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:
“Many women cut back what had to be done at home by redefining what the house, the marriage and, sometimes, what the child needs. One woman described a fairly common pattern: “I do my half. I do half of his half, and the rest doesn’t get done.””
—Arlie Hochschild (20th century)
“But alas! I never could keep a promise. I do not blame myself for this weakness, because the fault must lie in my physical organization. It is likely that such a very liberal amount of space was given to the organ which enables me to make promises, that the organ which should enable me to keep them was crowded out. But I grieve not. I like no half-way things. I had rather have one faculty nobly developed than two faculties of mere ordinary capacity.”
—Mark Twain [Samuel Langhorne Clemens] (1835–1910)
“When we speak the word “life,” it must be understood we are not referring to life as we know it from its surface of fact, but to that fragile, fluctuating center which forms never reach.”
—Antonin Artaud (1896–1948)
“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)