GB2203243A - An apparatus for drawing samples of radioactive and/or toxic substances from process components - Google Patents

Description

8 1 An apparatus for drawing samples of radioactive and/or toxic

substances from process components 2203243 The instant invention relates to an apparatus for drawing radioactive and/or toxic substances from process components, for example for use where the process components are arranged in shielded inaccessible cells.

An apparatus comprising an examining station located remote from the process components, a sampling station located near the process components, a conduit system between the examining and sampling stations, and a carrier movable in the conduit system and containing sample containers which are filled with the samples at the sampling station is known from EP-Al-0093609 in which it is proposed that the sampling of process liquid in a nuclear fuel reprocessing plant be undertaken in the plant itself. To accomplish that, a pipeline or conduit system of pneumatic conveyor type is provided leading from the hot cell to an analyzing station. A bottle carrier for sampling bottles is conveyed pneumatically in this pipeline system. At the sampling station within the hot cell a manipulator under remote control is arranged in a housing so as to withdraw the bottle containing the sample from the carrier or vehicle and transport it to the tapping station where it is pressed on the tap. This handling procedure is not suitable for nuclear fuel reprocessing facilities as the two processing cells which receive and shield process components comprises a plurality (about 80) of frame structures for the process components, and there is a great number of sampling locations per frame structure. In accordance with the known apparatus a separate, manipulator-like device would have to be provided at each of these sampling places to discharge thE sample bottles and dock them on to a needle head.

It is another disadvantage of the known apparatus that the transportation medium used for the bottle carriers is air.

The hot cell of a reprocessing plant is to be sealed as tightly as possible. This means that the shielding should be broken to the least possible extent,or not at all, by radioactive process flows. Air acting as conveying medium from the interior of-the cell to the outside would Affect this conception and cause leakage problems as the cell atmosphere might escape from the enblosed cell into side spaces or even into the open.

4_ In any nuclear plant, especially in reprocessing installations for irradiated nuclear reactor fuel elements many samples drawn from the process currents always must be examined in a central laboratory. Usually pipeliness pass from the shielded hot cells containing the chemical process components to a remotely located central laboratory for connection of the sampling places to the laboratory or to a sampling gallery located outside the hot cell. From the sampling gallery the samples drawn by needle heads into sample bottles are guide by suitable conveying means to the radiochemical work places in the central laboratory. Again, the partition between the hot cell and the sampling gallery is broken "constantly" by radioactive process streams.

US patent 4,493,792 describes an apparatus having the sampling station located outside of the hot cell but largely shielded. In this case, too, there is a manipulator- like device at the sampling station.:A sample bottle body is introduced sideways into the sampling station and the manipulator furnished with a needle punctures a diaphragm on the sample bottle and fills the desired sample through the needle into the bottle.

1 1 3 This also presents the problem mentioned above, namely that radioactive process streams get out of the hot cell.

It is, therefore, desirable to ---------------------improve the apparatuas of the kind described initially such that, while being highly efficient, it is characterized by a minimum risk of diversion of radioactive components.

In accordance with one embodiment of the invention, with.an apparatus of the generic type in question in that the carrier is controlled to move by an electric drive means between the sampling and examining stations, conduits pass from a plurality of sampling locations at the various process components to a commonhead of the sampling station, and the carrier comprises a counter- head, the two heads being designed such that linear movement alone of the car- rier with respect to the head causes the sample containers to bec.ome connected to the associated conduits so that samples can be filled into the sample containers.

Advantageous modifications and further developments of the invention may be gathered from the subclaims.

In the case of a preferred embodiment the sampling takes place inside the hot cell. It is only the samples that get to the outside, but not any process streams. Moreover, no interchange of air worth mentioning occurs between the hot cell and its surroundings since the bottle carrier is movable by an electric drive. Besides, the hot cell normally is kept at slight low pressure so that at best air will enter into the cell. The sampling is accomplished in parti- xularly simple manner since the docking of the carrier or of the vessels containing the sample is effected exclusive- ly by-linear motion of the carrier. No manipulators or any other remote- controlled devices are needed.

