However radioactive decay is a natural process because of the unstable nucleus as it has a surplus of neutrons, these neutrons are ejected as radioactive energy there is no chain reaction. [200]
The main difference is that nuclear fission is forced to bombard with a neutron as the reaction on earth is quite slow and spontaneous and so is artificially induced.
2. A star consists mainly of hydrogen nuclei. We assume that stars start of as a ball of hydrogen nuclei which are single protons. Hydrogen is situated at the core of a star where the temperature are so high they fuse hydrogen nuclei together at high speed and kinetic energy to over come repulsion an to form 4-helium nucleus and create a p-p chain this process is known as nuclear fusion.
Once all the hydrogen is converted the core of the star collapses on itself this causes it to increase in heat until it reaches a certain temperature where the star undergoes more fusion in this case helium 4 fuses with a nucleus of tritium to form a nucleus of lithium with 3 protons and 4 neutrons for a mass number of 7. [200]
4He + 3H --> 7Li
The heavier elements formed will continue to fuse to create heavier elements until it reaches elements with a mass of sixty this is when the star has reached the end of its life span.
3. Nuclear fission is splitting an unstable heavy atom in to two lighter nuclei which are roughly equal in size, this process releases vast quantities of energy and with neutrons can cause further fusion in other nuclei, leading to a chain reaction. Nuclear fusion is combining smaller nuclei to form heavier nuclei e.g. hydrogen nuclei’s to create a helium nuclei, this process also releases lots of energy and only happens in the sun as it has the right temperature to fuse the nuclei’s together.
Energy released in nuclear fission can be harnessed to generate electricity but if all the energy is released at once it can cause an atomic bomb and that’s why we have nuclear power plant to control the reaction. Inside nuclear reactor uranium atoms are splitting apart in a controlled chain reaction. To keep splitting regulated control rods are used so the reaction doesn’t go to quick control rods absorb the neutrons and depending on were you put the [200] control rod you can decrease the rate of reaction just enough so that the reaction occurs. The energy produced in the chain reaction of atom splitting can be converted into heat energy which boils the water which then produces steam, the steam produces enough power to turn the turbine and generate electricity.
Nuclear fusion doesn’t lead to a chain reaction and so there is no danger of it melting down like a fission reaction by simply turning the power of the reaction stops. On earth it is very difficult to control fusion as we don’t have metal strong enough to resist heat of around 100 million Kelvin. Here is an example of nuclear fusion.
To control fusion on earth you would need high enough temperature so that you can overcome their electromagnetic repulsion and fuse. And the density the higher the density the more chance of collision. And contain the hot temperature of plasma on earth.
Fission is a very useful as it emits much less waste than the millions of tonnes of ash and greenhouse gasses that coal produces, emits much less radiation than a fossil fuels. Coal is also a limited nuclear power plants can continue to produce [200] when they run out. Nuclear fission requires less fuel than fossil fuels. 1 tonne of uranium can produce more than 7 million tonnes of coal so it would be ideal to use as electricity.
However it also has its flaws fission produces radioactivity which can make people ill and in most cases kill them, another disadvantage is that the nuclear reactor can go out of control creating a meltdown which releases incredible amount of radioactivity devastating people all around. Nuclear reactors are also short lived and can live for 40-50 years.
Advantages for using fusion are that the reactants, deuterium and tritium, are readily available in nature.They are more environmentally friendly than fossil feuls and fission. fusion is much safer to use than fission.
4. Although nuclear fusion is a safe source of power, scientists have yet to figure out ways to match the conditions that the sun has on earth. Doing so would supply the earth with millions of years of energy. ‘The ITER is being built at Cadarache in the south of France and should be ready for operation in 2015.’[5]
http://www.solcomhouse.com/nuclear.htm
http://www.thetartan.org/2007/4/30/scitech/work/
-
Nuclear reactions, SAC Chemical ideas – second addition George Burton et al, Heinemann, 2000, page 15, ISBN: 9780435631208.
-
http://library.thinkquest.org/27954/alpha.htm Alpha and beta decay reaction, website is owned by think quest.com
