Nuclear Fusion - Definition, Formula and Examples
To make fusion occur, the atoms of hydrogen must be heated to very high temperatures (100 million degrees) so they are ionized such that forming a plasma and have enough energy to fuse, and then be held together such that defined, long enough for fusion to occur. The sun and the stars do this by gravity. More effective procedures on earth are magnetic bonds, where a strong magnetic field holds the ionized atoms together while they are heated by microwaves or other sources of energy, and inertial confinement, where a small pellet of frozen hydrogen is compressed and heated by a powerful energy beam, such as a laser, so quickly that fusion occurs before the atoms can travel apart.
Who cares? Scientists have attempted to perform fusion work on earth for over 40 years. If we are successful, we will have an energy source that is endless. One out of every 6,500 atoms of hydrogen in normal water is deuterium, giving a gallon of normal water the energy content of 300 gallons of gasoline. In addition to this, fusion would be environmentally friendly, producing no combustion outcomes or greenhouse gases. While fusion is a nuclear process, the results of the fusion reaction such that helium and a neutron are not radioactive, and with proper design, a fusion power plant would be passively safe and would give no long-lived radioactive waste. The Design studies determine that electricity from fusion should be about the same cost as present-day sources.
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We get benefits from this energy and we classify these energies into 2 main types:
Non-ionizing radiation has enough energy to excite atoms, making them move more swiftly. Some examples of non-ionizing sources are microwave ovens, radio transmissions, cell phones, and visible light.
Ionizing radiation has enough energy to alter atoms by eliminating electrons from them, a process known as ionization. Some examples of ionizing sources are X-rays, nuclear power.
Nuclear Basics
Things you need to know:
The mass number of an element (A) is the total number of nucleons in a nucleus. The number of neutrons in a nucleus is said to be A-Z.
The Atoms of an element can contain different numbers of neutrons. These different number forms are known as isotopes. The nucleus of an isotope is said to be a nuclide.
NOTE: Every part of matter in the Universe, as far as we know, they are made up of one or more elements from the Periodic Table. The smallest part of an element in the periodic table that can exist is an atom.
Detecting Non-Ionizing Radiation (NIR)
Detecting Ionizing Radiation
Ask we have already covered all the basic required to understand the concept better. Now let us study what is Nuclear Fusion?
Nuclear Fusion:
This is most simply achieved on Earth by combining two isotopes of hydrogen such that the deuterium and tritium. Hydrogen is the lightest of all the elements in the periodic element, which is made up of a single proton and an electron. Deuterium has an additional neutron in its nucleus; it can replace one of the hydrogen atoms in water to make what is called heavy water. Tritium has two additional neutrons, and is, hence, 3 times as heavy as hydrogen. In a fusion cycle, tritium and deuterium are combined and appear in the formation of helium, the next heaviest element in the Periodic Table, and the gives out a free neutron.
Deuterium is seen in one part per 6,500 in common seawater, and is hence globally available, eliminating the problem of uneven geographical distribution of fuel resources. This indicates that there will be fuel for fusion if there is water on the planet.
Fusion Power:
E=mc2.
For a nuclear fusion reaction to happen, it is important to bring two nuclei so close that their nuclear forces become active and join the nuclei together. Nuclear forces are small distance forces and must act against the electrostatic forces where the positively charged nuclei repel from each other. This is the reason nuclear fusion reactions occur mostly in very high density and high-temperature environment.
At very high temperatures, electrons are stripped away from atomic nuclei to form a plasma such that an ionized gas. Under such conditions, the positively charged nuclei that have repulsive electrostatic forces are kept apart, and the nuclei of select light elements can be taken together to fuse and form other elements. Nuclear fusion of light elements gives out vast amounts of energy and is the fundamental energy-producing process in stars.
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FAQs on Nuclear Fusion
1. What is nuclear fusion? Provide a key example.
Nuclear fusion is a nuclear reaction in which two or more light atomic nuclei collide at very high speeds and join to form a new, heavier nucleus. During this process, a portion of the mass is converted into a significant amount of energy, as described by Einstein's mass-energy equivalence equation, E=mc². A primary example of nuclear fusion is the process that powers the Sun and other stars, where hydrogen isotopes fuse to form helium.
2. What is the main difference between nuclear fusion and nuclear fission?
The main difference lies in the process. Nuclear fusion is the process of combining or 'fusing' two light atomic nuclei to form a single heavier nucleus, releasing energy. In contrast, nuclear fission is the opposite process: it involves splitting a heavy, unstable nucleus into two or more smaller nuclei, which also releases a large amount of energy. Fusion powers stars, while fission is the process used in conventional nuclear power plants.
3. What are the essential conditions required to initiate a nuclear fusion reaction?
To initiate nuclear fusion, two critical conditions must be met to overcome the electrostatic repulsion between positively charged nuclei:
- Extremely High Temperature: Temperatures of the order of 10⁸ Kelvin are required to give the nuclei enough kinetic energy to overcome their mutual repulsion (Coulomb barrier) and fuse together.
- Extremely High Pressure/Density: The nuclei must be confined in a very small space to increase the probability of collision. In stars, this is achieved by immense gravitational pressure.
4. How is energy released during a nuclear fusion reaction?
Energy is released in nuclear fusion due to the mass defect. The mass of the single heavier nucleus formed after fusion is slightly less than the total mass of the individual light nuclei that fused. This 'lost' mass is converted directly into a tremendous amount of energy according to the formula E = Δmc², where Δm is the mass defect. This happens because the nucleons (protons and neutrons) are more tightly bound in the new nucleus, resulting in a higher binding energy per nucleon.
5. What is the proton-proton cycle that powers the Sun?
The proton-proton cycle is the primary nuclear fusion reaction that occurs in the Sun to produce energy. In this multi-step process, four hydrogen nuclei (protons) are ultimately converted into one helium nucleus, two positrons, two neutrinos, and a significant amount of energy. It is the main source of the Sun's light and heat, demonstrating a sustained, large-scale example of nuclear fusion.
6. Why is achieving sustained nuclear fusion on Earth so challenging?
Achieving sustained nuclear fusion on Earth is incredibly difficult because it requires replicating the extreme conditions found inside stars. The main challenges are:
- Temperature and Confinement: Creating and maintaining temperatures of over 100 million Kelvin is a major hurdle. At this temperature, the fuel becomes a plasma that cannot be held by any physical container. It must be confined using powerful magnetic fields (as in a tokamak) or inertial confinement (using lasers).
- Energy Balance: A fusion reactor must produce more energy than is consumed to heat and confine the plasma. This break-even point, known as ignition, has only recently been achieved for brief moments.
7. What are the potential advantages of nuclear fusion as an energy source?
Nuclear fusion offers several significant advantages over current energy sources, including nuclear fission. These include:
- Abundant Fuel: The primary fuels, deuterium and lithium (to breed tritium), are abundant in seawater and the Earth's crust.
- Inherent Safety: Fusion reactions are not chain reactions. Any malfunction would cause the plasma to cool and the reaction to stop, preventing meltdowns.
- Clean Energy: Fusion does not produce greenhouse gases.
- Less Radioactive Waste: It produces far less long-lived radioactive waste compared to fission reactors. The activated materials have a much shorter half-life.
