GB2249048A - Machine for replacing the access door to an irradiated zone - Google Patents

Description

MACHINE FOR THE REPLACEMENT OF ACCESS DOORS TO IRRADIATED ZONES AND USE OF SUCH A l'ACHlNE DESCRIPTION The invention relates to a machine for replacing access doors to irradiated zones and to the use of such a machine.

Such a machine is described in French patent 2 544 542.

It is designed to operate from the outside and has a mouth which is engaged against an opening on a biological protection wall.

The irradiated zone extends into a cell located behind the biological protection wall and defined by a second wall, which is tight but radiation-permeable and which is equipped with access doors to the irradiated zone. These doors are frequently provided with means which must be periodically replaced, such as sensors or stirrers if a gas flows within the cell. The contaminating product is able to flow out of the cell as soon as the door is removed. Therefore the door replacement machine must have fhe necessary sealing to prevent this outflow and at no time must there be any connection between the irradiated zone and the outside.

The machine contains a rotary shuttle mechanism comr prising two door supports in the form of recesses, which are equipped with means for gripping the access doors. A first support is placed in front of the biological protection wall opening. The door to be extracted is gripped, then removed and kept in the recess. A rotation of the shuttle mechanism then makes it possible to bring another support in front of the opening of the biological protection wall, whose recess contains a replacement door. The latter door is introduced into the opening up to the wall of the cell. The machine must satisfy the biological protection and sealing functions, which makes it heavy and cumbersome due to the large amount of radiation-absorbent material which must be placed around the shuttle mechanism.

The necessary sealing can only be obtained by using numerous gaskets or joints. which do not offer total security.

Finally, the use of such a machine makes it necessary to equip the cell with sleeves connecting the opening of the biological protection wall to the opening of the cell on which the door is located. The door is then fixed to a rod which extends into the sleeve. Before using the machine pulling takes place on the rod to make the door slide in the sleeve into the vicinity of the biological protection wall. The rod is then dismantled from the door. Obviously, the door and the sleeve are produced in such a way that the seal is never broken.

However, this entire construction is complicated and costly. It is even necessary at times to locally deform the cells by moving together the doors of the biological protection wall in order to prevent excessively long sleeves.

Therefore the object of the machine according to the invention is to avoid this complexity in the installation and the process. The fundamental originality is that the novel machine is used between the biological protection wall and the cell wall.

The machine is no longer responsible for the bid logical protection and merely has to be tight. As its structure is greatly simpli- fied and as slight sealing defects are less serious than in the case of a machine used from the outside, the sealing can be ensured much more easily, It is in particular possible to obviate the need for a multiple effect gasket or joint, which is used at present in this technology and which is placed around the opening of the biological protection wall and whose special shape guarantees the absence of contamination of external zones. With the novel machine, a slight contamination is accepted, but a decontamination carried out subsequently is sufficient to bring about an admissible cleanness around the cell opening.

Therefore the invention relates to a machine for the replacement of access doors to contaminated zones, comprising an enclosure having an opening and containing t'ao door manipulation systems. each door manipulation system comprising a door support and means for locking the door to the support, the enclosure also containing a shuttle mechanism on which depend the door supports and which is constructed so as to be able to alternately place each of the door supports in the opening, the machine also comprising a first gasket placed around the opening and creating a seal between the enclosure and a wall defining a contaminated zone, characterized in that it has a second gasket placed in the opening and producing a seal between the enclosure and a support placed in the opening. a third gasket placed on said support and producing a seal between the door and the said support, as well as a device for decontaminating a tight volume defined by the three gaskets.

The invention is described in greater detail hereinafter relative to non-limitative embodiments and the attached drawings.

wherein show: Fig. 1 An overall view of the invention.

Fig. 2 An overall view of another embodiment of the invention.

Fig. 3 The sealing device.

Fig. 4 An access door construction diagram.

Fig. 5 The envirorment of the invention.

Fig. 6 A front view of the door supports.

The first embodiment of the machine comprises an enclosure or case having an opening 2 on one side. The enclosure 1 contains two identical door manipulation systems 3, each substantially occupying half the volume of the enclosure and whereof each has two parallel Archimedean screws 4. The Archimedean screws 4 are oriented with an axis corresponding to the passage direction through the opening 2. They are interconnected by one end to a first pivoting bar 5 and by their other end to a second pivoting bar 6. The second pivoting bar 6 is fastened to a pivot 7 fixed to the enclosure 1 not far from the opening 2. whilst the first pivoting bar 5 is fastened to a mobile pivot 8 traversing the face of the enclosure 1 opposite to the opening 2, which is a detachable cover 9. A first motor 10 fixed to the outside of the cover 9 drives the mobile pivot 8.

