Abstract: An inspection apparatus for inspecting welds in a nuclear reactor jet pump includes a probe subassembly rotatably and linearly movably coupled to a frame structure configured to attach to a top flange of the reactor pressure vessel. The probe subassembly includes a plurality of probe arms pivotably coupled to a housing, with each probe arm including a sensor. The probe arms are pivotably movable between a first position where the probe arms are parallel to a longitudinal axis of the probe subassembly, and a second position where the probe arms are at an angle to the longitudinal axis of the probe subassembly. An insertion subassembly couples to the jet pump suction inlet. The insertion subassembly is sized to receive the probe subassembly and guide the probe subassembly into the jet pump through the jet pump suction inlet.

Abstract: Within an upper plenum of a nuclear reactor, a portion of a heated coolant flows radially outward from a central portion of a core barrel (30) towards outlet nozzles (12) in a region of an upper core plate (21) extending outside of an outer periphery of the core along an inner wall of a core barrel (30). Portions of the coolant flows beneath the outlet nozzles (12). Thus, streams of heated coolant flowing in opposite directions may collide with each other. After collision, the flow directions of the heated coolant are changed to flow upward. Due to the collision, the coolant flow behavior becomes complicated and unstable, making it difficult to measure the temperature of the heated coolant with an outlet pipe (42) connected to the outlet nozzle (12).

Abstract: In order to support a shroud against bending, shear, stress and torsion, straps which are preferably formed of the same material as the shroud, are placed in strategic positions with respect to cracks or the like type of weaknesses which have been detected, and fastened in place using a suitable fastening technique. In the preferred embodiments of the invention holes a formed using an EDM technique and bolt units which have an expanding portion are inserted into the holes, torqued and expanded in a manner which fastens the strap to the shroud. Welding and the like type of fastening techniques are not excluded and may used alternatively or in combination with the bolting technique as required.

Abstract: A method and an apparatus for inspecting a core shroud by remote operation. The apparatus is a robotic scanning device which can be installed in the narrow space between the core shroud and the jet pumps and which can scan azimuthally and vertically around the circumference of the core shroud. The scanning device provides gross positioning to the area of interest and precise motion control in a limited scanning range. The scanning uses a thin wide arm to support a bank of transducers at its bottom end, and is rigidly mounted to a precision two-axis positioner at its top end. The arm is of narrow thickness to pass through the 0.5-inch access opening and to allow radial flexibility to absorb surface contour variation over the inspection area. The transducer mounting includes a water jet thruster to provide a radially inwardly directed reaction force to maintain the transducers in contact against the shroud. The arm is fabricated with a row of longitudinal holes extending throughout its length.

Abstract: In order to eliminate the need to weld, drill or otherwise machine a shroud structure which is used to surround a plurality of fuel assemblies in a nuclear reactor, a plurality of upper hanger rods interconnect a structure above the shroud to a support ring which is clamped about the upper periphery of the shroud. Lower hanger rods interconnect a lower edge or shoulder portion of the shroud with the support ring. Thus, through the upper and lower hanger rods and the support ring, the shroud can be supported within the RPV. The upper support ring is arranged to clamp the lower ends of the upper hanger rods against the upper outer peripheral portion of the shroud while the lower ends of the lower hanger rods are clamped against the lower peripheral wall portion of the shroud by a lower support ring.

Abstract: In order to eliminate the need to weld, drill or otherwise machine a shroud structure which is used to surround a plurality of fuel assemblies in a nuclear reactor, a plurality of upper hanger rods interconnect a structure above the shroud to a support ring which is clamped about the upper periphery of the shroud. Lower hanger rods interconnect a lower edge or shoulder portion of the shroud with the support ring. Thus, through the upper and lower hanger rods and the support ring, the shroud can be supported within the RPV. The upper support ring is arranged to clamp the lower ends of the upper hanger rods against the upper outer peripheral portion of the shroud while the lower ends of the lower hanger rods are clamped against the lower peripheral wall portion of the shroud by a lower support ring.

Abstract: A method for converting a vertically downward flow of bypass coolant through coolant flow holes in a core barrel and former plates in a nuclear reactor to a vertically upward flow. Coolant flow holes are provided in the normally solid top former plate by suitable means such as drilling. These new coolant flow holes are located so as to be substantially in coaxial alignment with the existing coolant flow holes in the intermediate and lower former plates. Existing coolant flow holes in the core barrel adajcent the top former plate are plugged. Existing coolant flow holes in the lower former plate are plugged in an alternating pattern with each fifth hole being plugged having only forty-four percent of its flow area plugged.

Abstract: Container system for a high-temperature nuclear reactor, including an outer metallic pressure vessel having an inwardly-protruding flange, an inner metallic core barrel resting tightly on the flange, and means disposed below the flange at a lower end of the core barrel for feeding and discharging cooling fluid, the core barrel being gas-tight above the flange.