Due to the neutron flux density the FRM II provides a maximum undisturbed thermal neutron flux density of 8x10¹⁴cm^-2s^-1 at an nominal thermal power of 20MW. Beam tubes are arranged in the area of maximum thermal neutron flux density inside the moderator tank. Beam tubes and neutron guides supply the experiments with neutrons.

The relation between maximum thermal neutron flux density and reactor core nominal thermal power is better than at another neutron sources. Due to this, FRM II provides the high thermal neutron flux density at very low background radiation (gamma radiation, fast neutrons). This is of big advantage for experiments at FRM II.