Shots Across The Bow

Nuclear Power--at last!

Mr bubba asked me to do a bit on nuclear power, pros and cons. I've been putting off the job, mainly because it's been the holidays, and I'm lazy. But the holidays are over, and while 'm still lazy, since I've been writing some science stuff lately, I figured now was as good a time as any. besides, some of the stuff I talked about on global warming comes in to play here as well (which is where I learned it in the first place).

So saddle up boys and girls for a quick primer on nuclear physics.

First I have to tell you that I'm simplifying this stuff tremendously. If any real nuclear physicists read this, please take that into accountbefore you laugh and call me names.

My parents used to ask me what I did in the Navy. Since I didn't want to tell them what I did while on liberty in foreign ports, I told them about my job as a reactor operator.

"I boil water," I'd tell them.

That's really all a nuclear reactor is; it's a big tea pot. See, the best way way we've found to generate electricity is through electromagnetism. If you move a wire through a magnetic field, you induce a current in the wire. It's like magic, only without the wand. The rub is that you have to keep moving the wire through the magnetic field to keep generating electricity. So what we did was make the wire into a coil, and stick a magnet in the middle. Then we attached a rod to the wire, and spun the rod. This is called a generator. The guy spinning the coil would get tired after a while, so next we had to find a way to keep the rod turning. Now this was an easy problem to solve, because we had these steam engines lying around that were great at keeping things turning, so we attached a steam turbine to the coil, and made a turbine generator, which takes heat energy from the steam and converts it to electricity.

Now our next problem is how to boil the water, and this is where the nuclear part comes in. We've used fuels like wood, coal, oil, and alcohols, all of which work to varying degrees, but we wanted something better, something that didn't take quite so much effort, didn't cause acid rain and smog, something that wouldn't run out in a few centuries.

About that time, Ms Curie and several thousand of her closest friends discovered how to get at the energy inside an atom.

Now, if you remember your science from high school, you'll remember that the atom has electrons (negative charge), protons (positive charge), and neutrons (no charge). The electrons hang out in a cloud around the nucleus, which is made up of protons and neutrons. This nucleus is what we are interested in. We've all messed around with magnets when we were kids and we know that like charges repel each other. So how then does the nucleus hang together, since it is filled with protons, which all have like charges?

Well the answer is that there is another force at work in the nucleus, one that is stronger than the repellant force of the like charges, and as long as the protons and neutrons are kept close enough, this force holds the nucleus together. We'll call this the binding energy of the nucleus. What scentists discovered was that if you hit a nucleus hard enough, and at the right spot, you overcome this binding energy, and the nucleus splits, or fissions. When this happens, the binding energy is released as heat.

Now, working at the atomic level, the heat released is too small to be noticed. What we have to do is make this happen in millions of atoms, and go on happening. Until we want it to stop. A guy named Oppenheimer found a way to get the energy to come out, but it comes out all at once, and doesn't stop until all the fuel is used. Not very good for our purposes.

Well, what we found was that one of the best ways to split a nucleus was to hit it with a neutron. We also found that when a nucleus splits, it doesn't split evenly, but in different sized chunks, and a few stray neutrons. All we had to do was find a way to get those stray neutrons to cause more fissions, releasing more neutrons, and so on, creating a chain reaction. Sounds simple, yes?

No. It took years, and many experiments before we found the proper configuration where the number of neutrons released in each generation would be enough to keep the reaction going, without growing out of control, or dying out. What we did was to pile large amounts of uranium in very tightly defined arrays, with graphite rods between them. We use uranium because it is naturally radioactive, and fissions all by itself. The rods absorb the neutrons, keeping a chain reaction from occurring. When we want to start the reactor, we pull the rods out, allowing the neutrons to build a chain reaction and grow in strength to generate the heat we need to boil the water. If we need more power, we pull the rods out further; less, we push the rods in.

Obviously we are generating a lot of heat when we operate the reactor, and we have to cool it to keep everything from melting. (Not to China. Like nearly everything else out of Jane Fonda's mouth, the China Syndrome is BS. A reactor when it melts loses the configuration to maintain the chain reaction. Fission halts and the metal cools. It leaves a hell of a mess behind, but it isn't going to bore a hole all the way to the core. We proved that with Three Mile Island) To keep the reactor cool, we run water through it. It takes the heat out of the reactor, (through conduction and convection), and carries it off. Now this is the cool part, because this water is so hot, it flashes to steam, which we use to run our turbine generator to make the electricity.

It's like we planned this or something....

It sounds so simple; what's all the fuss about?

If that was all that was going on, it would be simple. Unfortunately, there are some other types of radiation given off, and other efects that we have to deal with.

Which we will discuss tomorrow.....

Posted by Rich at January 5, 2003 3:08 AM