The two bars 5 and 6 pivot and one of the two door manipulation systems 3 passes in front of the opening 2 during each half-turn. In this position, a square-section end 11 of the Archimedean screws 4 engages in a member 12 at the end of a spindle 13 pivoting in the cover 9 in accordance with the axis of the Archimedean screws 4. A second motor 14 fixed to the outside of the cover 9 drives the two spindles 13 with the same movement as a result of a transmission comprising universal or gimbal joints 43.

A panel 15 is attached to the Archimedean screws 4 of each door manipulation system 3. It is possible to see a rear flange 16 carrying engagement nuts for the Archimedean screws 4, a cylindrical zone 17 extending from the rear flange 16 in the direction of the opening 2 and a substantially planar closing or sealing plate 18 surrounded by the cylindrical zone 17. The cylindrical zone 17 and the closing plate 18 forwardly define a door receiving cavity 19.

In the state in which the machine is shown, one of the panels 15 has been moved to the end of the Archimedean screws 4 which support it in such a way as to block the opening 2, whereas the other panel 15 is retracted into the enclosure 1 close to the first pivoting bar 5. It carries a door 20 located in the cavity 19 and which itself carries a component such as a measuring device 21.

Several systems can be used for locking a door 20 on a panel 15. It is possible to envisage the use of a small pneumatic jack 44 having two states, articulated to the inner face of the closing plate 18 and whereof the displacement of the rod 45 controls the rotation of a spindle 46, which drives a disk 47 in front of the outer face of the closing plate 18. Means 48 fixed to the periphery of the disk 47 displace the rods 49, which are articulated thereto and which slide in bearings 50 on the panel 18. The end of the rods 49 enters the not shown recesses of the door 20 and thus locks it against the closing plate 18. This system. which is also shown in Fig. 6, is present on both panels 15, but is only shown on one of them so as not to overburden Fig.

1.

In this design, the door manipulation systems 3 are subject to a circular movement, which imposes a certain width dimensioning to the enclosure 1. For certain applications, the dimensional constraints may require a narrower enclosure, like that designated 1' in Fig. 2.

The preceding description can in general terms be transposed to the present embodiment, except with respect to the shuttle system by which the door manipulation systems 3 are moved.

In this case the mechanism is constituted by two sliding bars 5' and 6', which replace the pivoting bars 5 and 6. The second sliding bar 6' is moved on fixed supports 7' on the enclosure 1', whereas the first sliding bar 5' hasa rack on which meshes a pinion 51 at the end of the mobile pivot 8. Not shown support systems fixed to the enclosure 1' keep the first sliding bar 5' against the pinion 51.

This construction makes it necessary to position the opening 2 towards the centre of the enclosure 1, whilst two recesses are provided on either side in order to house that door manipulation system which is not in use.

Reference should now be made to Fig. 3. A first gasket 22 is placed around the opening 2 on a front face 23 of the enclosure 1 and has been pressed against a cell wall 24, around an access door 25 to an irradiated zone 26. A second gasket 27 is placed on the outside of the cylindrical zone 17 and is pressed against the edge 28 of the opening 2 when the panel 15 is advanced. A third flat gasket 29 located on the outer face of the closing plate 18 and surrounded by the front part of the cylindrical zone 17 is pressed against a door 25 to be replaced, whilst a fourth gasket 30 is pressed between the front face of the door 25 and the cell wall 24. The four gaskets 22, 27, 29 and 30 define a tight annular volume 52 with the door 25, the cell wall 24, the panel 15 and the enclosure 1.

A liquid circuit issues into said annular volume 52.

The drawing shows a perforated pipe 31 through the enclosure 1 and which terminates on an injection pump 32 and a liquid tank 53 at its other end. There is an identical circuit constituted by a pipe, a suction pump and a liquid tank at the diametrically opposite point of the annular volume 52. The assembly makes it possible to bring about the circulation of a decontamination fluid in the annular volume 52 with the aid of two pumps. It is possible to see one of the nuts 33 equipping the rear flange 16 for engagement on the Archimedean screws 4. Finally, the cell wall 24 is provided with pins 34, whose shape is complementary to slots 35 in the enclosure 1 in order to permit a correct centring of the opening 2 around the door 25.

The door replacement process consists of firstly placing the enclosure 1 on the cell wall 24 by correctly fitting the pins 34 into the slots 35. The gaskets 22 and 29 are pressed against the cell wall 24 and the door 25. This pressing can be obtained by the weight of the machine if the cell wall 24 is a ceiling. If not, the enclosure 1 can be flanged to the cell wall 24 or pressed by a random mechanical means.

