Patent Number: 047818824
Section: description

DETAILED DESCRIPTION The present invention provides an improved refueling machine for a nuclear reactor and an improved guide means for aligning the inner and outer mast of a refueling machine. An apparatus 101 for loading or unloading a fuel assembly in a nuclear reactor and improved guide means 103, as illustrated in FIGS. 5 to 8, has a means 105 for positioning a fuel assembly 107 above a nuclear reactor (not shown). The apparatus includes a housing 109 which carries concentric inner mast 111 and outer mast 113, the inner mast having at the lower portion thereof a means 115 for gripping the upper nozzle 117 of a fuel assembly 107, and means for releasing or engaging the fuel assembly. The means 105 for positioning a fuel assembly comprises a movable bridge 119 that is mounted on opposite walls 121 of a reactor containment, the bridge 119 having structural members 123 for strength and rigidity. The bridge 119 is adapted to travel horizontally on wheels 125 and rails 127 fixed on the top of containment walls 121. Wheels 125 are driven by a motor 129 and shafts 131. A motor driven trolley 133 is mounted on wheels 135 which run on rails 137 mounted on the bridge 119 for horizontal travel transverse to the travel of the bridge 119, such that the housing 109 and inner and outer masts 111, 113 are positionable over any one of the fuel assemblies in the reactor or a refueling pool to either insert or remove a fuel assembly 107 from the reactor core. A platform 139 is provided on the trolley 133 as well as a control console 141 which contains equipment to control drive motors, hoists and air compressors. The housing 109 for concentric masts 111, 113 is attached to the platform 139 such as by welding, with one end of the housing 109 extending below the platform 139 while the other end projects thereabove. A window 143 may be provided to observe the position of the upper end of the masts, and an electrical control 145 may be welded to the mast housing 109. A stationary plate 147 is mounted on the upper end of housing 109 and has an opening through which hoist, electrical and air lines extend. This opening also serves to permit removal or insertion of the inner mast 111 for maintenance. Cable reels, such as reel 151 enclose reels which support air lines or electrical cables arranged to be played out or taken in as the mast is raised or lowered. Plate 147 also supports hoist 153, which hoist carries hoist cable 155 that supports the inner mast 111 which, in turn, carries the fuel assembly 107. In operation of the fuel assembly loading or unloading apparatus 101, to remove a fuel assembly 107 from a reactor core, means 105 for positioning the fuel assembly 107 is operated and the bridge 119 and trolley 133 positioned directly above the fuel assembly that is to be removed. The inner mast 111, which is in an upper stored position within outer mast 113, is then lowered and the gripping means 115 engages the upper nozzle 117 of the fuel assembly. The inner mast 111 is reciprocally mounted in the outer mast 113 and movable as indicated by the double arrow in FIG. 6. Upon gripping of the fuel assembly 107, the hoist is engaged to lift the fuel assembly from the reactor core. The hoist 153 raises the inner mast 111 and engaged fuel assembly 107 into the confines of the outer mast 113 to a housed portion. The positioning means, trolley and bridge are then moved to another position and the fuel assembly lowered to a storage chamber and released from the inner mast. Loading of a fuel assembly in a reactor core involves reverse operation of this procedure. During the coaxial movement of the inner mast 111 relative to the outer mast 113, guide means are provided to maintain a concentric relationship between these two masts. The guide means 103 of the present invention is illustrated in detail in FIGS. 7 to 10 in association with a rectangular-shaped inner mast and circular-shaped outer mast, although the cross-section of the masts could be of another shape. The guide means 103 has a plurality of inner members 161 on the inner mast 111 and a plurality of complementary shaped cooperating outer members 163 on the outer mast 113, with means 165 for supporting the outer members 163 on the outer mast 113 and means 167 for pivoting the outer members 163 relative to the support means 165 towards and away from the inner members 161. The inner members 161 are illustrated as a corner 169 of the rectangularly-shaped inner mast 111, and a pair of vertically extending rods 171, having a convex surface or rounded face 173, secured to the wall 175 of the inner mast by means of bolts 177. The convex surface or corner 169, acting as an inner member also has a rounded outer