How is energy in a solar or nuclear powerplant made?

Question

I need to find out the type of powerplant and how the electricity or the energy is made so please help me!! i need the info by this friday!!

Answer 1

nuclear fission

Nuclear power can come from the fission of uranium, plutonium or thorium or the fusion of hydrogen into helium. Today it is almost all uranium. The basic energy fact is that the fission of an atom of uranium produces 10 million times the energy produced by the combustion of an atom of carbon from coal.

Natural uranium is almost entirely a mixture of two isotopes, U-235 and U-238. U-235 can fission in a reactor, and U-238 can't to a significant extent. Natural uranium is 99.3 percent U-238 and 0.7 percent U-235.

Most nuclear power plants today use enriched uranium in which the concentration of U-235 is increased from 0.7 percent U-235 to (nowadays) about 4 to 5 percent U-235. This is done in an expensive separation plant of which there are several kinds. The U-238 "tails" are left over for eventual use in "breeder reactors". The Canadian CANDU reactors don't require enriched fuel, but since they use expensive heavy water instead of ordinary water, their energy cost is about the same.

In 1993 there were 109 licensed power reactors in the U.S. and about 400 in the world. They generate about 20 percent of the U.S. electricity. (There are also a large number of naval power reactors.) The expansion of nuclear power depends substantially on politics, and this politics has come out differently in different countries. Very likely, after some time, the countries whose policies turn out badly will copy the countries whose policies turn out well.

For how long will nuclear power be available? Present reactors that use only the U-235 in natural uranium are very likely good for some hundreds of years. Bernard Cohen has shown that with breeder reactors, we can have plenty of energy for some billions of year.

Cohen's argument is based on using uranium from sea water. Other people have pointed out that there is more energy in the uranium impurity in coal than could come from burning the coal. There is also plenty of uranium in granite. None of these sources is likely to be used in the next thousand years, because there is plenty of much more cheaply extracted uranium in conventional uranium ores.

A power reactor contains a core with a large number of fuel rods. Each rod is full of pellets of uranium oxide. An atom of U-235 fissions when it absorbs a neutron. The fission produces two fission fragments and other particles that fly off at high velocity. When they stop the kinetic energy is converted to heat - 10 million times as much heat as is produced by burning an atom of the carbon in coal. See the supplement for some interesting nuclear details.

Besides the fission fragments several neutrons are produced. Most of these neutrons are absorbed by something other than U-235, but in the steady-state operation of the reactor exactly one is absorbed by another U-235 atom causing another fission. The steam withdrawn and run through the turbines controls the power level of the reactor. Control rods that absorb neutrons can also be moved in and out to control the nuclear reaction. The power level that can be used is limited to avoid letting the fuel rods get too hot.

The heat from the fuel rods is absorbed by water which is used to generate steam to drive the turbines that generate the electricity.

A large plant generates about a million kilowatts of electricity - some more, some less.

After about two years, enough of the U-235 has been converted to fission products and the fission products have built up enough so that the fuel rods must be removed and replaced by new ones.

What to do with the spent fuel rods is what causes most of the fuss concerning nuclear power.