Patent Number: 056446071
Section: summary

BACKGROUND OF THE INVENTION The present invention relates to an automatic refueling apparatus for a nuclear power plant, especially to an automatic refueling apparatus suitable for transferring a fuel assembly at high speed. An existing refueling apparatus is manually operated from an operation box provided on a carriage of the refueling apparatus, and a travel motion and a traverse motion are separately carried out. Further, AEG company in Germany has developed an automatic system for the refueling of a nuclear reactor. However, this is only partially automatic, the operation being dictated by automatic control commands sent from an operator console on a carriage. Further, simultaneous control of travel and traverse motions has not been realized. Furthermore, in JP-A-19238/1983, there is disclosed a travel and traverse motion simultaneous control system for a refueling in which a carriage moving route from a present position to a target position is automatically calculated for a complicated travel route, and the limits of the traverse region, and speed control commands for travel and traverse motions are obtained and issued. However, in this control system, only the simultaneous control of travel and traverse motions is aimed at, and a more multidimensional simultaneous control, which may reduce the time for refueling, is not considered or provided. As mentioned above, in the existing techniques, reducing the time for transferring a fuel assembly between a fuel pool and a reactor core is realized by adopting only simultaneous control of travel and traverse motions in two dimensions, and so a multidimensional control taking elevation and rotation of a fuel assembly grappling apparatus into consideration, that is, a X-Y-Z-.theta. axis simultaneous control, has not been devised for reducing the time of refueling. SUMMARY OF THE INVENTION The present invention has been proposed in consideration of the above-mentioned problems, and an objective of the present invention is to provide an automatic refueling apparatus aimed at reducing the time for refueling by realizing a multidimensional simultaneous control. One of the features of the present invention to attain the above-mentioned objective is to provide an automatic refueling apparatus which is capable of automatically transferring fuel assemblies between a fuel pool and a reactor core in a nuclear power plant, and which has a traveling carriage moving on an X-Y axis on a horizontal plane between a reactor core and a fuel pool in a nuclear power plant, a fuel assembly grappling apparatus which is provided at the traveling carriage and is moved in a Z axis direction perpendicular to the X-Y axis plane, a rotation machine provided at the traveling carriage to rotate the fuel assembly grappling apparatus around the Z axis in a .theta. direction, and driving means for moving the traveling carriage, the fuel assembly grappling apparatus and the rotation machine in each of X, Y, Z and .theta. directions, the automatic refueling apparatus comprising: input means for inputting positions of a start point and a target terminal point in a fuel assembly transferring operation, position detection means for detecting a position of the fuel assembly grappling apparatus along X-Y-Z-.theta. coordinates, calculation means for taking in outputs of the input means and for obtaining the shortest route between the start point and the target terminal point through a preset fuel transferring permitted region, and control means for generating control command signals to move the fuel assembly grappling apparatus along the obtained shortest route based on outputs of the position detection means and for sending the control command signals to the driving means. Another feature of the present invention is to provide means for storing the coordinates and an indication of the presence of a fuel assembly for each lattice of a fuel rack in the fuel pool, and the coordinates and an indication of the presence of a fuel assembly for each fuel cell of the reactor core, in the automatic refueling apparatus. Another feature of the present invention relates to the fact that a fuel assembly transferred by the automatic refueling apparatus passes not less than one point prescribed in the shortest route set in advance in the preset fuel transferring permitted region. Further another feature of the present invention relates to the fact that the control means of the automatic refueling apparatus selects one of the prepared control modes corresponding to intervals obtained by dividing the shortest route between the start point and the target terminal point, each interval being designated by preset points. With the automatic refueling apparatus, the calculation means judges whether the present position of the fuel assembly grappling apparatus is in an area where X-Y-Z-.theta. axis simultaneous control is possible in the preset fuel transferring permitted region, based on the detected present position of the fuel assembly grappling apparatus, and if the grappling apparatus enters the above-mentioned area, the control means selects the X-Y-Z-.theta. axis simultaneous control mode and sends the control command signals of the four-dimensional control mode to the driving means. By executing the above-explained controls, it is possible to transfer a fuel assembly by the shortest route between the start point and the target terminal point.