Materials and nuclear power from cradle to grave
The nuclear process chain, the technical system making nuclear power possible, comprises a number of industrial processes, each of which requires the input of ordered materials, such as chemicals and construction materials. All materials entering the nuclear system end up in the biosphere in some form: the mass of the output equals the mass of the input.
A part of the output mass is discharged into the environment as wastes: solids, liquids and gaseous effluents. Another part is recyclable and reenters the economic production system. A third part has become radioactive and has to be removed from the human environment forever. In addition to these three mass flows the nuclear system mobilizes large quantities of raw materials (waste rock, uranium ore) during the uranium mining activities.
How does the specific material consumption, measured from cradle to grave and normalized to gram per delivered kilowatt-hour, of the nuclear energy system compare to the specific material consumption of renewable energy systems, for example wind turbines? For this comparison we choose two reference systems, a nuclear energy system and a wind energy system of the same power capacity, each based on the most advanced currently proven and operational technology.
Not included in the material balances of both systems are:
• materials required for mining and processing of the construction materials
• materials for the distribution grid
• materials for maintenance and refurbishments of the systems.
Here we limit the scope to the nuclear-specific mass flows. Nuclear specific are the need for a mineral energy source (enriched uranium), the need for cooling water and the need for definitive isolation of the radioactive waste from the biosphere.
Specifications of the reference nuclear power system
• PWR, pressurized water reactor, nominal power capacity 1 GWe,
• operational lifetime 24.6 full-power years, (current world average: 22 FPY) corresponding with 30 calender years at average load factor of 0.82
• lifetime elctricity production E = 215.5 billion kWh
• total construction mass 1 035 000 tonnes
• lifetme nuclear fuel consumption natural uranium 5212 tonnes (current world average: about 6000 tonnes) zirconium 1218 tonnes
• assumed uranium resource ore grade 1 kg uranium per tonne rock (0.1% U) (current world average 0.1 Ð 0.05% U) open pit mine, stripping ratio 3, that means 3 tonnes of waste rock to be removed per tonne ore
Materials balance of nuclear power from cradle to grave
Not included in the material balance of nuclear power, in addition to the items cited above, are:
• cooling water of the nuclear power plant during its operational lifetime and during waste processing
• construction materials, chemicals and fresh water needed for interim storage of spent nuclear fuel during at least 30 years; these are also left out of the material balance, due to lack of published operational data
• diesel fuel consumed in mining operations (uranium, bentonite), transport and excavation of the geologic repositories.
A major part of the construction materials, about 1 million tonnes, is basically recyclable, if the reactor has operated nominally. All other materials of the table above are lost forever because of radioactive contamination. The lost materials include the high-grade materials of the reactor and its appendages and the zirconium of the nuclear fuel cladding. The bentonite and sand are used to isolate the radioactive wastes from the biosphere in the depleted mining pit and in the waste repository [more i11, i18]. The amounts of chemicals needed for the extraction of uranium from the earth's crust increase with time due to the declining grades of the still available uranium ores [more i38].
Specifications reference wind power system
• Wind park of 200 wind turbines of 5 MWe each
• nominal power capacity 1 GWe
• operational lifetime: offshore 6.6 full-power years corresponding with 20 calender years at average load factor of 0.33; onshore 5.2 full-power years corresponding with 20 calender years at average load factor of 0.26
• lifetime elctricity production: offshore E = 57.82 billion kWh, onshore E = 45.55 billion kWh
• total construction mass: offshore 600 000 tonnes (1500 tonnes each turbine), onshore 300 000 tonnes (750 tonnes each turbine)
Materials balance of wind power from cradle to grave
These materials are basically recyclable, especially the high-grade materials of the generator.
Figure 13.1 Materials consumption
Consumption of materials by a nuclear energy system and an onshore wind energy system, both at 1 GWe capacity, from cradle to grave. Materials for maintenance and refurbishments of both systems are not included. For details see text. The materials of the wind system are basically recyclable at the end of its operational lifetime. The materials consumed by the nuclear system are lost forever due radioactivity, except 4.6 grams/kWh of construction materials.