Most depleted uranium arises as a by-product of the production of enriched uranium for use as fuel in nuclear reactors and in the manufacture of nuclear weapons.

Dependent and independent variables are variables in mathematical modeling, statistical modeling and experimental sciences.

the density of states (DOS) of a system describes the proportion of states that are to be occupied by the system at each energy.

The density of a substance is its mass per unit volume.

Demand-side management is the modification of consumer demand for energy through various methods such as financial incentives and behavioral change through education.

Demand response is a change in the power consumption of an electric utility customer to better match the demand for power with the supply.

The electrical input required to operate a ground source heat pump unit for space conditioning.

A type of three-phase electric power transformer design that employs delta-connected windings on its primary and wye/star connected windings on its secondary.

Temperature difference between two test sites such as supply and return air or entering and leaving water in ground loop.

Difference in pressure between two test points

A delayed neutron is a neutron emitted after a nuclear fission event, by one of the fission products, any time from a few milliseconds to a few minutes after the fission event.

A degasser is a device used in drilling to remove gasses from drilling fluid which could otherwise form bubbles.

Deformation refers to the change in size or shape of an object.

Deep water source cooling (DWSC) or deep water air cooling is a form of air cooling for process and comfort space cooling which uses a large body of naturally cold water as a heat sink.

Water depths greater than 60 meters.

A deep geological repository is a way of storing toxic or radioactive waste within a stable geologic environment (typically 200–1000 m deep).

Relatively constant temperature at a given depth which vary when heat is extracted or rejected by ground loops.

Deep cycle batteries are used to provide continuous electricity to run electric vehicles such as forklifts or golf carts.

Deep borehole disposal is the concept of disposing high-level radioactive waste from nuclear reactors in extremely deep boreholes instead of in more traditional deep geological repositories that are excavated like mines.

Decontamination is the process of removing contaminants on an object or area, including chemicals, micro-organisms or radioactive substances.