Abstract: A method and apparatus for positioning stud affecting apparatus comprising: sequentially positioning a plurality of flange cover sectors about the flange of a nuclear pressure vessel; rotating each flange cover sector until the entire flange is covered by said flange cover sectors; moving a caddy containing stud affecting tools including stud tensioners and stud drive tools into a position adjacent a point on the flange of the nuclear reactor pressure vessel; moving apparatus sector vessels containing stud affecting apparatus to a point on the flange of the nuclear pressure vessel and positioning them on a specific flange cover sector; rotating all flange cover sectors to bring another flange cover sector into registration with the caddy; sequentially moving the apparatus sectors onto each flange cover sector by rotating the flange cover sectors; and actuating the stud affecting tools to perform the appropriate function to tension or untension the studs and/or to remove and/or to insert studs into the pressur