Hi guys, I have a question that I can't seem to wrap my head around. This is the question: A power reactor is fueled with slightly enriched uranium. At the end of core life (i.e., when it is about to be batch refueled), 30% of the power comes from the fissioning of the built up Pu-239. Calculate the effective value of β at the beginning and end of life; determine the percent increase or decrease. I don't really know how to go about solving it but I assumed that the total number of neutrons born in fission is equal to those born from Uranium (U-233 and U-238) plus those born from Plutonium (Pu-239). So my fraction at the beginning is equal to β(Pu-239) + β(U-233) + β(U-235) = 0.0021 + 0.0026 + 0.0065. But the how does power relate to how I would calculate β anyway and how would I use that to find my fraction at the end of life?