US 3483380 A
Abstract available in
Claims available in
Description (OCR text may contain errors)
D c- 9, 1959 K. ANTONSEN ETAL 3,483,380
SHIELDED CASK FOR RADIOACTIVE MATERIAL Filed April 9, 1965 10 Sheets-Sheet l Dec. 9, 1969 K. ANTONSEN ETAL 3,483,380
SHIELDED CASK FOR RADIOACTIVE MATERIAL l0 Sheets-Sheet 2 Filed April 9, 1965 9, 1969 K. ANTONSEN ETAL 3,483,380
SHIELDED CASK FOR RADIOACTIVE MATERIAL 1969 K. ANTONSEN ETAL 3,483,380
SHIELDED CASK FOR RADIOACTIVE MATERIAL l0 Sheets-Sheet 4 Filed April 9, 1965 f1: vszzzar's A A/Z/D A VTOA/SEA/ F/CA APD FUSE/V5696 HADZEYK 4 44/79 M Mml-mjmflw K. ANTONSEN ETAL SHIELDED CASK FOR RADIOACTIVE MATERIAL l0 Sheets-Sheet 5 Dec. 9, 1969 Filed April 9, 1965 270a #401044 w/nep Zfi D 1969 K. ANTONSEN ETAL 3,483,330
SHIELDED CASK FOR RADIOACTIVE MATERIAL Filed April 9, 1965 10 Sheets-Sheet 6 Lfld AR I D 9, 1969 K. ANTONSEN ETAL 3,483,380
SHIELDED CASK FOR RADIOACTIVE MATERIAL 10 Sheets-Sheet Filed April 9, 1965 ffl Lim lm, 6w
1969 K. ANTONSEN ETAL 3,483,380
SHIELDED CASK FOR RADIOACTIVE MATERIAL l0 Sheets-Sheet 8 Filed April 9, 1965 m 5 2 /Z 2 5% m [Key M A 1969 K. ANTONEEN ETAL. 3,483,380
SHIELDED CASK FOR RADIOACTIVE MATERIAL 1O Sheets-Sheet 10 Filed April 9, 1965 United States Patent O 3,483,380 SHIELDED CASK FOR RADIOACTIVE MATERIAL Knud Antonsen and Richard Rosenberg, San Diego, and Hadley K. Wiard, La Mesa, Calif., assignors, by mesne assignments, to Gulf General Atomic Incorporated, San
Diego, Calif, a corporation of California Filed Apr. 9, 1965, Ser. No. 447,003 Int. Cl. G21f 7/00 U.S. Cl. 250-108 21 Claims ABSTRACT OF THE DISCLOSURE A shielded cask particularly adapted to receive radioactive elements, such as nuclear fuel cells, including a housing having an access passageway at one end, a rack rotatably mounted in the housing and defining a plurality of compartments each adapted to receive an element. In certain specific embodiments, means are provided for varying the position of the acces passageway relative to the housing, to maintain the elements in compartments, and to shift the rack within the housing to enable it to be supported by an interior wall of the housing for shipment.
The present invention relates to a shielded cask for receiving, storing, transporting and delivering radioactive elements of a nuclear reactor.
It is a necessary incident to the operation of a nuclear reactor system to periodically remove radioactive elements, such as spent fuel elements, from the nuclear reactor and to transport such radioactive elements to vari ous places in the nuclear plant or other installations. It also may be necessary to transport and replace in the reactor radioactive elements such as fresh fuel elements. It is also necessary that radioactive reactor elements be shipped to and from the plant. During the handling of such elements, it is very important that personnel are adequately shielded from the radioactive elements themselves and from equipment which may be exposed to, and thereby contaminated by, the elements. Other primary considerations are the time required for the operation, and the cost of the equipment and/or plant structure required.
'In presently known systems, handling and transportation of reactive elements, such as nuclear fuel elements, by a movable shielded cask with a high element capacity frequently requires an overhead bridge or trolley system and submergence in water unless very large isolation valves are employed. Such plant construction and/or equipment is costly. In dry reactor systems, such as gascooled reactor systems, installation of such reactive elements in a high load capacity movable cask, which does not include a movable rack arrangement such as is incorporated in the cask of the invention, would require either a seal-tight canning of each of the elements and subsequent wet installation in the cask in a separate water-filled facility, or some type of very large isolation valve or other heavy equipment for dry installation. Again large costs are involved.
The present invention has the advantage that it provides a high capacity, shielded cask from which elements may be rapidly loaded or unloaded through an isolation valve which is small relative to the cross sectional area of the cask while personnel and other equipment are ade- It is another object of the present invention to provide a novel and improved shielded cask for handling a plurality of radioactive elements.
It is a more specific object of the invention to provide such a cask for receiving, storing, transporting, and/or delivering radioactive elements of a nuclear ireactor.
It is another object of the present invention to provide such a cask wherein radioactive elements may be loaded and unloaded through a relatively small passageway and through relatively small and less costly isolation valve equipment while personnel and other equipment are adequately protected from radiation from the elements.
Another object is to provide such a cask into which a plurality of radioactive elements may be loaded, or from which a plurality of elements may be unloaded, in a minimum of time.
A more specific object of the present invention is to provide such a cask which is operable to selectively position at least one compartment of a rnulti-compartment element-receiving rack within the cask in alignment with an access passageway of the cask.
It is another more specific object of the present invention to provide such a multi-compartrnent cask in an alternative form where compound movement is utilized to afford access to a large number of compartments.
It is another object of the invention to provide such a cask capable of receiving and delivering elements from different spaced locations while the cask itself is in a fixed position.
It is another object of the invention to provide such a cask that incorporates particularly suitable handling means for positioning the elements relative to the cask.
It is another object of the invention to provide such a cask that includes particularly suitable means for supporting the elements in the cask.
It is also an object of the present invention to provide a novel and improved cask in a form particularly adapted for shipment of a plurality of elements.
It is a more specific object to provide such a shipping cask which incorporates means for readily radially repositioning acentered rotatable element-holding arrangement to an eccentric, non-rotatable, supported position for shipment of the elements.
It is also an object of the present invention to provide such a shielded cask which is simple, durable, and relatively economical to produce and maintain.
Other objects and advantages of the present invention will become more apparent from the following description and the accompanying drawings, wherein:
FIGURE 1 is a partially broken away, fragmentary elevational view, partially in section, of a nuclear power plant illustrating in particular the reactor of the plant, a fuel transfer cask, and a fuel shipping cask, embodying various features of the present invention;
FIGURE 2 is an enlarged side view of the fuel shipping cask shown in FIGURE 1;
FIGURE 3 is an enlarged plan view of the fuel shipping cask of FIGURE 2;
FIGURE 4 is an enlarged sectional plan view taken generally along line 44 of FIGURE 2;
FIGURE 5 is an enlarged partially broken-away sectional plan view taken along line 5-5 of FIGURE 2;
FIGURE 6 is an enlarged fragmentary sectional elevational elevational View taken along line 6-6 of FIG- URE 3;
FIGURE 7 is an enlarged fragmentary sectional plan view taken generally along line 77 of FIGURE 6;
FIGURE 8 is an enlarged side sectional view of the fuel transfer cask shown in FIGURE 1, said cask having a rotary support rack arrangement and presenting a preferred form of transfer cask which embodies various features of the invention;
FIGURE 9 is a fragmentary sectional plan view on a reduced scale taken generally along line 9-9 of FIG- URE 8;
FIGURES 10 and 11 are enlarged plan sectional views taken generally along lines 10-10 and 11-11, respectively, of FIGURE 8;
FIGURE 12 is an enlarged fragmentary partially broken away side sectional view of portions of the cask shown in FIGURES 8 through 11, showing in particular the supporting and retaining structure of the cask;
FIGURES 13 and 14 are enlarged side sectional views of portions of the structure shown in FIGURE 12;
FIGURE 15 is an enlarged side sectional view of the' grappler of the cask shown in FIGURES 8 through 14;
FIGURES 16 through 18 are sectional plan views taken generally along lines 16-16, 17-17, and 18-18, respectively, of FIGURE 15;
FIGURE 19 is a fragmentary side sectional view of a modified form of fuel transfer cask having a compoundmovement rack arrangement;
FIGURES 20 and 21 are enlarged plan sectional views taken generally along lines 20-20 and 21-21, respectively, of FIGURE 19; and
FIGURE 22 is an enlarged side view of a portion of the positionable grappler carrier for the cask shown in FIGURES 19 through 21.
