FR2725551A1 - SUCTION DEVICE AT THE BOTTOM OF A NUCLEAR INSTALLATION TANK - Google Patents

Abstract

The present invention relates to a suction device at the bottom of a tank of a nuclear installation, comprising a body (30) comprising a suction tube (32) and a receiving barrel, a head (31), ensuring the depression of the body, comprising two nozzles (35) and two discharge nozzles, a retaining screen, a hose (38) for supplying compressed air and an O-ring ensuring the seal between the body (30) and the head (31), and a locking means (34), for securing the body and the head.

Description

"Suction device at the bottom of a tank of a nuclear installation"

DESCRIPTION

  Technical Field The present invention relates to a vacuum device for

  bottom of a nuclear installation tank, for example at the bottom of a dissolver.

  STATE OF THE PRIOR ART In the context of the reprocessing or treatment of irradiated fuel elements, that is to say after their use in a nuclear reactor, the irradiated assemblies are first sectioned, then immersed in a reagent, which is usually hot nitric acid, in which they are dissolved. Fragments of fuel from a shear containing oxide powder are thus dropped into a dissolver tube. This can be in the form of a well, that is to say a large vertical tube of cylindrical or rectangular section containing a basket immersed in a solution of nitric acid. This dissolver tube comprises several pipes necessary for its operation, in particular pipes for the evacuation of vapors and dissolving gases towards a condenser and pipes belonging to the circuit for draining the solution of solution to

  a storage tank. It can also include a bubbling circuit

  stirring to homogenize the solution.

  The possible cleaning of a dissolving tube, and in particular of its lower part, can only be done by means of robotic machines, access to it being prohibited to human persons, taking into account the irradiation rate of this zoned. Indeed, the bottom of such a tube is cluttered with debris comprising shells and dissolving fines, with the risk of clutter

  due to shells that pass through baskets during dissolution.

  The fines and the hulls block the dissolver nozzles and the ejectors, which leads to high curative maintenance (very high costs) and therefore waste and integration of doses of radioactivity for the staff. French patent application FR-A-2,500,199 describes a device for sucking irradiated materials under water such as chips, particles, cut pieces, fragments and other substances in a location under the water that protects the technician, or other people who

  work, against dangerous exposure to radiation.

  This suction device consists of a pressurized water injection tube, a decreasing inside diameter nozzle and a radioactive material suction tube, the first end of which is a shaped element. funnel and the second end of which ends with a separable and disposable filter. Pressurized water is injected through an injection tube into the suction tube connected to the collecting filter. the device is operated by means of a positioning pole articulated on the injection tube or the suction tube. A locking mechanism mounted on the pole is remotely controlled by the user who uses a rope to discontinuously adjust the orientation of the suction tube and that of the filter. The device is installed for use in the reactor pool adjacent to the pressure vessel of a nuclear reactor. The irradiated materials are collected by means of the device on a working platform above which machining operations are carried out from time to time on elements or parts of the reactor. In this device there is the use of pressurized water injection, and therefore the intervention of a water tube, with poor efficiency because there is only raising of the hulls with creation of effluents and there is no solution for fines. In addition there is no vision of the work area because it

  there is no camera association due to the presence of water.

  The subject of the invention is a suction device for recovering hulls and fines in dissolvers, making it possible to overcome these drawbacks. This suction device must allow the recovery of hulls and fines (dry intervention), preventive maintenance being possible in particular during the inter-campaign, the hulls and fines after

  suction being returned into the process via the shears.

  Disclosure of the invention The invention therefore proposes a suction device at the bottom of a tank of a nuclear installation, for example at the bottom of a dissolver, characterized in that it comprises a body comprising a tube for raising hulls and a receiving barrel, a head ensuring the depression of the body, comprising at least two nozzles and at least two delivery nozzles, a shell retaining screen, a flexible air supply hose and an O-ring ensuring the seal between the body and the head, and a locking means, for securing the body and the head, This device has the following advantages: - in operation, no part is in motion; - it allows dry interventions, without creating additional effluents; - it allows preventive maintenance instead of maintenance

  curative (clogging of dissolver nozzles and ejectors).

  In an advantageous embodiment, the body is of cylindrical sheet metal shape with the suction tube in the lower part and a bend in the upper part machined after welding. Around the body, several

  centralizers are welded. A pawn serves as a key to the establishment of the head.

  Two rotating axes are used to lock the body on the head by acting on the

  locking means which is a locking ring.