Another important aspect is that a plurality of samples may v be drawn at the same time from different process liquids at the same sampling station. Hereby the expenditure involved at a sampling station is reduced dramatically. It is another substantial advantage of at least a preferred embodiment of the invention that ---------- the individual component parts of the sampling system can be exchanged easily by the remote manipulating equipment which is present anyway'in the hot cell,and in keeping with the necessary remote control requirements.

Decontamination of the carrier, the sample containers, and the entire sampling system also can be effected very easily so that the risk of diversion of radioactive substances can be reduced still further.

Finally, disturbances can be eliminated rather easily, such as a carrier which got stuck in the conduit system. For a better understanding of the present invention, and to show how the sanie may be carried into effect, reference will now be made by way of example to the accorrpanying drawings in which:- Fig. 1 is an exploded view of a device according to Fig. 2A shows the drive portion of the carrier; Fig. 2B shows the sample container portion of the carrier; Fig. 2C shows the needle head portion of the carrier; Fig. 2D shows the sampling station; Fig. 3 is an orifice diagram (top plan view) of the sampling station shown in fig. 2D; Fig. 4 is a view partly in section of a valve at the sampling station; Fig. 5 is a perspective view of part of a hot cell including the.process components and conduits for the sarrpling system of an embodiment of the invention.

Reference will be had, first of all, to fig. 5. In a hot cell 1Z 1 1 1 - 5 1 of a nuclear fuel reprocessing plant there are several frame structures 2 in which the process components 3 are arranged. The process steps for reprocessing of the nuclear fuel are carried out in the process components 3. The process components are interconnected by pipelines or conduits in accordance with the course of the process flows.

Samples are to be drawn from the process media at different locations of the reprocessing system. In the case of the embodiment illustrated in fig. 5 the two frame structures 2 shown each include a sampling station 4. Pipelines (not shown) lead from the individual process components 3 of the respective frame structure to the associated sampling station 4, and the corresponding process medium circulates permanently in these pipelines during normal operation (i.e. at times when sampling does not take place).

Conduits 5 lead to the individual sampling stations 4, passing through the wall 6 of the hot cell 1. In a shielded duct 7 outside the hot cell 1 these conduits 5 are joined in a manifold 9 by way of remote-controlled line switches 8. The manifold 9 leads to an examining station (not shown) which is located outside the hot cell 1. This examining station corresponds to the central laboratory mentioned above. A sample carrier 10 is movable in the lines 5 and 9 between the examining station and the sampling stations 4. Such a carrier 10 may be directed to any desired sampling station 4 by reversal of the line switches 8.-It is likewise possible to use several carriers 10 at the same time, provided -certain minimum spacings between two moving carriers are observed.

Reference now will be had to fig. 1. It is an exploded view of part of the conduit 5 just ahead of the sampling station. The individual pipe sections illustrated, of course, form a continuous, sealed conduit. A carrier 10 is 6 movable in this conduit and, for the sake of clarity, this carrier too is illustrated in three portions 10a, 10b, and 10c. Actually these components form a single body. The severed portion 10a presents the drive portion, while portion 10b is the sample container portion of the carrier and portion 10c is the needle head portion of carrier 10.

Inside conduit 5 there is a continuous rail in the form of a flat plate having a guide groove 12. Electrical cables 13 are laid in the guide groove 12 to be tapped by a slider 14 arranged in the drive portion 10a. The carrier 10 receives control signals for its motions and possibly for its drive, too, through these electrical cables 13. Alternatively, the carrier may have its own energy supply in the form of batteries. The drive portion 10a further comprises a drive unit 15 with an electric motor, a transmission if desired, and a wheel set 16 as well as a thrust roller 17. The wheel set 16 travels on the rail 11, while the thrust roller 17 is supported along the inside wall of the conduit 5 at the side opposite the rail 11. A box 18 at the rear end of the carrier 10 may house the batteries mentioned and control electronics for control of the drive unit 15 (fig. 2A).

The sample container portion 10b is connected firmly to the drive portion loa although shown separately in fig. 2B. It may likewise comprise wheel sets. The essential part of this portion, however, is a magazine 19 adapted to take up a plurality of sample containers 20 or bottles in parallel chambers 20' which are aligned with their longitudinal axes in parallel with the main axis 21 of the carrier 10.