Briefly, a shielded cask, in accordance with the invention, for receiving, storing, transporting, or delivering a plurality of elongated radioactive elements of a nuclear reactor includes a closed, shielded housing having at least one openable access opening or passageway. Within the housing a support rack arrangement is mounted for movement relative to the access passageway. The rack arrangement defines at least two elongated compartments or channels each adapted to receive and support one of the elements. The rack arrangement is movable to align any selected one of the compartments with an access passageway so that an element can be moved through the passageway into or out of that compartment.
The cask can be operated remotely and the access opening may be small in size compared with the size of the storage area of the cask. Such a cask affords positive positioning of elements in the cask, requires a minimum of shielding material and a minimum of additional equipment, and serves to minimize radiation exposure to personnel and equipment. Further, the use of such a cask for refueling -a nuclear reactor substantially reduces refueling time.
NUCLEAR POWER PLANT As shown in FIGURE 1, which discloses a portion of a nuclear power plant, a gas-cooled nuclear reactor which includes a primary containment vessel 32 and a secondary containment vessel 34 is housed within the lower level of a reactor building 36. The reactor building 36 includes an intermediate wall 38 which overlies the reactor 30 and is provided with an access opening 40 above the reactor vessels. A bridge 42 is movably supported over the opening 40 generally level with the wall 38. The bridge 42 includes tracks 44 which extend transversely to the direction of movement of the bridge and which may be aligned with other tracks (not shown) of a track or rail system which extends to other portions of the reactor building 36 and to other portions of the power plant. In particular, the rail or track system leads to a fuel storage vault (not shown) and a shipping cask loading area or installation 48, both of which are positioned like the reactor, below the level of the tracks. The shipping cask loading area 48 has an access opening 49 above it extending through the intermediate wall 38.
The track system has a centrally open construction to afford extension of equipment and passage of material or elements through the tracks and openings 40 4 and 45 in the wall 38. A self-propelled wheeled fuel transfer cask 50, hereinafter described in detail, is movable along the tracks 44 from the reactor 30 to the fuelstorage vault (not shown) and to the shipping cask loading area 48. The lower portion of the cask 50 extends, as shown in FIGURE 1, through the open track construction to communicate with the reactor and other equipment in the lower level.
The combined movement of the bridge 42 relative to the opening 40, and the fuel transfer cask 50 relative to the bridge, serve to position the cask over a preselected one of a plurality of control rod nozzles or special refueling nozzles 51 of the reactor. The nozzles 51 extend upwardly from the primary containment vessel 32 and are in communication with the reactor core 52 which is housed within the vessel 32. The core 52 is a generally cylindrical package or bundle of elongated upright core elements which include control rod guide tube elements 53, control rod elements, and fuel rod elements 54. The core may also be surrounded by suitable reflector elements (not shown). Preparatory to refueling, either the control rod drive mechanism with its two associated control rod elements, or, in the case of a special refueling nozzle, the shielding plug, in the pre-selected nozzle is removed from the reactor. In brief, the fuel transfer cask 50 is then positioned over and connected to the selected nozzle 51. Spent elements are transferred from the reactor through the nozzle and into the transfer cask. The cask is also used to transfer fresh elements into the reactor.
The cask 50 transports spent radioactive elements to a fuel storage vault (not shown) in which they are stored for a cooling period. The cooled elements are subsequently taken by the fuel transfer cask 50 and delivered to a fuel shipping cask 60 (FIGURES 1 to 7), disposed in the lower level loading area 48, as shown in FIG- URE 1. More specifically, the fuel transfer cask 50 is moved along the tracks 44 to a position over the opening 49 leading to the area 48 from which position the cask 50 delivers the spent elements to the fuel shipping cask 60. The fuel transfer cask 50 is also used to transfer fresh elements from the shipping cask 60 to the reactor.
FUEL SHIPPING CASK The fuel shipping cask 60- is shown in FIGURES 2 through 7. In general, the illustrated cask 60 includes an elongated generally cylindrical closed shielded housing or casing 62 positionable for loading and unloading with its longitudinal axis vertical. For convenience, the cask and its components will be described in terms of its vertically extending operational position. The casing 62defines a closed cavity 65 within which a rack or support arrangement 66 (FIGS. 6 and 7) is supported for rotation about the vertical central axis of the casing.
The rack arrangement 66 defines a plurality of elongated vertically extending channels or compartments 68 which are each adapted to receive one of the reactor elements. As shown particularly in FIGURE 7, the illustrated rack arrangement 66 provides four concentric rings or loops of compartments 68, and there are four relatively small openable access openings or passageways 70 in the upper end of the casing 62 (FIG. 3) which are each radially aligned with one of the rings of compartments. The cask 60 further includes driving means 72 (FIG. 6) which is operable to rotate the rack arrangement 66 to align a pre-selected compartment 68 with an access opening 70.
Now referring more specifically to the fuel shipping cask 60 illustrated in FIGURES 2 through 7, the generally cylindrical shielded housing or casing 62 for the cask is positioned in vertically extending position, as shown in FIGURES 2 and 6', for loading and unloading, and, in this regard, is provided with a pair of opposed trunnions 73 and a second pair of. trunnions 73!), the latter of which provide suitable attachments for raising and lowering apparatus, such as a pair of hydraulically operated cylinders (not shown). For shipment, the cask is mounted on its side in horizontally extending position (not shown) on a heavy duty railroad fiatcar 74 with the trunnions 73 received in suitable mating supports 73a on the railroad car. Other external equipment (not shown) is used to complete the supporting and securing of the cask for shipment. Referring to FIGURE 1, the railroad car 74 is moved along suitable tracks 75 into the loading area 48 and the cask is pivoted about the pair of trunnions 73 at its lower end to the upright position where the access passageways 70 are uppermost. The railroad car is positioned so that the access passageways 70 are aligned below the opening 49 above the loading area. The casing 62 includes generally a receptacle or base section 76 and a cover or lid section 78.
The illustrated base section 76 includes an exterior shell 76a and an interior shell 7617 (FIG. 6). The shells 76a and 76b are generally cylindrical vertically-extending containers open at their upper ends and closed at their lower ends. The interior shell 76b is somewhat smaller than the exterior shell 76a being located centrally of and spaced from the cylindrical wall of the exterior shell by three elongated, vertically extending, semicircular pipe sections 79 (FIG. 4) equally spaced circumferentially around the interior shell. The lower walls of the shells are also spaced from each other, and the space between the shells as well as the cavities of the three semicircular pipes 79, an filled with lead FIGS. 5 and 7). The upper edges of the shell are generally level and connected together by a generally horizontal, annular, interconnecting ring structure 82 (FIG. 6) which defines an internal annular recess 84 extending around the inside of the upper edge of the base section 76.
The illustrated cover or lid section 78 (FIGS. 2, 3 and 6) is in the form of a generally fiat circular disk or plate that is secured over the open upper end of the base section 76 to complete the shielded casing 62. The underside of the cover section 78 is formed with a downwardly extending centrally located cylindrical portion 86 which is adapted to mate with. the annular recess 84 at the upper edge of the base section 76 when the cover section 78 is positioned on the base section as illustrated in FIGURE 6. The cover section 78 is secured in place by a plurality of screws 88 disposed circumferentially adjacent the edge of the cover section (FIGS. 2 and 3).
When the cover section 78 is secured on the base section 76 to provide the shielded casing 62, the two sections define internally thereof the generally cylindrical upright cavity 64. The rack or support arrangement 66 is rotatably supported within the cavity 64, as hereinafter described.
