Refueling of nuclear reactor

Abstract

Refueling apparatus for a nuclear reactor including a bridge and a trolley. The bridge is moveable in tracks along the containment of the pit in which the reactor is immersed in water and the trolley moveable in tracks on the bridge at right angles to the tracks on the bridge. The trolley carries a mast assembly for engaging, raising, lowering a nuclear-reactor component assembly involved in refueling. The mast includes an elongated member for engaging control-rod and thimble plug assembly and a gripper for raising fuel assemblies. The elongated member is moveable upwardly or downwardly. The bridge, trolley and mast assembly each has a pulse generator which produces pulses in accordance with the movement of each. The number of pulses produced when the bridge, trolley or elongated member move to a position at a predetermined distance from a reference position is a measure of the new position of each. The mast assembly can be positioned over the reactor at positions whose location can be set in terms of number of pulses as coordinates of a Cartesian coordinate system. The axes of the coordinate system are parallel to the directions of motion of the bridge and trolley. The elongated member likewise can be positioned vertically at a height whose location can be set by a coordinate measured by its number of pulses. As the bridge, trolley or elongated member move, limit switches are actuated by each at a predetermined position in its track. The signal produced by actuation of each switch yields a reading of the position of the bridge, trolley or elongated member at the instant of actuation and this is compared with a computer entry of the position which the vehicle in question should occupy. The computer is programmed to make a compensating correction in the position of the vehicle or elongated member.