US3295700A - Method and apparatus for handling radioactive materials - Google Patents

Description

Jan. 3, 1967 A. ZIEGLER 3,295,700

METHOD AND APPARATUS FOR HANDLING RAfi'IOACTIVE MATERIALS Filed March 6, 1964 4 Sheets-Sheet l Fig. 1

Jan. 3, 1967 A. ZIEGLER 3,295,700

METHOD AND APPARATUS FOR HANDLING RADIOACTIVE MATERIALS Filed March 6, 1964 4 Sheets-Sheet 2 Jan. 3, 1967 A. ZIEGLER 3,295,700

METHOD AND APPARATUS FOR HANDLING RADIOACTIVE MATERIALS Filed March 6, 1964 4 Sheets-Sheet 5 Jan. 3, 1967 A. ZIEGLER 3,295,700

METHOD AND APPARATUS FOR HANDLING RADIOACTIVE MATERIALS Filed March 6, 1964 4 Sheets-Sheet 4 United States Patent 3,295,700 METHOD AND APPARATUS FUR HANDLING RADIOACTIVE MATERHALS Albert Ziegler, Erlangen, Germany, assignor to Siemens- Schuclrertwerke Alrtiengesellschaft, Berlin-Siemensstadt, Germany, a corporation of Germany Filed Mar. 6, 1964, Ser. No. 350,134 Claims priority, application Germany, Mar. 8, 1963, 84,065 20 (Ilaims. (Cl. 214l My invention relates to method and means for handling radioactive materials, such as machining, inspecting and transporting the same, in closed spaces.

The handling of radioactive materials is carried out today generally in so-called hot cells. In addition to the radioactive material, devices, apparatuses and machines necessary for inspection, machining, transporting and the like are surrounded by shielding so that the service personnel on the outside thereof can move about without danger and can carry out their operations from the outside with the help of remotely controlled manipulators. This method is very suitable for relatively simple operations; however, it becomes very troublesome and costly when the parts to be operated on become larger and when a transfer of material must take place from operating machine to operating machine, such as, for example, in the case of the production of nuclear fuel elements from irradiated fuel such as plutonium and the like. A particular disadvantage of such remotely controlled plants, is the great ditliculty in the repair of apparatuses and machines, often only possible after shutdown of the hot cell and after a suitable decontamination period.

It is accordingly an object of my invention to provide a method and apparatus for handling radioactive materials which avoids the foregoing disadvantages of the known methods and apparatuses.

With the above and other related objects in view, and in accordance with my invention, each member of the servicing personnel is protected by his own radiation shielding, is freely movable within a chamber that is shielded from the outside, and supervises or controls the working operations or transports the material or tools himself.

There is thus a conscious departure from the aforementioned hot cell devices and the operating principle employed till now has actually been reversed. In the conventional workshop, in which machines of customary construction are installed and in which the tools that are to be employed are subjected more or less to radioactive radiation, the service personnel can now move about freely and independently of one another, shielded individually from the radiation. Entirely independent of the fact that such a manufacturing plant requires no excessive and consequently costly automatic machinery, all of the operating devices are also always accessible to the service personnel and can, when necessary, be repaired during the regular operating period.

The radiation-proof device for each member of the service personnel furnishes protection similar to the concrete Walls of hot cells that are often meters thick, and is consequently of relatively heavy construction. Thus, it is not merely a matter involving a simple special protective suit, but rather mobile one-man compartments or cabins constructed of steel or lead for instance, are pro vided. From these cabins the service personnel can observe the surroundings and any machine tools, that are to be serviced or operated, through radiation-proof glass -or an optical device which prevents direct passage of nuclear radiation. Depending upon the activity that is to take place, a cabin of this type is either provided with air-tight rubber gloves by means of which the service attendant can directly manipulate the operating machine, or

3,295,760 Patented Jan. 3, 1967 alternately, simple manipulators that are operated mechanically, electrically or hydraulically from inside are provided on the outside of the cabin.

