A fuel element failure is a rupture in a nuclear reactor's fuel cladding that allows the nuclear fuel or fission products in the form of dissolved radioisotopes or hot particles to enter the reactor coolant or storage water.
The de facto standard nuclear fuel is uranium dioxide or a mixed uranium/plutonium dioxide. This has a higher melting point than the actinide metals. Uranium dioxide resists corrosion in water and provides a stable matrix for many of the fission products; however to prevent fission products (such as the noble gases) from leaving the uranium dioxide matrix and entering the coolant, the pellets of fuel are normally encased in tubes of a corrosion resistant metal alloy (normally Zircaloy for water-cooled reactors).
Those elements are then assembled into bundles to allow good handling and cooling. As the fuel fissions, the radioactive fission products are also contained by the cladding, and the entire fuel element can then be disposed of as nuclear waste when the reactor is refueled.
If, however, the cladding is damaged, those fission products (which are not immobile in the uranium dioxide matrix) can enter the reactor coolant or storage water and can be carried out of the core, into the rest of the primary cooling circuit, increasing contamination levels there.
In the EU, some work has been done in which fuel is overheated in a special research reactor named PHEBUS. During these experiments the emissions of radioactivity from the fuel are measured and afterwards the fuel is subjected to Post Irradiation Examination (PIE) to discover more about what happened to it.
It can be seen that the fuel has failed mechanically and has formed a pool near the bottom of the bundle, it is interesting to note that the bottom of the bundle did not melt.
Famous quotes containing the words fuel, element and/or failure:
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—Gwendolyn Brooks (b. 1917)
“Justice has its anger, my lord Bishop, and the wrath of justice is an element of progress. Whatever else may be said of it, the French Revolution was the greatest step forward by mankind since the coming of Christ. It was unfinished, I agree, but still it was sublime. It released the untapped springs of society; it softened hearts, appeased, tranquilized, enlightened, and set flowing through the world the tides of civilization. It was good. The French Revolution was the anointing of humanity.”
—Victor Hugo (1802–1885)
“War is bestowed like electroshock on the depressive nation; thousands of volts jolting the system, an artificial galvanizing, one effect of which is loss of memory. War comes at the end of the twentieth century as absolute failure of imagination, scientific and political. That a war can be represented as helping a people to “feel good” about themselves, their country, is a measure of that failure.”
—Adrienne Rich (b. 1929)