Abstract: An elongate metal needle 23 is used to detect blockage in a throughbore in a nuclear fuel pellet 20 or other article. The pellets are fed along a tube 11 having a reject slot 30 and horseshoe magnets 14, 15. 14a, 15a support the needle so that the pellets pass along the tube with the needle in the pellet bores. When a blockage is sensed, feed is interrupted and a switch 41 is operated to energize magnets 35 to rotate the tube 11 so that the defective pellet passes through slot 30 assisted by gravity operated reject element 33. Visual indicators 39, 40 are operated by flap 50, responsive to discharge of satisfactory pellets, to indicate a blockage has occurred.