An improved bottom nozzle of a fuel assembly includes a housing and a modified adapter plate formed by a network of ligaments which extend across the housing and are connected to the side walls of the housing a short distance below its upper peripheral edge so as to define an open region therein. The improved bottom nozzle also includes a debris trap having a structure disposed within the open region of the housing upon the adapter plate and adapted to capture and retain debris carried by collant flowing from openings in the lower core plate of the nuclear reactor to the fuel assembly. The trap structure is composed of a plurality of straps aligned with one another in a crisscross arrangement and defining a plurality of interconnected wall portions which form a multiplicity of small cells each having open opposite ends and a central channel for collant flow through the trap. A plurality of spring-like fingers are punched out of the wall portions and bent to extend into the cell channels toward the downstream end of the trap structure to provide means to capture and retain pieces of debris carried through the channels by flowing coolant. Also, leaf springs are attached to periphery of the structure and engagable with a plurality of recessed shoulders in the housing for releasably locking the trap structure in place in the open region with intersections formed by the straps aligned below the fuel rods of the fuel assembly.