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:
“We therefore commit his body to the ground; earth to earth, ashes to ashes, dust to dust; in sure and certain hope of the Resurrection to eternal life.”
—Book Of Common Prayer, The. The Burial of the Dead (1662)
“The real stumbling-block of totalitarian régimes is not the spiritual need of men for freedom of thought; it is men’s inability to stand the physical and nervous strain of a permanent state of excitement, except during a few years of their youth.”
—Simone Weil (1909–1943)
“The analogy between the mind and a computer fails for many reasons. The brain is constructed by principles that assure diversity and degeneracy. Unlike a computer, it has no replicative memory. It is historical and value driven. It forms categories by internal criteria and by constraints acting at many scales, not by means of a syntactically constructed program. The world with which the brain interacts is not unequivocally made up of classical categories.”
—Gerald M. Edelman (b. 1928)
“The emotional security and political stability in this country entitle us to be a nuclear power.”
—Ronald, Sir Mason (b. 1930)
“Beware the/easy griefs, that fool and fuel nothing./It is too easy to cry “AFRIKA!”/and shock thy street,/and purse thy mouth,/and go home to thy “Gunsmoke,” to/thy “Gilligan’s Island” and the NFL.”
—Gwendolyn Brooks (b. 1917)