The magazine 19 is held fixed against rotation in the housing 22 1 of the carrier 10, whereby the alignment or position of the individual sample containers 20 is clearly defined (in cooperation with the position of the carrier 10 as defined by the guide groove 12).

l> 1 - 7 The magazine 19 has a central opening 22 formed with lateral enlargements or bayonet slots 23, and at the lower inner side of the central opening 22 there are small detent recesses 24, as is known in general with bayonet-type cat5 ches. The central opening 22 with its lateral enlargements 23 and the detent recesses 24 serves to establish connection between the magazine 19 and a needle head plate 25 (fig. 2C) which forms part of the needle head portion 10c. The needle head portion 10c comprises the needle head plate 25 to which a central tube 26 is fastened by bayonet pins 27. The tube 26, together with the bayonet pins 27, is introduced into the central opening 22 and then the needle head plate 25 is turned until the bayonet pins 27 become caught in the detent recesses 24, whereby a distinct rela- tive rotational position is fixed of the needle head plate 25 and the magazine 19. A compression spring 28 surrounds the central tube 26 and rests on the backside of the needle head plate 25 and the front side of the magazine 19, respectively.

The needle head plate 25 is provided with a plurality of needle-pairs 29, one pair each being coordinated with a sample container 20. At their ends associated with the needle pairs 29, the sample containers 20 in turn include a diaphragm 30 adapted to be pierced by the needles. During the regular conveying state the tips of the needles are spaced from the respective diaphragms 30. But when the needle head plate 25 is pushed against the magazine 19, against the force of the compression spring 28, the needle pairs 29 puncture the diaphragm 30. This also shows that the needle head plate 25 is movable back and forth in axial direction with respect to the housing 22 1 of the carrier 10.

The other ends of the needle pairs 29 extend through the needle head plate 25 which thus is formed at its outside or at the front with corresponding apertures 31 communicat ing with the needles. Two such apertures 31 each terminate 8 in a depression32 at the outside or front of the needle head plate 25.

Likewise providedat the outer side or front of the needle head plate 25 is a central opening 33 communicating with the central tube 26. The central tube 26 has a plurality of radial apertures 34 which are located, as seen in axial direction, approximately in the range of the tips of the needle pairs 29. They are orifices for the outlet of a decontamination liquid..

The sampling station 35 will now be described with reference to fig. 2D. An annular flange 36 is welded to the end of the conduit 5 and a corresponding flange 37 of the housing 38 of the sampling station is connected to the same by a clamp connector 39.

The sampling station comprises a valve block 40 to which there are attached a plurality of paired conduits 41a to 41f. The process liquids circulate in these conduits. This means that the conduit pairs are joined to the respective process components 3 (fig. 5). Each conduit 41 of a pair opens through bores 42 in the valve block 40 into an associated valve chamber 43, the arrangement being such that the bores 42 terminate at spaced apart locations in the valve chamber 43. Each valve chamber 43 has an extension 44 in which the respectiVe valve member 45 is guided while being rotationally fixed. The valve members 45 are displaceable in the axial direction of their central axis 46 and can adopt either one of two end positions. In the first end position in which the valve members 45 project partly out of the valve block 40 in the direction of the carrier 10, an annular groove 47 formed in the valve member 45 is located directly opposite the mouth of the bore 42 so that the process medium can circulate from one bore 42 to the other of a pair of conduits 41. This position is referred to below as the "closed position".

- 9 In the other limit position in which the valve members 45 are pushed farther into the valve block 40, the circulation is interrupted. Instead, the process medium now flows from the one bore 42 through a recess 48 and another bore 55 extending from this recess 48 parallel to the central axis 46 in the valve member 45 to an aperture 50 (fig. 4) at the end of the valve member 45 facing the carrier 10. In similar manner the other bore 42 for the return flow is located opposite another recess 48' and bore 551 having aperture 501 in the valve member. The two apertures 50 and 50' of the valve member 45 are positioned such that they lie exactly opposite the two apertures 31 for a needle pair 29 in the carrier 10. In this manner fluid communication is established between the paired conduits 41, the needle pairs 29, and the sample containers 20.

