EP0442791B1 - Device for the radiation-proof passage of a flexible supply through the shielding wall of a hot cell - Google Patents

Description

The present invention relates to the field of biological protection with respect to ionizing and / or neutron radiation, as is the case for example in nuclear energy where enclosures, subjected to such radiation and called hot enclosures , are separated by a special concrete wall from the work area in which the staff work.

More precisely, to ensure the supply of the various materials which are present in the hot cell prohibited to humans, it is necessary to be able to pass, through the wall of the cell, flexible supplies, such as by example of electric cables or pipes for the supply and / or evacuation of certain fluids.

In a conventional and known manner, these flexible supplies cross the protective wall in cylindrical conduits having a curved shape (called S-shaped crossings) or having a rectilinear shape (called straight crossings).

In both cases, the conduit is made up of a curved (straight S-shaped) or straight (straight-through) metallic tube embedded directly during the manufacturing process in the concrete wall itself.

In the case of the straight crossing, a plug is placed at each end of the conduit, this plug being made of a material absorbing radiation (alpha and / or beta and / or gamma and / or neutron) and in this plug baffles have machined through which the flexible feed passes. The function of such caps is to ensure non-passage of radiation and contaminants from the cell and through the crossing.

In the case of the S crossing, the S shape of the conduit is sufficient to stop the radiation by collimation. Figure 1 shows this realization.

In this Figure 1, there is shown schematically in section, the concrete wall 2 which separates in a nuclear installation, the radioactive hot enclosure 4 from the work area 6 where the staff evolves. The actual crossing of the wall is carried out by a curved conduit 8 hollowed out in the concrete and coated internally with a sheath 10 intended to protect the concrete from any mechanical degradation. The personnel protection is supplemented by a cast iron or steel plate 12 located on one of the faces of the wall 2. In this case, the sheath 8 obviously also passes through this metal plate 12. The sheath 10 which opens at one of its ends in the hot zone 4 and at the other end in the non-active zone 6 is therefore perfectly suitable for serving as a passage for any flexible supply such as cables or flexible tubes for conducting fluids, which thus makes it possible to supply the active zone 4, generally closed, in energy and in a certain number of fluids necessary for carrying out the operations which take place there.

The sheath 10 does not contain materials capable of stopping the radiation, the protective function against these is only ensured by its S shape which opposes the progression in a straight line of the electromagnetic photons and also of the neutrons, thus that possibly by the plates 12 of suitable material embedded in the concrete wall.

Unfortunately, in an embodiment of this kind, the calculation shows that to guarantee biological protection of an acceptable quality, one cannot exceed for the sheath 10 an internal diameter of the order of 35 mm, otherwise there is a risk of direct leaks, either by collimation of photons or neutrons on the wall of the sheath 10. Indeed, if theoretically, a photon appearing at the entry of the sheath 10 in cell 4 and propagating in a straight line cannot exceed point B marked in FIG. 1, it is not excluded that, by phenomena of subsequent successive reflections in C and D on the walls, according to paths marked in dotted lines in FIG. 1, certain photons nevertheless cross the entirety from the wall 2.

This is the reason why the diameter of the sleeves 10 is limited to around 35 mm because, for a given wall thickness and a given curvature of the duct 8, it is clear that the risk of leaks is all the greater as the diameter of the sheath 10 is large.

The present invention specifically relates to a device for the radiation-tight passage of such a flexible supply through the biological protection wall of a hot enclosure which allows, while possibly increasing the diameter of the crossing sleeves beyond 35 mm, to maintain a total seal against radiation.

This device for the passage, radiation-tight, of a flexible supply through the biological protection wall of a hot enclosure, comprising a curved conduit, in particular of S shape, crossing the wall, coated with a sheath in radiation absorbing material and open to its two ends located respectively one in the hot zone and the other in the working zone, is characterized in that the flexible supply is provided, at least on a portion of the part corresponding to its path in the duct, massive removable parts, made of a radiation protection material compatible with the sheath material, said parts surround the flexible supply at least in place in the manner of the beads of a necklace and ensure both its setting in place by sliding in the conduit and the sealing of this curved conduit with respect to the rectilinear propagation of the photons of electromagnetic radiation which may be introduced therein.

As can be seen, the main means of the invention consists of removable solid parts which are surrounded from place to place by the flexible supply which must pass through the conduit, the location, the size and the material of which these different parts are made. being massive enough to completely block all possible paths for electromagnetic radiation.

According to the invention, the massive parts which surround the flexible supply in its path inside the curved conduit in the manner in which pearls are threaded on a collar, can take on extremely varied shapes as long as they fulfill the function assigned to them.

In a first particularly simple embodiment, these solid parts are spherical balls of diameter substantially equal to the internal diameter of the sheath and pierced along one of their diameters with a passage for flexible feeding.

