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ALISON STEWART, host:

With calls from all ends of the political spectrum to address climate change, the idea of nuclear power, once an anathema, well, let's welcome back into the conversation.

Today, we present part two of the BPP's four-part series on nuclear energy. Today, it's time to get smarter. Hopefully, by the end of this segment, you'll be able to explain to somebody, somewhere, how nuclear power works. And with 103 operable nuclear reactors in the U.S., 445 worldwide, providing a fifth of the world's electricity, it might be a good idea to know how it all happens.

Doctor David Morgan is a big hit, was a big hit on our blog for his explanation of the tesseract and time travel. He is back now to tackle nuclear energy. He's a Physics professor at Eugene Lang College in Manhattan. Can I just call you David instead of Doctor Morgan?

Doctor DAVID MORGAN (Physics Professor, Eugene Lang College): Absolutely.

STEWART: Okay. David, first, what elements do I need - not me personally - does one would need to create power in a nuclear reactor?

Dr. MORGAN: Well, the way we get power from the nucleus is through a process called fission, where you take a big, heavy sort of somewhat unstable nucleus and cause it to split in half. The element that we use for that is uranium, which is sort of the biggest, heaviest natural occurring element in the periodic table. And in particular, there's one isotope of uranium that's best for that, which is Uranium-235. And only one percent of the uranium that we dig out of the ground is the sort of fissionable type. So we have to dig it up. We have to purify it or what's called enrich it to get more of the good kind of uranium. And then, when we get enough of it together, those atoms - or the nuclei out of those atoms actually split in half and that process of splitting generates energy and heat. And we use that heat to heat water and make steam and spin a turbine and make electricity.

STEWART: So what actually causes the split? What causes the fission?

Dr. MORGAN: It's - from the fact that a uranium atom is kind of big. And in any atomic nucleus, there are two sort of forces opposing one another. There's the electrical repulsion that comes from the fact that an atomic nucleus is made mostly of protons - well, protons and neutrons. But the protons are electrically charged, and we probably all learned in middle school that that like charges repel one another, opposite charges attracts. So when you put all these protons in a nucleus, they're all pushing apart and so they want to come flying out of there. What cues them from flying out is the nuclear force, which is when you get enough protons and neutrons together stronger than the repulsive force. So you can think of what happens to the uranium atom when it fissions as imagine you had two magnets, two really strong magnets and you try to push the north poles together and they push apart. Now I'm mentioning gluing some Velcro to those two magnets, so you can Velcro them together. The magnetic…

STEWART: And they're still pushing apart.

Dr. MORGAN: Right. The magnetic field is still trying to push them apart, but the Velcro is holding them together. That's like the positive charge of the proton is trying to blow the nucleus up and the nuclear force is trying to hold it together. If you give those magnets a little nudge, they'll come flying out and that is the kinetic energy of that uranium atom or that uranium nucleus coming apart that is - generates the heat that we then use to make energy.

STEWART: This type of uranium, is it plentiful?

Dr. MORGAN: I was reading yesterday that the abundance of uranium in the Earth's crust is about the same as tin. So uranium is not as rare as you would think - as it is being uranium. I mean, if you go dig up a shovel full of dirt out in your yard, there's uranium in it.

STEWART: All right. You explained how you heat the water and then you get the electricity out of that, where is the waste? Where does the waste come in?

Dr. MORGAN: Well…

STEWART: Sorry I was going to cut to the chase on that one.

Dr. MORGAN: …the waste comes from the fact that the place the energy comes from is by taking the nucleus of that uranium atom and splitting it in half. And then you've got two smaller nuclei that are generally something radioactive and it's no more good for making energy so it's just leftover and that's your sort of solid nuclear waste. You know, they put that underwater for a few years to cool off and then you seal it in a barrel and try to find a place to hide it for 10,000 years.

STEWART: Okay. That's our next two segments of where we put that stuff in the next 10,000 years.