As best shown in FIGURES 6 and 7, the illustrated rack arrangement 66 includes a generally circular horizontal lower support plate 102 having a somewhat smaller diameter than the Casing interior. The support plate 102 is supported generally coaxially within the casing and spaced a short distance above the lower end wall of the casing. Secured upon and supported by the support plate 102 are five generally cylindrical tubes or barrels 104 which are secured with their axes generally vertical and concentric with the vertical axis of the casing. The cylindrical barrels 104 are generally of equal height with their upper edges spaced a short distance below the cover section 78, but vary in diameter from the largest outermost barrel 104a, which is approximately the diameter of the plate 102, through intermediate barrels 104b, 1040 and 104d, to the smaller and innermost barrel 1046. Thus, the barrels 104 are in generally concentric telescoped relation, secured at their lower edges to the horizontal plate 102, and define four generally cylindrically or annular spaces between adjacent barrels. The annular spaces are designated a, b, c and d, with largest annular space a being defined inwardly of barrel 104a and outwardly of barrel 104b, with space 11 defined inwardly of barrel 6 104b, with space 0 defined inwardly of barrel 104s, and with space 0! defined inwardly of barrel 104d. It may also be noted that the spacing between the adjacent barrels 104- is approximately equal so that the radial widths of the various annular or ring-like spaces are approximately equal to one another.
Each of the annular spaces is subdivided into the individual element-containing channels or compartments 68 of the rack arrangement. More particularly, each of the annular spaces is provided with a plurality of generally vertical radially extending dividers 106 which are secured in position between adjacent barrels 104. The dividers 106 in adjacent annular spaces are generally offset or staggered to provide stability to the rack arrangement. As shown in FIGURE 7, the rack arrangement 66 of the illustrated cask 60 provides six elongated vertical channels or compartments 68 around the innermost space a, twelve such compartments around the next intermediate annular space a, eighteen such compartments around the next intermediate annular space b, and twenty-four such compartments around the outermost annular space a for a total of sixty compartments.
As shown in FIGURE 7, there is secured in a corner of each compartment 68 of the intermediate annular space 0 an elongated vertically disposed absorber rod 110 which serves, in case of an emergency as where the cask becomes flooded by a moderating .material such as water, to absorb neutrons and thereby ensure that the fuel in the cask 60 does not become critical. Each of the illustrated rods 110 is in the form of a hollow tube capped with steel end plugs and filled with a suitable neutron absorbing material such as boron carbide granules.
As shown in FIGURE 6, a generally circular upper bearing race or ring 112 is secured to the underside of the horizontal support plate 102 in inwardly spaced relation to the edge of the plate approximately half the distance to the center thereof. Secured directly beneath the bearing race 112 is a generally circular bearing cage or ring 114. The race 112 and the cage 114 are secured to the plate 102 as by means of screws 116. The illustrated bearing cage 114 is provided with a plurality of circumferentially spaced-apart recesses in each of which is partially received a bearing-ball 118. Disposed immediately below the cage or ring 114 is a generally circular lower bearing race or ring which is secured to the horizontal lower end wall of the interior shell 76b as by means of screws 121. The bearing-balls 118 abut the lower race 120 to vertically support the rack arrangement 66 while permitting it to rotate with a minimum of friction between thr rack arrangement and the supporting parts.
The illustrated rack arrangement includes a generally tubular upper collar or bushing 122 which is mechanically secured in the upper end of the innermost and smallest barrel 104a. A generally tubular lower collar or bushing 124 is secured in the lower end of the barrel 104e. The horizontal support plate 102 is provided with a central opening or aperture through which the lower end of the bushing 124 extends downwardly. The lower end of the bushing 124 is provided with an outwardly extending flange which is secured to the underside of the plate 102 as by means of screws 126. The illustrated bushings 122 and 124 are both generally cylindrical externally to mate with the respective ends of the cylindrical barrel 104e, while the central opening through each of them is enlarged at either end to provide a narrowed or restricted intermediate annular contact area or zone 122a and 124a, respectively, for each bushing.
Received in, and extending through, the upper bushing 122 is an elongated vertically extending upper cam 128 which includes a generally cylindrically lower portion, an irregularly shaped upper portion, and an upper extension. The upper portion of the cam 128 is cut away to form a recess on the left, as viewed in FIGURE 6, and is provided with an upwardly outwardly enlarging wedge or projection 12811 on the right. The upper end of the cylindrical lower portion is recessed inwardly to meet the lower inward end of the wedge 128a. When the cask is in operating position, the lower portion is received in the bushing 122, as shown in FIGURE 6, with that lower portion engaging the contact zone 12.211 of the bushing. The upper extension of the cam 128 is connected to the casing 62 in a manner permitting vertical movement but preventing rotation of the cam. More particularly, the upper extension is received in a recess in the under-surface of the cover section 78. A pair of keys 130 are arranged between the extension and the cover section 78 to prevent relative rotation between the cam and the casing while permitting vertical movement of the cam.
An elongated generally tubular vertically extending lower cam 132 is received by the lower bushing 134. The lower cam 132 is somewhat similar in construction to the upper cam 128, having a generally cylindrical lower end portion adjacent an irregularly shaped upper portion formed to provide a recess at the left and a wedge or projection 132a at the right. The lower cam 132 is connected through a pair of keys 134 and a housing 135 to the base section 76 of the casing in a manner permitting vertical movement but preventing rotation of the 'lower cam.
The lower cam 132 is provided with a generally cylindrical vertically-extending threaded central aperture through which a generally cylindrical threaded lower center shaft 136 is rotatably disposed. The lower end of the shaft 136 is rotatably mounted in the housing 135 which is supported in the lower end wall of the base section 76. The upper end of the shaft 136 is secured to the lower end of a cylindrical vertically-extending tube or hollow rod 140. The tube 140 extends upwardly through the center of the rack within the innermost barrel 104s. The upper end of the tube 140 is secured to the lower end of a generally cylindrical vertically extending threaded upper center shaft 142. The shafts 136 and 142 and the center tube 140 thus comprise a unitary center shaft construction. The upper end of the shaft 142 is rotatably threaded into a threaded central aperture or recess 144 in the lower end of the upper cam 128.
Thus, when the cask is in its vertically extending operational position and the parts are in the respective positions shown in FIGURE 6, the rack arrangement 66 is rotatable about the central axle assembly which com prises the cams 128 and 132 as well as the rotatable center shaft construction. When the cask is in this operational centered position, the central axle assembly is rotationally fixed as will be understood from the further description. The rotational engagement between the rack arrangement and the center axle assembly is between the upper and lower contact zones 122a and 124a of the bushings and the cylindrical lower portions of the cams 128 and 132. The rack arrangement 66, as noted above, is supported vertically by the bearing-balls 118 for low-friction rotational movement.
As shown in FIGURES and 6, the lower end wall of the interior shell 76b defines a generally rectangular well or recess 146 located centrally of the casing. The well 146 is adapted to receive the rectangular housing 135, within which the lower shaft 136 is rotatably supported, and to restrict rotational movement of the housing. The illustrated housing 135 includes a generally rectangular upwardly-open body portion 135a and a hori zontal cover or lid portion 135b. The lower portion of the shaft 136 extends downwardly through a suitable hearing in the cover portion 135b with the lower end of the shaft rotatably supported in a suitable bearing in the lower wall of the base portion 135a. The cover portion 1351) includes a generally central, upwardly-open, recessed area or cavity around the shaft 136 where the lower end of the cam 132 is received and is secured against rotation by the keys 134.
As shown in FIGURE 6, within the housing 135 and fixed on the lower portion of the shaft 136, is a centering worm gear 150 which engages a centering worm 152 fixed to a horizontal shaft 154 rotationally supported in the housing 135. The shaft 154 is adapted to operatively connect to suitable motor means (not shown) through a closable passageway 156 which, as shown in FIGURE 5, extends from the recess 146 to the exterior of the casing. When the cask is positioned in a suitable installation such as the loading area 48, the shaft 154 is operatively connected to motor means of the installation. When the cask is being shipped, the passageway 156 will be sealed.
Rotation of the centering worm 152 rotates the worm gear 150 and the center shaft construction to move the cams 128 and 132 vertically. More specifically, the rotation of the threaded shafts 142 and 136, which comprise the center shaft construction, move the threaded cams 128 and 132 either both upwardly or both downwardly due to the fact that both are threadedly engaged with the shafts but are keyed to prevent their rotation. The cams 128 and 132 are shown in FIGURE 6 in their elevated or uppermost positions where the cylindrical lower portions extend through the contact areas 122a and 124a of the bushings to center the rack arrangement 66 in its operating rotational position.
