Patent Number: 046997539
Section: description

DESCRIPTION OF THE PREFERRED EMBODIMENTS The invention will be described in connection with the detachable control console of the nuclear reactor refueling machine described in U.S. Pat. No. 4,511,531 which is hereby incorporated by reference into this application to provide a complete description of such a machine and its operation, but which is not required for a full understanding of the present invention. A schematic representation of such a refueling machine 1 is shown in FIG. 1. The machine 1 includes a bridge 2, a trolley 4 and a hoist 6 supported on a mast 8. It straddles a reactor 10 which is located under 20 to 30 feet of water 12 at the bottom of a pit 14 in a containment defined by massive walls 16. The bridge 2 is mounted on wheels 18 which ride on rails 20 extending along the sides of the pit 14 on the walls 16. The wheels 18 are driven by a bridge motor 22 through a gear reducer 24 and drive shafts 26. Similarly, the trolley 4 is mounted on wheels 28 for movement on rails 30 extending longitudinally along the bridge 2. A trolley motor 32 drives the wheels 28 through a gear reducer 34 and drive shaft 36. The hoist 6 is driven by hoist motor 38 to raise and lower an elongated tube and an inner mast (neither shown) inside a guide mast 40. The details of the elongated tube and the inner mast which are positioned by the hoist 6 are described in U.S. Pat. No. 4,511,531. The bridge, trolley, and hoist motors, 22, 32 and 38 are equipped with pulse generators 42, 44 and 46 respectively which generate pulse feedback signals representative of incremental rotation of the motor, and hence of movement of the associated refueling machine component The control console 48, which is mounted on the trolley 4 during refueling operations, responds to operator inputs and feedback from the refueling machine, such as the feedback signals from the pulse generators 42, 44, and 46, to generate various control signals for the operation of the refueling machine. A CRT 50 on the console provides the operator with a visual display of pertinent refueling machine parameters. The control console 48 is removed from the refueling machine during operation of the reactor at power to protect the solid state electronic equipment in the console from the high levels of radiation, temperature, and humdity present in containment. As shown in FIG. 2, a refueling machine simulator 52 is connected to the detached control console 48 by a group of cables 54, 56, and 58 having quick disconnects 60 at each end. These cables replace the cables by which the control console is connected to the refueling machine 1 during refueling operations. Power cords 62 and 64 provide 220 volt three phase and 115 VAC power respectively to the simulator 52, which it will be seen, supplies these services to the control console through cable 54. The simulator 52 includes a steel enclosure 66 which houses a single three phase simulator motor 68 which drives a single rotary pulse generator 90. The simulator 52 also includes a number of relays 72, the functions of which will be discussed in detail below, and associated circuitry (not shown in FIG. 2). Switches 74 on the front of the simulator 52 control various test modes of the simulator. A removable lid 76 on the enclosure 66 is provided with a clear LEXAN window 78 for ease in viewing the moving parts. The simulator 52 is a compact self-contained unit which fits easily in a small suitcase for transportation and storage. As shown in the schematic circuit diagram of FIG. 3, three phase power applied to the simulator 52 through power cord 62 is supplied to the control console 48 by four leads of cable 54. The 120 VAC power received through power cord 64 is used to power a number of relays 72 in the simulator 52 and is also supplied to the control console through leads in cable 54. The 120 VAC is used by the control consoles to power its controls and logic circuits while the 220 volt three phase power is used to power a variable frequency, pulse width modulated motor controller. Logic circuits within the control console respond to operator inputs to control the motor controller and to connect the three phase drive signals D.sub.B, D.sub.T or D.sub.H generated by the motor controller to one of three sets of output leads 80, 82, 84 in cable 54 for powering the bridge, trolley or hoist motors 22, 32 or 38 respectively on the refueling machine 1. However, all of these drive signals are connected through a network 86 within the simulator to the single simulator motor 68. The logic circuits of the control console 48 also generate brake or control signals B.sub.B, B.sub.T or B.sub.H for the bridge, trolley or hoist motor respectively on the refueling machine, as appropriate, simultaneously with the selected drive signals. These signals are connected through separate leads 88, 90, and 92 in cable 54 to the coil of a bridge brake relay 72B, a trolley brake relay 72T, and a hoist brake relay 72H respectively in the simulator 52 to energize the same. Each of these brake or control signals is also connected through a lead 94 to the coil of an electrically releasable brake 96 on the signal simulator motor 68. Thus, generation of any of the brake signals releases the brake on the single simulator motor, but energizes only the designated relay coil. Each of the relays 72B, H and T has four sets of make contacts, 72B-1 to 4, 72T-1 to 4 and 72H-1 to 4, with one contact from each relay connected in parallel in one of