Modern gaseous diffusion plants typically require 2,400 to 2,500 kilowatt-hours (kW·h), or 8.69 gigajoules, (GJ) of electricity per SWU while gas centrifuge plants require just 50 to 60 kW·h (180220 MJ) of electricity per SWU.
For example, in the enrichment of LEU for use in a light water reactor it is typical for the enriched stream to contain 3.6% 235U (as compared to 0.7% in NU) while the depleted stream contains 0.2% to 0.3% 235U. In order to produce one kilogram of this LEU it would require approximately 8 kilograms of NU and 4.5 SWU if the DU stream was allowed to have 0.3% 235U. On the other hand, if the depleted stream had only 0.2% 235U, then it would require just 6.7 kilograms of NU, but nearly 5.7 SWU of enrichment. Because the amount of NU required and the number of SWUs required during enrichment change in opposite directions, if NU is cheap and enrichment services are more expensive, then the operators will typically choose to allow more 235U to be left in the DU stream whereas if NU is more expensive and enrichment is less so, then they would choose the opposite.
“ In order to produce one kilogram of this LEU it would require approximately 8 kilograms of NU and 4.5 SWU if the DU stream was allowed to have 0.3% 235U. “
Presume gaseous diffusion, and 60 kWh per SWU, then 4.5 SWU costs 270 kWh of electrical energy. Thats 270 MWh (megawatt-hours) per tonne.
So if 25,000 tonnes of NU annually are processed to fuel the USAs civilian reactors, that produces 21,875 tonnes of DU, and 3125 tonnes of LEU. Multiply by the energy cost per tonne of LEU, we get just under 844,000 MWh of energy cost per year. Divide by the number of hours in a year, thats 80 to 96 MWh per hour, to provide an average of about 90,000 megawatts. The energy cost of the enrichment process averages hardly more than one thousandth of the energy produced. Even if the obsolete gaseous diffusion process were used, costing 11,250 MWh per tonne, the enrichment costs only just over 4% of the energy produced.