Wednesday, July 06, 2005

Nuclear Power

ran a couple of terrific short articles related to nuclear power.

Thinking about nuclear power reminds me of Tevya in Fiddler on the Roof, always saying, "On the other hand..."
Tevya: A fiddler on the roof. Sounds crazy, no? But here, in our little village of Anatevka, you might say every one of us is a fiddler on the roof trying to scratch out a pleasant, simple tune without breaking his neck. It isn't easy. You may ask 'Why do we stay up there if it's so dangerous?' Well, we stay because Anatevka is our home. And how do we keep our balance? That I can tell you in one word: tradition!
Unlike burning fossil fuels, using nuclear fission to generate electricity produces no soot or greenhouse gases. This helps keep the skies clean and doesn't contribute to global warming. On the other hand... Nuclear waste is the spent nuclear fuel from a reactor. The waste is highly radioactive, so it must be stored in steel-lined concrete pools or in dry caskets. As of 2003, nuclear reactors in the United States had created about 49,000 tons of waste, according to the Department of Energy. On the other hand... The fuel used to power nuclear reactors is very compact in comparison to fossil fuels. For instance, one pound of uranium can supply the same energy as 3 million pounds of coal. On the other hand... The United States has not reprocessed nuclear waste since the 1970s. Instead, the country hopes eventually to bury all its waste deep in Yucca Mountain in the Nevada desert, where officials believe the waste will not be able to leak into the environment. On the other hand...
Tevya: He loves her. Love, it's a new starting. On the other hand, our old ways were once new, weren't they? On the other hand, they decided without parents, without the matchmaker. On the other hand, did Adam and Eve have a matchmaker? Oh, yes they did. And it seems these two have the same Matchmaker.

How does a nuclear power plant produce electricity?

A nuclear power plant is basically a steam power plant that is fueled by a radioactive element, like uranium. The fuel is placed in a reactor and the individual atoms are allowed to split apart. The splitting process, known as fission, releases great amounts of energy. This energy is used to heat water until it turns to steam.

From here, the mechanics of a steam power plant take over. The steam pushes on turbines, which force coils of wire to interact with a magnetic field. This generates an electric current.

Why does splitting a uranium atom release energy? The answer has to do with Einstein's most famous equation -- E=mc² -- which essentially says that energy is directly related to mass.

Under the right conditions, a uranium atom will split into two smaller atoms and throw off two or sometimes three neutrons in the process. (Neutrons are the glue that hold atoms together.)

The combined mass of these resulting particles tends to be roughly 99.9 percent of the mass of the original uranium atom. The other 0.1 percent of the original mass got converted to energy, as Einstein described. The energy is released in the form of gamma rays.

On the other hand... Gamma rays are similar to X-rays and can cause burns, cancer and genetic mutations in living things. They can be slowed or stopped with thick walls of concrete, lead or packed dirt.

On the other hand... When an atom splits, the extra neutrons go hit other atoms in the reactor core, starting a chain reaction. Initially, about 3 or 4 percent of the uranium atoms are uranium-235 -- the same as the first set of atoms that split. If these atoms are hit with neutrons, they split readily and throw off more energy and neutrons. But the other 96 or 97 percent of the uranium atoms in the core initially are of a type that is hard to split, known as uranium-238. If hit with a neutron, a uranium-238 atom will absorb the neutron and eventually turn into plutonium-239. It's not until these plutonium atoms are hit again with more neutrons that they finally split and release energy.

Nuclear fuel is considered spent when the fission byproducts -- the atoms left over from the splitting process -- prevent free neutrons from splitting more uranium or plutonium. It takes three or four years to get to this point in the process.
Tevya: As the good book says, when a poor man eats a chicken, one of them is sick.
Scientists are trying to perfect ways to use the element thorium to fuel reactors instead of uranium because it is three times more abundant in nature. Fueling nuclear reactors with the element thorium instead of uranium could produce half as much radioactive waste and reduce the availability of weapons-grade plutonium by as much as 80 percent.

Thorium Fuels Safer Reactor Hopes

Thorium reactors produce less waste because, in a nuclear chain reaction, thorium atoms break down into fewer unusable atoms than does uranium. A thorium-fueled reactor could actually eat up existing stockpiles of plutonium by using it as a "seed" fuel. A seed is necessary because it's harder to start a nuclear chain reaction with thorium than with uranium.

On the other hand...


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