AbstractA method of studying the burnup of high-cross-section materials in nuclear reactor control rods by neutron radiography is described. The technique has been applied to the examination of the burnup pattern of a CP-5 reactor control rod and has been found to provide a detailed picture of the burnup pattern, showing a very sharp transition region. The radiographic study has been made by a comparison method in which the neutron transmission of the irradiated cadmium control material has been compared to that of normal cadmium. In the regions in which the cadmium control material has been highly depleted in Cd113, the equivalent normal cadmium thickness comparison can be made to an estimated accuracy of 0.0006 inch.