Sources de rayonnements Cycle du combustible – Vue générale Jour 4 – Leçon 5 (1)

Objectif Pour avoir une vue d'ensemble sur les éléments du cycle du combustible à partir de l'exploitation minière de l'uranium jusqu’à l'élimination des déchets *: exploitation minière broyage conversion enrichissement Fabrication de combustible Génération de puissance combustible usé retraitement Élimination des déchets *Note: Ces éléments du cycle du combustible seront exposés en détail dans les présentations suivantes The various activities associated with the production of electricity from nuclear reactions are referred to collectively as the nuclear fuel cycle. The nuclear fuel cycle starts with the mining of uranium and ends with the disposal of nuclear waste. With the reprocessing of spent fuel as an option for nuclear fuel, the stages form a true cycle.

Contenus Ressources énergétiques Ressources de l’uranium Autres sources de combustible Propriétés de l'uranium Composantes du cycle du combustible The various activities associated with the production of electricity from nuclear reactions are referred to collectively as the nuclear fuel cycle. The nuclear fuel cycle starts with the mining of uranium and ends with the disposal of nuclear waste. With the reprocessing of spent fuel as an option for nuclear fuel, the stages form a true cycle.

Vue générale Dans cette session, nous allons discuter le cycle du combustible nucléaire, y compris: exploitation minière broyage conversion enrichissement Fabrication de combustible Génération de puissance combustible usé retraitement Élimination des déchets The various activities associated with the production of electricity from nuclear reactions are referred to collectively as the nuclear fuel cycle. The nuclear fuel cycle starts with the mining of uranium and ends with the disposal of nuclear waste. With the reprocessing of spent fuel as an option for nuclear fuel, the stages form a true cycle.

Resources énergétiques

Concentrations Typiques de l’Uranium ppm Source (parties par million)*  Minerai de très haute teneur (Canada) - 20% U 200,000 ppm U Minerai à haute teneur - 2% U, 20,000 ppm U Minerai faible teneur - 0.1% U, 1,000 ppm U Minerai de très faible teneur* (Namibia) - 0.01% U 100 ppm U Granite 3-5 ppm U Roches sédimentaires 2-3 ppm U Croûte continentale de la Terre (av) 2.8 ppm U L'eau de mer 0.003 ppm U Uranium is a slightly radioactive metal that occurs throughout the earth's crust. It is about 500 times more abundant than gold and about as common as tin. It is present in most rocks and soils as well as in many rivers and in sea water. There are a number of areas around the world where the concentration of uranium in the ground is sufficiently high that extraction of it for use as nuclear fuel is economically feasible. * Données de WNA (Aout 2012) http://www.world-nuclear.org/info/Nuclear-Fuel-Cycle/Uranium-Resources/Supply-of-Uranium/

Ressources d’Uranium Récupérables connues Pays tonnes percentage mondial* Australia 1,661,000 31% Kazakhstan 629,000 12% Russian Fed. 487,200 9% Canada 468,700 9% Niger 421,000 8% South Africa 279,100 5% Brazil 276,700 5% Namibia 261,000 5% USA 207,400 4% China 166,100 3% Ukraine 119,600 2% Uzbekistan 96,200 2% Autres 253,500 5% Total mondial 5,327,200 * données de WNA (Aout 2012) Current usage is about 68,000 tU/yr.  Thus the world's present measured resources of uranium (5.3 Mt) in the cost category around present spot prices and used only in conventional reactors, are enough to last for about 80 years.  This represents a higher level of assured resources than is normal for most minerals.  Further exploration and higher prices will certainly, on the basis of present geological knowledge, yield further resources as present ones are used up.  An initial uranium exploration cycle was military-driven, over 1945 to 1958. The second cycle was about 1974 to 1983, driven by civil nuclear power and in the context of a perception that uranium might be scarce. There was relatively little uranium exploration between 1985 and 2003, so the significant increase in exploration effort since then could conceivably double the known economic resources despite adjustments due to increasing costs. In the two years 2005-06 the world’s known uranium resources tabulated above and graphed below increased by 15% (17% in the cost category to $80/kgU). World uranium exploration expenditure is increasing, as the the accompanying graph makes clear. In the third uranium exploration cycle from 2003 to the end of 2011 about US$ 10 billion was spent on uranium exploration and deposit delineation on over 600 projects. In this period over 400 new junior companies were formed or changed their orientation to raise over US$ 2 billion for uranium exploration. About 60% of this was spent on previously-known deposits. All this was in response to increased uranium price in the market and the prospect of firm future prices. http://www.world-nuclear.org/info/Nuclear-Fuel-Cycle/Uranium-Resources/Supply-of-Uranium/

