This was actually the first question my shrink asked me <| sep |> an xshape is bad , the rod in the middle does not have any radiation boostraiation goes from each rod up to 4 blocks N S E W if another rod is radiated , it is boosted and does operate more efficient ! you should really look up the thermal and radiation absorbtion rates of materials , radiation is good for fuel efficiency , output efficiency is about how much heat you absorbin between rods you need high heat absorption and low radiation absorption , for the outer layers you only neat heat absorptionheat that radiates to the sidewalls reduces core temperature also increasing fuel efficiency but the heat is lost and will not be converted to energythe lower the casing temperature against the core temperature is the better is your output efficiencybut for your gerneal problem i have no clue