Suitable rotation of the center shaft construction moves or shifts the rack arrangement laterally of its center position, as shown in FIGURE 6, to the right to an offset or eccentric position. More specifically, the cams 128 and 132 are moved downwardly by the rotation of the center shaft construction. The downward movement of the projections 128a and 132a of the respective cams 128 and 132 shift or move the rack arrangement to the right and maintain it in that position. Then, when the entire cask is tilted or pivoted toward the right and onto its side for shipment, the rack arrangement will rest against and be supported by the casing rather than being suspended on the central axle assembly. This is desirable since it provides more uniform support of the rack arrangement.
A lock screw 157 is provided in the center of the cover section 78 for abutting the upper end of the cam 128 and locking the central axle assembly and the rack arrangement against linear movement. The lock screw 157 is operated through an aligned closable port 158 in the cover section 78.
When the cask is again pivoted to the upright position for loading or unloading, the rack arrangement is laterally shifted by rotation of the center shaft construction back to its centered position (FIGURE 6) to permit rotational positioning of the rack arrangement.
The rack driving means, designated generally 72, is illustrated best in FIGURE 6 within a driving means housing 160 disposed adjacent one side of the lower end of the casing. More particularly, the housing 160 is disposed in an upwardly open cavity or well 161 (FIGURE 5) in the horizontal lower wall portion of the interior shell- 76b. The housing 160, as viewed in plan, is generally rectangular, with one end being semi-circular and conforms to the shape of the well 161 which is of similar configuration, the semicircular end of the housing being directed radially outwardly to a point immediately adjacent the cylindrical wall of the casing. Extending from the radially inward end of the well 161 to the exterior of the casing is a generally tubular closable passageway 162. The passageway 162 extends generally parallel to the passageway 156, and its outer end is spaced relatively closely to the outer end of the passageway 156 at one side of the cask.
The illustrated housing 160 includes an upwardly open base portion 160a and an overlying horizontal cove or lid portion 16%. A vertical shaft 163 is rotatably supported in suitable bearings in the bottom wall of the housing base portion 160a and in the cover portion 160]). A drive worm gear 164 is fixedly secured to the shaft 163 and is meshed with a drive worm 166. The worm 166 is fixedly secured to a horizontal shaft 168 rotatably supported by the housing 160. The horizontal shaft 168 is aligned with the passageway 162, through which it is operatively connected to motor means (not shown) of the installation, when the cask 60 is supported in operative upright position in a suitable installation such as the loading area 48.
The upper end of the vertical shaft 163 extends outwardly of the housing 160 and has fixed to it a spur gear 170. When the rack arrangement 66 is in its centered operative position, the gear 170 meshes with a generally circular internal ring gear 172 secured as by means of screws 174 to the underside of the horizontal plate 102 of the rotary rack arrangement at the periphery of that plate. The selective operation of the associated motor means serves to rotate the rack arrangement. The matching configuration of the housing 160 and its well 161 prevents rotation of the housing.
An access, service or emergency port 176 is provided at the lower end of the side wall of the casing opposite the ring gear 172 and radially outwardly of the rack driving means 72 to permit manual rotation of the rack arrangement. As illustrated in FIGURE 6, a shielding or sealing plug 178 is normally removably disposed in the port 176 to close the port. An outer or exterior port cover 180 is removably secured over the outside of the port 176.
FIGURE 6 also illustrates indicating means 182 for the cask (located in the left side of the bottom of the cask as viewed in the drawing) which includes a micro-switch 184 and a box receptacle 185 that is secured as by means of screws 186 in a port 188 through the horizontal bottom wall of the casing. The switch 184 is positioned to be actuated by cam 190 secured to the underside of the horizontal support plate 102 of the rack arrangement 66 intermediate the outer edge of the plate and the ring of supporting bearing-balls 118. The rotation of the rack arangement serves to operate the switch 184 to indicate the rotational position of the rack arrangement.
As noted above, the fuel rod elements 54 and control rod guide tube elements 53 are inserted and removed from the cask 60 through the access openings or passageways 70 in the cover section 78 of the cask. Each of the illustrated access passageways 70 is generally cylindrical and vertically extending, having a larger diameter portion at its upper end to provide a support shoulder 192. As shown in FIGURES 3 and 6, the access passageways 70 are arranged along the centerline of the cover section 78 with one passageway radially aligned over each annular or ring-like space a-d of the rack arrangement 66. Because of space and shielding requirements, two of the access passageways 70 are located on one side of the cask, while the other two passageways are on the other side of the cask: one access passageway is over the outermost annular space a, while the other passageway on that side of center is over the alternately inward space 0n the other side of center, one passageway is over the innermost space d, and another passageway is over the alternate space b. As shown best in FIGURE 3, the size of each passageway is small relative to the storage area of the cask in plan so that the isolation valve required for moving an element into or out of the cask is quite small in comparison to the cross section of storage space in the cask.
The illustrated access passageways 70 are normally closed and sealed, each receiving a generally cylindrical shielding plug or insert 194. The" lower end of each of the plugs 194 is provided with a reduced diameter whereby each plug is supported within a passageway 70 by the annular shoulder 192 of that passageway. The uppermost end of each of the passageways 70 is threaded to receive a mated locking or securing nut 196 which serves to maintain the shielding plug 194 in the passageway.
The rack arrangement 66 may be rotated by means of the gears 170 and 172 to position any preselected channel or compartment 68 below the access opening 70 asso ment 53) to be placed into or removed from that compartment. The rack may be repeatedly rotated to provide access to successive compartments until the cask is fully or partially filled or emptied. For shipment, the rack arrangement is shifted, as noted above, so that its weight is directly supported by the casing when the cask is tilted onto its side into shipping position.
The illustrated cask 60 may be handled or shipped as a shielded, sealed self-contained integral unit. The illustrated cask provides adequate shielding for personnel and handling equipment during loading, unloading, shipment and storage for indefinite periods of time.
FUEL TRANSFER CASK WITH SINGLE MOVE- MENT ROTARY RACK ARRANGEMENT The shielded fuel transfer cask 50, which has a single motion rotary rack arrangement, is shown generally in FIGURE 1 and in further detail in FIGURES 8 through 18. The cask 50 illustrates a preferred form of fuel transfer cask and is illustrative of a reactor-element receiving, transporting, and delivering cask of the present invention.
Broadly, the operation of the fuel transfer cask 50 is to receive or deliver-one at a timea supply of fuel rod elements 54 and/ or control rod guide tube elements 53, and to transport a number of such elements between the reactor, storage facilities, and shipping facilities.
Briefly, the illustrated fuel transfer cask 50 includes a generally cylindrical, upright, closed, shielded casing or housing 200 which is mounted on a wheeled carriage 202 (FIGURE 1) movable along the rail or track system 44 of the nuclear power plant. The casing 200 defines an internal cavity 204 (FIGURE 8) within which a generally cylindrical rack arrangement 206 is supported for rotation about the vertical central axis of the cask. The rack arrangement 206 defines a plurality of elongated vertically extending compartments or channels 208 (FIGURE 10), each of which is adapted to receive one of the reactor elements 53 or 54. The illustrated casing 200 also includes a relatively small openable access passageway 210 in its lower end (FIGURE 8) with which each of the compartments 208 of the rack arrangement is adapted to vertically align incident to the rotation of the rack arrangement. Suitable rack driving means 212 are provided on the cask for selectively rotating the rack arrangement to align determined compartments with the access passageway. A grappler 214 for releasably connecting to an element and moving it into or out of a compartment is disposed in the upper end of the casing 200 above the rotary rack arrangement.
For refueling of the reactor 30, the fuel transfer cask 50 is fixedly positioned over the reactor 30, as shown in FIG- URE 1, and in conjunction with the operation of an isolation valve (not shown), the access passageway 210 of the cask is put into communication with the interior of the reactor through a selected empty control rod or refueling nozzle 51 which serves as an access port or passageway to the reactor interior. The selected control rod or refueling nozzle 51 is prepared for this use by' the prior removal of the" control rod drive mechanism or shielding plug which the nozzle ordinarily contains. The positioning of the fuel transfer cask 50 over the selected nozzle is achieved by the combination movement, as described above, of the cask itself and of the bridge 42. Once the cask is connected to the reactor, the cask is in a fixed position laterally or in horizontal directions, and it is not moved until the loading or unloading of the cask is completed.
