An experimental plate-type neutron absorber assembly containing 10B dispersed in Type 200 austenitic stainless steel was irradiated in the active lattice of the 10 MW-SM-1 Reactor for 1.2 full power years. The 10B was distributed in a concentration gradient, increasing from 1 wt% in the surface layer to a maximum of 3 wt% 0.024 in. below the surface, to ensure a uniform burnup of 10B atoms in each volume increment through an exposure to thermal neutrons resulting in an average 10B burnup of 20 at.%. Postirradiation evaluation did not reveal any significant dimensional changes or structural damage to the dispersions at this burnup, which is a demonstration that the use of the boron concentration gradient results in at least a fourfold increase in the reactor performance capability of plate-type neutron absorbers containing dispersions of 10B in stainless steel.