[en] The explosive plugging techniques developed in the Department of Mechanical and Industrial Engineering of the Queen's University of Belfast for the reheater and superheater of the PFR reactor and for the reheater of the AGR type reactor are described. For the PFR a point charge system was used which causes a spherical expansion of the plug, which gives two zones of welding. Using a parallel stand-off welding set up, it proved difficult or impossible to avoid a crevise. Consequently, a rim charge set up was developed which gives a circular ring expansion of the plug with two zones of welding. The problem is also considered of the distortion of holes adjoining the hole to which a plug is welded. Bunging of adjoining holes in order to reduce the distortion was also investigated. The described equipment is shown in drawings