scorie nucleari adriano duatti laboratorio di medicinanucleare, departimento di scienze c/a e...

Scorie NucleariAdriano Duatti

Laboratorio di MedicinaNucleare, Departimento di Scienze C/A e Radiologiche, Università di Ferrara,

Via L. Borsari, 46, 44100 Ferrara, Italy (email: dta@unife.it)

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

The Nuclear Fuel Cycle

Fuel Production

Uraninite(Pitchblende)

Yellowcake

U3O8 UO2

Uranium fuel

Fuel rods (UO2)

UF6

Uranium fuel

Reaction in standard UO2 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

Fission products

Nuclide T1/2, y Yield ,% E, keV 155Eu 4.76 0.0803 252 58Kr 10.76 0.2180 687

113mCd 14.1 0.0008 316 90Sr 28.9 4.505 2826

137Cs 30.23 6.337 1176 121mSn 43.9 0.00005 390 151Sm 90 0.5314 77

Medium-lived fission products

Nuclide T1/2, My Yield ,% E, keV 99mTc 0.211 6.1385 294 126Sn 0.230 0.1084 4050 79Se 0.295 0.0447 151 93Zr 1.53 5.4575 91

135Cs 2. 3 6.9110 269 107Pd 6.5 1.2499 33

129I 15.7 0.8410 194

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 m3 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: LLWIncineration

Waste Management in the Nuclear Fuel Cycle: ILWCompaction and Cementation

CompactionCementation

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: LLWDisposal

Waste Management in the Nuclear Fuel Cycle: HLW

Waste Management in the Nuclear Fuel Cycle: HLWVitrification

Vitrification

Typical Storage Container for Spent Fuel

Waste Management in the Nuclear Fuel Cycle: HLWThe Synroc method

Waste Management in the Nuclear Fuel Cycle: HLWDisposal

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

Waste Management in the Nuclear Fuel Cycle: HLWThe 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

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