four leads, 70A, B, D and E carrying the output signals generated by the single rotary pulse generator 70. The pulse generator 70 generates pulse signals on the leads 70A, B, D and E at a rate and in a pattern determined by the direction and rate of rotation of the single simulator motor 68. These respective signals are transmitted back to the control console 48 as feedback signals. When the contacts 72B-1 to 4 of the bridge relay 72B are closed, the pulse signals are routed back to the control console 48 as feedback signals FB through console input leads 98 in cable 56. These are the same leads over which the control console 48 receives pulse signals from the pulse generator 42 associated with the bridge motor 22 when the console is connected to the refueling machine 1. Similarly, with the contacts 72T-1 to 4 closed the pulse signals are directed to the console as trolley motor feedback signals FT over leads 100 in cable 58, and with contacts 72H-1 to 4 closed, as hoist motor feedback signals FH over leads 102 in cable 58. As mentioned, the refueling machine of U.S. Pat. No. 4,511,531 includes an inner mast which has grippers on the lower end for grasping fuel assemblies so that they may be lifted out of the reactor core and transported about in containment. The grippers are actuated by pneumatic cylinders which are controlled by solenoid valves. When the gripper is to engage a fuel assembly, the control console sends a fuel assembly gripper engage signal FE over an output lead in cable 54 to a fuel assembly gripper engage solenoid. When the gripper moves to the engage position, a limit switch is closed to generate a feedback signal EF which is sent back to the console on an input lead in cable 56. When the fuel assembly is to be disengaged, a fuel assembly gripper disengage signal FD is sent to a disengage solenoid which results in generation of a fuel assembly gripper disengage signal DF when the corresponding limit switch is closed. The machine of U.S. Pat. No. 4,511,531 includes a second set of grippers which is mounted on a tube which telescopes into the mast. This set of grippers, which is also pneumatically actuated, is designed for gripping other reactor components such as control rod clusters. The pneumatic cylinder is actuated to the engage position by a solenoid in response to a control road cluster engage signal, CE, which generates an engage signal EC when the corresponding limit switch is closed. Likewise, a control rod cluster disengage signal CD energizes the disengage solenoid which produces a disengage signal DC as the limit switch closes. The tube carrying the control rod cluster grippers in U.S. Pat. No. 4,511,531 is raised and lowered by the hoist 6. A pivotable stop plate on the inner mast carrying the fuel assembly grippers is actuated to a position wherein lugs on the tube engage the stop plate to lift the inner mast when a plate engage solenoid is energized by a plate engage signal PE from the control console to actuate a pneumatic cylinder. The stop plate is pivoted to a position where the plate is clear of the lug so that the inner mast is not lifted with the inner tube when a disengage solenoid is energized by a disengage signal PD. Limit switches generate corresponding engage and disengage signals EP and DP when the stop plate reaches the respective positions. When the simulator 52 is connected to the control console, the FE and FD signals carried by leads in cable 54, energize the coils of fuel assembly gripper engage and disengage relays 72FE and 72FD respectively. Similarly, the signals CE and CD, associated with the control rod grippers, and PE and PD, associated with the stop plate, energize the coils 72CE, 72CD, 72PE and 72PD in the simulator 52 respectively. A set of break contracts associate with each of these relays, such as 72FE-1, completes a circuit between leads in the cables 56 and 58 connected to the console to generate the respective feedback signals set forth above. The refueling machine is provided with a pair of load-cells which have an electrical resistance which is proportional to the load on the hoist. The signals generated by these load cells provide an indication of whether the weight of the fuel assembly or control rod cluster is supported by the hoist and whether there is any obstruction to free movement of the supported component. These load cells are simulated by potentiometers 104 and 106 which are connected to the control console through leads in cable 56. The potentiometers can be set to simulate a load condition for testing this feature of the control console. Another potentiometer 108 is provided to simulate the pneumatic system pressure transducer and thereby test the console's reading of the transducer output. Several switches provide means for checking certain functions of the control console 1. Switch 110 tests the console's response to a geared limit switch which protects against overtravel of the hoist. Switch 112 simulates a hoist motor overheat condition. Switch 114 indicates whether the mast has rotated out of its normal position. Since the positions of the bridge, hoist and trolley are determined by counting pulses indicative of incremental movement, check switches 116, 118 and 120 are mounted at a known location in the path of each of these components to provide a means for checking the calculated positions and to reset them if they are out of synchronization. The refueling machine can transport fuel assemblies to and from a transfer area where they can be removed