The last major remnant of Saddam Hussein’s nuclear program – a huge stockpile of concentrated natural uranium – reached a Canadian port Saturday to complete a secret U.S. operation that included a two-week airlift from Baghdad and a ship voyage crossing two oceans.

The removal of 550 metric tons of “yellowcake” – the seed material for higher-grade nuclear enrichment – was a significant step toward closing the books on Saddam’s nuclear legacy. It also brought relief to U.S. and Iraqi authorities who had worried the cache would reach insurgents or smugglers crossing to Iran to aid its nuclear ambitions.

What’s now left is the final and complicated push to clean up the remaining radioactive debris at the former Tuwaitha nuclear complex about 12 miles south of Baghdad – using teams that include Iraqi experts recently trained in the Chernobyl fallout zone in Ukraine.

“Everyone is very happy to have this safely out of Iraq,” said a senior U.S. official who outlined the nearly three-month operation to The Associated Press. The official spoke on condition of anonymity because of the sensitivity of the subject.

While yellowcake alone is not considered potent enough for a so-called “dirty bomb” – a conventional explosive that disperses radioactive material – it could stir widespread panic if incorporated in a blast. Yellowcake also can be enriched for use in reactors and, at higher levels, nuclear weapons using sophisticated equipment.

The Iraqi government sold the yellowcake to a Canadian uranium producer, Cameco Corp., in a transaction the official described as worth “tens of millions of dollars.” A Cameco spokesman, Lyle Krahn, declined to discuss the price, but said the yellowcake will be processed at facilities in Ontario for use in energy-producing reactors.

“We are pleased … that we have taken (the yellowcake) from a volatile region into a stable area to produce clean electricity,” he said.

The deal culminated more than a year of intense diplomatic and military initiatives – kept hushed in fear of ambushes or attacks once the convoys were under way: first carrying 3,500 barrels by road to Baghdad, then on 37 military flights to the Indian Ocean atoll of Diego Garcia and finally aboard a U.S.-flagged ship for a 8,500-mile trip to Montreal.

And, in a symbolic way, the mission linked the current attempts to stabilize Iraq with some of the high-profile claims about Saddam’s weapons capabilities in the buildup to the 2003 invasion.

Accusations that Saddam had tried to purchase more yellowcake from the African nation of Niger – and an article by a former U.S. ambassador refuting the claims – led to a wide-ranging probe into Washington leaks that reached high into the Bush administration.