Patent Number: 046997539
Section: summary

CROSS-REFERENCE TO RELATED APPLICATION Commonly owned U.S. patent application Ser. No. 382,269 filed May 26, 1982 in the names of John Kaufmann, Kenneth J. Swida and Leonard P. Hornak and entitled "Refueling of Nuclear Reactor". BACKGROUND OF THE INVENTION 1. Field of the Invention This invention relates to a simulator which is used in combination with a detachable control unit for a nuclear reactor refueling machine to simulate inputs to the control unit without it actually being installed on the machine, and is useful for operator training and testing. 2. Prior Art A reactor refueling machine is a device used to remove and replace, or rearrange, fuel assemblies and other components in the core of a shutdown nuclear reactor. Typically such a machine comprises a bridge which moves reciprocally on horizontal tracks straddling the water filled pit in which the reactor vessel is housed. A trolley is mounted on the bridge for reciprocal horizontal movement along the bridge so that by appropriate movement of the bridge and trolley, a mast assembly mounted vertically on the trolley can be positioned over any desired location in the pit. The mast assembly includes an inner mast telescopically mounted inside a fixed mast. A hoist mounted on the trolley raises and lowers the inner mast which carries on its lower end grippers for engaging and lifting fuel assemblies. When a fuel assembly has been lifted clear of the reactor vessel by the hoist, the bridge and trolley are repositioned to locate the fuel assembly over a new location in the core, or to move the fuel assembly to a storage area in the pit or to a transfer system which removes the fuel assembly from the pit. New fuel assemblies supplied through the transfer system are inserted in the core by reverse operation of the refueling machine. Some of the newer refueling machines also have mechanisms for transferring separately from the fuel assemblies other reactor components, such as fuel rod clusters and control rod thimble plugs. An example of such a machine is described in U.S. Pat. No. 4,511,531. In this machine, a rod telescoped inside the inner mast carries grippers adapted to engage these other reactor components. The hoist is connected to this rod, which in turn is selectively coupled to the inner mast by lugs on the rod which engage a pivotable stop plate on the inner mast. With the stop plate raised, the inner mast is raised and lowered with the rod for servicing fuel assemblies. With the stop plate lowered, the rod moves independently of the inner mast for servicing the other reactor components. The bridge, trolley and hoist of a refueling machine are positioned independently by separate motors. These motors are controlled by an operator from a control console mounted on the trolley. Signal generators generate feedback signals indicative of movement of each of these components in response to operation of the respective motors. The control console uses these signals in a control loop to accurately position these components and to generate indications to the operator of their respective locations. In the refueling machine disclosed in the above cross-referenced application, the feedback signal generators produce pulses representative of incremental movement of the respective components. The control console includes a programmed digital computer which counts the pulses to track movement and generate a visual display of component position on a cathode ray tube. The earlier control consoles for reactor refueling machines utilized relay logic which is relatively immune to the harsh conditions inside containment, and therefore these units were left in place on the trolley during operation of the reactor. The digital computer and its associated interfaces are less tolerant of the high temperature, humidity and radiation levels found within containment during reactor operation. Since the refueling machine has no function during reactor operation, it has become the practice to remove the control console from containment during plant operation and to place it in storage until the next refueling cycle. SUMMARY OF THE INVENTION It has been recognized by us, that since the detachable refueling machine control console is accessible and available during plant operation it would be desirable to test it and use it for operator training at that time, rather than during a refueling operation when there are competing demands for access to the reactor and any extension of down time is very costly. Accordingly, we have developed a simulator that can be used with the detachable control console to simulate the signals that would be generated by the refueling machine. All commands to the control console actually send signals to the simulator which responds to them as a refueling machine would and feeds responses back to the console. The invention embraces a combination which includes a detachable refueling machine control console which generates, one at a time, motor signals for the drive motors of a plurality of refueling machine components, and in particular the bridge, trolley, and hoist motors. Separate output leads from the control console apply each of the motor signals to the simulator. The simulator includes only one simulator motor which is connected to the output leads from the control console such that it is driven when any of the motor signals is generated. The simulator also includes only one feedback signal generator which is connected to the simulator motor and generates a simulator feedback signal representative of rotation of the simulator motor. The control console also includes a separate input lead for receiving a feedback signal associated with each of the drive motors. These input leads are also connected to the simulator. Switching means within the simulator, which is responsive to the motor drive signals received from the control console over the output leads, connects the single pulse generator to the console input lead associated with the motor drive signal received from the control console. Thus, the single motor and pulse generator in the simulator selectively simulate each of the refueling machine drive motors in response to the particular drive motor signal generated by the control console, and send back a feedback signal representative of operation of that motor over the appropriate dedicated console input lead. The motor signals generated by the control console include a motor drive signal and a control signal for each motor and separate output leads are provided for each signal. All of the motor drive signals are connected to the single simulator motor while the control signals are connected to the switching means to route the feedback signal to the appropriate console input lead. The separate control signals generated by the console are brake signals which are used to release the brake on the appropriate motor on the refueling machine. In the preferred embodiment of the invention, the one simulator motor is provided with a brake and all of the brake signals are applied to it so that the brake is released when any of these signals is generated. The brake signals are also connected to the switching means to effect routing of the feedback signal to the proper console input lead. The invention also embraces the simulator as described which is designed to be used in combination with a detachable control console. The invention permits the operation of the detachable refueling machine control console to be verified without being installed on the refueling machine, which minimizes the potential for critical path down time problems. It is also useful for training operators without requiring any reactor down time. While the invention is primarily intended for use while the control console is physically removed from the refueling machine and from containment, it can also be connected to the console when the latter is on the machine to assist in identifying the source of electrical problems during refueling operations.