Patent Number: 039502201
Section: description

DESCRIPTION OF THE PREFERRED EMBODIMENTS The drawing illustrates a portion of the pressure vessel 6 in a boiling water reactor. The vessel 6 (e.g., the bottom wall of the vessel) has an opening 1 which is provided therein for the purpose of installing a novel internal primary recirculating pump P. In addition, the opening 1 simultaneously serves for admission of feed water by way of an annular chamber 2 in the body 9 of the pump P. The chamber 2 is closely adjacent to the rotor 5 of the pump P. Prior to entering the pressure vessel 6, the stream of feed water flows from the annular chamber 2 between the blades of the wheel 4 of a single stage turbine which is mounted on the pump shaft 3, preferably at the suction side of the rotor 5. The shaft 3 is driven by an electric motor 7 which is mounted in the body 9 of the pump P. In the illustrated embodiment, the turbine wheel 4 serves as a carrier for the pump rotor 5. When the supply of current to the motor 7 is interrupted due to an unforeseen failure, the turbine wheel 4 prevents rapid deceleration of the shaft 3 to zero speed to thus insure that the cooling of the boiling water reactor proceeds for a sufficient interval of time. A bypass channel 8 between the pressure chambers of the turbine and pump rotor is preferably formed as a slightly enlarged sealing gap and serves to prevent an overheating of the turbine under certain operating conditions. If desired, the illustrated single-stage turbine can be replaced with a multi-stage turbine. The turbine replaces costly, bulky and complex motor generator sets which are used in conventional boiling water reactors to insure the supply of additional energy in the event of current failure. The turbine insures that the circulation of feed water in the pressure vessel 6 continues even if the motor 7 is disconnected from the energy source. Moreover, and as long as the quantity of feed water which is being admitted to the chamber 2 remains substantially unchanged, the turbine including the wheel 4 (or a multi-stage turbine) is capable of insuring that the pump P remains in operation at a reduced RPM. The cold feed water which is admitted by way of the chamber 2 is caused to mix with hot reactor water upstream of the pump rotor 5. This produces a desirable supercooling affect and a substantial NPSH gain. The motor 7 may be a normal electric motor or a wet or canned motor. Without further analysis, the foregoing will so fully reveal the gist of the present invention that others can, by applying current knowledge, readily adapt it for various applications without omitting features which fairly constitute essential characteristics of the generic and specific aspects of my contribution to the art and, therefore, such adaptations should and are intended to be comprehended within the meaning and range of equivalence of the claims.