In a second embodiment of the invention, the solid parts are straight cylinders with circular base of diameter substantially equal to the internal diameter of the sheath and pierced along their axis with a passage for flexible feeding.

According to another also very interesting variant of the present invention, these solid parts are cylindrical olives in two integral parts and having, for the passage of the flexible supply, a conduit eccentric relative to the axis of the cylinder, so as to allow the helical mounting of the different olives around the flexible food. This method of fixing massive parts to the flexible supply, allows, by virtue of the eccentric passage in the different successive parts, a helical distribution around the flexible supply of all of these same parts, which strengthens the seal. by further complicating the path for photons or neutrons which would nevertheless tend to enter and progress in the curved duct.

In another embodiment, also very interesting, the massive pieces are no longer, as in the previous embodiments, distributed discreetly along the flexible supply, but on the contrary constitute a continuous flexible reinforcement all along the crossing thereof in the curved conduit. For this purpose, these massive pieces are cylindrical olives in two integral parts each having a concave spherical end face and a convex spherical end face of the same radius of curvature, so that the different successive olives fit one into the other in a swiveling manner and constitute a continuous flexible frame around the flexible supply.

Of course, the material constituting the solid parts in each of the modes of implementation is chosen so as to have as good a coefficient of friction as possible on the material constituting the sheath which covers the interior of the curved duct. On this subject, the skilled person will know in each particular case to choose the suitable materials among those which have a high capture section with respect to ionizing radiation.

In certain embodiments, the invention also includes a cable gland traversed by power supply and closing at least one of the openings of the curved duct to improve protection against particulate radiation, such as in particular radiation alpha and beta.

This cable gland which can be placed, preferably on the side of the clean zone 6 for ease of access for personnel, can also be placed on the side of the contaminated cell 4, has the additional advantage of maintaining the supply flexible in place, since it passes through the cable gland.

• la figure 2 représente schématiquement le principe général de l'invention ;
• la figure 3 représente un modèle de pièces massives ou olives de forme rigoureusement sphérique ;
• la figure 4 représente une forme particulière de pièces massives ou d'olives sous forme de cylindre droit à base circulaire ;
• la figure 5 représente, avant leur assemblage, les deux parties d'une olive cylindrique droite percée d'un passage excentré par rapport à son axe de symétrie ;
• la figure 6 représente l'implantation possible des olives de la figure 5 selon une disposition en hélice autour de l'alimentation souple ;
• la figure 7 représente à plus grande échelle, une olive selon la figure 5 montée dans son fourreau ;
• les figures 8 et 9 représentent les coupes respectives selon A, B et X,Y de la figure 6 de deux olives montées avec un décalage de 180° autour de l'axe du fourreau ;
• la figure 10 représente enfin un autre mode de mise en oeuvre de l'invention dans lequel les différentes olives ou pièces massives sont constituées d'un assemblage continu de pièces cylindriques à extrémité sphérique alternativement concave et convexe s'emboîtant de façon rotulante les unes dans les autres.

In any case, the invention will be better understood by referring to the description which follows of several examples of implementation thereof, examples which will be given by way of illustration and without limitation with reference to FIGS. 2 to 10:

• FIG. 2 schematically represents the general principle of the invention;
• FIG. 3 represents a model of massive pieces or olives of strictly spherical shape;
• FIG. 4 represents a particular form of solid pieces or of olives in the form of a straight cylinder with a circular base;
• Figure 5 shows, before their assembly, the two parts of a straight cylindrical olive pierced with an eccentric passage relative to its axis of symmetry;
• FIG. 6 represents the possible implantation of the olives of FIG. 5 according to a helical arrangement around the flexible food;
• Figure 7 shows on a larger scale, an olive according to Figure 5 mounted in its sheath;
• Figures 8 and 9 show the respective sections along A, B and X, Y of Figure 6 of two olives mounted with a 180 ° offset around the axis of the sheath;
• FIG. 10 finally represents another embodiment of the invention in which the different olives or solid pieces consist of a continuous assembly of cylindrical pieces with spherical end alternately concave and convex interlocking in a swiveling manner others.

Referring to Figure 2, we will now describe the general means of the invention as it is common to all modes of implementation thereof.

In this FIG. 2, a certain number of elements have been shown common with those of FIG. 1, designating them using the same number of references.

