Wikipedia: Size of BWRs

A modern BWR fuel assembly comprises 74 to 100 fuel rods, and there are up to approximately 800 assemblies in a reactor core, holding up to approximately 140 tons[vague] of uranium. The number of fuel assemblies in a specific reactor is based on considerations of desired reactor power output, reactor core size and reactor power density.

That's 50 thousand to 80 thousand fuel rods, which means each rod is 2 to 3 tons of uranium. The density of uranium dioxide is about 11 tons per cubic metre.

So, in what may be my last act of "advising", I'll advise you to cut the jargon. -- My old PhD advisor, to me, 26/2/11