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1. THE FUEL CYCLE
The uranium ore is extracted, then purified and
concentrated into “yellow cake” on the mining sites.
The solid yellow cake is then converted into uranium
hexafluoride gas (UF
6
). This rawmaterial, whichwill be
subsequently enriched, ismade at the ArevaNCComurhex
plants in Malvési (which converts to UF
4
) and Tricastin
(which converts to UF
6
). The facilities in question –
most of which are regulated under the legislation for
Installations Classified on Environmental Protection
grounds (ICPEs) – use natural uranium in which the
uranium-235 content is around 0.7%.
Most of the world’s NPPs use uranium which is slightly
enriched in uranium-235. For example, the fleet of
Pressurised Water Reactors (PWR) requires uranium
enriched to between 3%and 5%with the U-235 isotope.
The gas centrifuge process used by theGB II plant replaced
the gaseous diffusion process, employed by the Eurodif
plant until June 2012.
The process used in the FBFC plant at Romans-sur-Isère
transforms the enrichedUF
6
into uraniumoxide powder.
The fuel pellets manufactured with this oxide are clad
to make fuel rods, which are then combined to form
fuel assemblies. These assemblies are then placed in the
reactor core where they release power by the fission of
uranium-235 nuclei.
After a period of use of about three to five years, the spent
fuel is removed from the reactor and cooled in a pool,
firstly on the site of the plant in which it was used and
then in the Areva NC reprocessing plant at La Hague.
At this plant, the uraniumand plutonium from the spent
fuels are separated fromthe fissionproducts and actinides
1
.
The uranium and plutonium are packaged and then
stored for subsequent re-use. However, at present, the
uranium obtained from reprocessing is no longer used
to produce new fuels. The radioactive waste produced
by these operations is disposed of in a surface repository
if it is low-level waste, otherwise it is placed in storage
2
pending a final disposal solution.
The plutonium resulting from the reprocessing of these
uranium oxide fuels is used in the Areva NC plant in
Marcoule, calledMélox, to fabricateMOX fuel (Mixture
of uraniumand plutoniumOXides) which ismainly used
in certain 900 MWe nuclear power reactors in France.
1. Actinides are chemical elements heavier than uranium.
2. Storage is temporary, while disposal is final.
T
he fuel cycle
begins with the extraction of uraniumore and ends with packaging
of the various radioactive wastes from the spent fuels so that they can be sent
for disposal. In France, all the uranium mines have been closed since 2000,
so the fuel cycle concerns the steps involved in the fabrication of the fuel and
then its reprocessing once it has been used in nuclear reactors.
Fuel cycle plants comprise all the facilities performing conversion, uranium enrichment,
design and fabrication of fuels for nuclear reactors, that is the front-end part of the cycle – in
other words before irradiation – as well as facilities for reprocessing spent fuel, that is the
back-end part of the cycle. These facilities utilise nuclear material, transformed into fuel,
based on uranium oxide or a mixture of uranium and plutonium oxides (called MOX), the
plutoniumhaving been generated by burn-up of the enriched natural uranium fuel in power
reactors and then extracted from the irradiated fuels during the reprocessing operations.
The main plants operating in the fuel cycle – Areva NC Tricastin (Comurhex and TU5/W),
Eurodif, Georges Besse II (GB II), Areva NP Romans-sur-Isère (ex-FBFC and ex-Cerca),
Mélox, Areva NC La Hague and Areva NC Malvési (which is an Installation Classified on
Environmental Protection grounds – ICPE) – are part of the Areva group (of which Areva NC
and Areva NP are subsidiaries). ASN regulates these industrial facilities and considers that
steps must be taken for all of the Group’s facilities in order to promote safety and radiation
protection coherently and allow the use of international best practices. ASN also monitors
the overall consistency of the fuel cycle in terms of safety and regulatory compliance. Areva
and EDF must in particular demonstrate that their industrial fuel management choices do
not compromise the safety of the facilities.
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CHAPTER 13:
NUCLEAR FUEL CYCLE INSTALLATIONS
ASN report on the state of nuclear safety and radiation protection in France in 2015