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3. DESCRIPTION OF THE FUEL CYCLES
Definition of partitioning and transmutation
Partitioning is a complex series of chemical and/or metallurgical operations, intended to
separate selected radiotoxic nuclides or groups of nuclides from the bulk of radionuclides occluded in
the spent fuel elements which are periodically discharged from nuclear reactors. The separated nuclides
or group of nuclides can be stored as such or transformed into new fuel elements or irradiation targets.
Transmutation is a general term covering as well elementary nuclear conversion through single
neutron capture as fission of heavy nuclides, spallation and other nuclear reactions involving neutrons.
The aim of transmutation in the context of this study is to reduce the long-term inventory of radiotoxic
nuclides by converting the initial nuclides either into short-lived radionuclides or into stable nuclides.
3.1 The nuclear fuel cycles
The nuclear fuel cycles include all the operations necessary to supply fresh fuel to the power
plants and to manage the spent fuels discharged from the reactors. Figure I.3 shows the main steps of
the reprocessing fuel cycle (RFC), which are the following for light water reactors:
• the front-end of the cycle covers operations ranging from uranium ore prospecting to the
transport of fuel elements to the power plant for refuelling: ore extraction and treatment to
produce a uranium concentrate, conversion of the concentrate to hexafluoride sent to
uranium enrichment plants to raise the content of the isotope 235 U from its natural level
(0.72%) to a level of 3 to 5%, and fuel element fabrication.
• the back-end of the cycle comprises two complementary alternatives today:
– the closed cycle based on spent fuel reprocessing, which is designed to separate and
recycle the energy materials (mainly plutonium) which they contain, and to optimise
waste management for disposal;
– the so-called “open cycle” with direct disposal of the irradiated fuels in a geological
repository after an interim storage period of variable length.
Figure I.4 shows an example of the annual material flows in a fuel cycle with a mixed
PWR-FR park. Figure I.5 shows a fuel cycle where only FRs are used for energy productions.
In the present report, four types of fuel management are considered.
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