from or introduced into containment by a transfer system. An interlock system prevents interference between the refueling machine and the transfer system. A lamp 122 on the simulator checks the generation of the interlock signal by the control console 48. In operation, the simulator is connected to the control console 48 by cables 54, 56 and 58 and power cords 62 and 64 are connected to a power source. When used as a simulator, the operator operates the controls of the console to produce the desired simulated refueling machine movement. For instance, if movement of the bridge is to be simulated, the proper console controls are actuated to generate a bridge brake signal, B.sub.B on output lead 88 in cable 54. This energizes the simulator motor brake coil 96 through lead 94 to release the brake. It also energizes the coil of relay 72B to close the contacts 72B-1 to 4. The control console also connects the motor controller to output leads 80 in cable 54 associated with the bridge motor and controls the phase and width of pulses generated by the controller to produce a three phase signal, D.sub.B, which is connected through network 86 to the single simulator motor 68. As the motor begins to turn in the direction and at the rate dictated by the signal D.sub.B, the pulse generator 70 generates a pattern of pulses on the leads 70A, B, D and E porportional to this movement. This pulse signal is fed back to the console 48 as feedback signal FB on the console input leads 98 in cable 56. The console 48 tracks movement of the bridge by counting the pulses in the signal FB and displays bridge position on the CRT display 50. When movement of the trolley is commanded, the console generates the signal B.sub.T on output lead 90 in cable 54 to release the simulator motor brake by energizing coil 96. The signal B.sub.T also energizes coil 72T to direct pulses generated by pulse generator 70 through contacts 72T-1 to 4 to console input leads 100 as feedback signals FT. Movement of the trolley simulated by the motor 68 and pulse generator 70, and represented by the feedback signal FT, is followed by the console and also presented on the CRT display 50. When hoist movement is desired, the operator actuates the console controls to generate a hoist brake signal B.sub.H which is applied to the simulator through lead 92 of cable 54 to energize the coil 96 of the simulator motor brake and the coil of relay 72H. Make contacts 72H-1 to 4 of relay 72H direct the pulses from pulse generator 70 to input leads 102 in cable 58 for transmission to the console as the hoist motor feedback signal FH. Movement of the hoist is also tracked by the console and displayed on the CRT 50. Thus, it can be seen that a single simulator motor 68 and pulse generator 70 simulate all three refueling machine motors. The separate leads which direct the three phase drive signals to the three separate refueling machine motors are all connected to operate the one simulator motor. In addition, the brake signals for each of the refueling machine motors which are each carried by a separate lead are also connected to energize the one brake coil for the single simulator motor. Whereas, in the refueling machine, these signals only release the appropriate brake; in the simulator they each energize a separate relay which closes contacts to direct the pulses generated by the single pulse generator to the appropriate separate console input line associated with the indicated refueling machine motor. When the operator provides an input to the console 48 for the grippers to engage a fuel assembly or a control rod cluster, a signal generated by the console energizes the appropriate relay 72FE or 72CE which opens its normally closed contacts 72FE-1 or 72CE-1 to simulate the engagement. When the gripper is to release the fuel assembly or control rod cluster, the console generates a disengage signal which energizes relay 72FD or 72CD to open its normally closed contacts and provide an indication of the disengagement. When a fuel assembly is to be lifted, the console generates a stop plate engage signal, PE, which energizes relay 72PE to generate an indication by opening contacts 72PE-1 of the stop plate being pivoted into position to couple the inner mast carrying the fuel assembly grippers to the tube lifted by the hoist. When the console generates a disengage stop plate signal, PD, the contacts of relay 72PD open to simulate pivoting of the stop plate to a position where the inner mast is disengaged from the tube connected to the hoist. The remaining features of the simulator are used during testing of the console. The load cell potentiometers and the pressure transducer potentiometer can be used to test the console load and pressure measurements. The various switches can be actuated to verify the response by the control console to the test conditions. The simulator of this invention may be used to troubleshoot the console when it is installed on the refueling machine as well as when the console has been removed from containment. While specific embodiments of the invention have been described in detail, it will be appreciated by those skilled in the art that various modifications and alternatives to those details could be developed in light of the overall teachings of the disclosure. Accordingly, the particular arrangements disclosed are meant to be illustrative only and not limiting as to the scope of the invention which is to be given the full breadth of the appended claims and any and all equivalents thereof.