Glossary letter U

Unconventional Oil

Oil that cannot be extracted using current technology or that entails additional technology or costs to produce. It includes extra heavy and highly viscous crude oil in shallow oil sands, shale oil, deep offshore oil or Arctic oil.

Unglazed PVT Collector

A simple type of solar thermal collector that absorbs the sun’s heat and is made from rubber, plastic or stainless steel. Unglazed PVT collectors are mainly used to heat pools and hot water.

Union Française des Industries Pétrolières (UFIP)

French oil industry association (UFIP) bringing together all companies doing business in the oil industry in France. Its role is to lobby elected officials, the French government, administrative authorities, the media and other groups.


Type of refinery that upgrades heavy, high-sulfur (sour) crude oil into light, low-sulfur synthetic crude oil. Examples include the José complex in Venezuela to process Orinoco heavy oil and the Scotford facility in Canada to process bitumen from the Athabasca oil sands.



Gray, very dense radioactive metal that is relatively abundant in the Earth's crust and oceans in the form of UO2 - uranium dioxide (uraninite). Once extracted, the ore undergoes various processes to produce a fuel that can be used in nuclear fission power plants.

Uranium 235

One of the three natural isotopes of uranium. Natural uranium contains approximately 99.3% U-238, 0.7% U-235 and traces of U-234. U-235 is naturally fissile and the only isotope that can be used as a natural nuclear fuel in nuclear power plants. To be used as a fuel, the uranium must be enriched with U-235 (3 to 5% for light water reactors and up to 19.75% for research reactors).


Urea, or carbamide, is an organic compound with the chemical formula (NH2) 2-C=O. Although mainly employed as a nitrogen fertilizer, it is also used in cattle and sheep feed and as an agent to reduce nitrogen oxide in diesel engine exhaust. Urea is also used to make certain thermosetting plastics such as urea-formaldehyde resins. Urea is produced on a commercial scale by synthesizing it from ammonia (NH3) and carbon dioxide (CO2).