Scorie Nucleari Adriano Duatti Laboratorio di MedicinaNucleare, Departimento di Scienze C/A e Radiologiche, Università di Ferrara, Via L. Borsari, 46, Ferrara, Italy (

Sources of waste

Classification of radioactive wastes

Low-level Waste

Intermediate-level Waste

High-level Waste

Radioactive medical source

Other low-level sources

The Nuclear Fuel Cycle

Fuel Production

Uraninite (Pitchblende) Yellowcake U3O8U3O8 UO 2 Uranium fuel

Fuel rods (UO 2 ) UF 6 Uranium fuel

Reaction in standard UO 2 fuel

Fission product yields by mass for thermal neutron fission of U-235, Pu-239, and U-233 used in the thorium cycle Fission products

NuclideT 1/2, yYield,%E, keV  155 Eu  58 Kr  113m Cd  90 Sr  137 Cs  121m Sn  151 Sm  Medium-lived fission products

NuclideT 1/2, MyYield,%E, keV  99m Tc  126 Sn  79 Se  93 Zr  135 Cs  107 Pd  129 I  Long-lived fission products

‘Front End’ Waste

‘Back End’ Waste

Annual operation of a 1000 MWe nuclear power reactor A typical reactor generates about 27 tonnes of spent fuel or 3 m 3 per year of vitrified waste

Decay in radioactivity of fission fuel in one tonne of spent fuel

Storage in ponds at reactor sites There are about 270,000 tonnes of used fuel in storage, much of it at reactor sites. About 90% of this is in storage ponds, the balance in dry storage. Annual arisings of used fuel are about 12,000 tonnes, and 3,000 tonnes of this goes for reprocessing. Final disposal is not urgent in any logistical sense

Waste Management in the Nuclear Fuel Cycle

Waste Management in the Nuclear Fuel Cycle: LLW and ILW

Waste Management in the Nuclear Fuel Cycle: LLW Incineration

Waste Management in the Nuclear Fuel Cycle: ILW Compaction and Cementation Compaction Cementation

Near-surface disposal facilities at ground level. These facilities are on or below the surface where the protective covering is of the order of a few metres thick. Waste containers are placed in constructed vaults and when full the vaults are backfilled. Eventually they will be covered and capped with an impermeable membrane and topsoil. These facilities may incorporate some form of drainage and possibly a gas venting system. Near-surface disposal facilities in caverns below ground level. Unlike near-surface disposal at ground level where the excavations are conducted from the surface, shallow disposal requires underground excavation of caverns but the facility is at a depth of several tens of metres below the Earth's surface and accessed through a drift. Waste Management in the Nuclear Fuel Cycle: LLW Disposal

Waste Management in the Nuclear Fuel Cycle: HLW

Vitrification

Typical Storage Container for Spent Fuel

Waste Management in the Nuclear Fuel Cycle: HLW The Synroc method

Waste Management in the Nuclear Fuel Cycle: HLW Disposal

 Disposal in strong fractured rocks  Disposal in clay  Disposal in natural rock salt  Disposal in outer space  Disposal at a subduction zone  Disposal at sea  Sub seabed disposal  Disposal in ice sheets Waste Management in the Nuclear Fuel Cycle: HLW

The Oklo natural reactor

Decay in radioactivity of high-level waste after recycling one tonne of spent fuel

Reprocessing: the PUREX method PUREX is an acronym standing for Plutonium and Uranium Recovery by EXtraction. Essentially, it is a liquid-liquid extraction ion-exchange method. The irradiated fuel is first dissolved into nitric acid. An organic solvent composed of 30% tributyl phosphate (TBP) in odorless kerosene (or hydrogenated propylene trimer) is used to recover the uranium and plutonium; the fission products remain in the aqueous nitric phase. Once separated from the fission products, further processing allows separation of the heavier plutonium from the uranium.

Reaction in MOX fuel

International organisations and safety standards

Grazie