In addition, also the valve block 40 has a central through bore with a tube 51 for flushing connected to both ends thereo:. The "inner" part of the flushing tube 51, i.e. the part facing the carrier 10 includes a flushing head 52 formed with a plurality of radial apertures 53 which are aligned with the apertures 34. The dimensions of the flushing head 52 are selected so that the head fits into the central opening in the carrier 10.

The mode of operation of the apparatus -------------- -------- now will be described. For sampling, the carrier 10 is fed with encoded sample containers 20 at the examining station. The code may be any automatically readable code, such as a bar code or color code, a magnetic code etc. At their open ends the sample containers 20 are sealed tight by the diaphragms30. Subsequently a needle head plate 25 is mounted and fixed by the bayonet catch (26,27;22,23,24) with the needle pairs 29 not yet iercing the diaphragms 30. The carrier 10 then is introduced into the manifold 9. The carrier 10, being driven electrically, moves to the selected sampling station 4 in correspondence - 10 with the position of the line switches 8 (fig. 5) and under control from the electrical cables 13. As the carrier 10 approaches the sampling station 35, first its central opening 33 will slide over the flushing head 52 until the bottom of each depression 32 touches the respective front end of the valve members 45. Continued forward movement of the carrier 10 will displace the needle head plate 25 against the action of compression spring 28 in the direction toward the magazine 19. Now the needle pairs 29 pierce the corresponding diaphragm of the associated sample container 20 so that the tips of the needles will be positioned in the interior of the sample containers. As the carrier continues to move in forward direction the valve members are pushed from their closing position into opening position, whereby circulation through the paired conduits 41 is interrupted and the flow instead is directed through the respective sample container 20 which thus is filled.

It may be seen that the entire docking operation of the carrier at the sampling station 35 is accomplished solely by the forward movement of the carrier. No further remote control manipulation is required. The undocking takes place in opposed sequence. As the carrier is withdrawn (backward movement), the valve members 45 once more adopt their closing position whereby fluid communication is established between the needle pairs 29 and the conduits 41. Upon further backward movement of the carrier, the compression spring 28 helps to remove the needle head plate 25 from the magazine 19, whereby the needles are pulled out of the sample containers 20. The carrier then can move back to the examining station under electrical control while it is taking along a plurality of samples of different nature.

It may also be taken from-the above description that it is no longer necessary, with the described embodimnt, to take the sample --------

1 containers out of the carrier for sampling and that the whole procedure of sampling is "controlled" exclusively by the forward and backward movements of the carrier 10. No other intervention is required to actually draw the 5 samples.

Furthermore, during docking or undocking the carrier may be decontaminated so as to prevent unnecessary spreading of radioactive and/or toxic substances. It is.for thit flushing that the tube 51 with its flushing head 52 and the apertures 53 as well as the central tube 26 with its apertures 34 are provided. - The decontamination preferably is carried out during undocking, specifically during the phase of return movement of the carrier 10 during which the valve members 45 have regained their "closed position", whereas the needles still are inside the sample containers. This is the best way of avoiding any cross- contaminations. During this phase decontamination liquid is conveyed under remote control through the flushing tube 51 toward the flushing head 52 where it issues through the apertures 53 and enters the central tube 26, leaving the same through the apertures 54 and decontaminating the needles and the outsides of the diaphragms 30. Decontamination of the outside of the needle head plate 25 and also of the space ahead of the valve block 40, i. e. of the valve members 45, too, may be obtained in response to the time selected for conveying the decontamination liquid.

An additional pipeline (not shown) opening into the space in conduit 5 ahea ' d of valve block 40 may be provided for discharge of the decontamination liquid. If the arrangement of the sampling station 35 is such that its axis extends perpendicularly, the flushing tube 51 may be embodied by a double-wall conduit, the inner tube serving for supply of the decontamination liquid and the outer one being a socalled "rework line" for discharge of the decontamination liquid.

Overall decontamination of the conduit system (5,9) is possible as well and required from time to time. To this end a separate decontamination vehicle powered by batteries may be placed in the pipeline system and, as it travels, it sprays out in front the decontamination liquid which it carries in a pressurized bottle. This vehicle. is moved through the full pipeline distance. Upon return of the vehicle, a drying procedure is required in order to safeguard the proper functioning of slider contacts and energy transfer to the carriers. This may be accomplished by sending a drying gas from the examining station through the conduit system. The gas will flow through the rework line mentioned out into the hot cell.