Because of the great weight of shielding cabins of this type, a special means of propulsion is necessary since wheels alone do not afford an absolutely stable position, and loading the bearing of the wheels with a weight of this type can prove to be very troublesome. Therefore, the principle of the Hovercraft or of the air cushion is employed, that is, the cabin whose lower edge is first placed directly on the floor of the work chamber so that the cabin has excellent stability, is then raised by an air cushion which is produced by a blower. It is only necessary for this purpose, that the cabin, for example, be raised only a few millimeters, so that for a cabin Weight of 10 tons and 1 square meter of floor area a pressure of only about 1 atmosphere is suilicient. In its raised condition, the heavy cabin can be moved practically frictionfree in all directions. The drive wheels, for example, that are provided therefor, are accordingly pressed against the floor by springs in order to furnish the necessary frictional contact.

In accordance with another aspect of my invention,

the cabin is provided with its own air-conditioning plant which produces circulation, cooling and drying of the air and maintains besides a slight over-pressure Within the cabin due to which no radioactive particles can infiltrate from the outside through any possible leaks in the cabin walls. Such devices can be installed, for example, inside the cabin under the seat of the service attendant. These devices are suitably driven by electricity as are the Wheels hereinafter described, the power being supplied through a drag cable or by an overhead trolley-wire mesh or grid and a takeoff contact brush, as well as through an electrically conducting floor of the work chamber and Wheel rollers which are made of conducting metal.

In very small work cabins, the wheels or component rollers as hereinafter described, may be driven by the service attendant himself, for example by means of a suitably variable bicycle transmission.

Other features which are considered as characteristic for the invention are set forth in the appended claims. Although the invention has been illustrated and described as method and apparatus for handling and fabricating radioactive materials, it is nevertheless not intended to be limited to the details shown, since various modifica tions and structural changes may be made therein without departing from the spirit of the invention and Within the sco e and range of equivalents of the claims.

The construction and method of operation of the invention, together with additional objects and advantages thereof, will be best understood from the following description of the method and of specific embodiments of the apparatus when read in connection with the accompanying drawings, in which:

FIG. 1 is a top plan view of a workshop or chamber in which the shielding cabin constructed in accordance with my invention is to be located.

FIG. 2 is a front elevational view of FIG. 1 showing several of the shielding cabins at various locations.

FIG. 3 is a longitudinal sectional view of one of the shielding cabins shown in FIG. 2.

FIG. 4 is a diagrammatic plan view of the drive wheels which constitute a component of the cabin shown in FIG. 3.

FIG. 5 is a longitudinal sectional view of the cabin of FIG. 3 showing the manner in which a service attendant gains access thereto and is sealed therein.

FIG. 6 is an enlarged perspective view partly in section of one of the drive wheels forming part of the drive mechanism of the cabin shown in FIG. 4.

FIG. 7 is a top plan view of FIG. 6.

FIG. 8 is a plan view of another component of the drive mechanism of the cabin.

FIG. 9 is a perspective view of a shielding cabin in a work chamber showing means for electrically energizing the drive mechanism of the shielding cabin.

FIG. 10 is a circuit diagram showing the means for driving the cabin from within the same.

Referring now to the drawings and first particularly to FIGS. 1 and 2 thereof, there is schematically shown a workshop or work chamber 2 in which two rows of operating machines and apparatuses 21 are located. The workshop is sealed off from the outside by strong walls 22, such as of reinforced concrete, and can be additionally embedded at least partly, for example about two meters deep, in the earth. Furthermore, the walls extending out of the ground can be at least partly covered with earth on their sides so that there is no danger of any harmful radioactive radiation penetrating through the sides. A system of locks 23 located on two opposite sides of the work chamber permits the machines and materials to be brought in and to be taken out of the chamber. In a side passage of this work chamber there is provided a decontamination space 24 through which the service personnel are required to pass in order to reach the access shaft 25.

