Patent Number: 055815863
Section: description

DESCRIPTION OF THE PREFERRED EMBODIMENTS A first embodiment of this invention will now be described with reference to the drawings. Structural items which are the same as in the prior art described above are given the same reference numerals and further detailed description is omitted. As shown by the block diagram of FIG. 2, the 205 control rod drive mechanisms 1 that drive the 205 control rods, not shown, are combined in groups of four mechanisms apiece, a single inverter power source 20 being provided for each group of four control rod drive mechanisms 1. In more detail, the arrangement is constituted by 52 control rod changeover devices 22 that select the control rod drive mechanisms 1 to be driven, from the 205 control rod drive mechanisms 1, coupled to the 205 control rods, not shown; 52 inverter power sources 20 constituting drive power sources of the electric motors in control rod drive mechanisms 1; and 52 inverter controllers 24 that control the inverter power sources 20; as well as a control unit 26 and man-machine device 28 which serves as an interface with a human operator. Each inverter power source 20 is coupled to receive power from a conventional plant power source or a standby power source. Also, the current control rod position is input from each control rod drive mechanism 1 to control unit 26 as a control rod position signal S1, and drive information S2 is output from man-machine device 28. Furthermore, control unit 26 outputs to inverter controller 24 an inverter control signal S3 and, to control rod changeover device 22, a selected control rod signal S6. The changeover timing information of the switching elements in the output unit of the inverter power sources 20 is output from inverter controller 24 as inverter drive signal S4. Inverter power unit 20 outputs its inverter output S7 to control rod changeover device 22. Control rod changeover device 22 is constructed such that the control rods, not shown, are driven by the control rod mechanisms 1 in response to output of a selected control rod drive mechanism drive signal S8 to the selected control rod drive mechanism 1 in response to changing over of the inverter output S7 through an electrical switching device included in changeover device 22 in accordance with the selected control rod signal S6. For example, control rod changeover device 22 can comprise a plurality of separately controllable electrical switches, such as mechanical or solid-state switching devices, for selectively coupling the inverter output S7 to one of the control rod drive mechanism associated therewith. Operation of the above construction will now be described. As shown in FIG. 2, control unit 26 receives from man-machine device 28 (1) control rod selection mode, (2) control rod drive mode, or (3) control rod insertion/withdrawal mode, and drive information S2 of the target position calculated from these three modes. It also continually receives from the 205 control rod drive mechanisms 1 control rod position signals S1 that indicate where the control rod drive mechanisms S1 are stopped, i.e., at what part of the reactor core the control rod is stopped. As shown by the block diagram of FIG. 3, control unit 26 includes: a drive control rod selection unit 30, an inverter power source selection unit 32, and a control rod drive mechanism drive information evaluation unit 34, and executes the following control in response to control rod position signal S1 from the control rod drive mechanism 1 and drive information S2 from man-machine device 28. A selected mode signal (single mode or ganged mode) S9 included in drive information S2 is input to drive control rod selection unit 30. When this identifies the number of the control rod changeover device 22 that drives the selected control rod drive mechanism 1, it outputs this information, as selected control rod signal S6, to the control rod changeover device 22 corresponding to the selected control rod drive mechanism 1. Control rod changeover device 22 switches to the selected control rod drive mechanism 1. Simultaneously, drive control rod selection unit 30 outputs to inverter power source selection unit 32 a control rod changeover device signal S10 that controls the appropriate inverter controller 24 to control the associated inverter power source 20 to provide power for the control rod drive mechanism 1 that is driven. Also, drive mode signal S11 (step, notch or continuous) included in drive information S2, insertion/withdrawal command signal S12, and target position signal S13 are input to control rod drive mechanism drive information evaluation unit 34. This control rod drive mechanism drive information evaluation unit 34 generates an inverter operating signal S14, which continues output of the control rod drive mode (step, notch or continuous), and insertion/withdrawal command (control rod drive mechanism rotation direction) of inverter power source 20 to inverter power source selection unit 32 until the control rod position signal S1 of the control rod drive mechanism 1 in question has reached the target position. Inverter power source selection unit 32 selects an inverter power source 20 to be driven in accordance with the number of the control