Lower end fitting locknut for nuclear fuel assembly

An apparatus comprising:

• a lower end fitting having a top planar surface, a bottom planar surface and a plurality of counterbores defined therebetween, and at least one lock recess that extends both radially outwardly from a corresponding counterbore and extends inwardly into the lower end fitting from the bottom planar surface,
• end plugs connected with corresponding lower ends of a plurality of guide tubes and having threaded male shafts extending from the lower ends of the guide tubes and passing through openings of the lower end fitting, and
• female lock nuts threaded onto the threaded male shafts of the end plugs, each female lock nut including at least one swaged locking portion that extends radially outwardly into a corresponding lock recess of the lower end fitting to secure the lower end fitting to the lower ends of the guide tubes, wherein each female lock nut is fully disposed in a corresponding counterbore between the top and bottom planar surfaces,
• wherein the at least one lock recess remains visible as viewed from the bottom planar surface of the lower end fitting when each female lock nut is fully disposed in the corresponding counterbore.