE] I hope so. That's my plan.

[SULLIVAN] In Spring City, Tennessee, Lee Patrick Sullivan, "energyNOW!"

[ASSURAS] The Watts Bar unit 2 is scheduled to go online in 2013 and is expected to provide energy for 650,000 homes in the Tennessee Valley.