Question: how many atoms in one mole of uranium?
Answer: Avogadro's constant is the number of particles in a mole of the substance. This number is always the same. For example if we have 2 kg of uranium in a fuel rod we have 2000/235 = 8.51 moles and this contains 8.51x6. 02x1023 = 5.12x1023 atoms and so 5.12x1023 uranium nuclei.