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:
“Human life in common is only made possible when a majority comes together which is stronger than any separate individual and which remains united against all separate individuals. The power of this community is then set up as “right” in opposition to the power of the individual, which is condemned as “brute force.””
—Sigmund Freud (1856–1939)
“There is nothing that man fears more than the touch of the unknown. He wants to see what is reaching towards him, and to be able to recognize or at least classify it. Man always tends to avoid physical contact with anything strange.”
—Elias Canetti (b. 1905)
“Of the three forms of pride, that is to say pride proper, vanity, and conceit, vanity is by far the most harmless, and conceit by far the most dangerous. The meaning of vanity is to think too much of our bodily advantages, whether real or unreal, over others; while the meaning of conceit is to believe we are cleverer, wiser, grander, and more important than we really are.”
—John Cowper Powys (1872–1963)
“The reduction of nuclear arsenals and the removal of the threat of worldwide nuclear destruction is a measure, in my judgment, of the power and strength of a great nation.”
—Jimmy Carter (James Earl Carter, Jr.)
“The particular source of frustration of women observing their own self-study and measuring their worth as women by the distance they kept from men necessitated that a distance be kept, and so what vindicated them also poured fuel on the furnace of their rage. One delight presumed another dissatisfaction, but their hatefulness confessed to their own lack of power to please. They hated men because they needed husbands, and they loathed the men they chased away for going.”
—Alexander Theroux (b. 1940)