Common Physical Forms of Nuclear Fuel
Uranium dioxide (UO2) powder is compacted to cylindrical pellets and sintered at high temperatures to produce ceramic nuclear fuel pellets with a high density and well defined physical properties and chemical composition. A grinding process is used to achieve a uniform cylindrical geometry with narrow tolerances. Such fuel pellets are then stacked and filled into the metallic tubes. The metal used for the tubes depends on the design of the reactor. Stainless steel was used in the past, but most reactors now use a zirconium alloy which, in addition to being highly corrosion-resistant, has low neutron absorption. The tubes containing the fuel pellets are sealed: these tubes are called fuel rods. The finished fuel rods are grouped into fuel assemblies that are used to build up the core of a power reactor.
Cladding is the outer layer of the fuel rods, standing between the coolant and the nuclear fuel. It is made of a corrosion-resistant material with low absorption cross section for thermal neutrons, usually Zircaloy or steel in modern constructions, or magnesium with small amount of aluminium and other metals for the now-obsolete Magnox reactors. Cladding prevents radioactive fission fragments from escaping the fuel into the coolant and contaminating it.
-
Nuclear Regulatory Commission (NRC) Image of unirradiated (fresh) fuel pellets.
-
NRC Image of fresh fuel pellets ready for assembly.
-
NRC picture of fresh fuel being inspected.
Read more about this topic: Nuclear Fuel
Famous quotes containing the words common, physical, forms, nuclear and/or fuel:
“I will not adopt that ungenerous and impolitic custom so common with novel writers, of degrading by their contemptuous censure the very performances, to the number of which they are themselves adding—joining with their greatest enemies in bestowing the harshest epithets on such works, and scarcely ever permitting them to be read by their own heroine, who, if she accidentally take up a novel, is sure to turn over its insipid leaves with disgust.”
—Jane Austen (1775–1817)
“Patience, that blending of moral courage with physical timidity.”
—Thomas Hardy (1840–1928)
“There are these sudden mobs of men,
These sudden clouds of faces and arms,
An immense suppression, freed,
These voices crying without knowing for what,
Except to be happy, without knowing how,
Imposing forms they cannot describe,
Requiring order beyond their speech.”
—Wallace Stevens (1879–1955)
“We now recognize that abuse and neglect may be as frequent in nuclear families as love, protection, and commitment are in nonnuclear families.”
—David Elkind (20th century)
“I had an old axe which nobody claimed, with which by spells in winter days, on the sunny side of the house, I played about the stumps which I had got out of my bean-field. As my driver prophesied when I was plowing, they warmed me twice,—once while I was splitting them, and again when they were on the fire, so that no fuel could give out more heat. As for the axe,... if it was dull, it was at least hung true.”
—Henry David Thoreau (1817–1862)