The unloading and loading of radioactive elements from and to the portion of the reactor core serviced by each nozzle involves two distinct phases or steps. For unloading, first, the seven center elements, i.e., the elements directly below the selected nozzle, are lifted from the reactor into the fuel transfer cask 50 by the direct action of the grappler 214 of the cask. Second, the cask 50 is removed, a fuel transfer machine (not shown) is inserted into the selected nozzle, and the cask 50 is replaced over the nozzle. Additional or outer elements which are laterally displaced from positions directly below that nozzle are individually removed from the reactor core by the fuel transfer machine. The fuel transfer machine delivers each element to the grappler 214 of the fuel transfer cask which lifts the element into the cask. For loading, the steps or phases are reversed.
While the fuel transfer machine delivers all outer elements to the grappler in a single delivery position, the center elements are each in a different lateral position. Inasmuch as the cask is laterally fixed in position once it is connected to a reactor nozzle, but the center elements are located in various positions, the access passageway 210 and the grappler 214 of the illustrated cask arelaterally movable or positionable so that they can be aligned with each of the center elements. The alternative of rerepositioning of the cask 50 for each center element is undesirable since it would involve appreciable time. Similarly, the provision of a large passageway with only the grappler being laterally movable is undesirable as requiring at least a larger and more expensive door arrangement on the cask to deal with the increased escape outlet for radioactivity.
After the cask 50 has been loaded with radioactive elements from the core, the elements are transported to a storage vault into which they are transfererd from the cask and retained for a cooling period of some months.
The fuel transfer cask 50 is used subsequently to take cooled elements from the storage facility, transport them to a fuel shipping cask, and load them into the shipping cask for shipment to a suitable fuel reprocessing plant.
While fresh fuel elements made from new fuel may not require such shielding as in the case of spent fuel elements, the cask 50 is used to transport fresh but radioactive fuel elements made from reprocessed fuel from a storage facility or directly from a shipping cask to the reactor, and to load the reactor with the elements.
When elements are being transferred between a shipping cask, such as the illustrated cask 60, and the transfer cask 50, the shipping cask 60 is supported in the lower-level loading area 48 and the transfer cask 50 is positioned directly above it. The respective rack arrangements of the two casks are independently rotated to successively index or align the compartment containing the element to be transferred with the empty compartment of the other cask into which the element is to be loaded. This transfer operation between casks 50 and 60 is facilitated with adequate protection against radiation exposure to personnel and other equipment by a relatively small isolation valve that affords passage of the elements through the passageway 49 of the shipping cask loading area or installation 48.
Casing Now considering the fuel transfer cask 50 in further detail, as shown best in FIGURE 8, the generally cylindrical upright closed shielded casing or housing 200 defines therein the generally cylindrical internal cavity 204. The walls of the illustrated casing or housing 200 may be of a suitable shielding construction, as by including an inner and outer shell or layer of a material such as steel with an intermediate layer of a shielding material such as lead.
The illustrated cask is provided with a door arrangement 216 at its lower end operable to provide the openable and positionable access passageway or opening 210 of the cask. The illustrated door arrangement 216 comprises two sections: a smaller inner section 216a and a larger outer section 2161). The sections 216:: and 21 6b are each provided with an aperture 210a and 210b, respectively. The apertures 210a and 210b are moved relative to one another by the relative movement of the two door sections 216a and 21617 to either align with one another to provide the access passageway 210 or to be out of alignment with one another to provide a sealed closure to the interior of the cask.
More particularly, as shown in FIGURES 8 and 9, the short, generally cylindrical, outer door section 21611 is supported generally centrally in the open lower end of the casing with its axis vertical. The section 2161) includes the aperture 210b which extends vertically through the section, but which is also of oval configuration in plan cross section (FIGURE 9) and is positioned with one of its ends located cenatrally of the section and with the remainder thereof extending radially of the section. The hole 210a of the section 216a is of similar configuration but is offset relative to the axis of the section with its longitudinal or principal axis lying on a non-diametrical chord of the section when viewed in plan (FIGURE 9). A generally circular horizontal internal ring gear 220 is rotatably supported from the underside of the outer section 2161). The gear 220 is generally coaxial with the outer section 21617 and is rotatable about the axis of the section. The outer section 216b is provided with a generally cylindrical vertical cavity or recess in its undersurface in which the mating generally cylindrical inner section 216a is received. The recess is positioned eccentrically of the outer section 21612, and while it is generally below the aperture 21% and in communication therewith, it is positioned with its center or axis 221 (FIGURE 9) angularly offset from the aperture 210k.
The inner section 216a is supported in the recess by suitable bearings for rotation about its own axis and includes the aperture 210a which is elongated and extends transversely across the cylindrical section 216a offset to one side of its axis. A small external ring gear 222 is secured to the underside of the inner section 216a and engages the larger internal ring gear 220. Rotation of the larger ring gear 220, by suitable selectively-operable dooropening driving means 224 on the casing (FIGURE 9), rotates the smaller ring gear 222 and the inner section 216a relative to the outer section 216b to position the apertures 210a and 21% into and out of vertical alignment.
More particularly, the apertures 210a and 21% are shown in full alignment in FIGURES 8 and 9 to provide the fully open access passageway 210. The passageway 210 is thus formed by the aperture 210a aligning with the aperture 210b, with the upper aperture 21% defining the position of the passageway. As shown best in FIG- URE 9, the fully open passageway 210 extends radially outward from the center of the cask, and as will be seen, when fully open, it can afford access to a center channel or compartment 208 as well as to one outer compartment. When the inner section 216a is rotated about its axis, which coincides with the center 221 of the mating recess, the aperture 210a can be brought to the position shown in broken line in FIGURE 9 to completely close the cask, or can be rotated to an intermediate position (not shown) where only portions of the apertures 210a and 21% are aligned to provide a smaller access passageway to either the center compartment of the cask or an outer compartment. It should be noted that even the fully open passageway 210 is relatively small compared to the cross section of the storage area of the cask and that the partially aligned apertures provide an even smaller passageway.
The outer section 216b is supported for rotation about the vertical center axis of the casing by an annular hearing 226 between the lower edge of the cylindrical wall of the section 216b and the casing. The upper portion of the section 21617 has a reduced diameter to provide an annular horizontal ledge 228 on which a circular ring bevel gear 230 is mounted, The ring gear 230 is engaged by a bevel gear 232 which is secured on the end ofa horizontal shaft structure 233 that extends outwardly through and is rotatably supported in the adjacent casing wall. The shaft structure 233 is in driving connection with a selectively-operable door-positioning driving means 234 mounted on the outside of the casing. Operation of this driving means 234 serves to rotate both door sections as a unit to selectively position the passageway 210 laterally of the casing to facilitate handling of the center elements which, as explained above, must each be handled directly by the cask 50 in laterally different positions.
A generally cylindrical annular shield skirt 235 is disposed externally around the lower end of the casing 200. A generally horizontal annular flange 236 is fixed to the casing wall above the skirt 235. Thefiange 236 supports a selectively operable jack mechanism including a worm gear rack 238, a flexible drive shaft 238a and a gear motor 239 (FIG. 9) which is operatively connected to the skirt 235 and which functions to raise and lower the skirt incident to connecting the cask to other equipment such as an isolation valve for transfer of elements to or from the cask.
Rack arrangement The rack arrangement or means 206 for the illustrated fuel transfer cask 50 is disposed in the cavity 204 above the door arrangement 216. The illustrated rack arrangement 206 is a generally cylindrical, vertically extending, open structure supported for rotation about the central axis of the casing. The rack arrangement 206 includes a horizontal, generally circular, upper rack plate 240 which extends across the cavity 204 intermediate its height and is supported for rotation by a suitable annular bearing 242 between the outer edge of the plate 240 and the adjacent inner wall of the casing. Suspended from the plate 240 are a plurality of downwardly extending vertical support and guide rods 244. Supported at spaced intervals along the rods 244 are a plurality of horizontal, generally circular channel-defining plates 246. Suspended from the lowermost plate 246 are a plurality of spaced vertical bars 247 which support at their lower ends a generally circular, horizontal lower rack plate 248 (FIGURE 11) that extends across the cavity 204 just above the door arrangement 216. An annular lower flange structure 249 between the lower rack plate 248 and the adjacent casing wall laterally positions and maintains the lower end of the rack arrangement, particularly incident to its rotation. A generally tubular vertical shell structure 250 is supported in the cavity 204 around the rack arrangement and spaced from the casing inner wall.