Chaine de décroissance de l’Uranium Isotopes Primaires 238U - alpha émetteur 235U et 234U –alpha/gamma émetteurs Produits de décroissance 231Th et 234Th - beta/gamma émetteurs 234mPa - beta/gamma émetteur Most of the radioactivity associated with uranium in nature is in fact due to other minerals derived from it by radioactive decay processes, and which are left behind in mining and milling. The table shows only the 238U decay chain.

Autres Sources du combustible Armes nucléaires déclassés Plus de 90% 235U (doit être transformé en combustible commercial) Thorium convertit en 233U après la capture de neutrons 3 fois plus abondant que l'uranium Nuclear Weapons as a source of fuel An increasingly important source of nuclear fuel is the world's nuclear weapons stockpiles. Since 1987 the United States and countries of the former USSR have signed a series of disarmament treaties to reduce the nuclear arsenals of the signatory countries by approximately 80 percent by 2003. The weapons contain a great deal of uranium enriched to over 90 percent U‑235. Some weapons have plutonium‑239, which can be used in diluted form in either conventional or fast breeder reactors. From 2000 the dilution of 30 tonnes of military high‑enriched uranium is displacing about 9000 tonnes of uranium oxide per year from mines, which represents about 14% of the world's reactor requirements. Thorium as a nuclear fuel Today uranium is the only fuel supplied for nuclear reactors. However, thorium can also be utilised as a fuel for CANDU reactors or in reactors specially designed for this purpose. Neutron efficient reactors, such as CANDU, are capable of operating on a thorium fuel cycle, once they are started using a fissile material such as U‑235 or Pu‑239. Then the thorium (Th‑232) captures a neutron in the reactor to become fissile uranium (U‑233), which continues the reaction. Some advanced reactor designs are likely to be able to make use of thorium on a substantial scale. Thorium is about three times as abundant in the earth's crust as uranium.

Propriétés de l’Uranium Natural L’Uranium naturel se compose de trois isotopes: Isotope % Abondance Demi-vie (106 ans) 238U 99.284 4,500 235U 0.711 704 234U 0.005 0.245

Propriétés de l’Uranium Isotope d’uranium Pourcent 100 238U est plus abondant 234U augmente avec l’enrichissement Note rapports d’activités 10 1 U-238 0.1 U-235 0.01 U-234 0.001 0.0001 LEU Naturel appauvri

Activités spécifiques de l’Uranium Type (enrichissement) Activité Spécifique (Bq/gram) Appauvri (0.2%) 1.5 x 104 Naturel (0.71%) 2.6 x 104 Enrichi (4%) 8.9 x 104 Enrichi (93%) 4.1 x 106

Composés d'uranium UF6 produite dans les usines de conversion U3O8 est yellowcake provenant du traitement UO2 est le type de combustible dominante (céramique) utilisé pour produire des granulés UF4 est la forme intermédiaire dans la conversion Le nitrate d'uranyle est important dans la reprise

Cycle du combustible We will now discuss each step in the fuel cycle.

Cycle du combustible dans le monde This map provides an overview indicating which countries participate in each step of the fuel cycle. Nations such as the USA and Russia conduct all the activities from mining to fuel fabrication while other nations may only conduct one or two of the steps.

Références http://www.world-nuclear.org/info/Nuclear-Fuel-Cycle/Uranium-Resources/Supply-of-Uranium/ International Atomic Energy Agency, Postgraduate Educational Course in Radiation Protection and the Safety of Radiation Sources (PGEC), Training Course Series 18, IAEA, Vienna (2002)