Burn up

Burn up refers to the process of consuming fuel in a controlled manner, often in the context of nuclear reactors or spacecraft reentry. The term can also refer to the total amount of fuel consumed over a given period or event.

Nuclear Reactors

In a nuclear reactor, burn up is a measure of how much energy is extracted from a unit of nuclear fuel. It is usually expressed in terms of megawatt-days per metric ton of uranium (MWd/MTU). The burn up rate in a reactor is determined by the reactor's power level and the amount of time the fuel has been in the reactor.

The burn up process in a nuclear reactor involves the fission of uranium-235 or plutonium-239 atoms, which releases energy in the form of heat. This heat is used to produce steam, which drives a turbine to generate electricity.

Spacecraft Reentry

In the context of spacecraft reentry, burn up refers to the process of a spacecraft or satellite heating up and disintegrating due to friction with the Earth's atmosphere. This is a common fate for many man-made objects in low Earth orbit, including defunct satellites and spent rocket stages.

During reentry, the kinetic energy of the spacecraft is converted into heat by the friction of the atmosphere. This heat can cause the spacecraft to glow brightly, creating a streak of light in the sky. This is often referred to as a "shooting star" or "meteor."

See Also

• Nuclear fission
• Space debris
• Reentry (spacecraft)