Assuming that PuO2
is stoichiometric, the ratio O/Pu = 2. That's a simple chemical balance. There might be a surplus or deficiency of O depending on how the material is fabricated, e.g., reducing or oxidizing environment. But O/M is usually well controlled and probably on the order of 2 +/- 0.002.
Note that 94-Pu-234 decays by alpha emission to 92-U-234 (also formed from Th-234 following two successive beta decays), but U likes to form UO2
as well, and ThO2
is also likely.
Now if the measured density is greater than 100% theoretical density (of stoichiometric PuO2
), then there is likely a deficiency of O. If the density is less than 100% theoretical, then there is a possibility of an excess of O, or there is some porosity, or the metal is not entirely Pu.