This is followed by the locking of the door 25 to the panel 15 with the aid of the pneumatic jack 44, after which the Archimedean screws 4 are moved in order to raise the panel 15 and remove the door 25. The contaminated content of the irradiated zone 26 can be introduced into the enclosure 1. However, the gaskets 22 and 29 prevent any flow to the outside and in front of the closing plate 18. Without moving the enclosure 1 from the cell wall 24, the shuttle mechanism rotates by a half-turn, so as to place the replacement door 20 in front of the opening 2. The panel 15 is then advanced until the door 20 is on the irradiated zone 26 and the door 20 is then unlocked from the panel 15.

However, the tight annular volume 52 has been reconstituted and is decontaminated by injecting into it washing liquid which is then sucked out.

The enclosure 1 can then be removed. The panel 15 remains in the state shown in order to completely isolate the contaminated content of the enclosure 1 from the outside by means of the gasket 27 which hermetically blocks the opening 2.

The contaminated doors such as 25 are moved out of the enclosure 1 after placing the machine on a container having a shape similar to that of the cell wall 24. The contaminated door is placed on the container opening in the manner described and then a decontamination is performed and the machine is removed.

In numerous cases, the total weight of the door and the possible measuring device 21 is adequate to bring about a correct support or bearing on the cell wall 24. If not, it is possible to use a system like that of Fig. 4. .A bracket 39 is placed on two diametrically opposite centring pins 34. A pressing pad 40 is placed on the door 20 above the bracket 38.

A threaded shaft 41 completed by a handwheel 42 is engaged in a tap of the bracket 39 in such a way that its end touches the pressing pad 40 and exerts a stress or load thereon, which maintains the door 20 in place. The centring pins 34 are terminated by threads, which extend through the perforations of the bracket 39 and nuts are screwed on to the threads to keep the bracket 39 in place.

Fig. 5 shows the way in which. the machine is used. A biological protection wall 55 surrounds the cell wall 24. Two rails 56 are fixed against the inner face of the biological protection wall 55 and a carriage 57 runs on them. Two slides 58 on the carriage 57 enable a lower carriage 59 to run perpendicular to the rails 56.

The enclosure 1 is located at the end of the rod of a jack 60, whose cylinder is fixed to the lower carriage 59. The extension of the rod of the jack 60 makes it possible to engage the machine against the cell wall 24. A camera 61 monitors the volume between the two walls 24 and 55 and indicates whether the machine is at the desired location. The rails 56 can lead at their opposite end to a lock where interventions on the machine take place. This is particularly where the containers receiving the contaminated doors or the new doors are put into place.

Fig. 5 shows a device placed on rails 56 and where the cell wall is a ceiling, as is the case in the preceding drawings.

This device could be used with rails 56 and cell walls 24 having a random orientation.

In the same way as the pneumatic jack 44, the motors 10 and 14 are controlled by means of electric cables or the like, which lead to the outside of the biological protection wall and which are not shown so as not to overburden the representation.

Claims (8)

1. A machine for the replacement of access doors to contaminated zones, comprising an enclosure having an opening and containing two door manipulation systems, each door manipulation system comprising a door support and means for locking the door to the support, the enclosure also containing a shuttle mechanism on which depend the door supports and which is constructed so as to be able to alternately place each of the door supports in the opening, the machine also comprising a first gasket placed around the opening and creating a seal between the enclosure and a wall defining a contaminated zone, wherein a second gasket is placed in the opening and produces a seal between the enclosure and a support placed in the opening, a third gasket is placed on said support and produces a seal between the door and the said support, and a device for decontaminating a tight volume is defined by the three gaskets.

2. A machine according to claim 1, wherein the third gasket is a flat gasket placed at the bottom of a cavity of the support.

3. A machine according to claim 1, wherein the enclosure is provided with means for centring the opening around the door.

4. A machine according to claim 1, wherein the shuttle mechanism has a rotary structure for bringing each support in front of the opening and motor means for sliding the supports in the opening.

5. A machine according to claim 1, wherein the shuttle mechanism has a mobile structure in alternating translation for bringing each support in front of the opening and motor means for sliding the supports in the opening.

6. Use of a machine according to claim 1 in an installation constituted by an outer biological protection wall and the wall defining the contaminated zone, wherein the machine is used between the two walls.

7. A machine for the replacement of access doors to contaminated zones substantially as described hereinbefore with reference to the accompanying drawings and as shown in Figure 1 or figure 2 of those drawings, or modified as shown in either Figure 3 or Figure 4, or Figure 5 or Figure 6 of those drawings.

8. Use of a machine as claimed in Claim 7 and as shown in Figure 5.