Nuclear steam generator wrapper closure assembly and method of installing same

A nuclear steam generator, comprising:

• a shell having a hole;
• a plurality of tubes forming a tube bundle and disposed within the shell;
• a wrapper, having an access hole, encircling the tube bundle and forming an annulus between the shell and the wrapper;
• a cover positioned on the hole of the shell;
• a plate, attached to the wrapper, having a bore therethrough and a first mating connection, the first mating connection having at least one aperture;
• a plug having a first end and a second end, the first end of the plug having a second mating connection for engagement with the first mating connection of the plate to prevent entry of said plug through the access hole and into the steam generator, the second mating connection having at least one aperture which aligns with the aperture through the first mating connection;
• a sleeve having a first end, a second end, and a bore therethrough, the first end of the sleeve being positioned adjacent the first end of the plug when the sleeve is disposed on the plug, the first end of the sleeve having at least one aperture which aligns with the apertures in the first and second mating connections;
• and
• a pin positioned in the apertures of the sleeve, the first mating connection, and the second mating connection.

A method for plugging an access hole in a nuclear steam generator, having a shell, a wrapper, and an annulus positioned between the shell and the wrapper, comprising the steps of:

• attaching a plate, having a first mating connection and at least one aperture, to the wrapper of the steam generator;
• positioning a plug, having a second mating connection and at least one aperture, within a bore of the plate;
• rotating the plug approximately 90.degree. for engaging the first mating connection of the plate with the second mating connection of the plug and for aligning the aperture of the plug with the aperture of the plate;
• positioning a sleeve, having a bore therethrough and at least one aperture, on the plug;
• aligning the aperture of the sleeve with the apertures of the plate and the plug;
• and
• installing a pin in the aperture of the plate, the aperture of the plug, and the aperture of the sleeve when the apertures are aligned.