Patent Number: 052689409
Section: description

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring to the drawings, the invention embodied in FIGS. 1 and 4 comprises an inspection device for the upper internals 4 of a nuclear reactor which includes a generally tubular elongated upper probe support generally designated 10 having one or more bearings 11 for guiding a probe body upward and downward inside the system's outer housing support designated 100. The system's outer housing support 100 acts to hold the probe body 12 and probe support 10, and to position the probe on the upper internals and to provide axial positioning via a lead screw or other means. The probe body 12 is rotatably mounted at a bearing 13 to the lower end of probe support 10, for rotation around its longitudinal axis. Rotation is achieved by rotation drive means in the form of a motor 15, gear reducer 101 and encoder 14 connected thereto so that the exact rotational position of the probe body is known at all times. A profile transducer 16 is mounted to the probe body 12 for radial movement on transducer drive means generally designated 18. Transducer 16 advantageously comprises a pair of opposite arms 19 equipped with strain gauges 102 as best shown in FIG. 5, which can be brought into contact with the surface of a channel, for measuring the profile of the channel as the transducer 16 moves radially along the channel. The transducer drive means 18 comprises a pair of arms 17 which each have one end pivotally mounted to the transducer 16, and an opposite end pivotally mounted to respective upper and lower follower blocks 20, 22 which are mounted for vertical sliding movement within the probe body 12. An upper lead screw 24 is threaded into the upper block 20 and is rotated through appropriate couplings and a gear train, by a transducer drive motor 30. A gearhead 28 connects the shaft of motor 30 to a second encoder 26 for providing an exact measurement of the rotational position for the motor shaft, and thus the radial position for transducer 16. A lower lead screw 25 is threaded into the lower block 22 and is coupled by a rotation coupling 32, to the upper lead screw 24. The threads on lead screws 24 and 25 are reverse with respect to each other so that as the two lead screws rotate in the same direction, blocks 20 and 22 move in opposite directions to either advance or retract the transducer 16, in the radial direction. Before describing further details of the inspection device illustrated in FIG. 1, reference should be made to FIG. 4 and FIG. 2 which illustrate the environment of the invention. The upper internals of a nuclear reactor include a vertical structure approximately 14 feet tall with a small central aperture 8 at its top with horizontally extending support plates 40 containing a central aperture 42 having a plurality, in this case 16, of radially extending channels 44 projecting outwardly from the central aperture 42. Each radial channel 44 communicates with one or more vertically extending control rod apertures 46 which receive control rods 48 shown in FIG. 3. Referring to FIG. 3, the hatched area 45 in the vicinity of communication between channel 44 and aperture 46, is the site of most probable wear due to control rod vibrations. This is the area of greatest interest to be monitored with the device of the present invention. In operation, the outer housing support 100 lowers the probe body 12 vertically through the central aperture 42 so as to align the transducer 16 with the support plates 40 and channels 44. Motor 15 is operated and its rotational position is monitored by encoder 14 to rotate transducer 16 into a correct rotational orientation to access one of the channels 44. Motor 30 as monitored by encoder 26 is then operated to radially move the transducer 16 outwardly of the probe body 12. The transducer 16 measures the profile, and in particular areas of wear, of the channel 44. The encoders, motors and transducer are all connected to a computer (not shown) for either automatically or manually positioning and moving the transducer in acquiring data for each channel profile. A typical profile plot generated by this inspection device is illustrated in FIG. 6. Although strain gauges are illustrated, any other transducer or sensor can be utilized to measure the channel profile, for example, non-contact ultrasonic transducers. As seen from FIG. 1, a spring 54 is connected between an ejector assembly 52 and the probe body 12. In the event of a probe drive malfunction while the transducer arms 17 are extended, the transducer 16 can be quickly retracted back into the probe body 12 by deactivating a pneumatic cylinder 50 thereby releasing the ejector assembly 52 which moves downward as the spring 54 contracts. The release of ejector assembly 52 causes coupling 32 to disengage the lead screws 24 and 25 from each other so as to retract the transducer 16. This method of recovery ensures that the probe can be retrieved, during a malfunction of the drive mechanism, without damage to itself or the upper internals of the nuclear reactor. The probe body 12 is centered in the central aperture 42 by an upper bladder 60 and a lower bladder 62 which are both spooled around the probe body 12. Air or other pneumatic fluid is provided to the upper hollow interior of probe body 12 to inflate the upper bladder 60. Air reaches channel 66 to inflate the bladder 60 outwardly to center the upper part of the probe against the inner walls of the central aperture 42. In likewise fashion, tubing 105 is provided for supplying air or other pneumatic fluid to a T-shaped channel 70 within the lower portion of the probe body 12 which inflates the lower bladder 62. Tubing 68 supplies holding air to pneumatic cylinder 50 so that a loss of pressure inside the probe body 12 retracts the transducer 16. An end cap 72 has a rounded outer surface to facilitate entry of the inspection device into the upper internals. The probe body 12 is hermetically sealed above and below the area of transducer 16, the probe body 12 is cylindrical with a longitudinal slot 74 for permitting the transducer 16 and its arms 17 to be extended and retracted in the radial direction. The probe body 12 is thus sealed in all areas except for the area of the transducer 16. While a specific embodiment of the invention has been shown and described in detail to illustrate the application of the principles of the invention, it will be understood that the invention may be embodied otherwise without departing from such principles.