How much uraniums sits in stockpiles?

From my understanding of this sector, one significant reason for the depressed prices is the amount of stockpiles of uranium that exists. Plenty of the stockpiles are represented by fuel from Cold-War era weapons that are downgraded to suit nuclear reactors in addition to uranium that has been mined and just sits in reserves.

I've been trying to find estimates of how much is out there. I came across this paragraph in an article from WSJ (that incorrectly predicted that the rally in uranium prices wouldn't last) from September:
"Still, some analysts are convinced that the uranium market is strengthening gradually. Macquarie Group Ltd. reckons that an oversupply of almost 12,000 metric tons last year will shrink to 3,200 tons this year." (http://online.wsj.com/articles/rally-in-uranium-prices-is-unlikely-to-last-1410726782)

For background to those that don't know: Macquarie recently bought Deutsche's uranium book, whilst Goldman Sachs is exiting uranium trading.

By oversupply I believe that Macquarie were referring to inventory, not overproduction.

Does anybody out there know if there are any realiable estimates of how much uranium sits in reserves around the world? It's clear that annual uranium production is less than uranium consumed, so to work out how the supply / demand forces will influence the price of U3O8 we need to know how many years of supply sits out there. But I haven't been able to get to the bottom of it.