Thermal neutron

Thermal neutron is a type of neutron that has achieved thermal equilibrium with its surroundings. This means that its kinetic energy is similar to the average kinetic energy of the particles in its environment. Thermal neutrons are a vital component in nuclear reactors and nuclear weapons due to their ability to cause nuclear fission in materials like uranium-235 and plutonium-239.

Characteristics

Thermal neutrons have a speed of about 2.2 kilometers per second at room temperature. This speed corresponds to a kinetic energy of about 0.025 electron volts (eV). The term "thermal" refers to this neutron being in thermal equilibrium with a surrounding medium, but it does not imply that the neutron's energy is necessarily equivalent to the temperature of the surrounding material.

Production

Thermal neutrons are typically produced in nuclear reactors through a process called neutron moderation. In this process, fast neutrons produced by nuclear fission are slowed down through collisions with light atoms in a moderator, such as water, heavy water, or graphite.

Applications

Thermal neutrons are essential in the operation of nuclear reactors and in the design of nuclear weapons. In a nuclear reactor, thermal neutrons are used to sustain a nuclear chain reaction by causing the fission of uranium-235 or plutonium-239. In nuclear weapons, they are used to initiate the fission process that releases the weapon's energy.

Detection

Thermal neutrons can be detected using a neutron detector. These devices work by absorbing the neutron and then emitting a charged particle, which can be detected electronically. Common types of neutron detectors include proportional counters, scintillation detectors, and solid-state detectors.

See also

• Neutron temperature
• Neutron cross section
• Neutron radiation
• Neutron source