Uranium - when do you get it?

[Hasdrubal]

I've been digging through the archives to find an answer to an old question of mine. But couldn't find one. So:

What gives a city the ability to build uranium caravans?

This commodity is supplied so seldomly that I've sometimes thought it could be a bug. I guess it may have something to do with any of the nuclear techs/units/plants. But none of my testing suggested a connection with any of those. Can anyone help me? Or for that matter, tell me what affects the commodity supply of cities in general?

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Ceterum censeo Romanem esse delendam.

[SCG]

if i had a guess, it would be once a civ has nuclear fision, it is a possible trade commodity. After that, my guess would be that it is a weighted probability (with small weight) that it is one of the three your city can produce. I've seen it listed in supply and demand before, but I tend to slow science down before we get nuclear techs, so naturally I haven't seen it too often.

[Carolus Rex]

SCG is right, discovering Nuclear Fission makes uranium available as a tradable commodity.

Carolus

[Hasdrubal]

My word, those replies came fast!
Thanks, both of you.

So, after NF is discovered, is there any way in which you can have an influence on which cities supply uranium? Or is it all just a matter of a weighted probability? And the other commodities, are these tied in with advances as well? All I know is, that the available comm's shift to below and to the right as the game progresses. How does the AI decide which three comm's a city supplies?


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Ceterum censeo Romanem esse delendam.

[Carolus Rex]

Oil appears with Industrialization.

I (gladly!) leave the rest of your questions to the trade gurus.

Carolus

[Case]

From my experiances it seems that the more trade you conduct, the greater the likelyhood of Uranium being supplied by one of your cities is.