With reference to fig. 4 the valve will be explained in more detail. The diagrammatic section shows the valve block 40 with the valve member 45 inserted into the same as well as the two associated bores 42 which open into the valve chamber 43. A spring 54 urges the valve member into its one limit position in which the annular groove 47 permits fluid communication between the two bores 42.

It should be mentioned here that the sum total of spring pressures of the springs 54 acting on the valve members 45 is greater than the spring pressure of the compression spring 28 in the carrier 10. In this manner it is guaran- teed that, upon docking, the valves do not open until after the needle pairs 29 have punctured the corresponding diaphragm 30 and inversely, upon undocking, first the valves close and then the needles are pulled out of the sample containers.

Fig. 4 also offers a better view of the recesses 48 and 48' formed in the valve member 45. They pass over into axially extending bores 55 and 55', respectively, ending in apertures 50 and 50', respectively, at the outer side of the valve members 45. When the valve member 45 is urged X 1 - 13 inwardly into the valve block 40 against the action of the spring 54, one bore (the left one in fig. 4) is in fluid communication with the aperture 50 and the other bore 42 (the right one in fig. 4) is in fluid communication 5 with the aperture 501.

As both apertures 50 and SO' must be aligned with the apertures 31 in the needle head plate 25, the valve member 45 must be guided in exact orientation in the valve block and, at the same time, fixed against rotation. There are various possibilities to achieve that. One is to give the extension 44 and associated portion 56 of the valve member an accurate definition by suitable shaping (e.g. square, triangular, etc.). Another possibility is the provision of a tongue and groove joint with so-called fin guidance. Any other structural solution is applicable, as long as it allows axial displacement of the valve member while prohibiting any rotation thereof.

The electrically driven carriers are to travel at rather high speed through the conduit system. To avoid too much "impact" upon docking, however, marks may be provided ahead of the respective sampling stations for detection(mechanically, optically, electrically, magnetically, etc.) and recognitionby sensors mounted on the ca.rrier in order to then slow down the advancing speed of the carrier or initiate a braking operation.

In case of disturbance in the sampling system the following measures may be taken:

The sampling station itself may be changed readily by remote control means disposed inside the hot cell, while ob- serving the customary remote control aspects.

Furthermore, that part of the conduit 5 located just in front of the sampling station in the interior of the process 14 cell is designe& as a pipe jumper so that it can be replaced easily even under remote handling conditions. Thus, if a defect occurs during docking or undocking, the pipe jumper can be exchanged by remote control, together with the 5 carrier 10 contained in it.

In case of failure during the carrier conveyance within the conduit system, an electrically driven salvage box is caused to travel through the conduit system up to-the defective carrier which-then is hauled back to the examining station. The coupling in this case may be made by an automatic coupling means or by magnetic forces, and the like. If this should not turn out to be successful, then the salvage box may push the defective carrier forward to any sampling station 4 where the carrier will be exchanged to- gether with the pipe jumper by remote handling.

If even that procedure should fail because, for example, the carrier is completely stuck inside the tubing, its position will have to be determined as accurately as possible and then the whole pipe section with the carrier in- side must be exchanged by using remote handling tools. This is why the conduit system is made in sections which are flange-connected to each other.

As already mentioned, slight excess pressure prevails in the entire conduit system. while there is minor low pres- sure inside the hot cell. Any undesired spreading or diversion of radioactive or toxic substances into the open thus is avoided. In addition, there should be a slight pressure gradient in the conduit system from the outside to the hot cell so that the decontamination liquid used for decontami- nation of the whole system, as described above, always will flow off toward the hot cell.

Various sensors may be provided within the conduit system for determining the.exact position of a carrier. This func- 1 A - is - tion may be fulfilled by induction lines or any other known sensors which detect the presence or absence of a carrier.

In conclusion reference is made to fig. 3 showing an aperture diagram of the valve block. The respective paired conduits 41a to 41f are illustrated as well as their fluid communication through the respective bores with the corresponding valve chambers 43a to 43f. Likewise to be seen is the central flushing tube 51.

