The Union of Concerned Scientists summarises water issues associated with uranium fuel fabrication [1]:
Processing uranium requires mining, milling, enrichment, and fuel fabrication, all of which use significant quantities of water.
- Mining − Uranium mining consumes one to six gallons (3.8−22.7 litres) of water per million Btus of thermal energy output, depending on the mining method. Mining uranium also produces waste that can contaminate local water sources, and which can be especially dangerous given the radioactivity of some of the materials involved. (A Btu or British Thermal Unit is a measure of energy content, usually used to describe the energy content of fuels. One kilowatt hour is the rough equivalent of 3,400 Btus.)
- Processing − Uranium processing consumes seven to eight gallons (26.5−30.3 l) of water for every million Btus of thermal output.
- Milling − The milling process uses a mix of liquid chemicals to increase the fuel's uranium content; milling leaves behind uranium-depleted ore that must be placed in settling ponds to evaporate the milling liquids.
- Enrichment − The next step, enriching the gaseous uranium to make it more effective as a fuel accounts for about half of the water consumed in uranium processing. The conventional enrichment method in the US is gas diffusion, which uses significantly more water than the gas centrifuge approach popular in Europe.
- Fuel Fabrication − Fabrication involves bundling the enriched uranium into fuel rods in preparation for the nuclear reactor.
At the 'back end' of the nuclear fuel cycle, the large commercial reprocessing plants in France and the UK are major sources of radioactive marine pollution. Cogema's reprocessing plant at La Hague in France, and the Sellafield reprocessing plant in the UK, are the largest sources of radioactive pollution in the European environment.[2]
References:
[1] Union of Concerned Scientists, 'Water for Nuclear', www.ucsusa.org/clean_energy/our-energy-choices/energy-and-water-use/wate...
[2] WISE-Paris, Study on Sellafield and La Hague commissioned by STOA, www.wise-paris.org/english/stoa_en.html
More information:
Friends of the Earth, Australia, 'Impacts of Nuclear Power and Uranium Mining on Water Resources', www.foe.org.au/anti-nuclear/issues/oz/water-nuclear