This would be a nuclear item that caused all adjecent cells to generate a set amount of energy more each reactor tick say 5 eu/t, it would not cause adjecent cells any extra heat build up, however it would give 5 heat at reactor hull while reactor is in use. ( secound fission rod would give 10 heat , 3 would give 15 , 4 th 20 ,,,)
crafting recipe would of coure be HAYO-ishly expencive :
DHD D: diamond H : heat dispencer
URU U= uranium R= reactor plating
DHD