face 179. Preferably three such inner members 161 are provided equally spaced about the inner mast on an angle of about 120 degrees apart to provide a balanced support of the inner mast 111 in the outer mast 113. The complementary outer members 163 on the outer mast 113 which cooperate with the inner members 161 on the inner mast 111 are illustrated as rollers 181 that are pivotally attached to the means 165 for supporting the same, the rollers 181 having a groove 183 therein in which the rounded faces 173 and 179 will ride. The support means 165 comprises a framework 185 comprised of top wall 187, above an opening 189 in the wall 191 of the outer mast 113 and a bottom wall 193, below the opening 189, with a rear wall, or plate, 195 extending between top and bottom walls 187 and 193. The plate 195 has two spaced apertures, upper and lower apertures, 197, 199, therethrough, through which upper and lower bolts 201, 203 are inserted, the bolts 201, 203 threadedly engaging in threaded bores 205 in the wall 191 of the outer mast 113. The bottom wall 193 is in the form of a block 207 with an aperture 209 therethrough coaxial with lower aperture 199, through which the lower bolt 203 also extends, to provide additional rigidity, while the top wall 187 is of a lesser thickness than the block 207 and may have a concave groove 211 in the lower face 213 thereof in which upper bolt 201 will seat. A bore 215 is formed through the block 207 transverse to aperture 209 and a pivot pin 217 is positioned in the bore 215. The pivot pin has opposite ends 219 and 221 to which upwardly extending side bars 223 and 225 respectively are secured. The side bars 223 and 225 each carry an inwardly directed arm 227 between which a shaft 229 extends, with the roller 181 mounted on the shaft 229 between the arms 227. Adjacent the upper end 231 of the side bars and extending between the upper ends of the side bars 223 and 225 is an alignment means 232 such as an alignment beam 233 which is fixed at opposite ends 235 and 237 to the side bars 223 and 225. The side bars 223 and 225, being secured to the pivot pin 217 are movable towards and away from the inner mast 111, such that the roller 181 on the shaft 229 extending between arms 227 of the side bars are also movable towards and away from the inner mast 111. Precise alignment of the position of the rollers 181 is effected by use of an adjustable device 241 which contacts the alignment beam 233. Adjustable device 241, as illustrated, is in the form of a threaded shaft 243 which is movable towards or away from alignment beam 233 and can be locked in various positions relative to the same, the threaded shaft secured, such as by welding, to a sleeve 245 that encloses the alignment beam 233, but is adapted to permit rotational movement of the alignment beam relative to the sleeve. The threaded shaft 243 extends from the sleeve 245 outwardly through an opening 247 in the plate 195 and has threads 249 thereon. A hollow stud 251 having a shoulder 253, engageably with the inner wall of plate 195, has threads 255 on the internal wall 257 thereof and threads 259 on the external wall 261 thereof. The threads 255 on the internal wall 257 are engageable with the threads 249 on the threaded shaft 243. A lock nut 263 having threads 265, is threadedly engageable with the threads 259 on the external wall 261 of the hollow stud on the opposite side of the plate 195 from threaded shoulder 253. In operation of the adjustable device to move the roller 181 on shaft 229 inwardly towards the inner mast 111, the lock nut 263 is loosened and the threaded shaft 243 and hollow stud are moved inwardly which moves sleeve 245 and alignment beam 233. Side bars 223 and 225 secured to the alignment beam 233 also move inwardly, pivoting on pivot pin 217. When the desired placement is achieved, the hollow stud 251 is threaded along threaded shaft 243 until shoulder 253 abuts the inside surface 267 of plate 195. The threaded lock nut 263 is then threaded along the hollow stud 251 until the nut abuts the outside surface 269 of the plate 195 to lock the shaft 243, alignment beam 233, and the roller 181 in position. An alignment pin or knob 271 extends from an end 273 of alignment beam 233, which provides an external reference surface. The surface or pin facilitates field alignment of all elevations of guide rollers by using a plumb line or an optical sighting device to align the pins vertically. By so aligning the pins 271, the vertically spaced plurality of rollers 181 are aligned along a common vertical axis for easy field alignment of all of the rollers. The present guide means can be provided on new refueling machines or can be used as an alteration to existing refueling machines as a retrofit system.