Case Studies of Illicit Procurement Networks

• Off-Shore Agents or Companies
  
• Partial or Complete Control of EstablishedCompanies
  
• Middlemen
  
• Experts

• Banking, Financial Transfers
• Transportation and Shipping

Quick Links to Case Studies

• EMIS Procurement
• Matrix Churchill
• H+H Metalform
• Iraq's Acquisition of Gas Centrifuge Technology
  • Part I
  • Part II
  • Part III
• Schaublin
• SMB
• Karl Otto Brauer
• Banca Nationale de Lavoro

• Ernest Piffl/Team GmbH
• Pakistani Scientists' Nuclear Assistance to Terrorists
  

• Glossary
• Glossary of Key Names
• Link to Urenco

In nature, uranium contains less than 1 percent of the fissile isotope uranium 235 (U-235). A nuclear explosive needs uranium enriched to at least 20 percent U-235. Ideally greater than 90% U-235 is used. In order to increase the percentage of U-235 in relation to the more prevalent U-238 the uranium must be processed, or “enriched.” One technique to enrich uranium uses gas centrifuges.

A gas centrifuge (diagrams below) comprises an evacuated casing containing a cylindrical rotor which rotates at high speed in an almost friction-free environment. The uranium is fed into the rotor as gaseous uranium hexafluoride (UF6)² which also rotates.

The centrifugal forces push the heavier uranium 238 (U-238) closer to the wall of the rotor than the lighter U-235. The gas closer to the wall becomes depleted in U-235 whereas the gas nearer the rotor axis is enriched in U-235.

The arrows in the first illustration depict the gas flowing within the rotor. The gas flow can be produced by a temperature gradient over the length of the centrifuge. UF6 depleted in U-235 flows upwards adjacent to the rotor wall, while UF6 enriched in U-235 flows downwards close to the axis. The two gas streams are removed through small scooped pipes, called "scoops."

The enrichment effect of a single centrifuge is small, so they are linked together by pipes into cascades. Passing through the successive centrifuges of a cascade, the U-235 is gradually enriched to the required level. For civil applications, natural uranium containing about 0.7 percent U-235 is enriched to about 3-5 percent U-235 and the depleted uranium contains typically about 0.2-0.3 percent U-235. For military applications, highly enriched uranium (HEU) containing greater than 20 percent U-235 is usually produced.

Once started, a modern centrifuge runs for more than 10 years with no maintenance. An advantage of the centrifuge process is its low energy consumption.

¹Source: www.urenco.com

² Uranium hexafluoride (UF6) is a solid white material at room temperature, which evaporates into gaseous material at elevated temperatures.

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