rod changeover device 22 of the control rod drive mechanism 1 to be driven, which is received in the form of control rod changeover device signal S10 from the drive control rod selection unit 30. Unit 32 also outputs the input inverter operating signal S14 received from control rod drive mechanism drive information evaluation unit 34, in the form of an inverter control signal S3, to the inverter controller 24 of the corresponding inverter power source 20. Continuing the description of the various signals that are output by control unit 26 with reference to FIG. 2, the inverter controllers 24 are driven to output inverter drive signals S4 to inverter power units 20 by means of inverter control signal S3, which is output from control unit 26. The inverter output S7 that is output from the inverter power source 20 that is driven is supplied to the corresponding control rod changeover device 22. With reference to control rod changeover device 22, a switch within control rod changeover device 22 corresponding to the control rod drive mechanism 1 that is to be driven is selected and closed in response to the selected control rod signal S6 that is output from control unit 26. Inverter output S7 that is output from the inverter power source 20 is thereby supplied, as selected control rod drive mechanism drive signal S8, only to the control rod drive mechanism 1 that is selected by man-machine device 28, thereby driving this control rod drive mechanism 1. It should be noted that, in this invention, when the control rods are operated in a ganged group, the load capacity of a single inverter power source 20 is that of a single control rod drive mechanism 1. Even if 26 control rods, which is the maximum in a ganged group in the present embodiment, are operated simultaneously, there is no possibility of two or more of the four control rod drive mechanisms 1 which constitute the load of the same inverter power source 20 being driven simultaneously. This is achieved by the 52 inverter power units 20 being assembled with the 205 control rod drive mechanisms 1 being constituted with four mechanisms in each group. An example of the apportionment of the 205 mechanisms to the 52 inverter power sources is: 4 mechanisms.times.50; 3 mechanisms.times.1; and 2 mechanisms.times.1. When, in reactor scram, ere, an "all control rods to be fully inserted" command is output from the reactor emergency shutdown system, the control rods are temporarily separated from the electric motors of the control rod drive mechanisms 1, and are all inserted at high speed by water pressure from a separate water pressure source, not shown. Furthermore, as shown by the logic diagram of FIG. 4, control unit 26 outputs an "all control rods to be fully inserted" command signal S15, included in drive information S2, to drive control rod selection unit 30 and inverter power source selection unit 32. Inverter power source selection unit 32 receives "all control rods to be fully inserted" command signal S15, and outputs an all-inverter drive command signal S16 to all 52 of inverter power sources 20. Also, drive control rod selection unit 30 receives "all control rods to be fully inserted" command signal S15 and closes an arbitrary one of the switches for control rod drive mechanisms 1 in control rod changeover device 22. Thereby, 52 control rod drive mechanisms are inserted at once. After the 52 control rod drive mechanisms 1 whose switches have been closed have reached the fully inserted position, the switches of other control rod drive mechanisms 1 that have not yet been fully inserted are closed. By carrying out this operation a total of 4 times sequentially, all of the 205 control rod drive mechanisms 1 are put into the fully inserted position. Thus, the control rods are maintained in fully inserted position as a backup system of the control rods which were previously fully inserted by water pressure. It should be noted that although an arrangement was described in which four control rod drive mechanisms 1 were driven by a single inverter power source 20 in the above embodiment, with this invention, it is possible to drive an arbitrary number N of control rod drive mechanisms with a single inverter power source 20. Thus, the number of inverter power sources 20 can be further reduced by determining the number N of control rod drive mechanisms 1 that is permitted from the relationship with the ganged mode operation of control rod drive mechanisms 1 in accordance with the operational requirements of the plant. With this invention, in an atomic power plant equipped with control rod drive mechanisms operated by electric motor drive, the number of inverter power sources, constituting the drive power sources, that need to be provided can be greatly reduced without affecting the control rod operating performance. Thus, the noise generated by the inverter power sources can be reduced and the control equipment can be simplified, thereby also facilitating maintenance. Numerous modifications and variations of the present invention are possible in light of the above teachings. It is therefore to be understood that, within the scope of the appended claims, the present invention can be practiced in a manner other than as specifically described herein.