In FIG. 2 a shielding cabin 3 furnished with manipulators 33 is shown in the work chamber. The service attendant or operator, who is located inside the cabin 33, is shown operating a machine tool 21. Another shielding cabin is shown in the decontamination space 24 and is being sprayed with water so that any possible radioactive dust that might have settled thereon is not carried any farther. A third shielding cabin is shown at the access shaft 25. The access shaft is installed in such a way that the cabin is held by a shaft-way 251 which extends downwardly from the upper story and the lid 39 of the cabin (FIG. 5) is able to be loosened and also raised upward from it. On the inside, secured to this lid, there is located, for example, a suspension 5 in the form of a trapeze on which the service attendant places himself when he is prepared to leave the cabin, and is accordingly raised upwardly in this manner as the lid is raised. The access shaft 25 has a side opening 252 in its upper portion through which the service attendant can step out into a radiation-free chamber. Entrance into the shielding cabin by the service attendant is effected in an exactly opposite manner as that described hereinbefore for leaving the cabin.

As shown in FIG. 3, the shielding consists of an essentially cylindrical part 31 and the aforementioned lid 39 which are separated from each other by a centering gap or joint 40, i.e. having a centering shoulder. The joint 40 can additionally hold a gasket ring so that a fully airtight closure of the lid against the cylindrical housing is assured. The lid and housing can be screwed to each other or secured by belts or by any other suitable means. The operating attendant observes the surroundings through a reflecting device such as a periscope 32 or a radiationproof window in the cylindrical wall, and can, for example, actuate manipulators that are mounted on the outside of the shielding cabin by means of the lever 33. An air-conditioning unit 35 is located under the seat of the cabin which is additionally suitably connected with an oxygen apparatus. The operator normally stands on a base plate 34, as is shown in top plan view in FIG. 8, which is movable on ball bearings 349. By means of these ball bearings 349, the plate 34 can be displaced sidewise within the periphery limited by the surrounding stops 341. It is held in its central position normally by springs such as represented diagrammatically by the dotted lines in FIG. 8. For any side displacement of the plate 34 by the operator, various non-illustrated contacts are actuated to switch on individual drives, of the rollers 37. The blower 36 (FIG. 3) located beneath the base plate 34 is simultaneously switched on with the switch mechanism actuated by displacement of the plate 34, thereby providing an air cushion which raises the lower sealing edge 38 of the cabin so that the drive rolls 37 which rest on the floor of the workroom, due to the aforementioned spring biasing force, are in a position to move the cabin.

The arrangement of the drive wheels is readily seen in FIGS. 3 and 4 and the rather unique construction of the component rollers 62, 63 is shown in FIGS. 6 and 7, this construction affording the cabin complete freedom to move about in all directions. This is made possible by the fact that these drive wheels do not consist of a simple circular disc with rubber tires but are rather constructed of individual spokes 61 with the rollers 62 and 63 mounted thereon and secured by means of a common hub 64 on the drive shaft 6. A drive wheel consists of two rings of rollers of this type located alongside one another and further located at any given time in staggered and overlapping relationship to one another as shown in FIGS. 6 and 7. These rollers 62 and 63 are of barrel-shape construction, the generatrix lines thereof constituting a segment or intercepts of the periphery 60. The drive wheels are consequently able to roll around the shaft 6 like an ordinary wheel without jogging the support or base and can, however, also be moved relatively without friction, in the embodiment illustrated, in the direction of its shaft 6, since the rolls 62 and 63 forming the periphery of the Wheel can be so arranged that they are easily rotatable about a shaft 65 extending perpendicular to the drive shaft 6.

The method of operation of the apparatus for handling and fabricating radioactive materials in accordance with my invention is as follows:

After the operator has gained access through the access shaft 25 into the individual shielding cabin 3, the latter is moved into the work chamber -2. The individual drive motors of the four drive wheels 37 are switched on by the base plate 34 in the following manner:

