In the 1950's, a group of scientists invented a new reactor
which revolutionized the world. It's name was the Fast Breeder. It
gets this name from its ability to "breed" fuel. It can produce
up to 3% less fuel than it uses. One Fast Breeder has been running from
when it was built in 1958. It also is unbelievably faster than the normal
reactor. The Fast Breeder uses liquid metal sodium instead of water to
heat up pipes in the reactor, but it uses water to turn the turbine, which needs
to spin. The turbine is what produces the spark to create electricity.
Parts Used in a Fast Breeder Reactor
Coolant
In a reactor, there is something called a
coolant. It has two purposes. It prevents the reactor from melting
and it is what turns the turbine. In a Fast Breeder, there are two
coolants. The liquid metal sodium is one, and water is the other.
The liquid sodium comes into the core from a containment building. The
containment building stores the sodium at a controlled temperature so the sodium
won't damage anything. The second coolant, water, is heated and made into
steam by the liquid sodium, after the sodium is heated. The water is then
sent to the turbine.
Pumps
This reactor also has pumps all
over the place to move the liquid metal sodium. Being metal, it doesn't
want to move on it's own. The pumps move the liquid sodium to the steam
generator where the water is heated and transformed into steam and transported
to the turbine. The turbine spins because the steam is sent to one side of
the turbine and the steam blows the turbine on that side. The turbine then
turns because of the uneven balance of energy.
Moderator
In all normal reactors, a moderator is
used. Moderators are small rods which are placed inside of the fuel
rods. They are strategically placed to slow down the chain reaction of
atom splitting and to absorb the stray atoms that may cause damage the fuel rod
chamber. Fast breeders don't have moderators, therefore earning the name fast
breeder. It is still experimental because there is nothing to absorb stray
sub-atomic particles inside of the fuel rods, which could lead to a huge
meltdown or a hole splitting in the chamber.
Steam Generator
A steam generator is what causes the water
in a reactor to turn into steam. The liquid metal sodium goes through a pipe
which heats up the water around it. This occurs only in the
Fast Breeder, because in a normal reactor, there is no liquid metal
sodium.
Control Rods
Every reactor needs a set of control
rods. These are made of a mixture of materials that are very strong and
can take a large amount of heat. They are placed inside of the fuel rods
and do the same sort of thing that moderators can. They are meant to stop
the chain reaction of atoms inside of the fuel rods, which, in turn, stops the
plant. They are also able to stop the coolant from flowing.
Inside the reactor, there are things
called fuel rods. They contain pellets of uranium and plutonium. Protons, neutrons, and electrons are what atoms are made of. These are the
three sub-atomic particles that carry the charge. There are 3 different types of uranium used in nuclear power production.
One's atomic weight, the
number of neutrons plus the number of protons, is 235. This is the
radioactive form of uranium, and its abbreviation is U-235. Another has an
atomic weight of 238, and you can guess that it's abbreviation is U-238.
The third and final form of uranium used in nuclear power production is
U-234. I think you can guess what the atomic weight is. (234) U-234
and U-238 are the two major forms of uranium in the fuel. There is a small
amount of U-235 in the breeder's fuel, though. The major radioactive material, radioactive
means that the element changes, is plutonium. To be specific, it is
Pl-239, which, again, has an atomic weight of 239. Inside the fuel
rods, the pellets are stacked very carefully. One atom in one pellet is
disturbed when the power plant is online, and it starts a chain reaction which
heats up the core.
This is an animated clip of
fission. An incoming neutron hits an atom. The atom absorbs
the nuetron but becomes unstable and splits apart immediately. The neutron
is sent along with the remaining part of the atom. This is what
occurs inside of the fuel rods of a Fast Breeder Reactor.
The reactor breeds its fuel by just
letting it sit in a containment plant. The wasted Pl-239 and U-235 is put into a
toxic waste dump and the U-234 and U-238 are mixed together. Since
plutonium is a byproduct of uranium, uranium can produce it over about a
year. It just so happens that U-234 and U-238 mixed together very
thoroughly can produce Pl-239, which is what is needed to run the power
plant.
The containment system is the same as
what is used to store the liquid metal sodium. The uranium is stored at a
very controlled temperature. As soon as the plutonium is produced, it is
separated and put into a containment system until it is needed. The
uranium that has already produced as much plutonium as it can is put in a
separate containment plant. When it is needed, it is packed into the fuel
pellets with plutonium that it may or may not have created.
The reactor also has three loops, unlike the normal reactor.
The fast breeder reactor has to have three, however, to keep
the plant from having a meltdown. This is because the reactor has no
moderator and can go out of control. This is highly unlikely, however, with ten foot
walls, and even more unlikely with three loops. The loops run starting at
the reactor core with the liquid sodium being heated up by the fuel
rods. It is brought into a steam generator
with water in it. The steam that was just created then goes to another
steam generator. More water is heated up and transformed into steam.
The new steam is sent to the turbine which spins and creates electricity.
This is a diagram of a fast breeder reactor. Notice the
three loops.
This is a picture of a
generator at the Diablo Canyon
An Experimental Speed Demon
This is a picture of a
generator at the Diablo Canyon