Head-end

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Term from reprocessing technology; the first process step of reprocessing. The head-end comprises all process stages of mechanical sectioning of fuel elements up to chemical dissolution of the spent fuel in order to prepare extraction. The individual steps are: the fuel elements are fed into a sectioning machine which cuts the fuel element bundles, or the individual fuel rods after dismantling of fuel elements into approx. 5 cm long pieces. To dissolve the irradiated fuel, the fuel rod pieces fall into a dissolution device where uranium, plutonium and fission products are dissolved in concentrated nitric acid. Once the dissolution process is finished, the fuel solution is purified of solid particles by filtering or centrifuging and passed to a buffer container for assessment of the uranium and plutonium content. Zircaloy, the cladding material of the fuel rods resistant to nitric acid remains in the dissolution device. (See 'Tail-end')