Was the bootle neck getting Uranium ore? Or refining it to Uranium Oxide? or enriching it? If it was enriching it then getting more ore or Uranium oxide is nice but it doesn't address the bottleneck. Of course that's why Plutonium was selected as the bomb material for most of the planned bombs. It was easier to make in adequate concentrations. One of the things you are running against here is those of us that frequent these forums have seen some significant and often acrimonious debates over whether or not these things are fact or fiction. Take for example the question of just what was on U-234. Was it just Uranium oxide or was it enriched and if enriched to what level? Or look at the "Grey Wolf" thread(s) for example or any of the German or Japanese atomic bomb threads over on the axis history forum. I know it's not your fault but in the not too distant future I expect to see someone quoteing your book as if it were fact. If some of the bases for the fiction is open to question but is taken as real then it becomes even more problematic. It is unfair but I tend to be a bit more critical of such subjects than I should for that reason. I suspect I'm not the only one.