The channel-forming plates 246 and the lower rack plate 248 are each formed to provide seven generally circular apertures 251 which are vertically aligned to define the seven elongated vertical compartments, channels or racks 208 of the illustrated rack arrangement 206. As shown best in FIGURE 10, the vertical rods 244 are disposed around the periphery of the channel-forming apertures 251 to partially define the channels and maintain the reactor elements moving through the channels in proper vertical alignment, The illustrated rack arrangement 206 is provided with a center compartment and six outer compartments annularly arranged around the center compartment. These seven compartments are relatively disposed in positions corresponding to the positions of the seven center fuel elements in the core.
A circular ring gear 252 is secured to the upper sur face of the upper rack plate 240 and is engaged by a gear 254 secured on the end of a radially extending horizontal shaft structure 256. The shaft structure 256 extends outwardly through and is rotatably supported in the casing wall and is in driving engagement with the selectively-operable rack driving means 212 mounted on the outside of the casing. The operation of the rack driving means 212 serves to rotate the rack arrangement 206 to any desired position.
The illustrated fuel transfer cask 50 includes a retaining mechanism 260 that is operable to selectively support and maintain reactor elements within channels 208 into which they have been positioned.
As shown best in FIGURES ll, 12 and 14, an elongated normally horizontally disposed support bar or platform 262 is provided at the lower end of each channel 208. Each bar 262 is pivotally supported at one end by the lower rack plate 248 adjacent to one of the channelforming apertures 251 in the plate for rotation about a horizontally disposed pin 264 (FIG. 14) so as to permit its movement between a vertical, raised, open position (shown in broken line) and a horizontal, lowered, or closed, supporting position (shown in full line). When a bar 262 is raised, it is positioned sufliciently out of the associated channel or compartment 208 so that it will not obstruct movement of an element or handling means through the channel. When a bar is lowered, it extends horizontally transversely across the associated channel with its free outer end resting on a block 265 mounted on the plate 248 across the aperture 251 from where the bar 262 is supported, to thereby support the element 54 in the channel (FIG. 12).. The pivoted end of each bar 262 is formed with teeth and engages a toothed block 266 that is secured to the lower end of a vertically extending rod 268. Each rod 268 is supported by the plates 246 for vertical movement and is connected at its upper end, through a compression spring 270, to an actuator pin 272 that is supported by the upper rack plate 240 for vertical movement.
More particularly, each actuator pin 272 is supported in a generally tubular, vertical, pin housing 275 for vertical movement. The housings 275 are supported by and extend downwardly from the upper rack plate 240. A biasing spring 276 in each housing 275 urges the associated pin 272 upwardly to a raised position where its upper end extends above the plate 240 as shown in FIG- URE 14. Suspended from the lower end of each pin 272 is a generally tubular vertical, connector housing 278. Each housing 278 is open at its lower end to receive the spring 270 and a guide member 279 that is secured to the upper end of the associated vertical rod 268. When a pin 272 and its rod 268 are so raised, the associated support bar 262 is in its horizontal closed position as shown in FIGURE 14.
The pins 272 are actuated to open the channels by a horizontal actuating plate 280 supported across the cavity 204 above the rack arrangement for vertical movement. More specifically a plurality of spaced studs 281 that are secured to the actuating plate 280 each extend downwardly through a suitable aperture in the upper rack plate 240 into a tubular, vertical, cushion housing 282 secured to the plate 240 and extending downwardly therefrom. The lower end of each housing 282 is closed and a compression spring 283 is disposed in each housing to resiliently support the actuating plate 280 and permit its downward movement.
Driving means 283 and jack mechanisms 285 are supported by suitable brackets on the casing inner wall above the actuator plate 280. The driving means 284 operates the jack mechanisms 285 to lower the plate 280 against the springs 283. In particular, the lower ends of vertically movable shafts or pins 286 of the jack mechanisms 285 are received in an upwardly open annular slot or trough 287 formed in the upper surface of the plate 280. This construction permits the plate 280 which is mounted on the rack arrangement to rotate with the latter while a driving engagement is maintained between the plate 280 and the fixed jack mechanisms 285.
When the actuating plate 280 is lowered to depress the pins 272, the support bars 262 are pivoted upwardly to their vertical open positions. With regard to a compartment already containing an element, the assocated bar 262 is held down by the element and the associated rod 268 remains stationary, the downward movement of the associated actuator pin 272 being absorbed by its compression spring 270. When an element is in place and it is desired to close the compartment, the actuating plate 280 is elevated to release the pins 272 and the bar associated with that channel or compartment is allowed to tilt back to its lowered closed position. Of course, the
reactor element initially is raised far enough in the compartment to permit the downward swing of the bar; then the element may be lowered onto the bar and deposited there. The bar, as noted above, will support the element in the compartment.
As shown best in FIGURE 8 a grappler or handling mechanism or means 290 is disposed in the upper end of the cavity 204. It is thus positioned above the rack arrangement 206 and operates in general to selectively position the grappler 214 in any desired position laterally of the rack arrangement as well as to raise, lower and operate the grappler.
-A generally circular, horizontal transverse plate 291 is secured across the cavity 204 above the rack arrangement 206. The transverse plate 291 is provided with a large central irregularly-shaped aperture 292.
A grappler carrier 293 which includes an elongated horizontal carrier plate 294 is mounted for pivotal movement on the transverse plate 291. More particularly, a short vertical post or shaft 295 is secured at one side of the plate 291 adjacent the central aperture 292. The post 295 extends upwardly from the plate and pivotally supports one inner end of the elongated carrier plate 294, with the remainder of carrier plate 294 extending across to' the other side of the aperture 292. The carrier plate 294 is supported in spaced relation above the transverse plate 291. An elongated horizontally extending shaft structure 296 is rotatably supported below the carrier plate 294, extending generally longitudinally and centrally of the elongated carrier plate. The shaft structure 296 is supported for rotation by three vertical support plates 297, 298, 299 which are secured to, and extend downwardly from, the underside of the carrier plate 294. The support plates each extend transversely of the elongated carrier plate 294 and are positioned at spaced-apart intervals along the carrier plate. One of the support plates 297 is secured at the outer end of the carrier plate with an intermediate plate 298 and an inner plate 299 being progressively spaced inwardly from the outer support plate 297. The intermediate support plate 298 has a greater height than the other two support plates and is provided with roller means along its lower edge. The roller means rest upon an upper surface of the transverse plate 291 to thereby support the outer end of the elongated carrier plate 294 while permitting its rotation.
A gear 300 is secured on the shaft structure 296 between the outer support plate 297 and the intermediate support plate 298 and is thereby positioned to engage a segment of a circular ring gear 302 which is secured to the upper surface of the transverse plate 291.
A large intermediate bevel gear 304 is rotatably disposed on the pivot post 295. A two-part connector mechanism 306 provides a driving rotational connection between the intermediate gear 304 and the inner end of the shaft structure 296. One part 306a of the connector mechanism 306 is secured to the underside of the carrier plate 294. The other part 306b of the connector mechanism 306, which includes a small bevel gear 306a that engages the intermediate gear 304, is fixed to the upper surface of the transverse plate 291. The two parts 306a and 30612 are movable relative to one another about a vertical joining axis so that the driving connection between the gear 304 and the shaft structure 296 will be maintained regardless of the rotational position of the carrier plate 294 about the pivot post 295. The large intermediate gear 304 is also engaged by a bevel gear 308 which is fixedly secured on the inner end of a horizontal shaft structure 310 rotatably supported in the adjacent wall of the casing. The shaft structure 310 is drivingly engaged to a suitable driving means 312 which is mounted on the outside of the casing and which is selectively operable to rotate the gear 300 and thereby cause the carrier plate 294 and the grappler 214 which it supports, as will be described below, to assume any desired azimuth position.
