GB857558A - Improvements in radioactive handling plant - Google Patents

Abstract

857,558. Handling nuclear fuel elements. BABCOCK & WILCOX Ltd. July 29, 1959 [July 29, 1958], No. 24431/58. Class 39(4). In a hoist apparatus for moving nuclear fuel elements between upper and lower stations means are provided to free the fuel elements from the hoist carriage and deposit the elements below a biological shield of water in the event of the carriage becoming fixed in position through some defect. As shown in Figs. 1, 3, 4, 7 a main hoist track 2 extends from a loading station 4 adjacent the top of a gas-cooled reactor, fuel element handling means 6 being provided to load the elements into a removable skip 8 carried within a tank 10 supported by the hoist carriage 12. A crane 14 removes the skip 8 at the bottom of the track 2 in a panel 15. The tank 10 is secured to the carriage by sliding bolts 20 which enter holes 24 in tank flanges 26 and are movable to disengage the holes by levers 25 pivoted to the carriage 12 at 29, the levers being connected to the bolts by slots 31 receiving projections on the bolt ends. The carriage is controlled by a hoist winch and brake 9 having a rope 11. An auxiliary hoist which is brought into operation in the event of the main hoist becoming fixed, comprises a track 28 having an auxiliary carriage 30 supported by a rope 38. The carriage 30 comprises spaced frame members 32 having wheels 34, spaced lifting arms 44 being pivoted to the members at 46. Trip levers 48 normally support the arms 44 in the position shown in Fig. 4 by engaging recesses 49 in the arms, the levers 48 being pivoted at 50 to the members 32. When it is required to operate the auxiliary hoist a portable hand capstan 58 is connected to the auxiliary hoist barrel 59 and the carriage 30 is lowered to the bottom of the pond 15 where the levers 48 engage a lip 62 and are rotated thereby releasing the arms 44 which rotate in a counter clockwise direction, a cam roller 64 mounted on a spindle 65 extending between the arms then engaging a cam face 66. The carriage is raised, movement of the roller 64 along the face 66 permitting further counter clockwise movement of the arms 44 until arm notches 68 are supported upon a member 70 extending between the members 32. As the carriage 30 approaches the carriage 12 the tips 71 of the arms 44 engage flanges 27 on the bolt levers 25 so that the bolts 20 are withdrawn from the holes 24. Further upward movement of the carriage 30 causes trunnions 78 on the tank 10 to be engaged by the arm tips 71 and the tank is lifted off the carriage 12. When the carriage 30 approaches the top of the track 28, Fig. 7, the roller 64 engages a cam surface 82 so that the arms 44 pivot clockwise and the trunnions 78 are propelled along the upper edges 84 of the frame members 32 until they enter recesses 86 in the members 32. The carriage 30 is then lowered to the bottom of the pond 15 the water level is lowered to a minimum safe level and the fuel elements are transferred by tongs from the skip 8 to a skip 94. The skip 94 is then removed to a storage pond and workmen may enter the plant to rectify the defect. Water sprays 88 may be directed on to the main carriage 12 and a television camera 92 permits the entrance of the trunnions 78 into the recess 86 to be observed. In another arrangement, Figs. 8, 9, for transporting fuel elements from the bottom of a pond 106 to a flask 115 in which they are removed through a shaft 124, a hoist 100 comprising an inclined track 130 leading to a vertical track 128 having bifurcated portions 127, 129 has a carriage 132 which is maintained horizontal as the carriage bogies 134 are moved along the track by a rope 145 connected to a winch and brake 147, the bogies being pivotally mounted at 139, 141 to side members 140 connected to the carriage 132. A tank 148 is pivotedon the carriage 132 by a shaft 176 and is held in its normal position by a pair of slidable stops 150 which support rollers 56 mounted on tank brackets 158. The stops 150 may be moved by rods 160 connected to an actuating piston and cylinder 166 upon the admission of pressure liquid to the latter so that should the carriage become jammed as it is being raised the stops may be caused to disengage the rollers 56 so that the tank 148 swings under gravity action to an inverted position shown in dashed lines and the skip 102 and fuel elements therein are jettisoned into the pond 106. In a normal operation the loaded skip is removed from the carriage 132 at the upper station 108 by a skip handling machine 174 and is then lowered into a flask 115 mounted on a truck 114 which is positioned beneath the machine 174. The truck is then returned to the shaft 124 after replacement of the flask lid 122 by a machine 120.