|Publication number||US3746190 A|
|Publication date||Jul 17, 1973|
|Filing date||Dec 8, 1970|
|Priority date||Dec 9, 1969|
|Also published as||CA930937A, CA930937A1, DE1961575A1|
|Publication number||US 3746190 A, US 3746190A, US-A-3746190, US3746190 A, US3746190A|
|Original Assignee||Siemens Ag|
|Export Citation||BiBTeX, EndNote, RefMan|
|Patent Citations (4), Referenced by (16), Classifications (14)|
|External Links: USPTO, USPTO Assignment, Espacenet|
United States Paw... v r Q ca ROOM 7 v Hotz 1 July 17, 1973  FILLING APPARATUS FOR NUCLEAR FUEL l,578,072 3/1926 Canning et al 2l4/34 PELLETS OR THE LIKE  Inventor: Karl l-lotz, Erlangen, Germany Primary Examiner-Robert Sheridaf Att0rneyCurt M. Avery, Arthur E. wllfond, Daniel J.  Assignee: Siemens Aktiengesellschaft, Tick and Herbert L Lerner Erlangen, Germany  Filed: Dec. 8, 1970 57 T C PP 96,175 A filling apparatus for inserting material in pellet form into long envelope tubes where the pellets have a diam-  Foreign Application Priority Data eter that insures a close fit with respect to the inner wall of the envelope tube has a magazine for holding a large Dec. 9, l969 Germany P 19 61 575.9 number of stacks of the pellets and a guide Structure connectable to the magazine for holding and guiding  Cl 214/34 gl7 g the stacks individually. An insertion mechanism is dis-  Int Cl 621C 19/06 posed in operative proximity to the guide structure for Fie'ld CN 18 R inserting the stack disposed in the guide structure into I 214/23 226/l72 one of the envelope tubes to be filled. The insertion mechanism includes a tubular housing, a pusher slid- References Cited ably disposed in the housing and a drive device which engages the pusher for reciprocally moving the pusher UNITED STATES PATENTS to push the pellet stack from the guide structure into 2,725,993 l2/1955 Smith 214/18 N X th envelope tube, 3,009,868 ll/l96l Moulin 176/30 3,567,095 3/1971 Geist et a] 226/172 7 Claims, 2 Drawing Figures L JLZL Patented July 17, 1973 l/l/IY/ I FILLING APPARATUS FOR NUCLEAR FUEL PELLETS OR THE LIKE My invention relates to a filling apparatus for inserting pellet-shaped material into long envelope tubes. The pellets having a diameter substantially the same as the inner diameter of the tube so that a close fit between the pellets and the inner wall of the envelope tube is insured. The filling apparatus of my invention is especially suitable for use in connection with pellets of nuclear fuel material. Since the diameter clearance between the pellets and the envelope tube lie only in the order of magnitude of l l mm, a small fragment split off from a pellet can cause damage to theinner wall of the envelope tube as well as cause a severe impediment in the tube filling procedure. It is therefore necessary to provide for the complete mechanization of the filling proceudre. This is also necessary in view of the size of the tube to be filled, such tubes having a length of up to 5 m and a diameter of from to mm.
Up to the present time, it has been conventional to use so-called filling tappets. These tappets are used to insert in a horizontal position pellet columns into envelope tubes. The pellet columns are put together outside of the tube and have a length of 30 cm. This result can be achieved with one of two methods. One arrangement involves applying the same tappet stroke and using a relatively short tappet rod. The tappet would be required to move an ever longer pellet column in the envelope tube and this has as a consequence that an ever increasing friction force and likewise an ever increasing insertion force must be applied to the tappet. This arrangement not only places great requirements on the holding of the envelope tube to be filled, but also introduces the danger that the pellets will become damaged within the envelope tube so that under certain circumstances the entire filling procedure as well as the later operation of the finished fuel rods can be affected.
The other or second arrangement is that a very long tappet can be used to urge the pellet stacks or pellet columns to their final position in the envelope tube. With this arrangement, no increase in the friction within the envelope tube arises and the pressure load is always the same and does not increase. Accordingly, the possibility of damage is precluded. However, this arrangement requires the use of a very long tappet,'so that aside from space needed for accommodating such a filling apparatus, there is the danger of bending the long rod.
