Patent Number: 050842315
Section: description

DESCRIPTION OF THE PREFERRED EMBODIMENTS A fission reactor complex 100 includes a concrete containment structure 102 enclosing a reactor vessel 104 containing a reactor core 106, as shown in FIG. 1. Reactor core 106 includes a frame for holding a multitude of fuel elements 108 in position to promote a controlled chain reaction. Additional fuel elements 110 are stored in a storage area 112. Fuel elements are transferred between storage area 112 and core 106 by a transfer mechanism 114 which includes a conventional refueling bridge 116, a conventional grapple 118, and an interconnecting refueling mast 120. Bridge 116 is moved on tracks on a refueling floor 122 which extends over water 124 which submerses storage area 112 and core 106. A gate 126 can be opened to permit a fuel element to be transferred between storage area 112 and core 106 without lifting the fuel element out of water 124. Mast 120 is shown in an extended condition over core 106 so that it can deposit a fuel element 128 therein. Mast 120 includes four tubes: an outermost tube 130, a first intermediate tube 132, a second intermediate tube 134 and an innermost tube 136 are visible when mast 120 is extended. Intermediate tubes 132 and 134 are referred to herein as "inner tubes" in relation to outermost tube 130 and as "outer tubes" in relation to innermost tube 136. Shown in dashed lines are transfer mechanism 114 and fuel element 128 in a prior position in transit from storage area 112 to core 106 with mast 120 in a retracted condition. Bridge 116 includes a hoist mechanism 138 which provides for extension and retraction of the inner tubes 132, 134 and 136, as well as control of grapple 118. Hoist mechanism 138 is linked to innermost tube 136 through hoist cables 202, shown in FIG. 2. A respective flange 210, 212, 214, 216 is welded on the lowermost end of each tube 130, 132, 134, 136. As hoist mechanism 138 forces innermost tube 136 to retract from a fully extended condition, innermost tube 136 slides within and relative to intermediate tube 132 until flange 214 is contacted by grapple mounting bolts on flange 216. Further retraction causes tubes 134 and 136 to retract together and slide within and relative to tube 132 until flange 214 contacts flange 212. Inner tubes 132, 134 and 136 retract together into outermost tube 130 until flange 212 contacts flange 210 which serves as the stop for retraction. Four roller assemblies 220 are bolted to and circumferentially spaced around each outer flange 210, 212 and 214. Each roller assembly 220 comprises a roller housing 222, a guide roller 224 and an axle 226 used for rotatably attaching the roller 224 to the roller housing 222, as indicated in FIGS. 2 and 3. Guide rollers 224 help centralize inner tubes 130, 132 and 134. Further guidance is provided by bushings 230 on the top ends of inner tubes 132, 134 and 136 and sleeves 232 attached to the inner surfaces of outer tubes 130, 132 and 134. Sleeves 232 are held in place by portions of roller housings 222 which protrude through respective flanges 210-214. Sleeves 232 serve as downward stops for inner tubes 132-136 as they define the lower limit of travel for bushing 230. As shown in FIG. 3, springs 334 space sleeves 232 from roller housings 222. As indicated with respect to innermost tube 136 in FIG. 4, each inner tube 132, 134, 136, has multiple grooved longitudinal (vertical) tracks 402 formed thereon. More specifically, each outer flange 210, 212, 214 supports four guide rollers 224 for engaging four tracks 402 of the next inner tube 132, 134, 136. As indicated in FIG. 5, rollers 224 have grooves 506 for mating with grooves 504 of tracks 402. Grooved tracks 402 are cold-formed using a groove forming tool 600, shown in FIG. 6. Tool 600 includes an annular die holding fixture 602 and four die assemblies 604 evenly spaced about the circumference of fixture 602. Each die assembly 604 includes a roller die 606, mounting 608 for holding roller die 606 and permitting it to rotate, and a bolt 610 which is welded to mounting 608. Roller dies 606 can be of a hardened tool steel. Threads of each bolt 610 are engaged with mating threads of fixture 602 so that turning a bolt 610 forces the respective roller die 606 in or out as desired. To form grooved tracks 402, tool 600 is mounted on a tube, e.g., tube 136, at a longitudinal position at which tract 402 is to be formed. Bolts 610 are adjusted so that roller dies 606 contact the outer surface of tube 136. Tool 600 is then moved repeatedly over the length of tube 136 over which track 402 is to be defined. Bolts 610 are gradually tightened between traversals, increasing the pressure with which roller dies 606 apply to tube 136. Grooved tracks 402 are formed progressively in this manner. As depicted in FIG. 5, this process results a flattening of tubes 132, 134 and 136 on which tracks 402 are formed and along the regions in which tracks 402 are formed. In addition, the cold forming hardens the steel of the tube being worked. This hardening and flattening contribute to the torsional rigidity of the tube. Tubes 130, 132, 134 and 136 have respective diameters of about 3", 4", 5" and 6" respectively, with wall thicknesses of 1/2". These dimensions provide for "nestability" of tubes 130-136. The tubes are fabricated using stainless steel 304. Individual tube lengths are about 20' each, providing a retracted mast length of about 21' and an extended length of about 69 ft. The dimensions and materials listed above can be varied according to the context. Tracks 402 can be cold formed or machined. Other variations upon and modifications to the disclosed embodiments are provided by the present invention, the scope of which is limited only by the following claims.