Patent Number: 047560673
Section: summary

BACKGROUND OF THE INVENTION This invention relates to nuclear reactors and it has particular relationship to the replacement of damaged old split-pin assemblies (OSPA's) by new split-pin assemblies (NSPA's). Split-pin assemblies are secured to the lower guide tubes (LGT's) of a nuclear reactor. The bifurcated ends, i.e., the tines, of each split pin engage in holes in the upper core support plate supporting the associated guide tube. The guide tubes to which the OSPA's are secured typically include a lower section or lower guide tube (LGT) and an upper section or upper guide tube. The LGT and the upper guide tube are secured together coaxially by abutting flanges which are bolted together. In some guide tubes the LGT includes a lower flanged section and an upper flanged section joined axially by bolts through the flanges. The LGT has a lowermost flange having counterbores spaced circumferentially by 180.degree. in which OSPA's are secured. Application Ser. No. 617,857 filed June 6, 1984 to Calfo et al. for Replacement of Split Pins in Guide Tubes assigned to Westinghouse Electric Corporation and the related applications referred to in Calfo et al. disclose an automatic system including robotic tooling for replacing OSPA's by NSPA's. This process has proven highly useful in situations where the split pins on all guide tubes (typically 37 to 61) of a reactor are to be replaced. Typically, the automatic system is conveyed to the site of the replacement by seven trailers and several weeks are consumed in a replacement. The damage to an OSPA is typically a crack in the old pin. Sonic apparatus is available to determine if there is a crack in an OSPA so that replacement by an NSPA is required. Typically the use of this apparatus uncovered cracks in the OSPA's of some of the guide tubes; the OSPA's in the other guide tubes were crack free. In such cases, it is only necessary to replace the defective OSPA's and the complexity, time consumed and cost involved in the use of the automatic system outweighs its benefits. It is an object of this invention to provide a method and apparatus (tooling) less complicated and costly than the above-described automatic system for replacing OSPA's by NSPA's, particularly when a limited number of guide tubes are to be processed but also having more general use in situations where all split-pin assemblies are to be replaced. SUMMARY OF THE INVENTION In accordance with this invention, there are provided, for complete replacement of an OSPA by and NSPA, a saw-and-drill stand, an installation stand, unique runner-and-torque tools and a unique crimping tool. The saw-and-drill and the installation stand are suspended from the wall of the refueling pool of the nuclear reactor plant at a depth of about 20 feet of water. The runner and torque tools and the crimping tool are long-handled tools which are manipulated from a platform above the pool to perform their functions on OSPA's and NSPA's on the respective stands. There are also long-handled auxiliary tools such as clamps or grippers for removing the fragments of an OSPA from the saw-and-drill stand, a tool for releasing the flange fragment of the OSPA from the guide tube flange, and a tool for positioning the NSPA in the installation stand. The saw-and-drill stand includes a rotary saw of abrasive material such as tungsten carbide and a drill. The guide tube with the OSPA's secured to it is mounted in the saw-and-drill stand so that it can be rotated. Each OSPA is severed by the saw into a pin fragment and a second fragment. The pin fragment is the part of the pin which extends below the under surface of the guide tube flange. This fragment is severed without damage to the guide tube and is separated from the guide tube. The second fragment includes the flange of the OSPA and the remainder of the pin and the nut secured to it. The second fragment remains secured to the flange of the guide tube. The drill is spaced by a predetermined angle, circumferentially from the saw. Where there are two diametrically positioned OSPA's in the guide tube, this angle is 180.degree.. The drill is oriented so that its bit may be advanced generally vertically into the second fragment. The bit has a diameter slightly greater than, or approximately equal to, the diameter of the shank of the old split pin. To remove the second fragment, the guide tube is rotated through the circumferential angle so that the drill bit is generally coaxial with the remainder of the old pin of the second fragment. The drill bit is advanced into the second fragment separating the second fragment into a third fragment including predominantly the flange of the pin and a fourth fragment including the remainder of the pin with the nut secured to it. Where the guide tube has two pins, the above-described process is then carried out on the second pin. The guide tube sans the OSPA's is then moved to the installation stand. This stand has facilities for mounting a new split pin. Such facilities are shown in FIG. 25 of application Ser. No. 617,854 filed June 6, 1984 to Nee et al. for Replacement of Split-Pin Assemblies in Nuclear Reactor and assigned to Westinghouse Electric Corporation. The guide tube sans the OSPA's is mounted on the installation stand with the lower counterbores in its flanges coaxial with the new split pin and with the flanges of the new split pins to be engaged with the bases of the lower counterbores. The new nut is then threaded onto each pin by the long-handled runner and is secured with a predetermined measured limited torque by the long-handled extension torque tool. The cup extending from each new nut is then crimped to the new pin to complete the installation of the NSPA's. A significant feature of the runner is that its socket is connected through a gear train to the long rod handle which is turned to thread a new nut onto a new split pin. The necessary offset between the handle and the socket is thus provided. A measured torque is impressed near the upper end of the long-rod handle of the torque wrench to torque the new nut onto the new pin. The socket of the torque wrench is connected to the rod by an offset arm, but the arm is so short compared to the rod that the measured torque is substantially equal to the torque applied to the new nut. The crimper tool is characterized by fixed jaws with tapered cam surfaces. The crimping is produced by moving the jaws downwardly generally parallel to flutes in the new split pin.