A method of replacing reactor pressurizer heating element of nuclear and device used in such a process.

A method of replacing heater pressurizer water reactor under pressure and device used in such a method wherein, after removal of the heating element to be replaced, is welded automatically under inert or substantially inert atmosphere, the inner face of the end (23) of the outlet pipe of the heating element of the pressuriser with the inner face of the upper end of a sleeve (27), under an inert atmosphere automatically welds the outer face of the end (23) of said tube with the outer face of the upper end of said sleeve (27) is introduced into the vessel through the sleeve and the corresponding pipe, the new heating elements (6 ") and are welded automatically the outer face of the top end stop means (9 ") of the heating element (6") with the outer face of the lower end of the sleeve.