Iran defies calls for freeze on nuclear research, restarts program-(50,000 centrifuges to be built)

mercury news ^ | Jan. 10, 2006 | Jonathan S. Landay

[Flavius]

WASHINGTON - Iran on Tuesday resumed nuclear research that will include enriching small amounts of uranium, a process used to make nuclear weapons, defying calls by the United States, Europe, Russia and China to maintain a 26-month freeze.

Iran's move raised the likelihood that the International Atomic Energy Agency will report Iran to the U.N. Security Council for violating the Non-Proliferation Treaty, the keystone of the global system to halt the spread of nuclear weapons.

[Flavius]

centrifuges

[Flavius]

ENRICHMENT

A number of enrichment processes have been demonstrated in the laboratory but only two, the gaseous diffusion process and the centrifuge process, are operating on a commercial scale. In both of these, UF6 gas is used as the feed material. Molecules of UF6 with U-235 atoms are about one percent lighter than the rest, and this difference in mass is the basis of both processes.

Large commercial enrichment plants are in operation in France, Germany, Netherlands, UK, USA, and Russia, with smaller plants elsewhere.

click to enlarge
The large Tricastin enrichment plant in France (beyond cooling towers)
The four nuclear reactors in the foreground provide over 3000 MWe power for it.

The capacity of enrichment plants is measured in terms of 'separative work units' or SWU. The SWU is a complex unit which is a function of the amount of uranium processed and the degree to which it is enriched (ie the extent of increase in the concen-tration of the U-235 isotope relative to the remainder) and the level of depletion of the remainder. The unit is strictly: Kilogram Separative Work Unit, and it measures the quantity of separat-ive work performed to enrich a given amount of uranium a certain amount. It is thus indicative of energy used in enrichment when feed and product quantities are expressed in kilograms. The unit 'tonnes SWU' is also used.

For instance, to produce one kilogram of uranium enriched to 3% U-235 requires 3.8 SWU if the plant is operated at a tails assay 0.25%, or 5.0 SWU if the tails assay is 0.15% (thereby requiring only 5.1 kg instead of 6.0 kg of natural U feed).

About 100-120,000 SWU is required to enrich the annual fuel loading for a typical 1000 MWe light water reactor. Enrichment costs are substantially related to electrical energy used. The gaseous diffusion process consumes about 2500 kWh (9000 MJ) per SWU, while modern gas centrifuge plants require only about 50 kWh (180 MJ) per SWU.

Enrichment accounts for almost half of the cost of nuclear fuel and about 5% of the total cost of the electricity generated. It can also account for the main greenhouse gas impact from the nuclear fuel cycle if the electricity used for enrichment is generated from coal. However, it still only amounts to 0.1% of the carbon dioxide from equivalent coal-fired electricity generation if modern gas centrifuge plants are used, or up to 3% in a worst case situation.

Early processes

[Ernest_at_the_Beach]

Thanks for posting this.