There is only minor uranium prospecting at the moment, since the demand is declining. Additionnally, it doesnt take into account new technology for extracting uranium (from sea water, for example) When demand will increase, propsection will as well, and reserves will "magically" appear out of prospection, same as gas reserves, or "Peak Oil"

https://en.wikipedia.org/wiki/Peak_oil

So 5 years takes into account stockpiles and known sources. Is there any back of the envelope estimate of how much mine-able uranium may be out there?

rebuttal: source and figures?

That might be true with stockpiles of already-mined uranium, but we can definitely mine more uranium.

we can also burn the "waste" we are insanely intent on burying in different reactor designs.