How much Uranium is there in the Earth's Crust?
According to wikipedia, there are around 5.5 million tonnes of uranium in ore deposits that are commercially viable at current prices, and perhaps 35 million tonnes that are potentially viable if prices increase.

Also according to wikipedia, the Earth's crust (to 25 km depth) contains an estimated 10^14 tonnes (100 trillion tonnes), while the oceans may contain 10^10 tonnes (10 billion tonnes). This presumably includes the ore figures stated above.

The previous link states that "The decay of uranium, thorium, and potassium-40 in the Earth's mantle is thought to be the main source of heat", however no estimate is given for quantities. Allègre, Lewin and Dupré (1988) state that "The concentration of U in the primordial mantle (bulk Earth) has been determined to be ~21±1 ppb". Back of the envelope calculations would then give us that the mantle is 84% of the Earth by volume (probably slightly less than that by mass?), and the mass of the earth is 6*10^21 tonnes, which would give us, very approximately, 0.84 * (6*10^21) * (2.1*10^-8) ~= 10^14 tonnes, or roughly the same as is in the Earth's crust.


Allègre, C.J., Lewin, E. &amp; Dupré, B., 1988. A coherent crust-mantle model for the uranium-thorium-lead isotopic system. 
Chemical Geology, 70(3), pp.211–234.