<body> NYGH 304 Physics SIA: Nuclear Energy-
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    Saturday, April 26, 2008


    Hellox.
    This is some information I found on a book. It is quite brief, so maybe we can use it as an introduction in our poster or something like that. =)

    Nuclear Energy

    Nuclear energy is the energy stored in the nucleus of an atom. It is released as heat when a nucleus splits apart (called nuclear fission) or when two nuclei fuse together (called nuclear fusion). These events are called nuclear reactions. We use nuclear energy for generating electricity, for propelling nuclear submarines, to make electricity in space probes and to power the destructive explosives in nuclear weapons.

    Nuclear fission

    The nucleus of an atom is made up of particles called neutrons and protons. When a nucleus is unstable, it can split into two smaller nuclei and spare neutrons. This process is called fission. The mass of the products of fission is a tiny bit smaller than the mass of the original nucleus. This lost mass id changed into energy. A tiny loss of mass is changed into a staggering amount of energy. Just one gram of mass is equivalent to 90 million million joules – enough energy to keep a light bulb going for 30000 years. A kilogram of uranium fuel produces as much energy as 5000 tonnes of coal.

    Nuclear reactors

    At a nuclear power station, the heat from nuclear reactions is used to boil water, producing steam that drives electricity generators. The nuclear reactions happen inside a nuclear reactor. The nuclear fuel (uranium or plutonium) is contained in fuel rods, which are grouped together in the reactor’s core.
    About 16% of the world’s electricity is generated at more than 400 nuclear power stations. France generates 75% of its electricity from nuclear electricity.

    A nuclear reaction

    Fission hardy ever happens naturally. In nuclear power stations it is made up to happen by firing neutrons into the uranium or plutonium fuel. When a neutron hits a nucleus, it makes the nucleus split. This releases more neutrons, causing other nuclei to split, producing heat energy.
    Only some uranium atoms have nuclei that will split. These are called uranium-235 atoms because each nucleus contains 235 neutrons and protons.

    Nuclear pros and cons

    Generating electricity from nuclear energy has advantages. It does not produce acid gases or particulates and there is enough uranium in the Earth’s crust to last for thousands of years. Nuclear energy’s two main problems are the safe transport and storage of deadly radioactive waste from power stations and the danger of accidents, such as the 1986 explosion at Chernobyl in the Ukraine that released radioactivity into the earth’s atmosphere.

    Nuclear Fusion

    Nuclear fusion is the opposite of nuclear fission. In a fusion reaction, two atomic nuclei are slammed together, releasing huge amounts of energy. Nuclear fusion could provide us with almost limitless energy, cleanly and safely, long to the future. But there are problems for researchers to overcome before energy from fusion comes into our homes.

    Fusing nuclei

    In a fusion reaction two light nuclei are fused together to form a larger, heavier nucleus. As in nuclear fission, the total mass of the products of the reaction is slightly less than the mass of the reacting nuclei and the lost mass is changed into energy.
    To make fusion happen, the atoms in the fuel must be stripped of their electrons, forming a substance called plasma, made up of nuclei and electrons. Then two nuclei must be slammed into each other at incredible speed. To get the nuclei moving fast enough, they must be heating to about 100 milliono C. This temperature is even hotter than the centre of the Sun and is difficult to achieve.

    Fusion research

    Scientists have made fusion happen in the laboratory in two days. The first is by heating a small pellet of fuel suddenly with powerful lasers. This creates immense pressure and temperature in the centre of the pellet for a tiny fraction of second.
    The second way is in a doughnut-shaped chamber called a tokamak. A small amount of vaporised fuel is put in the container and powerful electric currents heat it to turn it into plasma. If the plasma touched the side of the container it would cool and also melt the container, so it is held away from the sides with strong magnetic fields. Although fusion reactions have happened in experimental tokamaks, at the moment the electrical energy needed to heat the plasma and work the electromagnets is greater than the energy generated inside.

    Advantages of fusion

    If fusion reactors become a reality, they will use two forms of hydrogen – deuterium and tritium – as fuels. These do not occur naturally, but could be made from hydrogen and lithium, which are both abundant elements in the earth. The greatest advantage over nuclear fission is that there would be no radioactive nuclear waste to dispose of.

    A fusion reaction

    Deuterium and tritium are forms of hydrogen. Deuterium has one extra neutron and tritium has two extra neutrons. A fusion reaction happens when two nuclei, one from a deuterium atom and one from tritium atom, collide at high speed. The nuclei combine to form a helium nucleus, leaving one neutron spare, and heat energy.

    Chris Oxlade (2004). 21st century Science ENERGY. London: Frankin Watts

    -Ai Leng- JiaYoux! ^^

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