Nuclear Weapons and Other Cool Things

A report that I made.

Nuclear energy is made when atoms are split apart. Nuclear reactions happen naturally. We can only get an atom to split from certain atoms which are uranium, plutonium, and deuterium. It only takes two pounds of deuterium to make as much energy as 6.6 million pounds of coal.

Nuclear fission and nuclear fusion are two processes for releasing nuclear energy. Nuclear fission is when the nucleus of an atom splits. Nuclear fusion is when the nuclei of two or more atoms fuse together.

Nothing can get through an atom's nucleus because it's surrounded by circling electrons but a neutron athigh speed can go through and go into the nucleus. If the nucleus is unstable, nuclear fission occurs and the nucleus splits into two parts. A chain reaction can be caused by two or three neutrons being produced and they hit more atoms.

Nuclear fusion produces energy for the stars, including the sun. This happens when two or more nuclei fuse together. Two isotopes of hydrogen nuclei fuse to form helium in the sun. In the process, some mass is lost and it's converted to energy.

Nuclear power plants are a very efficient and good source of energy. They don't create a lot of pollution so they are good for our environment.

Nuclear power plants create an efficient way to generate electricity. The only problem is if something goes wrong with the cooling system, the core (where nuclear fission takes place) may overheat and melt. The fuel that nuclear power plants use, uranium, is radioactive and can injure and kill people. Uranium can be thrown into the air, water, and land when the core melts. This is called a meltdown.

Like all power plants, water or steam is pushed through a turbine to generate electricity. Most power plants heat water and make it into steam. There are a few ways to heat the water. They are coal power plants that burn coal to heat up water, gas power plants that use gas to heat up the water, and nuclear power plants that use nuclear fission to heat the water.

Nuclear fission happens when a neutron, a neutral particle, hits a uranium atom. The uranium atom splits into different parts. It splits into three more neutrons which keep the chain reaction going, a barium atom, and a krypton atom. Neutrons that break apart from the original uranium atom continue to hit and split other uranium atoms. Then those uranium atoms split and do the same thing. This is called a chain reaction. When the atoms are split apart they release heat.

Below is going to be a diagram of nuclear fission

The nuclear reactor is the place where nuclear fission takes place in a power plant. To control nuclear fission in a power plant, there are certain things that have to be done. Inside a reactor there are the fuel rods, a moderator and control rods.

The moderator is a material that slows down neutrons so that they can hit uranium atoms correctly and split them. If a neutron is moving to fast it might miss the atom and eventually stop the chain reaction. The moderator slows the atoms down so the will hit the uranium atom and continue the reaction.

The control rods absorb neutrons. The control rods are adjustable so the operators of the plant can control how much fission is taking place. If there were no control rods there would be an uncontrolled reaction like the atomic bomb.

Uranium-235 is the isotope of uranium which splits the easiest, so it is used for fuel in nuclear reactors. Uranium-235 is put into fuel rods in the form of little pellets which are inserted into the reactor. One fuel rod lasts over a year. Many fuel rods can be put into the reactor.

When heat is given off by the nuclear reaction, there has to be a way to take the heat away from the reactor to heat the water. The water needs to be turned into steam so it can be ran through the electric generators. There also needs to be a way to cool down the reactor so it doesn't cause a meltdown. That is done with a substance called the coolant. The coolant is usually water.

There are many different kinds of nuclear power plants. The main difference between the plants are the way they extract the heat and cool the reactor down. There are two main types of nuclear reactors. Most of the nuclear power plants use thermal reactors. They use natural or uranium which has been slightly enriched as their fuel and need a moderator to control the fission chain reaction. Fast reactors are used too but they are less common. They don't need a moderator to keep the fission chain reaction going.

The most common thermal reactor is the Light Water Reactor (LWR). They are also the most popular type of cooling system in the United States. Two kinds of LWRs are the Pressurized-Water Reactor (PWR) and the Boiling Water Reactor (BWR).

The Pressurized-Water Reactor (PWR) is what most U.S. power plants have. Pressurized water is pumped through the reactor and then it goes to a device called a heat exchanger. The hot, pressurized water is transferred into cold water which is then turns it into steam. The steam is then forced through the turbine. When the steam has gone through the turbine it is condensed back into a liquid by the cooling towers. Then the cycle starts all over again.

The Boiling-Water Reactor (BWR) is the other type of Light Water Reactor (LWR). The BWR pumps the coolant water through the reactor which makes the water turn into steam. The steam is then transferred to the turbine and then condensed to start the process all over again. The steam that comes out of the reactor is very radioactive.

