The iodine pit, also called the iodine hole or xenon pit, is a temporary disabling of a nuclear reactor due to buildup of short-lived nuclear poisons in the reactor core.

The Ion is a subatomic particle whose electric charge is negative one elementary charge.

Ionisation energy is the minimum amount of energy required to remove the most loosely bound electron of an isolated neutral gaseous atom or molecule

Ionizing radiation (ionising radiation) consists of subatomic particles or electromagnetic waves that have sufficient energy to ionize atoms or molecules by detaching electrons from them.

A private company in the business of generating and supplying electrical power to end users.

The International Renewable Energy Agency (IRENA) is an intergovernmental organisation supporting countries in their transition to a sustainable energy future .

Iron is a chemical element with symbol Fe and atomic number 26.

Iron ore stows at 0.4-0.5m3/t and is thus one of the densest materials carried in ships.

An automatic mooring device developed in New Zealand by Mooring International for the rail/vehicle ferry ARATERE.

Irradiation is the process by which an object is exposed to radiation.

In thermodynamics, a change in the thermodynamic state of a system and all of its surroundings cannot be precisely restored to its initial state by infinitesimal changes in some property of the system without expenditure of energy.

An isentropic process is an idealized thermodynamic process that is both adiabatic and reversible.

An island grid is constructed when an area is too far from or it is not cost efficient to connect it to a major power grid.

Islanding is the condition in which a distributed generator (DG) continues to power a location even though external electrical grid power is no longer present.

Islay LIMPET was the world's first commercial wave power device and was connected to the United Kingdom's National Grid. (Now decommisioned).

Isobars are atoms (nuclides) of different chemical elements that have the same number of nucleons.

An isobaric process is a type of thermodynamic process in which the pressure of the system stays constant.

The output of two or more generators which is controlled via the prime mover speed governors to maintain the desired frequency during load imbalances.

An isolated thermodynamic system has walls that are non-conductive of heat and perfectly reflective of all radiation, that are rigid and immovable, and that are impermeable to all forms of matter and all forces.

A switch used to break an electrical circuit thereby completely de-energising the circuit.