9.20. In most reactor designs, the power output is limited by the max­imum permissible temperature of the fuel elements, i. e., by the value of Pmax. In some cases, it is possible to increase the power output by decreasing Ртах/Рау. In other words, the power output of the reactor can be increased by a more uniform distribution of the power density. This is sometimes referred to as a “flattening” of the power distribution or of the neutron flux.

9.21. We have seen that the presence of the reflector provides some flux flattening (§3.136). In addition, reduction in the concentration of fissile atoms in fuel that would otherwise have a high neutron flux could provide a flattening effect. Such fuel management schemes, described in Chapter 10, may also provide improved utilization of the available neutrons and decrease the cost of the electricity produced by the reactor plant.