The technical problem to be solved consists in passing the wall 2 through a flexible electric cable 14 which crosses the wall 2 via the curved conduit 8 and opens at 16 at the same time at the end of the latter into the hot zone 4 and at 18 by the other end of this same conduit 8 in the working area 6. According to the invention, are placed, around the electric cable 14, a certain number of solid pieces or olives 20 which the cable crosses and whose external dimensions allow progression by sliding inside the sheath 10 coating the curved conduit 8. In FIG. 2, to better illustrate the invention, the space between the outer surfaces of the olives and the sheath has been exaggerated. It is obvious that the smaller this space, the less radiation or particle leaks. For example, the sheath 10 and the solid parts 20 can be made of a heavy metal such as lead which allows good sliding of the parts 20 in the sheath 10 while ensuring an almost total seal against electromagnetic radiation which could have tendency to enter the sheath 10 to pass through the wall 2. In general, any material which absorbs radiation and / or neutrons (as the case may be) and which has anti-friction properties is suitable for olives. This material can be homogeneous (lead) or heterogeneous (steel coated with an anti-friction material). It goes without saying that when there is a coating, it must resist the ambient irradiation. According to the invention, the solid parts 20 which surround the electric cable 14 from place to place are removable, that is to say that they can be put in place around the cable 14 and removed at will when the need arises. actually feel it. In accordance with the invention, the diameter of the sheath 10 no longer needs to be limited, as in the prior art, to a dimension of the order of 35 mm to achieve good sealing, and it is clear that this is simply the dimension of the solid parts 20 which, in conjunction with the diameter of the sheath 10, allows this sealing to be achieved.

In this FIG. 2, it can be seen that the curvature of the conduit 8 is such that the orifice 16 of the latter situated in the hot zone 4 is at a lower level of the orifice 18 of this same conduit 8 in the working zone 6. This arrangement is specially sought after and allows the introduction of the cable 14 provided with these massive pieces 20 by descent by gravity from the opening 18, a complementary traction of the latter from the active area 4 may nevertheless be necessary to ensure the installation of the assembly in the conduit 8.

As indicated above, the solid pieces 20 behave in a way like the pearls of a necklace surrounding the flexible cable 14 and these same pearls can receive, within the framework of the invention, all the possible desirable shapes, and in particular a certain number of which will now be described below.

In Figure 3, there is shown an embodiment of the parts 20 which is one of the simplest since they consist in this example of balls 22 having a diametrical passage 24 for the cable or flexible armature 14 which passes through it .

In the example of implementation of FIG. 4, the solid part is a straight cylinder with a circular base 26 also having an axial passage channel 24 for the cable 14.

In the embodiments of FIGS. 3 and 4, it is possible to equip the cable 14 with discrete masses or beads, simply by threading them through their central orifice on this same cable 14.

In Figure 5, there is shown another embodiment of the massive parts 20 which are produced in this case in the form of cylindrical olives 28 composed of two parts 28a and 28b which can be fixed to one another using any means known for this purpose, for example screws 30. In this exemplary embodiment of the olives 28, a channel 24 for passing the cable 14, not shown, is produced using two complementary and juxtaposable hollow half-cylinders 24a and 24b which, when secured using the screws 30 the two halves 28a and 28b of the olive 28 constitute a continuous circular cylindrical channel for the passage of the cable 14. One can note an important characteristic of this channel 24 which is its eccentricity by a distance e relative to the axis of the olive 28, which allows eccentricity of the cable 14 relative to the axis of the sheath, and, by successive mounting of the different olives 28 in a helix around this cable 14, as shown in FIG. 6, obtain an overall arrangement likely to reinforce the sealing tee to the radiation of the curved duct 8.

In the embodiment of FIG. 5, it is clear that the cable 14 is placed in one of the half-cylinders 24a or 24b of the passage 24 before the two half-olives 28a and 28b are joined together .

In Figure 6 where we find all the elements of Figures 1 and 2, the cable 14 is shown equipped with these different olives 28, which are mounted in a helix for reasons explained above around the cable 14 itself.

In this FIG. 6, provision has also been made for strengthening the protection against irradiating particles of small dimensions which arise in the hot enclosure 4, and which could pass through the crossing using two plugs. cable gland 32 and 34 located around the cable 14 in the openings of the conduit 8. In fact, dangerous radioactive radiation is not limited to only electromagnetic X or gamma photons but can also contain alpha and beta particles sometimes emitted with energy. important kinetics or neutrons. In this case, the cable glands 32 and 34 are sufficient to prevent them from accessing the conduit 8 and consequently the passage through the wall 2. In the example of FIG. 6, the biological protection is further reinforced at the using two local absorbent metal plates surrounding the orifices of the curved channel 8 and which may for example be made of steel or lead. In this FIG. 6, there is shown diagrammatically in dashed lines a remote manipulator crossing the wall 2 and allowing, by means of a driving handle 40, the remote manipulation by a driven clamp 41.

FIG. 7 represents in the sheath 10, one of the olives 28 in FIG. 5 crossed by the cable 14 which it can be clearly seen in this figure that it is eccentric relative to the axis of the olive 28 and , consequently, relative to the axis of the sleeve 10.

FIGS. 8 and 9 which correspond to sections AB and XY of the device of FIG. 6 make it possible to understand the helical mounting already explained of an olive 28 provided with its assembly screws 30 around the flexible cable 14. In fact, between FIG. 8 and FIG. 9 observe a 180 ° rotation of the olive 28 relative to the cable 14.

