Hello Greg, radiochemistry student here. If you don't mind we can spent some time improving nuclear science aspect of your mod. If you want to maintain Gregtech as scientific mod it's good to be scientifically correct wherever it is possible, but, of course without introducing overcomplicated and harmful to mechanics things.
So i would like to make first suggestions:
Rename Pu-244 to Pu-238. It is Pu-238 but not Pu-244 because of it's low half-life is hot glowing red and can be used in RTG fuel (it was used in Curiosity and Voyager-1,2 projects for example). Pu-238 the very same isotope of Pu that is contained in spent nuclear fuel and it can be separated from fuel rods just like in ic2_exp. So you don't have to change any crafting recipes.
Rename Pu-241 to Pu-239. Pu-239 is the isotope that really can be separated from Pu-238 (You already have this recipe in centrifuge: Pu-244 ---> Pu-241 + U-238, to be correct you just need to rename two Pu isotopes). Pu-239 is less useful in nuclear science and less radioactive, like you in-game Pu-241, so it will be nice to rename Pu-241 to Pu-239.