Mark Hibbs reveals that Pakistan’s Khan Research Laboratories (KRL) hid orders for prohibited centrifuge components within larger “junk” orders, in hopes of diguising the sensitive item or overhwhelming export control authorities:

After the late 1970s, when intelligence agencies in the Urenco countries—Germany, the Netherlands, and the U.K.—confirmed that Pakistani scientist Abdul Qadeer Khan had been trying to supply Pakistan’s fledgling uranium enrichment program by contacting firms used by Urenco in outsourcing engineering services and purchasing equipment, members of the Nuclear Suppliers Group (NSG) began identifying procurement channels and equipment sought by the Khan Research Laboratories (KRL) and affiliated procurement organizations. Those organizations then “resorted more and more to ordering large amounts of junk to hide the stuff they were really trying to get,” one government analyst said last month.

In some cases, officials said, KRL began by ordering from foreign suppliers a small number of items it needed for centrifuge-building together with similar, but not identical, items. That tactic hid the sensitive goods and established a record of credibility with customs agencies in countries where the goods were shipped. “Once the initial shipments got through customs, KRL would then just order the items they wanted,” one official said.

Hibbs reports that these techniques were used to acquire ball bearings and tubes for centrifuges. In the latter case, Khan ordered a number of useless lengths of tubing:

Intelligence documents elaborate that in some cases Khan specified to selected German and Dutch firms a tube length of 500 millimeters. When ordering the tubing, however, Khan requested that suppliers also provide tubes cut to a variety of lengths in “multiples of 60 millimeters” longer and shorter than 500 mm, in addition to the 500-mm tubes. In other cases, tube lengths of 420, 480, 500, and 540 mm were specified by Khan.

According to Western officials, there was no apparent use in Pakistan’s centrifuge program for tubes slightly longer or shorter than 500 mm. No effort was made by Pakistan at this time, officials said, to experiment with the rotor tube length.

See: Mark Hibbs, “KRL hid purchase of sensitive goods in orders for ‘junk,’ records say” Nuclear Fuels 30:24, November 21, 2005, 7.