Patent Number: 044951388
Section: summary

SUMMARY OF THE INVENTION The invention relates to a junction device between the delivery duct of a primary pump and a duct joined to the core support of a liquid metal cooled fast neutron nuclear reactor. BACKGROUND OF THE INVENTION In a liquid metal cooled fast neutron nuclear reactor, the liquid metal constitutes the primary fluid permitting the cooling of the fuel element assemblies which give off heat and which form the core of the reactor. The heat from the core is taken off by the liquid metal, generally liquid sodium, which is pumped to the bottom of the core by the primary pumps, which may be immersed in the liquid sodium filling the reactor vessel in the case of an integrated nuclear reactor, or be disposed outside the vessel in the case of a loop type nuclear reactor. The liquid sodium heated by the reactor core enters heat exchangers permitting the heating of a second liquid metal constituting the secondary fluid, which in turn is used to produce steam in the steam generators. On leaving the heat exchangers, the cooled primary fluid enters a zone of the vessel where, with the aid of the primary pumps, it is re-injected at the base of the reactor core. The sodium cooled in the heat exchangers, i.e., cold sodium, is nevertheless at a temperature higher than 300.degree., so that the primary pumps undergo expansions when the nuclear reactor is in operation. Furthermore, the temperature of the primary fluid is not constant in the course of the operation of the reactor, and consequently the expansion of the different parts of the pump is variable. In addition, the pumps and their accessories undergo vibrations, which are in particular due to the circulation of the liquid sodium at high speed. In nuclear reactors of the integrated type, and in particular, in which the primary pumps inject the liquid metal into ducts joined to the core support, it is necessary to assure continuity of circulation of this liquid sodium between the pump and the duct joined to the support, and at the same time to permit displacements of the pump relative to the core support or bed on which the fuel element assemblies rest and which enables them to be supplied with sodium. In order to carry out these functions, use is generally made of a connecting sleeve having its ends fixed on the pump delivery duct and on the bed respectively, in a non-rigid manner, and leading into the duct joined to the bed. A cylindrical sleeve of this kind nevertheless does not enable the speed of flow of the liquid metal to be controlled before it is injected into the duct joined to the bed. Moreover, in order to permit transverse displacements relative to the flow, it is necessary to provide a universal joint arrangement for the entire pump, thereby complicating the construction and the fastening of the latter. Finally, it is not possible to mount the pump sufficiently flexibly to absorb the displacements and at the same time sufficiently rigidly and with sufficient mechanical strength to withstand the various stresses (particularly earthquakes). OBJECT OF THE INVENTION An object of the invention is therefore a junction device between the delivery duct of a primary pump and a duct fastened to the core support of a liquid metal cooled fast neutron nuclear reactor, in which the liquid metal constituting the primary fluid of the reactor is pumped to the base of the core by primary pumps which inject the liquid metal into ducts joined to the core support for the purpose of cooling the core, this junction device permitting adequate displacements of the pump relative to the core support during the operation of the reactor while assuring a stable junction and withstanding mechanical stresses, particularly vibrations, and effecting a degree of regulation of the speed of the liquid metal before its injection into the duct joined to the core support. To this end, the junction device according to the invention comprises: a sleeve of frusto-conical shape disposed as an extension of the pump deliver duct and having its smaller base situated near the outlet of the delivery duct and its larger base near the inlet of the duct joined to the core support; PA1 a connecting member joined to the sleeve at its smaller base and symmetrical in revolution around the axis of the sleeve, this member carrying in its central portion, near the axis of symmetry, the movable portion of an articulated connection means whose fixed portion is carried by the pump, thus permitting at one and the same time lateral displacements and the retention of the sleeve on the pump duct despite the axial force exerted thereon, while the peripheral portion of the connecting member, which has a diameter larger than the diameter of the smaller base of the sleeve, has a spherical surface, symmetrical around the axis of the sleeve, which is complementary to a corresponding surface machined on the end of the pump delivery duct, fluid-tightness between these two surfaces disposed against one another being achieved with the aid of a labyrinth seal, while the pressure of the liquid metal delivered by the pump, applied to the portion of the connecting member which lies between its peripheral portion and its portion fixed to the sleeve, makes it possible to exert an axially directed force on the sleeve; PA1 a sealing device inserted between the outlet end of the sleeve and the duct joined to the core support, the end of this device on which the outlet end of the sleeve is engaged being of a different diameter from that of the end of the sleeve; PA1 an elastic means inserted between the end of the sleeve and a bearing member joined to the core support, this elastic means extending over the entire periphery of the sleeve for the lateral support of the sleeve, the outlet end of which can move freely in the axial direction relative to the duct joined to the core support.