Process and device for the electron beam welding of two parts of a component of large size and in particular of a steam generator of a pressurized water nuclear reactor

A device for the electron beam welding of two component parts of a component of large size interconnected along a joint region which is of substantially annular shape and opens onto an outer cylindrical surface of said component, said device comprising, in combination:

• (a) an enclosure having a first part including means for fixing said enclosure in a fluid-tight manner around said outer cylindrical surface of said component and a second part mounted on said first part in a fluid-tight manner and movable in rotation around an axis of rotation with respect to said first part;
• (b) an electron gun mounted on said second part of said enclosure in such a manner as to direct an electron beam toward an interior side of said enclosure;
• (c) means for moving said first and said second parts of said enclosure in rotation relatively to each other around said axis of rotation;
• (d) wherein said first part of said enclosure comprises two units, each unit comprising a ring defining radially extending recesses, and a plurality of annular sectors having said axis of rotation as a common axis guided in radial directions in said recesses in said ring, and means for radially displacing each of said sectors selectively in a direction toward and away from said outer cylindrical surface of said component, and an inflatable annular sealing element engaged in an inner peripheral part of said annular sectors.