Abstract: The adapter (12) and the mechanism housing (13) are made in a single piece, in the form of an integrated housing that is attached by means of the adapter tube (12) in a penetration opening (9a, 9b) of the vessel head (10). The tubular sheath (14) comprises a threaded part (14a) that is screwed into a tapped part (13c) at the end of the integrated housing (15), in a perfectly coaxial disposition. A sealing weld (18) is made between two respective sealing lips of the integrated housing (15) and of the tubular sheath (14). The weld joint (18) is made by melting a filler metal between two joining end parts of the sealing lips by an automatic orbital welding method. The step for mounting and welding the tubular sheath (14) onto the integrated housing (15) may be carried out on the nuclear reactor site with a faultless production of the welded joint (18).

Abstract: A thermal protection shield for a rotating shaft of a primary coolant pump shaft of a nuclear power station includes, in the thermal transition region between the hot fluid and the cold fluid, a ring of nickel alloy shrunk onto the shaft. An external ring of austenitic stainless steel is shrunk at each of its ends onto the ring of nickel alloy. Between the two shrunk-on ends, a cylindrical cavity forms a clearance with the external surface of the nickel alloy ring.

Abstract: The invention relates to a method of repairing the labyrinth seal of a diffuser in a primary pump, the diffuser being of the type comprising a peripheral skirt and a circular end wall having an orifice provided with the labyrinth seal. The method consists in making a bore in the circular end wall having a diameter greater than that of the orifice, in reducing the thickness of the remaining portion of the end wall, in forming a chamfer on the edge of the bore, in positioning a replacement part in said bore, the replacement part including a central orifice and a chamfer on its own peripheral edge, in making a bead of welding between the chamfers, and in making a new labyrinth seal in the central orifice of the replacement part.

Abstract: There is provided a nuclear power station primary pump of the type comprising a drive shaft for rotating a wheel, a heat exchanger, a thermal barrier cover comprising a peripheral skirt provided at its base with a circular end wall, and a diffuser comprising a peripheral skirt provided at its base with a rim. The circular end wall co-operates with the base of the heat exchanger to define a bottom chamber for cold water and includes a central bore provided with a succession of circumferential and superposed rings forming a lip seal of the labyrinth type, and a space is formed between the thermal barrier cover and the diffuser to maintain stagnant cooling fluid.

Abstract: Thermal protection shield for a rotating shaft The invention relates to a thermal protection shield for a rotating shaft, characterized in that it comprises, in the thermal transition region between the hot fluid and the cold fluid, a ring (11) of nickel alloy shrunk onto said shaft (1).

Abstract: The invention provides a nuclear power station primary pump of the type comprising a drive shaft for rotating a wheel, a heat exchanger, a thermal barrier cover comprising a peripheral skirt provided at its base with a circular end wall, and a diffuser comprising a peripheral skirt provided at its base with a rim. The circular end wall co-operates with the base of the heat exchanger to define a bottom chamber for cold water and includes a central bore provided with a succession of circumferential and superposed rings forming a lip seal of the labyrinth type, and a space is formed between the thermal barrier cover and the diffuser to maintain stagnant cooling fluid.

Abstract: The invention relates to a method of repairing the labyrinth seal of a diffuser in a primary pump, the diffuser being of the type comprising a peripheral skirt and a circular end wall having an orifice provided with the labyrinth seal. The method consists in making a bore in the circular end wall having a diameter greater than that of the orifice, in reducing the thickness of the remaining portion of the end wall, in forming a chamfer on the edge of the bore, in positioning a replacement part in said bore, the replacement part including a central orifice and a chamfer on its own peripheral edge, in making a bead of welding between the chamfers, and in making a new labyrinth seal in the central orifice of the replacement part.