Patent Number: 054835615
Section: summary

TECHNICAL FIELD This invention relates to devices for inspecting the internal structure of a nuclear reactor and more particularly to a device for inspecting the internal reactor structure during disassembly. BACKGROUND A core of a nuclear reactor is composed of a plurality of fuel assemblies which require periodic removal for refueling or repair. These fuel assemblies are typically composed of a group of fuel rods incorporated with plates which maintain the fuel rods in proper proximity to allow a cooling fluid to flow around the rods to maintain the rods at a proper temperature. Consequently, the fuel assemblies are usually surrounded by various auxiliary structures such as baffles, which direct cooling flow for optimum efficiency to cool the fuel rods. It is typical for the reactor core fuel assemblies to be aligned in the reactor vessel by lower and upper assemblies known as internals packages. During refueling, the upper reactor internals are lifted out of the reactor housing. Presently, it is difficult to determine if one of the fuel assemblies, during lifting, has become entangled with the reactor upper internals structures. If this occurs, a fuel assembly may be pulled out of the core and dropped. Thus, the fuel assembly or upper internals may be damaged, requiring costly and time consuming repairs. Prior attempts to inspect the upper internals package during lifting utilized a video camera. The distance of lift required to perform the inspection, generally above the reactors upper flanges, could cause damage before the entanglement was detected. Consequently, other inspection methods and apparatus are required. SUMMARY OF THE INVENTION It is an object of the present invention to avoid damage during refueling. It is a further object to provide apparatus for inspecting the reactor internals during removal to detect potential entanglements and thus halt the operation prior to damaging the fuel assembly. These and other objects of the present invention are achieved by an inspection assembly comprising: an inspection means sized for insertion into a partially raised reactor internals package, and having a radially oriented opening at a distal end thereof; PA1 detecting means located within the inspection tube adjacent the opening; PA1 means for lowering the inspection tube to a position where the opening is below the internals package; PA1 rotating means for rotating the inspection tube in a complete circle while inserted within the internals package, such that the detection means translate in a full circle below the package to detect any entangled articles. In a preferred embodiment, the inspection means is a tube having an ultrasonic transmitter located adjacent to the radial opening. After the internals package is partially lifted, the tube is lowered by a cable into a passage with the reactor, with the opening oriented in conformance with a degree wheel located on a rotating device. Once lowered into the reactor, to a point just below the lowermost portion of the internals package, the ultrasonic transmitter is activated and the probe rotated a full 360.degree.. Any anomaly in the reading will indicate that a fuel assembly may be entangled with the internals package, and allow an operator to lower the internals package or take other steps to disengage the fuel assembly before a second attempt is made to raise the internals package out of the reactor. Another option would be to continue with the lift in increments and periodic reinspections before the upper internals raised height exceeds that of the assembly length to determine if the assembly dislodged off the upper internals core plate. In a preferred embodiment, a central drive shaft is removed from the upper internals package to provide the passage for the tube. This provides a central location for the inspection.