Patent Number: 048470422
Section: summary

The invention relates to an apparatus for storing nuclear reactor fuel assemblies in a water pit, with a device for holding one end of a nuclear reactor fuel assembly and for transporting the nuclear reactor fuel assembly in the water pit. It is customary to associate such an apparatus and water pit with the nuclear reactor of a nuclear power station. In this water pit, nuclear reactor fuel assemblies which have been irradiated and discharged from the nuclear reactor can be inspected and stored until they are finally re-inserted into the nuclear reactor or transported off for re-processing. These nuclear reactor fuel assemblies are substantially formed of a fuel assembly frame holding the fuel rods containing the nuclear fuel proper. These fuel rods have a metal cladding tube which is hermetically sealed at both ends and which contains the nuclear fuel, such as UO.sub.2 in pellet form. It has been found that during the insertion into the nuclear reactor, deposits are frequently formed on the surface of the fuel assembly frame and the cladding tubes of the fuel rods. The deposits are radioactive and can impede the heat transfer from the nuclear fuel in the cladding tubes of the fuel rods to the working medium in the nuclear reactor. This is particularly true for the deposits on the surface of the cladding tubes. These deposits, however, can also drop off the nuclear reactor fuel assemby in an uncontrolled manner and can contaminate the water pit or the transport container. It is accordingly an object of the invention to provide an apparatus for storing nuclear reactor fuel assemblies in a water pit, which overcomes the hereinafore-mentioned disadvantages of the heretofore-known devices of this general type, and which removes these deposits on the surface of the fuel assembly and frame and the cladding tubes of the fuel rods in a sufficiently short time so that they cannot be carried off in an uncontrolled manner. With the foregoing and other objects in view there is provided, in accordance with the invention, an apparatus for storing nuclear reactor fuel assemblies in a water pit, comprising means for holding an end of a fuel assembly and for transporting the fuel assembly through the water pit, a vessel disposed in the water pit having a closed bottom and an open top in communication with a water space in the water pit forming a vertically elongated well or shaft in the vessel for at least partly receiving a fuel assembly, a suction connection in communication with or leading into the well through the closed bottom of the vessel, a suction pump connected to the suction connection, a shielding container, and a filter disposed in the shielding container and connected to the pump for collecting deposits suctioned from the well. In accordance with another feature of the invention, there is provided an ultrasonic oscillator disposed in vicinity of the top of the vessel for radiating into the well. In accordance with a concomitant feature of the invention, there are provided nozzles disposed in vicinity of the top of the vessel for spraying water aimed into the well. Through the use of the invention, an irradiated nuclear reactor fuel assembly discharged from a nuclear reactor can be vertically introduced into the elongated well and pulled out again from the well by the holding device. In the process, the nuclear reactor fuel assembly passes the ultrasonic oscillator and/or the spray nozzles which are disposed at the top of the well, in the lengthwise direction. By means of the ultrasound emitted by the ultrasonic oscillator, particularly firmly adhering deposits are removed from the surface of the nuclear reactor fuel assembly, while by means of the water sprayed by the spraying nozzles onto the surface of the nuclear reactor fuel assembly, particularly loosely adhering deposits are sprayed off the surface of the nuclear reactor fuel assembly. The deposits collect at the bottom of the well, are suctioned off from there by means of the suction pump and are finally filtered in the filter located in the shielding chamber. In this manner, uncontrolled spreading of these radioactive deposits, in the water pit or later on in a transport container for the nuclear reactor fuel assembly, is prevented. Other features which are considered as characteristic for the invention are set forth in the appended claims. Although the invention is illustrated and described herein as embodied in an apparatus for storing nuclear reactor fuel assemblies in a water pit, it is nevertheless not intended to be limited to the details shown, since various modifications and structural changes may be made therein without departing from the spirit of the invention and within the scope and range of equivalents of the claims.