Abstract: A method and apparatus for repairing nuclear reactor core shrouds having horizontal cracks in heat affected zones of welds joining a horizontal plate to upper and lower cylindrical sections of the shroud includes securing a plurality of braces between an upper shroud flange and a top surface of the horizontal plate near an inner edge of the plate. The braces are installed at a respective plurality of angularly spaced locations within the upper cylindrical section of the shroud and each have an upper notched end for bearing against a bottom edge of the flange and a lower notched end for bearing against the top surface of the horizontal plate and/or an outer peripheral edge of an upper core grid structure mounted on the top surface of the plate.

Abstract: A method and apparatus for repairing nuclear reactor core shrouds includes applying vertical compressive forces to the shroud in situ to urge opposed ends of the shroud toward one another using a plurality of tie-rods, each including a plurality of coaxial longitudinal members separated by a radial gap filled with reactor coolant or some other damping fluid. One of the longitudinal members is secured to upper and lower portions of the shroud for maintaining a sufficient preload to hold the shroud together and is coupled with one or more other longitudinal members in a manner to transmit axial loads thereto upon extending a predetermined axial distance. A plurality of radial spacers can also be positioned at longitudinally spaced locations along the length of the tie-rod to assure control rod insertion by limiting lateral movement of the shroud and can reduce the preload required for preventing the formation of new cracks and stabilizing existing cracks.

Abstract: A method of repairing nuclear reactor core shrouds having horizontal cracks in heat affected zones of welds includes applying vertical compressive forces to the shroud in situ to urge opposed surfaces of the cracks toward one another. A plurality of tie rods, angularly spaced about the shroud periphery, is used to selectively apply the longitudinally compressive forces. Preferably, the method utilizes existing hardware secured to the shroud for attaching the tie rods thereto. The tie rods may be used in communication with horizontal and/or vertical spacers inserted between the shroud and the reactor vessel. Horizontal spacers serve to resist horizontal seismic loads and hold the shroud in place in spite of cracking. Vertical spacers resist vertically upward loads resulting from main steam line breaks.

Abstract: A method of repairing nuclear reactor core shrouds having horizontal cracks in heat affected zones of welds includes applying vertical compressive forces to the shroud in situ to urge opposed surfaces of the cracks toward one another. A plurality of tie rods, angularly spaced about the shroud periphery, is used to selectively apply the longitudinally compressive forces. Preferably, the method utilizes existing hardware secured to the shroud for attaching the tie rods thereto. The tie rods may be used in connection with horizontal and/or vertical spacers inserted between the shroud and the reactor vessel. Horizontal spacers serve to resist horizontal seismic loads and hold the shroud in place in spite of cracking. Vertical spacers resist vertically upward loads resulting from main steam line breaks.

Abstract: A method of repairing a tubular nozzle made of Inconel 600 material and extending through a bore in an external wall of a pressure vessel to provide communication with the interior of the vessel from externally thereof includes mechanically rolling the inside diameter of a portion of the nozzle disposed within the external wall with a roll pressure in the range of 50,000 to 150,000 psi to form a circumferential rolled section in the nozzle having a wall thickness 3% to 12% less than the wall thickness of non-rolled sections of the nozzle, an outside diameter less than 1% greater than the outside diameter of the non-rolled sections and transition segments with a radius of curvature in the range of 1/2 inch to 2 inches joining the rolled section to the non-rolled sections.

Abstract: Built-up deposits on the top surface of a tubesheet and on adjacent tube sections in a tube bundle heat exchanger are removed by inducing vigorous turbulent flow of cleaning liquid radially along the surface of the tubesheet by repetitively and periodically injecting gas pulses into the liquid to form an expanding and retracting gas bubble proximate the plate center. The gas pulse rise time is smoothed by controlling the actuation time of a discharge valve and by a surge volume downstream of the valve to thereby avoid harmful pressure shock waves in the heat exchanger. The cleaning liquid is recirculated through an external filter loop to remove suspended foreign materials dislodged by the turbulent flow.

Abstract: A heavy shielded nuclear fuel cask is lowered into and removed from a water filled spent fuel pool by providing a vertical guide tube in the pool, affixing to the bottom of the cask a base plate that approximates the transverse dimension of the guide tube, and lowering and elevating the cask and base plate assembly into and out of the pool by causing it to traverse within the guide tube. The guide tube and base plate coact to function as a dashpot, thereby cushioning and controlling the fall of the cask in the pool should it break loose while being lowered into or raised out of the pool. A specified approach path to the guide tube insures that the cask assembly will not fall into the pool, should it break loose on its approach to the guide tube.

Abstract: A heavy shielded nuclear fuel cask is lowered into and removed from a water filled spent fuel pool by providing a vertical guide tube in the pool, affixing to the bottom of the cask a base plate that approximates the transverse dimension of the guide tube, and lowering and elevating the cask and base plate assembly into and out of the pool by causing it to traverse within the guide tube. The guide tube and base plate coact to function as a dashpot, thereby cushioning and controlling the fall of the cask in the pool should it break loose while being lowered into or raised out of the pool. A specified approach path to the guide tube insures that the cask assembly will not fall into the pool, should it break loose on its approach to the guide tube.