Define fuel burnup and state its common units.

Define fuel burnup and state its common units.

• A. Burnup is the energy produced per unit mass of fuel, commonly expressed as MWd/kgU.
• B. Burnup is the energy produced per unit mass of fuel, commonly expressed as MWd/tonneU.
• C. Burnup is the energy produced per unit mass of fuel, commonly expressed as MWd/tU.
• D. Burnup is the ratio of energy produced to the reactor core temperature.

Answer: (C)

Burnup tells you how much energy has been produced by a given amount of fuel, so it’s defined as energy produced per unit mass of fuel. The common way to express this is in megawatt-days per unit mass of uranium, with the mass usually taken as a tonne of uranium. Using per tonne makes the numbers convenient to compare for large reactor cores that contain many kilograms of U, and it’s a standard convention in industry. While per-kilogram units (MWd/kgU) are also used, MWd per tonne of uranium (MWd/tU) is the widely referenced standard, which is why it’s the best match among the options. The idea of burnup as a ratio to reactor core temperature isn’t applicable, so that option isn’t a burnup unit.

Burnup tells you how much energy has been produced by a given amount of fuel, so it’s defined as energy produced per unit mass of fuel. The common way to express this is in megawatt-days per unit mass of uranium, with the mass usually taken as a tonne of uranium. Using per tonne makes the numbers convenient to compare for large reactor cores that contain many kilograms of U, and it’s a standard convention in industry. While per-kilogram units (MWd/kgU) are also used, MWd per tonne of uranium (MWd/tU) is the widely referenced standard, which is why it’s the best match among the options. The idea of burnup as a ratio to reactor core temperature isn’t applicable, so that option isn’t a burnup unit.