Device for measuring the flow rate of cooling fluid at the inlet of the core of a water-cooled reactor

Claim 1

A removable device for measuring the flow rate of cooling fluid entering the core of a water-cooled nuclear reactor during tests before putting the reactor into operation, said reactor comprising a pressure-resistant vertical cylindrical vessel having at least one inlet and at least one outlet for cooling fluid and between which the cooling fluid flows in contact with fuel elements forming the reactor core during part of its travel where the fluid moves vertically upwards, a top core plate and a bottom core plate formed with apertures for the flow of said cooling fluid, the fuel elements and a bearing structure being disposed between said core plates and the bearing structure being disposed at the top part of the vessel for securing a cylindrical shroud open at its lower part coaxial with the vessel, disposed inside the vessel and surrounding the full extent of the reactor core, the vessel and the shroud being separated by a space having an annular cross-section and connected to the inlet for the cooling fluid, the cooling fluid outlet communicating with the inner part of the shroud containing the core, said removable device comprising a bearing and securing base adapted to be removably secured to the bottom core plate so as to replace a fuel element, the core being empty of fuel elements during the tests and defining a central aperture for communicating with at least one aperture in the bottom core plate, a vertical cylindrical casing called a measuring chimney secured at its lower end to said base and comprising a diaphragm at its upper end for adjusting the pressure drop in the device, the inner portion of which communicates with the aperture in the base, a bearing structure secured to the interior of said measuring chimney, two bearings disposed along the axis of said chimney and mounted on said bearing structure, a propeller comprising two blades of non-magnetic material and coaxial with the chimney and rotatable in said bearings mounted on said bearing structure, an element made of magnetic material provided on one of said propeller blades, a horizontal axis measuring coil mounted on said chimney at the level of said magnetic element secured to said one propeller blade, said coil being insulated from cooling fluid flowing in said chimney and being connected so as to be supplied with direct current to produce current pulses at the moment when said magnetic element moves in front of said coil when said propeller is rotated by cooling fluid flowing in said chimney, and a frequency-measuring device connected by a cable to said coil.