Nuclear fission is a process where the nucleus of an atom is split into two or more smaller nuclei, known as fission products. The fission of heavy elements is an exothermic reaction and huge amounts of energy are released in the process. This energy can be used to produce nuclear power or to make nuclear weapons, both of which we will discuss a little later.
- Definition 1: Nuclear fission
The splitting of an atomic nucleus into smaller nuclei
Below is a diagram showing the nuclear fission of Uranium-235. An atom of Uranium-235 is bombarded with a neutron to initiate the fission process. This neutron is absorbed by Uranium-235, to become Uranium-236. Uranium-236 is highly unstable and breaks down into a number of lighter elements, releasing energy in the process. Free neutrons are also produced during this process, and these are then available to bombard other fissionable elements. This process is known as a fission chain reaction, and occurs when one nuclear reaction starts off another, which then also starts off another one so that there is a rapid increase in the number of nuclear reactions that are taking place.
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The Atomic bomb - an abuse of nuclear fission
A nuclear chain reaction can happen very quickly, releasing vast amounts of energy in the process. In 1939, it was discovered that Uranium could undergo nuclear fission. In fact, it was uranium that was used in the first atomic bomb. The bomb contained large amounts of Uranium-235, enough to start a runaway nuclear fission chain reaction. Because the process was uncontrolled, the energy from the fission reactions was released in a matter of seconds, resulting in the massive explosion of that first bomb. Since then, more atomic bombs have been detonated, causing massive destruction and loss of life.
Discussion : Nuclear weapons testing - an ongoing issue
Read the article below which has been adapted from one that appeared in 'The Globe' in Washington on 10th October 2006, and then answer the questions that follow.
US officials and arms control specialists warned yesterday that North Korea's test of a small nuclear device could start an arms race in the region and threaten the landmark global treaty designed nearly four decades ago to halt the spread of nuclear weapons. US officials expressed concern that North Korea's neighbors, including Japan, Taiwan, and South Korea, could eventually decide to develop weapons of their own. They also fear that North Korea's moves could embolden Iran, and that this in turn could encourage Saudi Arabia or other neighbours in the volatile Middle East to one day seek nuclear deterrents, analysts say.
North Korea is the first country to conduct a nuclear test after pulling out of the Nuclear Nonproliferation Treaty. The treaty, which was created in 1968, now includes 185 nations (nearly every country in the world). Under the treaty, the five declared nuclear powers at the time (United States, the Soviet Union, France, China, and Great Britain) agreed to reduce their supplies of nuclear weapons. The treaty has also helped to limit the number of new nuclear weapons nations.
But there have also been serious setbacks. India and Pakistan, which never signed the treaty, became new nuclear powers, shocking the world with test explosions in 1998. The current issue of nuclear weapons testing in North Korea, is another such setback and a blow to the treaty.
Group discussion questions:
- Discuss what is meant by an 'arms race' and a 'treaty'.
- Do you think it is important to have such treaties in place to control the testing and use of nuclear weapons? Explain your answer.
- Discuss some of the reasons why countries might not agree to be part of a nuclear weapons treaty.
- How would you feel if South Africa decided to develop its own nuclear weapons?
Nuclear power - harnessing energy
However, nuclear fission can also be carried out in a controlled way in a nuclear reactor. A nuclear reactor is a piece of equpiment where nuclear chain reactions can be started in a controlled and sustained way. This is different from a nuclear explosion where the chain reaction occurs in seconds. The most important use of nuclear reactors at the moment is to produce electrical power, and most of these nuclear reactors use nuclear fission. A nuclear fuel is a chemical isotope that can keep a fission chain reaction going. The most common isotopes that are used are Uranium-235 and Plutonium-239. The amount of free energy that is in nuclear fuels is far greater than the energy in a similar amount of other fuels such as gasoline. In many countries, nuclear power is seen as a relatively environmentally friendly alternative to fossil fuels, which release large amounts of greenhouse gases, and are also non-renewable resources. However, one of the concerns around the use of nuclear power is the production of nuclear waste, which contains radioactive chemical elements.
Debate : Nuclear Power
The use of nuclear power as a source of energy has been a subject of much debate. There are many advantages of nuclear power over other energy sources. These include the large amount of energy that can be produced at a small plant, little atmospheric pollution and the small quantity of waste. However there are also disadvantages. These include the expense of maintaining nuclear power stations, the huge impact that an accident could have as well as the disposal of dangerous nuclear waste.
Use these ideas as a starting point for a class debate.
Nuclear power - An energy alternative or environmental hazard?
Your teacher will divide the class into teams. Some of the teams will be 'pro' nuclear power while the others will be 'anti' nuclear power.
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