These profiles are then analyzed by software to measure the fuel rod and determine whether it is acceptable or not.

Fig. 1 shows a profile of gamma rays emitted from the fuel pellets, collected at fixed intervals along the length of the fuel rod. These represent the amount of fissile element present (²³⁵U for UOX scanners and ²³⁹Pu for MOX scanners).

It is often convenient to incorporate additional measurements along with the gamma measurements taken along the length of the fuel rod Densitometer, Passive scanners might add Gadolinium or other neutron poison. Active scanners might adde Delaye Neutron measurements on Active scanners.

Rod Scanner is a more generic term for gamma scanner that performs these other measurements, in addition to measuring the gamma rays emitted by the fissile element in the fuel rods.

Fig 2 is a plot of gamma ray transmission through the fuel rod along its length. This is often called a Densitometer plot.