Nuclear fission and fusion – electricity generation

Nuclear physics is a field of science that explores the properties and behaviour of the atomic nucleus. Understanding this helps us harness nuclear reactions for various applications, especially power generation. The two fundamental processes in nuclear physics that produce energy are nuclear fission and nuclear fusion.

Nuclear fission

Nuclear fission is a reaction in which a heavy nucleus splits into two smaller nuclei, releasing a few neutrons and a large amount of energy. This process is used in nuclear power plants to produce electricity.

How nuclear fission works

Imagine a heavy atom such as uranium-235. When a neutron hits this uranium nucleus, it becomes unstable and splits into two smaller nuclei. This splitting, or fission, releases additional neutrons and a significant amount of energy. These released neutrons can then collide with other uranium nuclei, causing more fission reactions. This is called a chain reaction.

The basic fission reaction can be represented as:

        ^{235}_{92}U + ^{1}_{0}n rightarrow ^{236}_{92}U rightarrow ^{140}_{56}Ba + ^{93}_{36}Kr + 3^{1}_{0}n + text{Energy}
        ^{235}_{92}U + ^{1}_{0}n rightarrow ^{236}_{92}U rightarrow ^{140}_{56}Ba + ^{93}_{36}Kr + 3^{1}_{0}n + text{Energy}
    

Here, the nucleus of uranium-235 absorbs a neutron, splits into barium-140 and krypton-93, releasing three more neutrons and energy.

Chain reaction

A chain reaction in nuclear fission occurs when neutrons released from one fission event cause further fission events. If left unchecked, this process can become very fast and explosively release huge amounts of energy, as in nuclear weapons. However, in power plants, the reaction is controlled to use the energy safely.

Control rods made of materials such as cadmium or boron are used to absorb excess neutrons, thereby controlling the process. This management of neutrons helps maintain the desired rate of fission for continued energy production.

Applications of nuclear fission

The energy produced by nuclear fission is primarily used to make electricity. Nuclear power plants work in the same way as fossil fuel plants, but use the heat from fission instead of burning coal. The heat turns water into steam, which then drives turbines connected to electric generators.

Nuclear fusion

Nuclear fusion is the process in which two lighter atomic nuclei combine to form a heavier nucleus, releasing energy. Fusion is the process that powers the sun and stars, and it provides an abundant potential source of energy on Earth.

How does nuclear fusion work?

In fusion, extremely high temperature and pressure conditions are necessary to bring the nuclei of two atoms close enough to overcome the repulsion forces between them. At these high temperatures, electrons separate, leaving the positively charged nuclei—ions—free to collide. When the nuclei come very close, the nuclear force pulls them together, achieving fusion.

A simple fusion reaction involves isotopes of hydrogen - deuterium and tritium. The fusion of deuterium and tritium produces a helium nucleus, a neutron, and energy, as shown in the reaction:

        ^{2}_{1}H + ^{3}_{1}H rightarrow ^{4}_{2}He + ^{1}_{0}n + text{Energy}
        ^{2}_{1}H + ^{3}_{1}H rightarrow ^{4}_{2}He + ^{1}_{0}n + text{Energy}
    

The possibility of fusion energy

Fusion energy has several advantages over fission. First, the fuels used in fission (deuterium and tritium) are more abundant than uranium or plutonium. Water contains ample deuterium, and lithium, from which tritium can be made, is abundant in the Earth's crust.

Second, fusion produces minimal long-lived radioactive waste compared to fission. Also, there is no chance of an uncontrollable reaction like in fission reactors because maintaining the high temperatures and pressures necessary for fusion is inherently challenging.

The challenges of fusion

The main challenge in harnessing fusion energy is maintaining the conditions needed for fusion - extreme temperatures and pressures - long enough to extract the energy. Scientists are working on various methods, such as magnetic confinement (tokamaks) and inertial confinement, to achieve fusion reactions.

Comparison between fission and fusion

Understanding both fission and fusion reveals their strengths and limitations. Here is a simple comparison:

Aspect	Fragmentation	Merger
Fuel	Uranium-235, Plutonium-239	Deuterium, Tritium
Energy yield	High	Potentially more
Radioactive waste	Important	Minimum
Feedback control	Possible with control rods	Difficult to maintain at present

Conclusion

Both nuclear fission and fusion offer routes to large-scale energy production. Fission is currently used in nuclear power plants around the world, while fusion holds promise for the future. By constantly researching and improving these processes, we aim to find sustainable solutions to meet our energy needs.

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