It is an object of my invention to improve upon the stacks of pellets and is-provided with aguide structure connectable to the magazine for holdingand guiding the stacks individually. An insertion mechanism is disposed in operative proximity to the :guide structure for inserting the stack disposed in the guide structureinto an envelope tube to be filled. Theinsertion mechanism includes a tubular housing, a pusher slidably disposed in the housing and a drive that engages the pusher for reciprocally moving the same to push the tappet from the guide structure into the envelope tube to be filled.
According to another feature of the invention, the filling apparatus is provided with an enclosure surrounding the magazine, guide structure and insertion mechanism in gas-tight relation to the ambient. The enclosure is provided with a suitable means for evacuating and for filling the same with protective gas. Also provided is a receiving structure disposed on the enclosure for receiving the envelope tube to be filled in gastight relation to the ambient.
According to a further feature of the invention, the tubular housing is given a curved shape which permits the apparatus of the invention to be accommodated in a limited space. Also, the pusher can be a beaded chain that fits snugly in the housing and the drive can be a drive belt in lateral engagement with the beaded chain.
In place of a rigid tappet rod, the aforementioned flexible beaded chain is provided which, in contrast to the tappet rod, can be installed in minimal space and the bending of the chain is prevented with a simple retaining structure such as, for example, a tubular housing. The front pusher piece of such a beaded chain can be directed with practically no play at all, so that the insertion path for the pellet column can be precisely adjusted. This adjustment results in a measurement of the length of the insertion path and the measurement can be carried out with impulses.
The invention will now be described with reference to the drawing wherein FIG. 1 is an elevation view, partially in section, of a filling apparatus according to the invention; and
FIG. 2 is a plan view, partially in section of the filling apparatus illustrated in FIG. 1.
The-tube to be filled is connected to the gas-tight enclosure 23. Not illustrated, is a vacuum pump and a protective gas source which are connectable to the enclosure at passage means 43. Within the enclosure 23, there is located a nuclear pellet magazine 21 containing a row of prearranged columns of nuclear fuel pellets 2. The pellet columns that in turn are brought to lie in front of the envelope tube 1 are inserted into the tube 1 by the action of the bead chain 3. The envelope tube .1 is connected with an enclosure feed 24 in gas-tight relation to the ambient. The drive for the bead chain is disposed in a separate enclosure'42 and comprises rollers 4 on which drive belts 41 are mounted as illustrated. It is possible to drive either one or both drive belts by a drive motor via a slipping clutch so that the bead chain 3 is movable in either the forward or backward direction. The bead chain has a head 34 in which a cord 33 is secured. Sphere-like beads 31 and tube-like beads 32 are alternately strung on the cord 33. At the end of cord 33, the chain is held tight and at the same time elastic by a spring 35. In lieu of the spring 35 a stretchable elastic cord 33 could be used.
Outside of the enclosure 42 provided for the drive, a tubular guide 36 is provided for guiding 'the'bead chain. The tubular member 36 is closed gas-tight at its end so that the insertion procedure can be undertaken in a controlled atmosphere, so that neither the pellet column to be inserted into the envelope tube I 'nor the 'bead chain 3 can bend out of line 'before the pellet column'is introduced in the envelope tube 1, there isprovided within the magazine housing 23, a guiding and holding structure 23 that can, for example, be constructed from sheetmetal curved to correspond to the pellet diameter as well as being provided with a spring guide. To minimize friction, the magazine grooves in which the pellet columns 2 are disposed can be prismatically dimensioned. The material to be used to construct the grooves is determined by the pellet material. According to the application purpose of the fuel rods produced by this filling apparatus and procedure, the pellets can be made of material containing uranium or plutonium containing material and represent, for example, oxides, carbides or cermets. It is possible to expand the illustrated apparatus so that after the envelope tube is filled with the nuclear fuel material pellets in accordance with the principle delineated above, it is possible to insert still other bodies into the tube, for example, bodies made of ceramic, hollow members or springs. It is also possible to apply the end cap to the tube to be filled and, for this purpose, the envelope tube extension piece or enclosure feed 24 must be constructed in a different manner.
