Fusion reaction

Fusion reaction refers to a process in which two light atomic nuclei combine to form a heavier nucleus, releasing a significant amount of energy. This process is fundamental to the energy production in stars, including the Sun, and has potential applications in generating electricity through nuclear fusion reactors.

Overview

Fusion reactions are the primary source of the sun's energy, powering stars across the universe. The most common fusion reaction in stars is the conversion of hydrogen to helium. This process occurs under extreme conditions of high temperature and pressure, which overcome the electrostatic repulsion between the positively charged nuclei.

Types of Fusion Reactions

There are several types of fusion reactions, with the Deuterium-Tritium (D-T) reaction being the most studied for energy production. This reaction involves the isotopes of hydrogen, deuterium (D), and tritium (T), producing helium-4, a neutron, and releasing 17.6 MeV of energy.

Other notable reactions include:

• Deuterium-Deuterium (D-D) reaction
• Proton-Proton (P-P) chain reaction, predominant in stars like the Sun
• CNO cycle, which involves carbon, nitrogen, and oxygen as catalysts in more massive stars

Conditions for Fusion

To achieve fusion, the conditions must be such that the nuclei can overcome their mutual electrostatic repulsion. This typically requires temperatures of millions of degrees, known as the thermonuclear temperature, and sufficient pressure to maintain a high density of reactants. In laboratory settings, these conditions are achieved in tokamak reactors or using inertial confinement fusion techniques.

Challenges in Controlled Fusion

Controlled fusion, aimed at energy production on Earth, faces several challenges:

• Containment: Maintaining the reaction requires a method to contain the hot plasma. Magnetic confinement (e.g., tokamaks) and inertial confinement are two approaches.
• Materials: The reactor materials must withstand extreme temperatures and neutron bombardment.
• Neutron Activation: Neutrons produced in reactions like D-T can activate materials, posing a radiological hazard.
• Fuel Supply: Tritium is scarce and must be bred from lithium, adding complexity to the fuel cycle.

Potential and Research

Fusion energy is seen as a potentially limitless and clean energy source, with water and lithium as primary fuel sources. Major international research projects, such as the ITER and the National Ignition Facility, aim to demonstrate the feasibility of controlled fusion power.

See Also

• Nuclear fission
• Renewable energy
• Energy conservation