Finally, FIG. 10 shows a particularly advantageous embodiment of the invention in which the various solid pieces or olives are strung contiguously. on the cable 14 and produce a sort of flexible frame passing through the sheath 10 which they completely fill thanks to their characteristics explained below. In fact, in this embodiment of FIG. 10, each of the olives or solid pieces 20 consists of a straight cylinder with a circular base pierced in its center with a channel 24 for the passage of the cable 14, and the ends of each of the olives 20 are made of spherical pieces, alternately concave and convex, so that the different pearls 20 fit continuously and swiveling into one another to form a flexible frame which slides without difficulty at inside of the sheath 10 fitted to the walls of the curved duct 8.

• sur les installations actuelles en S : il permet de garantir l'absence de fuite par collimation. Des calculs par collimation sont en effet difficiles à exécuter et on prévoit en général un coefficient de sécurité important d'où des bouchons 'plus lourds, des murs plus épais etc. Le dispositif selon l'invention aboutira au même résultat avec un coût beaucoup plus faible ;
• en ce qu'il autorise des diamètres de conduit supérieurs à 35 mm. On pourra alors passer des convecteurs ou autres moyens volumineux dans des traversées en S ;
• dans les cas où le rayonnement neutronique est important : les neutrons diffusant mieux par collimation que les rayons gamma, il faudra - lorsque les cellules actuelles prévues pour traiter des combustibles de réacteurs à eau bouillante ou pressurisée devront traiter des combustibles de réacteurs rapides émetteurs neutroniques - ajouter des protections complémentaires sur les traversées actuelles. Les dispositif de l'invention convient alors parfaitement.

The device according to the invention is particularly advantageous:

• on current S installations: it guarantees the absence of collimation leaks. Collimation calculations are indeed difficult to carry out and a high safety coefficient is generally provided, hence heavier plugs, thicker walls, etc. The device according to the invention will achieve the same result with a much lower cost;
• in that it allows duct diameters greater than 35 mm. It will then be possible to pass convectors or other bulky means through S-shaped crossings;
• in cases where the neutron radiation is important: the neutrons diffusing better by collimation than the gamma rays, it will be necessary - when the current cells planned to treat fuels of boiling or pressurized water reactors will have to treat fuels of fast reactors with neutron emitters - add additional protection on current crossings. The devices of the invention are then perfectly suitable.

Claims (8)

1. Device for the radiation-sealed passage of a flexible feed (14), through a biological protection wall (X2) of a hot chamber and comprising a curved and particularly S-shaped pipe (8) traversing the wall (2), said pipe being lined with a radiation-absorbing material sheath (10) open at its two extremities (16, 18) with one situated in the hot zone (4) and the other in the working zone (6) respectively, characterized in that the flexible feed (14) is provided, on at least one section corresponding to its path in the pipe (8), with detachable solid pieces (20) which it traverses and made from a radiation protection material compatible with the sleeve material and which surround it at least at places like the pearls of a necklace, and ensuring both its placing by sliding it into the pipe (8) and the imperviousness of this curved pipe (8) against electromagnetic or neutron radiations.
2. Device according to claim 1, characterized in that the solid pieces (20) are spherical balls (22) with a diameter roughly equal to the internal diameter of the sheath (10) and pierced along one of their diameters with a passage (24) for the flexible feed.
3. Device according to claim 1, characterized in that the solid pieces (20) are straight cylinders (26) with a circular base and a diameter roughly equalling the internal diameter of the sheath (10) and pierced along their axis with a passage (24) for the flexible feed.
4. Device according to claim 1, characterized in that the solid pieces are cylindrical olive-shaped pieces (28) rendered integral in two sections (28a, 28b) and having, for the passage of the flexible feed (14), a pipe out of centre with respect to the axis of the cylinder so as to allow for the helical fitting of the various olive-shaped pieces (28) around the flexible feed (14).
5. Device according to claim 1, characterized in that the solid pieces (20) are cylindrical olive-shaped pieces rendered integral in two sections, each having one concave spherical end face and one convex spherical end face with the same bending radius so that the various successive olive-shaped pieces are rotating-nested inside each other and constitute a continuous flexible armouring around the flexible feed.
6. Device according to any one of the claims 1 to 5, characterized in that the material constituting the solid pieces has a good coefficient of friction concerning the material constituting the sheath.
7. Device according to any one of the claims 1 to 6, characterized in that it further comprises one stuffing-box (32, 34) traversed by the feed (14) and blocking off at least one of the openings (16, 18) of the curved pipe (8) so as to perfect protection against irradiating particles.
8. Device according to any one of the claims 1 to 7, characterized in that the flexible feed belongs to the group constituted by electric cables and fluid transport pipes.

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