The operator applies pressure against the Wall of the cabin in the direction in which he wishes to move. Due to the reactive force, the base plate 34 is pushed in the opposite direction and thereby automatically actuates ter minal switches which turn on the drive motor that is located thereunder at the time. This advantageously occurs somewhat slowly so that the blower 36 which has been switched on simultaneously therewith has an opportunity to build up the air cushion for raising the cabin. When the cabin has reached the location desired by the operation in this manner, the pressure on the base plate 34 is involuntarily relaxed as the operator straightens 11p and the cabin returns to its central position due to the restoring spring force, and the drive motor and blower are accordingly switched off. Thereafter the lower sealing edge 38 of the cabin settles to the chamber floor and the operator located in the cabin can then carry out the necessary operations from a steady position. The operator is also in a position, as the case may be, to raise heavy loads by means of the manipulators since an absolutely stable position is afiorded by the cabin that is set down on the floor and by the weight of the load itself. Naturally it is also possible to transport a load such as raw materials or semi-manufactured components held by the manipulators from one machine to another. Complicated automatic transporting equipment is, therefore, unnecessary, and the operations can be carried out flexibly as in the usual workshop. Since it is possible to push the base plates unintentionally while heavy objects are being handled and thereby to release the blower mechanism for raising the cabin and to cause a cabin displacement reaction, it is expedient, for example, to provide foot-operated switches which prevent those mechanisms from being turned on while work is taking place at any machine or apparatus. 0n the other hand, it is also, useful to provide additional switches which make the control or steering of the cabin for relatively long travel distances possible. An additional switch permits the four drive motors to be switched on at the same time when the cabin is raised and accordingly permits the cabin to turn around at the desired location. It is furthermore advantageous to provide, for example, a hand or footactuated valve for rapidly venting the air so that the cabin can be set down rapidly without having to wait for the blower to slow down and stop. Furthermore, an open valve offers assurance that no unintentional raising of the cabin can take place.

Actually, this movable cabin is also suited for carrying tools and the like about with it. Such tools are advantageously hung on the outside of the cabin so that they can be easily grasped with the manipulators.

With respect to size, the cabin can, for example, have a diameter of about 1 meter and can have an over-all height of about 2 /2 to 3 meters. The thickness of the cabin wall depends upon the activity which is to take place in the work chamber and is naturally kept as small as is at all possible. A steel wall of about 20 centimeters thickness corresponds, for example, in its shielding effect to a concrete thickness of about 1 meter. Naturally, it is also possible and advantageous to use various known materials for the shielding walls of the cabin according to the particular type of radiation that is present.

It is not particularly difiicult to provide energy for the drive mechanism of such one-man shielding cabins. It can, for example, be supplied by a builtin internal combustion engine or by electric motors energized from storage batteries or through drag cables connected to an electric main.

As shown in FIG. 9, an electrically conductive wire net 354 is located at a predetermined height in the work chamber and can be electrically energized. Each cabin is provided with its own take-off contact brush 355 which is in continuous engagement with the net. A circuit is completed by providing a metallic surface 353 on the floor of work chamber with which the metal rollers 62, 63 are in engagement.

FIG. 9 shows the mobile one-man cabin 3 as having two possible energy connecting means, one of which is redundant but employable in the event of the failure of the other means. It is, of course, self-evident that the shielding cabin constructed in accordance with my invention, is movable by employing only one of these energy connections and can in fact have only one of them if it is so desired. On the side of the one-man cabin, there is mounted a rotatable cable drum 352 which rotates as the cabin is displaced and is suitably biased by spring action or the like, as is well known in the art, to roll up any excess length of the electric current supply cable 351. One end of the cable 351 is connected to a main electric power line (not shown), while the other end is connected to the devices in the cabin. The other current supply means consists, as heretofore described, of the electrically conductive floor surface layer 353 connected to a terminal N of the electric power source and the wire net 354 with which the terminal P of the power source is connected. The electric current thus passes on the one hand through the drive rollers 62, 63 of the one-man cabin and on the other hand through the take-off contact brush 355 which is mounted on the lid of the cabin.