The profile belts for driving the bead chain 3 can, for example, be configured as a metal link chain or be made of a corresponding rubber profile or another elastic material. Basically, it is sufficient to only drive a single belt even though it is advantageous to drive all profile belts standing in engagement with the bead chain. As. already mentioned, a slip clutch is arranged between the drive rollers 4 and the motor. The clutch has a coupling force that is adjusted so that, in the event that an impediment arises during the loading of the pellet stack, damage to the latter is prevented. If desired, the slip coupling can be connected together with a signal apparatus which is actuated when such a situation occurs. In addition it is advantageous to permit the motor to rotate in a single direction and to provide a reversal mechanism that has a proper gearing ratio for providing a quick return of the bead chain. The coupling can also be used for bringing the filling apparatus to rest.
To operate the filling apparatus according to the invention, the envelope tube to be filled is provided with a vacuum tight stop at one end and secured to the enclosure at its other end. The apparatus and envelope tube are then evacuated. THe magazine is moved forward so that first row of nuclear fuel material pellets 2 are disposed in front of the envelope tube 1. The motor M is then placed in operation, the motor moving the bead chain 3 forward. The head chain 3 then comes into contact with the pellet stack 2 and pushes the latter into the envelope tube until the pellet stack comes in conatct with the end stop secured at end of the tube. The bead chain is then pulled back in a fast gear and the magazine 21 moves one position further and the bead chain 3 moves slowly foward to perform the filling procedure. The second pellet stack is then pushed forward until it is brought into contact with pellet stack already inserted in the envelope tube and the bead chain is again withdrawn in the fast gear. This procedure is repeated until the envelope tube is filled. Then the helium gas is permitted to fill the apparatus and penetrates also into the fin spaces between inner wall of the envelope tube and the pellets. Finally, an end stopper is placed in the end of the envelope tube which is still free and welded thereto. The helium filling enables the user to detect possible locations at which the fuel rod construction is not gas-tight. The helium filling also has the task of improving the heat transfer, during operation of the nuclear reactor, between the pellets and the envelope tube. The pellets and envelope tube have different coefficients of heat expansion. The specific configuration of the magazine 21 is dictated by the size and type of pellets to be inserted into the envelope tube as well as the technique used to produce the pellets. The pellets can be formed in tablet fonn or also in cylindrical configuration and are then provided with a guiding jacket.
. While the invention is described by means of specific example, I do not wish to be limited thereto, for obvious modifications will occur to those skilled in the art without departing from the scope of the invention.
1. Filling apparatus for inserting into long envelope tubes a material, such as nuclear fuel, in the form of pellets having a diameter that ensures a close fit with respect to the inner wall of the envelope tube, said apparatus comprising a magazine for holding a large number of stacks of the pellets, a guide structure connectable to said magazine for holding and guiding said stacks individually, and insertion means in operative proximity to said guide structure for inserting the stack diposed in said guide structure into an envelope tube to be filled, said insertion means including a tubular housing having a curved shape, flexible elongated insertion means slidably disposed in said housing, said insertion means comprising a beaded chain having a curved shape, and drive means engaging said insertion means for reciprocally moving said insertion means into the envelope tube to move said tablet stack from said guide structure into the envelope tube to a selected location therein, each successive stack being moved individually by said insertion means into the envelope tube, said drive means including a drive belt in lateral engagement with said chain.
2. Apparatus according to claim 1, said drive means including a second drive belt, a slipping clutch, and a drive mechanism coupled with at least one of said drive belts via said clutch, said drive mechanism including control means for controlling the speed at which said one drive belt is driven.
3. Apparatus according to claim 1, said drive belt being made of elastic material and having a profile corresponding to the profile of said beaded chain.
4. Apparatus according to claim 1, said beaded chain comprising a cord, sphere-like chain beads strung on said cord and having a diameter corresponding substantially to the inner diameter of said tubular housing, tube-like beads strung on said cord in alternating relation to said sphere-like chain beads, said tube-like beads having a diameter less than said diameter of said sphere-like beads, and spring means positioned with respect to said beaded chain for holding said chain taut.
5. Apparatus according to claim 4, said cord being made of elastic material.
6. Apparatus according to claim 4, said cord being made of an inelastic material, said spring means being a spring preloaded and disposed between the end of said cord and said beads.
7. Apparatus according to claim 6, said cord being made of steel.
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|U.S. Classification||414/146, 376/261, 976/DIG.283, 254/DIG.600|
|International Classification||G21C21/02, B65B31/02, B65B35/40|
|Cooperative Classification||B65B31/02, B65B35/40, G21C21/02, Y10S254/06|
|European Classification||B65B35/40, B65B31/02, G21C21/02|