Copy of `World Nuclear Association - Nuclear fuel terms`

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World Nuclear Association - Nuclear fuel terms
Category: Earth and Environment > Nuclear fuel
Date & country: 10/12/2007, UK
Words: 110


Thermal reactor
A reactor in which the fission chain reaction is sustained primarily by slow neutrons, and hence requiring a moderator (as distinct from Fast Neutron Reactor).

Transmutation
Changing atoms of one element into those of another by neutron bombardment, causing neutron capture and/or fission. In an ordinary reactor neutron capture is the main event, in a fast reactor fission is more common and therefore it is best for dealing with actinides. Fission product transmutation is by neutron capture

Transuranic element
A very heavy element formed artificially by neutron capture and possibly subsequent beta decay(s). Has a higher atomic number than uranium (92). All are radioactive. Neptunium, plutonium, americium and curium are the best-known

Uranium (U)
A mildly radioactive element with two isotopes which are fissile (U-235 and U-233) and two which are fertile (U-238 and U-234). Uranium is the basic fuel of nuclear energy

Uranium hexafluoride
(UF6) A compound of uranium which is a gas above 56°C and is thus a suitable form in which to enrich the uranium

Uranium oxide concentrate
(U3O8) The mixture of uranium oxides produced after milling uranium ore from a mine. Sometimes loosely called yellowcake. It is khaki in colour and is usually represented by the empirical formula U3O8. Uranium is sold in this form

Vitrification
The incorporation of high-level wastes into borosilicate glass, to make up about 14% of it by mass. It is designed to immobilise radionuclides in an insoluble matrix ready for disposal

Waste
High-level waste (HLW) is highly radioactive material arising from nuclear fission. It can be what is left over from reprocessing used fuel, though some countries regard spent fuel itself as HLW. It requires very careful handling, storage and disposal. Low-level waste (LLW) is mildly radioactive material usually disposed of by incineration and burial

Yellowcake
Ammonium diuranate, the penultimate uranium compound in U3O8 production, but the form in which mine product was sold until about 1970. See also Uranium oxide concentrate

Zircaloy
Zirconium alloy used as a tube to contain uranium oxide fuel pellets in a reactor fuel assembly