> Uranium is far, far energy denser than any fossil fuel, and thus much easier to stockpile
Sure. That doesn't remove stockpiles' inherent disadvantages: finiteness and vulnerability. Relying on uranium stockpiles would immediately put China at a known limit in a war of attrition that wouldn't constrain their adversaries.
A sufficiently large stockpile of uranium gives China time to simply pivot away from depending on imported Uranium (either by building new mines locally or building out solar or such). An equivalent stockpile of oil simply isn't feasible, if only because oil is usually used directly and not via a source-agnostic electrical grid.
I know. I am not saying I got the order of magnitude exactly right, just pointing out beyond a certain threshold the size of the stockpile doesn't matter. I suspect that if a nation state puts its mind to it, stockpiles great enough to last a war are totally possible.
Sure. That doesn't remove stockpiles' inherent disadvantages: finiteness and vulnerability. Relying on uranium stockpiles would immediately put China at a known limit in a war of attrition that wouldn't constrain their adversaries.