Patent Number: 048246336
Section: summary

BACKGROUND OF THE INVENTION This invention relates to a method and an apparatus for controlling fuel exchange and more particularly to refuelling control method and apparatus suitable for manipulating a plurality of fuel grippers. In a prior art atomic power plant, upon exchange of atomic fuel, the atomic fuel is transferred between a reactor core and a fuel storage pool by a single fuel gripper, as disclosed in JP-A-58-34392. To speed up the fuel transfer, the fuel gripper must therefore be operated at an increased speed but the speed of the fuel gripper is permitted to be increased within only a limited range because the highest safety is required of the power plant. With the view of reducing the time required for transfer, JP-A-61-65192 and JP-A-61-149897 also propose a method which uses a refuelling machine having a plurality of grippers for gripping a plurality of fuel elements, whereby a plurality of fuel elements are gripped simultaneously and then transferred between a reactor core, hereinafter called a core, and a fuel storage pool (hereinafter called a pool). In JP-A-61-65192, however, the simultaneity is only valid for the horizontal transfer between the pool and the core as well as for the horizontal motion in two directions namely, the X and Y directions, and, as a result, the effect of the paralleling (simultaneity) of operation is limited in part. However, JP-A-61149897, neither clearly describes the paralleling of operation nor discloses a specific means for realizing the parallel operation. Thus, under the circumstances, it is desired that as many operations as possible be performed in parallel in order to efficiently effect fuel exchange. Actually, however, a space for mounting the refuelling machine is so limited that mounting of a plurality of, even only two, grippers is almost impossible if the grippers are perfectly mutual non-interfering. Accordingly, a technical task is to provide the manner of performing as many operations as possible by using a plurality of grippers which mutually impose constraint. SUMMARY OF THE INVENTION An object of this invention is to solve the above task and effect fuel exchange with high efficiency. According to the invention, a refuelling machine of reactor comprises a plurality of grippers. Each gripper is comprised of a plurality of telescopic bars which are telescopically actuatable independently of each other and at least one gripping member (grapple) mounted to each telescopic bar. A method for controlling the reactor refuelling machine comprises deciding whether the movement of a particular gripper in the Z direction is constrained by a status of the movement of a different gripper, and performing the parallel operation when the movement of the particular gripper in the Z direction is not constrained and placing the particular gripper in condition for waiting when constrained. An apparatus for controlling the reactor refuelling machine comprises gripper manipulation procedure memory means for storing operations to be carried out by respective grippers in sequence of steps, allowed motion direction deciding means for determining a gripper which is manipulated preferentially hereinafter referred to as the preferential gripper during a step presently under course of execution, hereinafter referred to as an execution step, and determining every moment allowable directions of the movement (directions of allowed motion) of individual grippers inclusive of the preferential one, gripper controlling means for causing the individual grippers to perform the operations to be carried out thereby in accordance with the determined directions of allowed motion during the execution step and the succeeding step, and execution step managing means for deciding the end of the execution step and permitting the procedure to proceed to a subsequent execution step. In the case of manual operation, however, the gripper manipulation procedure memory means and the execution step managing means may be eliminated. The allowed motion direction deciding means determines a preferential gripper during an execution step and decides as to which directions, two horizontal directions, namely upward and downward directions namely, the individual grippers inclusive of the preferential gripper are allowed to freely move in, that is, decides directions of allowed motion of the individual grippers inclusive of the preferential gripper on the basis of a horizontal position and a vertical position or height of each gripper, whether each gripper suspends a fuel element, whether the suspended fuel element is shaking and whether a gripper in question is the preferential gripper. The gripper controlling means causes the preferential gripper to preferentially perform an operation during an execution step in accordance with its allowed motion direction while permitting a non-preferential gripper to perform an operation in parallel with the operation of the preferential gripper during the execution step and the succeeding step in accordance with its allowed motion direction as far as the operation of the non-preferential gripper does not interfere with the operation of the preferential gripper. In this manner, the paralleling of operation of the individual grippers can proceed efficiently while the individual grippers are prevented from interfering with each other and with various parts of facilities of the reactor.