Dr. MORGAN: Right.

STEWART: So one of the big issues when you're talking about nuclear energy, nuclear power - people touted as something that we should be considering is that it doesn't have the same kind of emissions that other energy sources do. But I have a question, do - are fossil fuels used anywhere in the process of creating the plants, of keeping them running?

Dr. MORGAN: Well, sure. I mean, if you build a plant with a bulldozer, you use some fossil fuels. If the mining equipment that you use to dig up the uranium runs on gasoline, then you use some fossil fuels. (Unintelligible)…

PESCA: Homer Simpson drives to work every day.

Dr. MORGAN: Exactly. So almost nothing that we do in our lives doesn't use a little bit of fossil fuel to get it done. But the plant itself releases no carbon dioxide of its own because it's not burning anything the way all fossil fuel plants do.

STEWART: Let's talk about accidents, because there's been at least one significant accident in the past decades - in the '90s, it was in Japan; in Chernobyl - from the '80s, it's Chernobyl; in the '70s, obviously, Three Mile Island. When something goes wrong in a nuclear power facility, is it human error? Is it the - just the function of something can go wrong so it will go wrong?

Dr. MORGAN: Things can go wrong with any machine, but in most modern nuclear plants, there are enough sort of fail-safes in place that when something does go wrong, control rods drop into the core and the nuclear action just stops. Even if the worst thing happened in a nuclear power plant that could, there's no danger of it blowing up like an atomic bomb. In terms of the quality or the enrichment of the uranium that's used in a nuclear power plant, it's many times less enriched than the type that you would use to make a nuclear weapon. So there's no risk of explosion. But there are risks of cores melting down and radiation being released, although I think those risks are fairly small and hopefully, manageable.

STEWART: France gets about 78 percent of its electricity from nuclear power; Belgium about 54 percent. Now if the United States builds the 28 proposed nuclear reactors - new nuclear reactors, would that make a dent in our energy consumption do you think?

Dr. MORGAN: I think it will make a dent but we will get no where near up to 80 percent, I don't think. I mean, we actually use more nuclear power than France does. It's just that we use a lot more power than France does. So I think it would make a dent, but I don't think we're going to replace coal plants anytime in the near future.

STEWART: What's the one thing you wish people would address about nuclear power and nuclear energy when they're having this conversation about whether or not it is a good alternative when wanting to talk about different energy sources for the future?

Dr. MORGAN: It's really difficult and I admit that even for me as a physicist, it's difficult for me to come down firmly on one side of the debate or the other. I don't think you can deny that there are issues with safety with nuclear waste, but as in any situation, it's a cost-benefit analysis. And when you, you know, when you think of the sort of bold promise of nuclear energy that they used to talk about 30 or 40 years ago, and I would go to a science museum as a kid and they'd always show you this aspirin-size pellet of uranium and a big, giant three-story mount of coal and say that they provide the same amount of energy. It begins to be a question of, you know, what are the costs of nuclear power environmentally as opposed to the cost of fossil fuels environmentally - and their different costs. I think what people need to do is to really discuss all of the issues at once and it becomes very complicated scientifically. I'll give you one example, I was reading something on the Internet today - and I'm not sure of the source - suggesting that coal plants actually release more radioactivity into the environment than nuclear plants, because they're digging up a bunch of stuff out of the ground and they're burning it and there's contaminants on that and it releases, you know, radiation into the air. So it's not a black or white and it's not a simple equation to answer. We really have to look at what are the costs of these things, what are the benefits of these things, and what are we doing to the environment every time we burn a pound of coal or create a pound of radioactive waste.

STEWART: Doctor David Morgan is a physics professor from Eugene Lang College. Thanks so much for walking us through all of that.

Dr. MORGAN: Thank you.

STEWART: If you want even more in the way of a nuclear power explainer, check out the original animated video on our Web site courtesy of our own producer Win Rosenfeld. It's at npr.org/bryantpark.

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