Improvements in material handling plant, more particularly plant for handling nuclear reactor fuel elements

摘要

836,563. Handling materials in radioactive environment. BABCOCK & WILCOX Ltd. Aug. 14, 1957 [Aug. 14, 1956], No. 24802/56. Class 39(4). [Also in Group XXX] In plant for handling spent nuclear reactor fuel elements as disclosed in Specifications 808,381 and 836,562 in which the elements removed from the top of the reactor by a loading machine are discharged into a shoot whereby they descend to a station situated above the level of a storage pond 27 where they drop into a container 25 carried by a hoist 26 which descends an inclined track 28 to convey the container to the bottom of the pond where it is removed by a crane from the hoist and replaced by an empty container, automatic indication and/or control means are provided to prevent the dropping of a fuel element from the shoot in the absence of a container at the loading station situated at the top of the track. Normally, when the hoist ascends with an empty container a two-armed pivoted lever 82 is moved by the container from its second to its first position to open an electric switch 83 and cancel flashing red lights 85 in the control cabins of the loading machine and crane. On arrival of the container at the top of the track an arm 62 on a shaft 63 carried by the hoist engages a lever 57 to move it against its spring bias and close a switch 54 to illuminate a green lamp 56 in the loading machine cabin. On descent of the hoist a lever 73 pivoted on the track 28 and biased against a stop 74 by a counterweight arm 75 engages the arm 62 whereby a counterweight arm 66 on the shaft 63 moves overcentre and the arm 62 is moved to an inoperative position in which it cannot engage the lever 57 ; also the lever 82 is moved to its second position to cause flashing of the red lights. Removal of a container by the crane resets the arm 62 and hence if the hoist inadvertently ascends with the filled container still on it the arm is not reset and the green lamp not illuminated. The hoist is controlled by a winch motor, the controller 88 for causing ascent of the hoist being controlled by a push button 86 in the crane cabin and the controller 91 for causing descent being controlled by a push button 89 in the loading machine cabin, the usual holding contacts 92, 94 and interlock contacts 93, 95 being provided. A nut rotated on a screwed rod by rotation of the winch drum, Fig. 6 (not shown), causes operation of switches 112, 113, 121, switch 112 being opened when the hoist reaches its upper limit, switch 113 when the hoist reaches its lower limit, and switch 121 being opened when the hoist ascends after the container has moved the lever 82 to its first position. The lever 82 also controls a switch 122 which is closed when the lever is moved to its first position ; thus if the container is absent the winch motor stops the ascent of the hoist upon opening of the switch 121, also the red lights continue to flash and the green light is not illuminated. A slide plate valve, Fig. 2 (not shown), in the upper end of the shoot may be prevented from opening by a further switch controlled by lever 57 connected in series in an interlocking circuit with a third switch controlled by lever 82.