16 The illustrated fuel transfer cask 50 is also provided with means for positioning the grappler 214 radially with respect to the pivot post 295. A generally rectangular, horizontal, movable platform 320 is supported on the elongated carrier plate 294 for movement longitudinally of that plate. The platform 320 is supported between a spaced-apart parallel pair of track members 322 which are supported on and extend longitudinally of the plate 294. Each of the track members 322 is provided with an elongated horizontal groove 323 in its opposed or inwardly directed vertical surface. Guide rollers (not shown) mounted on the opposite longitudinal edges of the platform 320 are received in the respective grooves 323 to support the platform for movement.
The elongated carrier plate 294 is provided with an elongated, central, longitudinally extending aperture 325, and a generally cylindrical, hollow, vertical, grappler guide cylinder 326, which extends through and is supported intermediate its height by the movable platform 320, extends downwardly through the carrier plate aperture 325. The downwardly extending portion of the guide cylinder 326 also passes downwardly through the aperture 292 of the transverse plate 291. The lower end of the guide cylinder 326 is disposed a short distance above the actuating plate 280 of the retaining mechanism. The upwardly extending portion of the guide cylinder 326 has mounted on its upper end a pulley support block 328. The block 328 is a generally fiat structure disposed in a vertical plane that extends in general alignment with the elongated carrier plate 296. As will be described more fully, pulleys supported by the block 328 maintain and guide cables, and the cables support and operate the grappler 214 for vertical movement through and below the guide cylinder 326.
The means for moving the platform 320 and the supported grappler 214 radially toward and away from the pivot post 295 includes an elongated, horizontal, threaded shaft 334 which is rotatably supported above the carrier plate 294 between a vertical post structure 335 extending upwardly from the outer end of that plate and a vertical support plate 336 extending upwardly from the inner portion of that plate. An internally threaded follower member 337 is disposed on the threaded shaft 334 for movement longitudinally of the shaft as the shaft is rotated. The follower member 337 is secured to the movable platform 320 so that the movement of the follower produces like movement of the platform. The inner end of the shaft 334 is connected by a two-part pivotal connector mechanism 338 to a horizontal shaft structure 340 extending through and rotatably supported in the casing wall. The shaft structure 340 is in driving engagement with radial positioning drive means 342 mounted on the outside of the casing. The connector mechanism 338 is generally similar in construction to the two-part connector mechanism 306, having one part 338a supported by the vertical plate 336 and operatively connected to the shaft 334. The second part 338b, Which is pivotally connected to the first part 338a about a vertical axis, is mounted by a bracket 344 to the wall of the casing and operatively connected to the shaft structure 340. Selective operation of the drive means 342 serves to move the follower 337 longitudinally of the carrier plate 294 to thereby move the platform 320 and the grappler 214 toward or away from the pivot post 295. This radial movement, coupled with the azimuth movement afforded by the rotation of the carrier plate about the pivot post 295, permits selective positioning of the grappler 214 over an infinite number of positions relative to the underlying rack arrangement, and in particular permits the grappler 214 to be vertically aligned above any selected reaction element.
In general, the grappler 214 is supported, vertically moved, and actuated by the selective operation of a pair of flexible cables: a lower lift or hoist cable 348 and an upper actuator cable 350.
The lower lift cable 348 is secured at one end to a block 352 supported at the upper end of the vertical post 335. The cable 348 then passes over a vertically extending lower outer pulley 354 supported for free rotation about a horizontal axis in the pulley block 328. The lift cable 348 then extends vertically downwardly into the guide cylinder 326, passes through the grappler itself 214, and returns vertically upwardly where it passes over and around a vertically extending lower inner pulley 356, also supported for free rotation in the pulley block 328. The lift cable 348 then extends generally horizontally to a pulley 357 mounted for free rotation about a vertical axis in a pulley block 358 secured to the easing wall by a bracket 359. The blocks 352, 328 and 358 generally lie in a common vertical plane and consequently the cable 348 to this point has been confined to that common vertical plane. However, from the horizontal pulley 357 the lift cable 348 extends generally horizontally out of the plane, passing under and around a vertically extending lower oifset pulley 360 mounted for free rotation by suitable means on the casing. The cable 348 extends vertically upwardly from the pulley 360, passing through a narrow aperture through the upper end wall of the casing. Finally, the cable 348 is wound about a suitable lifting drum or reel 362 rotatably supported in a housing 364 mounted atop the casing. The drum 362 is in driving engagement through a clutch-brake connector with and selectively rotatably by suitable motor means 366 also mounted atop the casing.
The upper or actuator cable 350 i similarly supported and guided. One end of the actuator cable 350 is fixed to the block 352, from whence the cable extends around a vertical upper outer pulley 370 supported in the block 328 into the guide cylinder 326, where it passes through the grappler 214, and upwardly to an upper inner pulley 372, also mounted on the block 328. The actuator cable 350 then extends horizontally to a pulley 374 mounted in the block 358,,around an offset vertical pulley 375, and upwardly through a suitable aperture or passageway in the upper end wall of the casing into the housing 364. Finally, the actuator cable 350 is secured to and wound around a suitable actuator drum or reel 376 rotatably supported in the housing 364. The actuator reel 376 is in direct driving engagement with the motor means 368.
To raise or lower the grappler 214, the cables 350 and 348 are both moved at the same rate by the motor means 368, which is operated to rotate both reels 362 and 376. To actuate or operate the grappler 214, the connector 366 is operated to release the clutch and to apply the brake to the lift cable drum or reel 362 while the actuator cable reel 376 continues to rotate. The actuator cable 350 is thereby moved to cause relative movement of the parts of the grappler to cause engagement or disengagement by the fingers of the grappler with the element being handled.
It may be noted that the cables 348 and 350 in essence pivot around the vertical axis of the pulleys 357 and 374, which is in general alignment with the vertical pivot post 295. The portions of the cables between the pulleys 357 and 374 at one end and the block 352 at the other are disposed in a common vertical plane and these portions of the cable remain generally in this plane incident to the pivoting movement of the carrier plate 294 about the pivot post 295. In this connection, the block 352 is fixedly secured to the carrier plate 294 through the vertical post 335 and the block 328 is also mounted on the carrier plate294 through the movable platform 320 and the guiding cylinder 326. While the platform 320 is movable toward and away from the axis of the pivot post 295 (which generally coincides with the axis of the horizontal pulleys 357 and 374), the platform 320 is not capable of rotationalor azimuth movement around that axis other than as a unit with the carrier plate 294 and associated parts. Thus,-the platform 320 and the guide cylinder 326 and the block 328, define a common vertical plane with the vertical post 335 and the block 352. The platform 320 and the parts it supports are movable only in that plane. The noted portions of the cables 348 and 350 are likewise maintained in this pivoting common vertical plane, with the flexible cable arrangement also affording ready movement of the platform 320 and the grappler 214 toward and away from the axis of pivot. Movement of the platform, guide cylinder, and block 328 toward the pivot merely causes rotation of the various pulleys and a repositioning of these parts, including the grappler 214, at more inwardly located portions of the respective cables. It may particularly be noted that the height of the grappler 214 remains unaffected by its radial movement.
The illustrated grappler 214, shown generally in FIG- URE 8, is shown in further detail in FIGURES 15 through 18.]As seen in FIGURE 15, the grappler includes a generally cylindrical vertically extending hollow grappler housing 378 which is open at its lower end and has a transverse wall at its upper end. The housing 378 forms a generally cylindrical vertical central cavity 379. A pulley 380 for the lift cable 348 of the grappler mechanism is mounted at an intermediate point within the cavity 379 in such a manner that an open actuator assembly 381 is disposed in the cavity around the pulley and vertically movable relative to the pulley.
The lift cable pulley 380 is positioned in the cavity 379 centered between opposite sides of the cavity, and is supported on a short shaft 382 for free rotation about a horizontal axis. The shaft 382 is supported by a hoist or lift pulley support block 383 which is fixedly mounted by means of a transverse support member 384 within the cavity. The lift pulley 380 and the associated supporting parts thus extend transversely of the cavity 379 in general alignment with the plane of that pulley, being secured in position at opposed sides of the housing, with a space being left at either face side of the pulley 380. The lower lift cable 348 extends down into the grappler, is looped under the pulley 380, and passes back upwardly. The cable passes through appropriate openings or apertures in the upper end wall of the grappler housing. The lift cable 348 is wound on to or unwound. from its reel 362 by the drive means 368 to selectively raise or lower the grappler housing which carries with it the other parts of the grappler.