All the technical details shown in the claims, specifica- tion, and drawings may form the substance of the invention, either individually or in any desired combination.

Claims (14)

CLAIMS:

1. An apparatus for drawing samples of radioactive and/ or toxic substances from process components arranged in shielded, inaccessible cells, comprising an examining station located remote from the process components, a sampling station located near the process components, a conduit system between the examining and sampling stations, and a carrier movable in the conduit system and containing sample containers which are filled with samples at the sampling station, wherein the carrier is controlled to move by an electric drive means between the sampling an examining stations, conduits pass from a plurality of sampling locations at the various process components to a common head of the sampling station, and the carrier comprises a counterhead, the two heads being designed such that linear movement alone of the carrier with respect to the head causes the sample containers to become connected to the associated conduits so that samples can be filled into the sample containers.

2. The apparatus as claimed in claim 1, wherein the counter-head of the carrier is designed as a needle head plate which is displaceable with respect to the housing of the carrier and comprises needles which pierce a diaphragm of the associated sample container when the carrier docks on the sampling station.

3. The apparatus as claimed in any of the preceding claims, wherein the carrier is guided fixed against rotation in the conduit system.

4. The apparatus as claimed in any one of the preceding claims, wherein the sample containers include a coding by which they can be recognized automatically.

Z 17-

5. The apparatus as claimed in any one of the preceding claims, wherein the head of the sampling station comprises valves which are closed in the inoperative position and are opened by the approach of the carrier so that the conduits enter into fluid communication with the associated sample containers.

6. The apparatus as claimed in claim 5, wherein each valve is associated with a conduit pair, circulation of the process medium in the conduits of a con- duit pair being possible with the valves in inoperative position, while the circulation passes through the associated sample containers, thereby filling them, when the valves are in open position.

7. The apparatus as claimed in any one of the preceding claims, wherein the valve members are axially displaceable in the head designed as a valve block and have an annular groove formed at their portion further inside in the valve block and two recesses not connected in fluid communication at their portion further outside in the valve block, these recesses communicating with axial bores which open at the front end of the valve members into apertures which are aligned with associated apertures of the needle head plate and thus with the needles.

8. The apparatus as claimed in claim 7, wherein the valve members are guided fixed against rotation in the valve block.

9. The apparatus as claimed in any one of the preceding claims, wherein the conduits of a conduit pair open through bores at separate, preferably opposed locations into a valve chamber in which the respective valve members are arranged to slide.

10. The apparatus as claimed in any one of the preceding claims, -18 wherein the needle head plate with the needles is adapted to be fixed by a bayonet-type catch at a magazine for sample containers of the carrier, whereby a clearly defined relative position between the needle head plate and the ma- gazine in the direction of rotation about the main axis of the carrier is obtained.

11. The apparatus as claimed in any one of the preceding claims, wherein the needle head plate is biased by a spring with respect to the magazine, the needles being located outside of the sample containers in the inoperative position of the needle head plate, and wherein the pressure of the spring is less than the force required to open all valves.

12. The apparatus as claimed in any one of the preceding claims, wherein the head of the sampling station and the needle head plate of the carrier each comprise an additional tube communicating with each other upon docking of the carrier on the sampling station, the tube in the carrier having outlet apertures for a decontamination liquid and these outlet apertures being arranged such that the decontamina- tion liquid exiting from them reaches at least the tips of the needles and the diaphragms of the sample containers.

13. The apparatus as claimed in any one of the preceding claims, comprising an additional retrieval box with an electric drive adapted to be moved through the conduit system and pushing a carrier stuck in the conduit system in the direction of the examining station or preferably in the direction of a sampling station, the section of the conduit just ahead of the sampling station being designed as an exchangeable pipe jumper suitable to be remotely handled..

14. Apparatus for drawing samples of radioactive and/or toxic substances frcm process cnents substantially as hereinbefore described with reference to or as shown in the accarpanying drawings.

Published-1968 at The Patent Office, Statte House, 66171 High Holborn, London WC1R 4TP. Further copies maybe obtained from The Patent Office, Sales Branch, St Mary Cray, Orpington, Kent BR5 3RD. Printed by Multiplex techniques ltd, St Mary Cray, Kent. Con. 1187.