Glossary - Letter I

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IFP Energies Nouvelles (IFPEN)

Formerly the Institut Français du Pétrole (French Petroleum Institute). It is a public sector research, innovation and training center active in the fields of energy, transportation and the environment.


Technique used to convert waste into energy. The waste is burned, producing heat, power or both.


In economics, linking adjustments made to the value of a good, service or other metric, to a predetermined index. For example, the price of natural gas is indexed to the price of oil. If the price of oil rises, the price of natural gas will also rise.

Induced Radioactivity

Radioactivity created by bombarding stable substances with ionizing radiation. These substances are used in power generation, medicine and industry.

Infrared Radiation

Electromagnetic radiation with a wavelength of approximately 0.7 to 1000 µm that falls between visible red light and microwaves on the electromagnetic spectrum. According to Planck’s law, the solar radiation absorbed by the Earth’s surface is radiated back into the atmosphere in the form of infrared radiation with a wavelength of 8 to 13 µm. This radiation, which warms the atmosphere, especially gases such as water vapor, carbon dioxide and methane, is what causes the greenhouse effect.


Secondary oil recovery method in which water or gas is injected into a deposit to increase pressure in the reservoir, improve the well's flow rate and optimize the field's ultimate recovery rate. In a subsequent step known as enhanced oil recovery, gas, steam or certain chemicals can be injected to reduce the crude oil's viscosity and enhance its displacement in the reservoir.

Installed Capacity

The power generation capacity of a particular plant. It is usually expressed in megawatts (or sometimes even gigawatts) and can come from nuclear, thermal, solar or wind energy or hydropower.

Institut de Radioprotection et de Sûreté Nucléaire (IRSN)

The French Institute for Radiation Protection and Nuclear Safety is active in research, training, monitoring and public education in the field of radiation protection. The IRSN also carries out assessments and provides technical and operational support in the event of a radiological emergency.

Intergovernmental Panel on Climate Change (IPCC)

Body established by the United Nations Environment Programme (UNEP) and the World Meteorological Organization (WMO) in 1988 to review and assess the most recent scientific, technical and socio-economic information produced worldwide relevant to the understanding of climate change.

Intermittence (Renewable Energy)

Inability of a renewable energy source to deliver a steady supply of electricity. For example, solar power stops at night and wind power stops when there is not enough wind. Intermittence is a major problem for grid operators, which must be able to count on a steady, reliable source of a specific amount of electricity at all times.

International Atomic Energy Agency (IAEA)

The IAEA was set up in 1957 within the United Nations family. It works for the safe, secure and peaceful uses of nuclear energy and to deter the proliferation of nuclear weapons by ensuring that states are honoring their international obligations and by being able to detect early any misuse of nuclear material or technology.

International Energy Agency (IEA)

An independent, intergovernmental organization founded within the framework of the OECD in response to the first oil crisis in 1974 to act as an energy policy coordinator to its 26 member countries, most of which belong to the developed world. Its aims are to ensure security of energy supply, support economic development and enhance environmental awareness.

International Nuclear and Radiological Event Scale (INES)

Scale used to classify the severity of nuclear incidents and accidents. It comprises 8 levels, from 0 to 7. Level 0 corresponds to an event of no safety significance; Level 7 is a major release of radioactive material with widespread health and environmental effects. Examples include the Chernobyl and Fukushima disasters. Levels 0 to 2 correspond to incidents with no impact outside the nuclear site.

International Organization for Standardization (ISO)

Independent, non-governmental membership organization. Its 165 members are the national standards bodies from 165 countries around the world. The ISO has published more than 19,500 international standards since it was created in 1947 (a standard is a document that provides requirements, specifications, guidelines or characteristics that can be used consistently to ensure that materials, products, processes and services are for fit for their purpose).

International Thermonuclear Experimental Reactor (ITER)

An international project to design and build the first experimental fusion reactor that produces more energy than it uses. The members of the project are the European Union, the United Sates, Japan, Russia, China, India and South Korea. Its objective is to successfully maintain fusion reliably and to qualify the key technologies needed to develop industrial fusion reactors in the future. The ITER reactor will be built in Cadarache, France. The DEMO reactor, which will follow on from ITER, is expected to begin producing electricity in 2040.

Ionizing Radiation

Radiation that possesses enough energy to ionize a material that it penetrates. In other words, it removes electrons from atoms, which have a neutral charge, and transforms them into ions, which have a positive charge. For example, ionization of the hydrogen H --> H+ + e- atom requires minimum energy of 13.6 eV. There are two forms of ionizing radiation: waves (X, gamma and certain ultra-violet rays) and particles (electron β-, positon β+, neutron, muon, proton, He2+ α, etc.). All of these are hazardous to health, especially in high doses.


The power of electromagnetic radiation per unit area, expressed in watts per square meter (W/m²). Irradiance defines the quantity of energy absorbed by solar panels, for example.


A variant of a chemical element that has the same number of protons in the nucleus, but different numbers of neutrons. An example is hydrogen (1 neutron and 1 proton), which has two naturally occurring isotopes: deuterium (2 neutrons and 1 proton) and tritium (3 neutrons and 1 proton).