The insertion of a control rod depresses the neutron flux in its vicinity and makes the curvature of the flux greater. The gradient of the flux will contrarily increase at a radial distance. Usually, multiple control rods are placed in the core. The control rods will distort the neutron flux around each other and will have an effect on the reactivity worth. The term “shadowing effect” has been used to describe this. The worth of the control rods will be less than the sum of the separate rod worth values or greater than the sum depending on the control rod locations. It is important to determine the shadowing effect of control rods.