Nuclear Reactors are now part of our daily need. This book intends to showcase how effectively the power can be calculated in hot channels and provide easy access to important information of reactor functionality. Many safety and design calculation codes are available. These can predict the important core parameters such as reactor power; thermal and fast flux distribution (depending on the type PWR, BWR, RBMK, BREEDER etc.) at an assembly level with high accuracy. Most safety studies concerning reactor cores take into account the local acceptance criteria like the maximal local power...