Fast reactors are another type of reactor. They don't need a moderator to keep the fission chain reaction going. Fast reactors use plutonium, which is radioactive, or a mixture of plutonium and uranium as a fuel. Plutonium isn't found natually. It's made by reprocessing spent fuel rods from thermal reactors.

The Breeder Reactor, which is a type of fast reactor, makes its own fuel. In all fast reactors the fission reaction is controlled so that each fission of an atom produces a few particles and atoms. In breeder reactors, extra neutrons are used to break up poor quality fuel and turn it into better fuel.

Breeder reactors use fuel very efficiently. If everything works correctly, a breeder reactor uses the same amount of uranium as the thermal reactor but it produces 60 times more energy. This helps save our resources. If we used fast reactors, it would take more than 1,000 years to use up the world supply of uranium.

There are problems with breeder reactors also. They have to be shut down a lot because of leaks which is a big problem and can take many years to fix. This kind of reactor is expensive to develop and people worry that the plutonium could be stolen to make nuclear weapons.

Another type of reactor is gas-cooled. It is less efficient than the PWR and can be expensive to build and can get corroded. The gas used is usually carbon dioxide or helium. The helium circulates through the reactor and comes out very hot. The heat is exchanged in a heat exchanger like the other ones where gas is turned into steam.

Another type of reactor is a liquid-metal coolant. Usually sodium is pumped through the nuclear reactor and it comes out very hot. The heat is exchanged in a heat exchanger but instead of being filled with water it is filled with sodium. That sodium is heated and pumped into another heat exchanger which is filled with water. The water is then turned into steam like all the others.

Radiation is what happens when an atomic nucleus decays. There are different kinds of radiation that is released. There are alpha, beta, and gamma rays.

Alpha rays are mainly made up of positive particles. The alpha particle has two neutrons and two protons which is like a helium atom.

When an unstable or radioactive atom gives off an alpha particle the atom is changed into a different kind of atom. For example, when radium gives off an alpha particle it becomes radon. Alpha radiation is not as penetrating than beta radiation but it can be stopped by wool or aluminum.

A beta ray is made of particles also but the particles are electrons. When a beta ray or electron is given off it is because a neutron decayed into a proton and an electron. The electron is thrown off but the proton stays in the nucleus. Then it becomes a new atom with one more proton than it had before.

Gamma rays are electromagnetic waves that have short wavelengths. All radioactive materials give off gamma radiation. Gamma rays can go through many things including the human body. You would need to have about three feet of lead to stop gamma rays.

Fission is easy to create because all you have to do is throw a neutron at a uranium atom to make it split. With fusion you have to make deuterium and tritium, two isotopes of hydrogen, fuse together. When deuterium and tritium are fused together they create an unstable atom. The atom then splits apart into a normal helium atom and a neutron. We have not been able to create a fusion reactor because we can't fuse deuterium and tritium.

Deuterium and tritium are both positive so it is hard to get them to fuse because they are both positively charged. In a hydrogen bomb, tritium hits deuterium at a very high speed therefore making them fuse. We can't do that to make power. In order to make them fuse we have to generate a very high temperature. Once we've started the reaction we have to continue feeding it.

When deuterium and tritium fuse at high temperatures they turn into plasma. No metal on earth can contain a substance at those high temperatures so the hot plasma touch the walls of the reactor.

A fusion reactor is called a tokamak. There are big magnets around it to keep the plasma off the walls. Researchers once got the tokamak to create 10.7 million watts of power.

Fusion reactors would be much cleaner and safer than fission reactors. The good thing about fusion is that the chemicals can be derived from an abundant source. If we could make a fusion reactor we would be able to provide cheap electricity. The nuclear fusion plants would be safe because if something went wrong they would automatically shut down. We would also have an almost unlimited fuel supply because deuterium can be made out of sea water and tritium can be made from deuterium. Deuterium is not radioactive and tritium is just slightly radioactive which is much safer than fission. The radioactive water produced by fusion plants wouldn't stay radioactive very long so we wouldn't have to bury it deep in the earth.

Unfortunately because no one has figured out how to build a working fusion reactor there's a lot of research being done. The Joint European Torus (JET) program is in Great Britain where there are almost 400 scientists and engineers from all over the world trying to come up with a solution. They want to have a working fusion power plant by 2030. They think that by the end of the twenty-first century, fusion will supply as much of the world's electricity we get now from fossil fuels.