FIG. 10 shows a diagrammatic circuit of the electrical system within the one-man cabin and its essential features. Switches 341 and 344 with contacts a and b for reversing directions constitute the switch mechanism aforementioned which are actuated by the displaceable base plate 34 of the one-man cabin. These switches have two contact pairs by which the blower 36 for producing the air cushion is started up each time before the drive motors 371 to 374, the delay elements 381 to 384 being connected in series with the motors 371 to 374 respectively. The delay elements can consist of one or more circuits or one or more separate units known to the man of ordinary skill in the art. The operation of all the actuating devices of the one-man cabin, with the exception of the air-conditioning device 6 35, is stopped by the multipolar foot switch 354 so that, for example, mechanical operations can be carried out without disturbance caused by accidentally actuating any of those devices. For each of the switches 341 to 344 a second switch is provided parallel thereto (although only one of these auxiliary switches 344' is actually illustrated in FIG. 10) which can, for example, be actuated by hand. A switch 346 permits the four drive motors to be switched on simultaneously so that the cabin can be turned in all directions at its desired location. The manipulator drive mechanism is shown symbolically at 81 and is also connected into this circuit network in the case where the manipulator is of the type known in the art that is electrically operated. A fuse is connected into the main supply line and is located within the cabin so that it can be readily replaced if necessary. The type of current and voltage is not a critical feature.

My inventive method permits a simple and efficient operation of handling and fabricating equipment with radioactive materials; special construction of machine tools and of automated apparatus is hardly necessary. The employment of shielding cabins which are freely rotatable and movable in any direction additionally permits the displacement of heavy loads on narrowly limited areas without great floor compression, for which obviously other cabin constructions are also possible. None of the bearings are heavily loaded because of the air cushion principle that is employed. The workshop floor can be completely fiat and smooth whereby the maintenance of cleanliness and the cleaning thereof which are of particular importance when radioactive materials are used, are essentially facilitated. Due to the weight of the settled cabin whose lower outer rim is supported on the floor, rather good stability is provided also for heavy loads. On the other hand, practically no vibrations or swaying motions occur during the displacement of the cabin.

In the event of failure of the raising mechanism of a cabin, a connecting nipple or valve (not shown) can be attached with the help of a second cabin so that the air cushion for the broken-down cabin can be restored by the blower of this auxiliary cabin. The cabin with the faulty lifting mechanism can then proceed under its own power or be drawn by the auxiliary cabin through the decontamination chamber to the access shaft. T hereby the greatest possible safety is afforded to the servicing personnel in the event of a possible accident or damage.

I claim:

1. Method of performing handling operations in a closed radioactive environment, which comprises shielding an operator individually in a radiation-proof enclosure freely movable within the closed radioactive environment, controlling the operations by the operator from within said enclosure, decontaminating the outer surface of the enclosure, and guiding the enclosure into a chamber shielded from the radioactive environment for permitting entry and exit of the operator.

2. Method of performing a handling operation in a radioactive environment, which comprises enclosing an operator individually in a freely displaceable cabin having walls impermeable to radioactive radiation and provided on the outside of said walls with manipulating means for performing the handling operation, displacing said cabin under the control of the operator to a location in the radioactive environment at which the handling operation is to be performed, moving said manipulating means under the control of the operator to perform the handling operation at said location, decontaminating the outer surface of the cabin, and guiding the cabin into a chamber shielded from the radioactive environment for permitting entry and exit of the operator.

3. An installation for performing handling operations in a closed radioactive environment, comprising means for shielding the surroundings from said radioactive environment, a radiation-proof enclosure for an individual operator freely movable within said radioactive environment, means controllable by the operator from within said enclosure for performing the handling operations in the radioactive environment, means for decontaminating the outer surface of the enclosure, and means for guiding the enclosure into said shielded surroundings for permitting entry and exit of the operator.

4. An installation according to claim 3, wherein the closed radioactive environment is maintained at a pressure lower than that of the surroundings.

5. An installation according to claim 3, wherein said surroundings are shielded from said radioactive environment by a pile of earth.

6. An installation according to claim 3, including a system of locks providing radiation-proof communication between the radioactive environment and the surroundings.

