PURPOSE: To prevent failure by projecting plural guide plates for loading spent fuel casks to an outside frame of spacers having an approximately square shape so as to incline from the rear face of said frame toward the inside thereof and providing notched parts having tapers to corner parts.

CONSTITUTION: A spent fuel assembly is loaded in the form of a fuel bundle consisting of many pieces of fuel rods and fuel rod spacers through an upper grating plate into the spent fuel transport cask after a channel box is removed. The guide plates 17A for loading the spent fuel transport casks are projected to the rear faces of the outer frame 11A of the spacers and the notches 19 are provided on the corner parts and, therefore, the guide plates 17A enter the upper grating plate first, then the guide plates 17A play the role of the guide at the time of loading. The interference of the corner parts with the upper grating plate is prevented by the notches 19 in the corner parts and the spacers 10A are passed throughly through the upper grating plate. The failure of the fuel rod spacers is, therefore, obviated.