Nuclear Reactor

1. In nuclear fusion, two or more small and light nuclei come together to form a heavier nucleus.
   
2. This process is accompanied by the release of a huge amount of energy.
3. Below are two examples of fusion reactions:
   
4. 
5. Fusion is much more difficult to achieve than fission because the hydrogen nuclei repel each other. Therefore, the nuclei must be heated to 108 K or more so that the nuclei will have enough of kinetic energy to overcome the electrical repulsion between the nuclei.
6. Example
   1. The Sun get its energy from the fusion of hydrogen nuclei.
   2. A hydrogen bomb uses the principle of nuclear fusion for its design.

1. If neutrons from the fission of uranium-235 continue to split other nuclei causing further fission, a chain reaction has occurred.
2. The number of nuclei which undergo fission multiplies rapidly.
3. In order for a chain reaction to take place, a minimum of one neutron from each fission must trigger further fission.
4. At the same time, the mass of fission material must exceed a certain minimal mass known as the critical mass. If the material is less than this value, too many neutrons escape without hitting nuclei, preventing a chain reaction from happening.

(Chain Reaction)

Nuclear Reaction

1. In a nuclear reaction, the mass of the parent particles will become less (know as mass defect). The defected mass is then converted into energy called the nuclear energy.
2. In short, nuclear energy is the energy released owing to the defect of mass in a nuclear reaction.
3. There are 2 types of nuclear reaction
   1. nuclear fission
   2. nuclear fusion
4. Nuclear fission is the process of splitting nucleus into 2 smaller nuclei whereas nuclear fusion is the process which 2 small nuclei combine to form a larger nucleus.

Nuclear Fission

1. Nuclear fission is a process involving the splitting of a heavy nucleus into two nuclei of roughly equal mass and shooting out several neutrons at the same time.
2. Nuclear fission seldom occurs spontaneously. Usually, it occurs when the heavy nucleus is bombarded by a neutron.
3. Fission reaction resulting from neutron absorption is called induced fission. Nuclei that undergo fission without initial neutron absorption are undergoing spontaneous fission.
4. Two typical examples of fission reactions:
   
   

1. In archaeology radioisotope carbon-14 is used to study and estimate the age of ancient artifacts. This method is named as the radiocarbon dating. 
2. Radiocarbon dating can be used to estimate the age of organic materials, such as wood and leather, up to about 58,000 to 62,000 years.

Monitoring Content of Food

Monitoring Thickness of Steel/paper Sheet

Detecting Underground Leakage

Measuring the Wearing Rate of Engine

Pest Control

1. Male insect is sterilised by exposing to radioactive radiation and then released back to the ecosystem.
2. This can ensure that their reproducing effort do not generate new generation and hence reduces the population of the insect.

Tracer

1. The metabolism of phosphorus by plants can be studied using phosphate fertilisers that contain phosphorus-32. 
2. A small amount of phosphorus-32 is used in fertilisers. 
3. The radiation produced by phosphorus-32decay is detected by a Geiger-Muller counter. 
4. This method can trace the passage of phosphate ions in plants.
5. Carbon-14 is used to study the passage of carbon during photosynthesis in plants.

Develop New Species of Plant

1. Radioactive radiation is targeted to the seeds of plants and hence causes mutation to the genes.
2. By chance, this may develop some superior agricultural products.

Preserve Food

1. The gamma rays from cobalt-60 are used to kill bacteria in food to make fresh vegetables and fruits last longer without any change in quality, flavour and texture of food.
2. Gamma rays are used to inhibit budding in potatoes.

Radiotherapy

Tracer to Detect Blood Clots or Tumour

1. A small amount of sodium-24 is injected into the patient's body. 
2. Radioactive imaging is then used to detect accumulation of sodium-24 and therefore detect tumours and blood clots before they become dangerous.

Sterilising Medical Instrument

1. Gamma ray emitted from radioactive cobalt-60 can kill germs such as bacteria and fungus. 
2. Medical instruments such as surgical equipment, syringes and bandages can be sterilised by using gamma rays.

Heart Pacemaker

(Heart Pacemaker)

1. A heart  pacemaker is a medical device which uses electrical pulses to contract the heart muscles, and hence to regulate the beating of the heart. 
2. Plutonium-238 in a nuclear battery is used to produce small electric shocks in the heart pacemaker. 
3. People with irregular heartbeats need to have a heart pacemaker implanted inside their chest.

Tracer to Investigate Activities of Thyroid Glands

1. There are two types of isotopes, namely
   1. the stable isotopes (non-radioactive)
   2. the non-stable isotopes (radioactive).
2. Unstable isotopes go through radioactive decay and emit radiation and they are known as radioisotopes.
3. Radioisotopes have many applications in the following field
   1. Industri
   2. Medical
   3. Agriculture
   4. Archeology