7. Installation according to claim 3 wherein said enclosure comprises a cabin having walls impermeable to radioactive radiation, drive means controllable by the operator within said cabin for universally displacing said cabin to a location in the radioactive environment at which the handling operation is to be performed, and handling means provided on the outside of said cabin walls and controllable by the operator from within said cabin for performing the handling operation at said location.

8. Installation according to claim 7, wherein said handling means comprises at least one glove of radiationimpermeable material adapted to receive a hand of the operator from within said cabin for directly performing the handling operation.

9. Installation according to claim 7, wherein said handling means comprises a remotely controlled manipulator.

10. Installation according to claim 9, wherein said manipulator is electrically controlled.

11. Installation according to claim 9, wherein said manipulator is mechanically controlled.

12. Installation according to claim 7, including airconditioning means in said cabin for providing radiationfree air to the operator therein.

13. Installation according to claim 7, wherein the lower edge of said walls is normally resting on the floor of the closed chamber, blower means carried by said cabin and actuated by the operator for providing an air cushion beneath said cabin whereby said cabin walls are raised from the floor, said drive means being relieved of the weight of said cabin by said air cushion and being spring-biased into frictional engagement with the floor of said chamber.

14. Installation according to claim 7, wherein said drive means comprise four individually driven wheels having axes extending radially to the vertical axis of said cabin.

15. Installation according to claim 14, wherein the axes of said four driven wheels are coplanar and substantially perpendicular to each other.

16. Installation according to claim 14, wherein each of said wheels comprises a pair of adjacent coaxial rings, said rings comprising a plurality of rollers rotatably mounted on shafts disposed substantially circumferentially about the respective wheel.

17. Installation according to claim 7, including switch means provided in said cabin for actuating said drive means to displace said cabin universally, and base plate means supporting the operator in said cabin and movable by the operator for selectively actuating said switch means to displace said cabin in a particular direction.

18. Installation according to claim 17, including blower means carried by said cabin for providing an air cushion beneath said cabin and switch means for actuating said blower means, said last-mentioned switch means also being actuated by movement of said base plate means.

19. Installation according to claim 7, including a drag cable carried by said cabin, electrically connected at one end to a power source distant from said cabin and at the other end to circuit means in said cabin for energizing said drive means.

20. Installation according to claim 7 wherein said radioactive environment is a closed chamber shielded from its surroundings, said drive means being electrically actuated and electrically conductive, an electrically conductive grid mounted at the top of said chamber substantially parallel and coextensive with the ceiling thereof, electric contact brush means carried by said cabin and slidingly engaging said grid, the floor of said chamber having an electrically conductive surface engaged by said drive means, said grid and said conductor floor surface being connected to opposite terminals of a power source, and circuit means in said cabin connected between said brush and said drive means for actuating said drive means.

References Cited by the Examiner UNITED STATES PATENTS 1,305,535 6/1919 Grabowiecki 301--5 1,645,437 10/1927 Lusse et a1. 191S4 2,285,860 6/1942 Jeffrey et al 191-122 2,603,301 7/1952 Sipior et al -21 X 2,985,129 5/1961 Kirkpatrick 214-1 3,043,448 7/1962 Melton 2141 3,125,232 3/1964 Brinkman et al 21417.4 3,174,571 3/1965 Cockerell 1807 FOREIGN PATENTS 77,717 3/ 1962 France. 822,660 11/ 1951 Germany.

GERALD M. FORLENZA, Primary Examiner.

R. G. SHERIDAN, Assistant Examiner.

Claims (1)

1. METHOD OF PERFORMING HANDLING OPERATIONS IN A CLOSED RADIOACTIVE ENVIRONMENT, WHICH COMPRISES SHIELDING AN OPERATOR INDIVIDUALLY IN A RADIATION-PROOF ENCLOSURE FREELY MOVABLE WITHIN THE CLOSED RADIOACTIVE ENVIRONMENT, CONTROLLING THE OPERATIONS BY THE OPERATOR FROM WITHIN SAID ENCLOSURE, DECONTAMINATING THE OUTER SURFACE OF THE ENCLOSURE, AND GUIDING THE ENCLOSURE INTO A CHAM-

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