As noted above, the actuator assembly 381 is vertically movable within the cavity 379. The illustrated actuator assembly 381 includes a pair of elongated vertically disposed, opposed bands or strips 386 which extend down the sides of the generally cylindrical cavity 379 at opposite face sides of the lift cable pulley 380 and associated mounting parts. Each of the band 386 is curved or formed about a longitudinal vertical axis to generally conform to the contour of the housing cavity. The bands 386 are secured at their upper ends to a transversely extending support member 387 on which a pulley block 388 is mounted. An actuator cable pulley 389, which is smaller than the pulley 380, is mounted in the block 388 on a short shaft 390 for free rotation about a horizontal axis. As shown in FIGURE 15, the pulleys 380 and 389 are disposed in a generally common vertically extending plane which generally bisects the grappler. The upper actuator cable 350 extends down into the grappler, is looped under the actuator cable pulley 389, and passes back upwardly. The cable 350 passes through a pair of suitable apertures or openings in the upper end wall of the grappler housing.
The lower ends of the vertical bands 386 are secured to the upper end of a generally cylindrically vertically extending weighted actuator element 392 which is disposed below the lift cable pulley 380 and associated support parts. An irregularly-shaped generally annular actuator block 393 is secured around the lower end of the element 392. The illustrated actuator block 393 includes a set of three horizontally extending upper actuator pins 394 and a set of three horizontally extending lower actuator pins 395 (FIGURE 18).
The grappler 214 is provided with means to engage either a fuel rod element 54 or a control rod guide tube element 53. More particularly, mounted in the lower end of the grappler housing 378 are two sets of elongated vertically extending circumferentially-equallyspaced arms, hooks or members, one set of three, long, first, fuel-rd-element-engaging arms 396 and one set of three, alernately-spaced, shorter, second, guide-tube-element-engaging arms 397. The arms 396 and 397 extend downwardly from the open lower end of the grappler housing 378, as shown generally in FIGURE 15. The arms 396 and 397 are pivotally supported at their upper ends on pins 398 and 399, respectively, in a manner permitting the lower ends of the arms to pivot radially toward and away from the vertical center line of the grappler. Each of the'three arms 396 is provided'with a formed elongated vertical slot 400 in which one of the actuator pins 395 of the actuator assembly is received. Similarly, each of the arms 399 is provided with an elongated formed vertical slot 401 in which one of the actuator pins 394 is received. In general, the vertical movement of the actuator assembly 381 relative to the grappler housing 379 causes the arms 396 and 397 to open and close.
More particularly, each of the three fuel-rod-elementengaging arms 396 is provided with a radially-inwardlydirected circumferentially-enlarged projection or finger 402 (FIGURE 16) and the vertical slot 400 of each of these arms 396 is provided with a radially inwardly offset portion 403 at the lower end of the slot. Thus, when the actuator assembly 381 is lowered relative to the grappler housing 378, the fuel-r0d-element-engaging arms 396 are spread open or outwardly by the action of the actuator pins 395 moving into the offset lower end portion 403 of their respective slots. When the actuator assembly 381 is raised relative to the grappler housing, the arms 396 are pivoted or drawn radially inwardly. This causes the enlarged fingers 402 to set under an annular lip or ledge 54a provided by the head at the upper end of a fuel rod element 54. As shown best in FIGURE 16, the fingers 402 are circumferentially equally spaced and provide firm three-point engagement of the fuel rod element to prevent its slippage or misalignment. While the weight of the fuel rod element 54 would tend to maintain the aforesaid connection, positive vertical location of the grappler relative to the fuel rod element is provided by an engaging and positioning plug 404 secured to the grappler and extending downwardly from the center thereof through the open lower end of the housing. The plug 404 is provided with a flared central recess 405 which engages the generally conical upper end of the fuel rod element 54 and ensures maintenance of the positive connection between the grappler and the fuel rod element.
Each of the control-rod-guide-tube-element-engaging arms 397 is provided with an outwardly extending circumferentially enlarged finger or projection 406 (FIG URE 16 at its lower end and the vertical slot 401 of each arm is provided with a radially outwardly offset portion 407 at the lower end of the slot. When the actuator assembly 381 is lowered relative to the grappler housing, the arms 397 are pivoted or drawn inwardly by the action of the actuator pins 394 entering the lower portions 407 of their respective slots. When the actuator assembly is raised relative to the grappler housing, the arms 397 are pivoted radially outwardly, causing the en larged fingers 406 to seat in an annular groove or recess 53a that extends around the inside of the control rod guide tube element adjacent its upper end. The proper height of the grappler relative to the control rod guide tube element 53 is defined by the engagement of the lower end of the grappler housing 378 with the upper end of the guide tube element. This also ensures that the positive connection between the grappler and the guide tube element is maintained.
It will of course be understood that while the movement of the actuator assembly 381 operates all of the arms 396 and 397, at any given time the grappler 214 will only be operated with respect to one of the elements, i.e., either a fuel rod element 54 or a control rod guide tube element 53. Both of the types of elements 54 and 53 are illustrated in FIGURE 15 in broken line merely to illustrate the alternate functions or uses of the grappler.
Thus, with the grappler actuator assembly 381 lowered, the entire grappler 214 is lowered to position the appropriate arms in proper position relative to the element to be handled. The grappler is lowered by the drive means 368 operating both reels 376 and 362 at the same rate to unwind both cables 350 and 348 at the same rate. Then the grappler actuator assembly 381 is raised relative to the grappler housing and other grappler parts to a position such as shown in FIGURE 15 to cause the grappler fingers to engage the element being handled. This relative movement of the actuator assembly 381 is achieved by releasing the clutch and engaging the brake between the lift cable reel 348 and the drive means 368. Then the drive means 368 will only function to rotate the actuator cable reel 376 and not the lift cable reel 362. When it is desired to raise or lower the element being held, both of the cables 350 and 348 are again operated at the same rate so that the actuator assembly 381 is maintained in raised, locking position relative to the grappler housing 378.
To release the element, the aforesaid action is reversed, i.e., the actuator assembly 381 is lowered relative tothe grappler housing to move the fingers 402 and 406 out of engagement with the element being handled.
Suitable locks and safety features may be incorporated to prevent improper, dangerous or hazardous operation of the grappler mechanism.
Thus, the same compact, relatively simple, yet sure and efiective mechanism or arrangement which serves to raise and lower the grappler also serves to operate the grasping or connecting fingers.
The operation of the fuel transfer cask 50 may now be more readily understood.
To remove elements from the reactor 30, the empty cask 50 is positioned over a selected empty nozzle 51, fixedly connected to that nozzle by an isolation valve, and is operated to remove the seven center elements from directly below the nozzle. In this connection, the rack arrangement 206 is rotated to vertically align 208 with a selected one of the center elements. The grappler mechanism 290 is operated to position the grappler 214 directly above the selected center element. The inner door section 216a is rotated to align at least partially its aperture 210a with the aperture 21% of outer door section 216b and the door sections are rotated as a unit to vertically align the small access pasageway 210 with the selected center element. The isolation valve is also opened. The retaining mechanism 260 is operated to open or raise the platforms or bars 262 of the empty compartments and the grappler 214 is lowered through the selected compartments with which the grappler is aligned, through the underlying access passageway 210, through the isolation valve and nozzle 51, into the primary reactor vessel 32 (FIGURE 1). The grappler engages the selected center element, is actuated by the cables to connect to that element, and lifts the element essentially straight upwardly through the nozzle and the isolation valve into the aligned compartment. The element is raised sufficiently in the compartment to clear the platform 262 and the platforms are then caused to pivot or swing down to their closed or horizontally extending position across the bottom of the compartment. The element is lowered to its platform, the grappler is actuated to disconnect from the element, and the grappler is raised clear of the rack arrangement.
Then the procedure is repeated for another center element. The grappler and the access passageway 210 are repositioned laterally to vertically align with another of the center elements. The latch mechanism is operated