That was old spent stuff that Saddam's minions had previously shown to UN inspectors before Saddam threw them out the first time. It was used for legitimate industrial/scientific purposes (at least in the UN's opinion). The stuff had UN seals on it, but the Iraqi scientists abandoned the facility when the war began, and the local looters broke the seals, dumped the spent fuel, and used the contaminated barrels for water.
The IAEA, of course, blamed it all on the U.S.
The Niger yellowcake was another matter entirely.
Okay, thanks for clearing that up.