By Rob Watson
BBC, Oak Ridge
It is one of the best protected and most secretive installations in the US.
The Oak Ridge centre made the uranium for the bomb of 1945
It is outside the town of Oak Ridge, in an attractive valley amid the green hills of eastern Tennessee.
The facility itself is known simply as Y12.
I was one of a planeload of journalists flown from Washington by the White House to visit Y12.
The purpose was to show us material from Libya's nuclear weapons programme sent to the US for evaluation and destruction.
Security is intense - and it is hardly surprising.
This is where the uranium for America's nuclear arsenal is processed - and where they made the uranium for the bomb that destroyed Hiroshima in 1945.
As you enter the complex there's a sign that says: "Think Security, Live Security".
And then there was a verbal warning. An official climbed on our bus to tell us we could not film or record anything other than at the event location.
The event location turned out to be decidedly bizarre - a large white marquee tent had been set up in the middle of a parking lot ringed closely by heavily armed guards.
Inside the tent were some 48 crates, which contained material sent by the Libyans, we were told.
Most of the crates were sealed, but 12 tubes were on display - which, we were told, were centrifuges used for making weapons grade uranium.
Our tour guide was the US Secretary of Energy Spencer Abraham, who said what we were seeing only represented a fraction of the 50,000 pounds of equipment the Libyans had sent. Another 500 tons is on the way in the next day or so.
The rest of the material was classified, he said.
The centrifuges themselves were nothing special to look out. To the untrained eye they look just like the piping you might find in any industrial facility.
But Mr Abraham insisted Libya had all the components needed to make a nuclear weapon.
None of the various officials could tell us how far away Libya was from making such a weapon.
Libya revealed the extent of its nuclear programme late last year
Interestingly, one official said he believed Libya was closer to making one than Iraq was this time last year.
We were also treated to detailed explanations of who was behind Libya's nuclear programme - and how it came to be abandoned.
One senior official said almost all of Libya's nuclear know-how had come from the network run by the top nuclear scientist AQ Khan.
It was lucrative work - the official said the Libyans paid the network some $100m for its services.
The US claims the programme was abandoned for two main reasons.
Firstly, US and British intelligence agencies found out about it - and even intercepted a boatload of material.
Secondly, Colonel Muammar Gaddafi had seen the build up of US-led forces in the Persian Gulf - and was worried he might be next.
The Libyans were the subject of much praise for what was repeatedly described as their active co-operation in dismantling their weapons programmes since Colonel Gaddafi's decision to abandon them last December.
Flying journalists to Oak Ridge has been dismissed by many as a propaganda and publicity stunt in a week in which the Bush administration is marking - and defending - the start of the war in Iraq.
Maybe. But officials here insist the Libyan disarmament is still on a remarkable scale - and it is an event that few would have predicted before last year's march to war.