Thursday, March 31, 2011

Learning From Events In Japan

I have a Master’s degree in electrical engineering, and I worked in the electric power industry for over ten years.

The amount of misinformation and outright wrong information that has appeared daily in the various media since the earthquake and tidal wave hit the nuclear power plants in Japan is startling. These people really ought to either keep quiet or get it right. To cite just a few examples, I heard a TV newscaster say that the control rods in the reactor were spinning (they don’t); another one was standing in front of a display board waving his arms around saying the heat from the reactor is applied to the turbine (it isn’t); one of them said a nuclear cloud was heading toward Tokyo (it wasn’t); one reporter who is apparently a kook said, right there on the radio, that millions and millions of people in Japan will die of leukemia and thyroid cancer (they won’t); then it was reported that radiation has been detected on the West Coast of the U.S. (a billion times lower than any danger level, we later learned), etc. etc. etc. All of this, and more, was right there on major networks and in major newspapers. How do these people have any remaining credibility?

Let’s review the technical basics of generating electricity and how electric power plants work. When we get through this information, you will know more about this subject than most of the talking heads on TV.

Electricity is generated in two ways: 1) When a conductor (a wire) passes through a magnetic field, and 2) by means of a chemical reaction, i.e., batteries. We will discuss the first method, since it is the one used in electric power plants.

I am excluding static electricity from this discussion, since only small amounts can be produced in that form.

To generate electricity by moving a conductor through a magnetic field, we need first to create the magnetic field. This is easily done with magnets. You probably did the little experiment in science class where you put a piece of paper over a magnet, sprinkled iron filings on the paper, and observed the interesting lines that the filings aligned themselves in. That was the effect of the magnetic field emanating from the magnet.

OK, so now we know where to get the magnetic field. Next we need to get some conductors, or wires, moving through it. This is most readily done by wrapping the wires around a rod (a “rotor”), and then causing the rotor to spin in close proximity to the magnets. When this happens, electricity will be generated in the wires that are wound around the spinning rotor. This is how a “generator” works.

We will also connect some other wires (transmission and distribution lines) to the generator to get the electricity to wherever we want it.

We won’t go into transformers.

OK, so somehow we must get the rotor of the generator to spin. We could do this by connecting a diesel (or gasoline) engine to it, and this is sometimes done in special situations. In most large scale electric power plants, though, we connect a steam turbine to the generator to get the rotor to spin. A water turbine could also be used (as at the Claytor Lake dam).

A steam turbine is another device that spins on an axis. A steam turbine contains a series of specially designed blades. Steam is admitted into the turbine and causes it to spin by pushing on the blades. It’s a type of steam engine.

Finally, we have to create steam, and a lot of it. We have to boil water on a large scale. That means we need a heat source that can produce a lot of heat

A large amount of heat is most readily created by burning something. In steam power plants, coal, oil, or natural gas can be used. Over 50% of the electricity in the U.S. is created in coal fired power plants, for example.

Another way to create a lot of heat is through a controlled nuclear reaction. This is what happens in a nuclear power plant. A nuclear reaction creates heat to boil the water to create steam to spin the turbine and generator rotor, thus producing electricity.

Control rods are in the nuclear reactor. They are made out of a special metal and are used to regulate the intensity of the nuclear reaction. This is done by moving them up and down into or out of the reactor core.

The nuclear reactor must also be cooled, since even at its lowest setting, it will create so much heat that it will literally melt itself (a meltdown). The cooling is done with water pumped through the reactor core. If that water flow stops, the reactor will over heat, much like your car engine if the water pump fails.

The cooling water pumps in a nuclear power plant are powered by the electricity network in the plant. There is also a back-up diesel engine and generator to provide electricity to the pumps if the primary power supply fails. Finally, there are usually batteries that can keep the pumps running for a few hours if the diesel generator also fails.

When the tidal wave hit the nuclear power plants in Japan, the primary electrical supply was wiped out, as were the diesel powered generators and the batteries. The crisis at the nuclear power plants was caused by the tidal wave, not the earthquake.

The big problem with nuclear reactors is not the reactor, but the spent nuclear fuel. This material is highly radioactive, and will remain so for thousands of years. Disposing of it is a problem. Generally it is put into lead containers and then stored deep in a mountain in a remote area.

Now that we are armed with this knowledge, amid all of the media hysteria and hype, we can remain cool, calm, and collected. And we can notice some very pertinent questions that the media isn’t informed enough to ask.

1. Why were these nuclear reactors located on the coast in an earthquake prone area?
2. Given that they were on the coast, why did the plant designers not think of a tidal wave when doing their safety analysis?
3. Why were all six of the reactors in the same physical location where they were all susceptible to one natural disaster in that local area? Why weren’t they built in dispersed locations?
4. Why was the spent nuclear fuel stored at the reactor site instead of somewhere else, again to avoid a “single point of failure” problem?

These are the types of lessons we need to learn from the events in Japan as we move forward with nuclear power plants here in the U.S.

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