Patent Number: 047626666
Section: summary

FIELD OF THE INVENTION The present invention relates to a swing gate closure assembly and more particularly to a swing gate closure assembly for a nuclear reactor which uses hydraulic forces coupled with the weight of the swing gate to provide a foolproof closure mechanism. BACKGROUND OF THE INVENTION When nuclear fuel is depleted, it must, of course, be removed from the reactor process area or core so that it may be replaced with fresh fuel. One current method for effecting removal involves introducing water under pressure into the tube holding the fuel charge. This causes the fuel charge to move through the tube to the end of the tube, where it is expelled. A fuel charge generally comprises about sixteen fuel elements arranged in the tube by spacers at either end. When a charge/discharge operation is not in effect, the reactor tubes are typically sealed by an arrangement such as that shown in FIG. 1. In FIG. 1, the nozzle end of the process tube is indicated by numeral 10. The arrow in outline indicates a direction of flow. Nozzle cap 40 is threaded onto the nozzle 10. The nozzle 10 is also sealed by a seal plate 20 and graphoil seal 30. The seal plate 20 is loaded by three loading bolts 50, two of which are visible in FIG. 1. When it is desired to effect fuel discharge, it is necessary for an operator to remove nozzle cap 40 and seal plate 20. This clears the way for the fuel charge to leave the process tube nozzle 10. A problem which exists, however, is that after the last spacer of the fuel charge has cleared the tube, water which has just traversed the radioactive core gushes out and sprays the operator. This imposes an undesirably high risk of radioactive contamination. It is therefore desirable to provide a mechanism by which the nozzle 10 can automatically close after the final fuel spacer has cleared the tube. At the same time, it is necessary that any such mechanism function extremely reliably given the high safety standards required for nuclear reactor applications. SUMMARY OF THE INVENTION It is therefore an object of the present invention to provide a reliable closure assembly. It is a further object of the invention to provide a swing gate closure assembly which permits fuel elements to be removed from a reactor core but which is responsive when the last fuel spacer has cleared the tube to swing closed automatically. Additional objects, advantages and novel features of the invention will be set forth in part in the description which follows and in part will become apparent to those skilled in the art upon the examination of the following or may be learned by practice of the invention. To achieve the foregoing and in accordance with the purposes of the invention, as embodied and broadly described herein, there is provided a swing gate closure assembly for a nuclear reactor tip off assembly comprising a closure assembly body having an inlet, an outlet, and a through bore dimensioned to permit passage of a fuel charge therethrough; a swing gate, moveable between a first position in which said swing gate does not seal said through bore and a second position in which said swing gate seals said through bore, is disposed in the closure body. The swing gate is moved to the first position by the fuel charge during passage of the fuel charge through the through bore; the assembly includes a device in the body and in fluid communication with the inlet to hydraulically move the swing gate to the second position when the last fuel spacer of the fuel charge has cleared the through bore. The swing gate closure assembly of the present invention does not obstruct egress of fuel elements or spacers, and is capable of ready, rapid, and reliable closure in the absence of a fuel element or spacer. Closure is not effected through the provision of mechanical closing means, but instead is effected by forces generated by the fluid itself. These forces, coupled with the weight and moments of the swing gate, provide a virtually foolproof closing mechanism.