  The cylindrical head has on top the air supply tube with a connector and the two tube nozzles terminated by a cone whose upper part is obstructed by a welded mesh to prevent any intrusion of objects. Under the flange are the two discharge nozzles. A determined distance under the flange and the coaxiality with respect to the nozzles are very important. A pin acts as a key for setting up the screen. The O-ring serves as a seal between the head and the body. The locking ring is used to lock the head on the body and also allows the handling of

  all. An indexing screw positions and immobilizes the locking ring.

  The two axes are welded after the lifting ring is placed on the head. The screen is made of perforated sheet. A full sheet metal inclined at 45 serves as a deflector (cone portion). A captive screw allows mounting and dismounting on the head. The supply hose is introduced into the cell through a partition passage and is connected to the supply reel of the device. The hose reel can be used for both feeding and handling the

  device. In this case the supply hose is connected to a reel.

  Taking into account the simplicity of the assembly, it is possible to mount on the head (standard) bodies of different geometries adapted to the

specific situation.

  This device was designed to recover shells and fines from the bottom of the dissolver tubes. It can be used for the recovery of various objects, it is used

  thus cleaning the bottom of the dissolving boxes.

  Various tests have led us to design a compact device which makes it possible to lower the assembly to the bottom of a tube of ten

  meters below the cell work plan.

  The reduced suction height thus makes it possible to recover

high density particles.

Brief description of the drawings

  - Figure 1 illustrates a device of the prior art; - Figures 2, 3 and 4 illustrate the device of the invention respectively during the descent into a well, in an elevation view and

  in a view partially in longitudinal section.

  Detailed description of embodiments Figure 1 shows the characteristics of a device

  underwater suction described in the French patent application FR-A-

  2,500,199 already cited above. This device comprises a positioning or operating pole 11, a pivoting locking mechanism 12 with variable positions comprising a rope 13 for controlling the locking mechanism 12, and a suction tube 14 comprising a funnel element for receiving the materials irradiated 16. More specifically, the locking mechanism 12 is mounted on a curved injection tube 17 comprising a support element 18. The injection tube 17 receives pressurized water from an external source using, for example, a flexible pipe 19 suitably connected to the injection tube 17 by means of a connector 20. The injection of pressurized water from the injection tube 17 is carried out by a nozzle 21 of decreasing internal diameter, the longitudinal axis of the nozzle 21 preferably being in the extension of the longitudinal axis of the straight part of the suction tube 14. This injection creates a current of water in the tub e suction 14 and a resulting suction force which causes the irradiated materials or waste 16 to be sucked into the funnel element 15 and through

  the suction tube 14 to a separable and disposable filter 22.

  Figure 1 shows the use of the suction device in

  the reactor pool to collect irradiated materials from a platform

  working form 23 mounted laterally in the pool.

  By means of the locking mechanism 12, the operating pole 11 is articulated on the suction device and this mechanism comprises a plunger 24 constrained downward, which has at its upper end a ring 25 for attaching or fixing thereto in another way the rope 13. A part 26 allowing the articulation is appropriately fixed to

the end of the pole 11.

  On the other hand, the inventon suction device, which is a powerful vacuum cleaner with a reduced head having no moving part, is composed of two parts: a body 30 and a head 31 as shown in the

Figures 2, 3 and 4.

  The body 30 comprises a tube 32 for raising the shells and a barrel 33 for receiving the latter. It carries a locking means 34, for example a ring, which secures the body 30 and the head 31 at the time of

assembly.

  The head 31 ensures the depression of the body. It is composed of two air ejectors 35 comprising discharge nozzles and injectors, an interchangeable shell retaining screen 36, a tube 37 for connection to a supply hose 38 and an O-ring 39

  ensuring tightness between the body and the head.

  More precisely, the body is of cylindrical sheet metal shape with the suction tube 32 at the bottom, which can be connected to the side (as in FIGS. 2, 3 and 4) of the barrel 33 or on the bottom of the latter. ci, and a flange 40 in the upper part machined after welding. On the periphery of the body, several centralizers 42, for example six, are welded. A pawn serves as a key to the establishment of the head. Two rotating axes 43 are used for

  locking of the body on the head by action on the locking ring 34.

  The head is of cylindrical shape comprising on the top the air supply tube 37 with a fitting 44 and the two nozzles 35 in tube terminated by a cone the upper part 46 of which is closed by a welded mesh

  to avoid any intrusion of objects.

  Under the flange 40 are the two delivery nozzles 47.

  A determined distance under the flange and coaxiality with respect to the nozzles are very important. A pin serves as a key for setting up the sieve. The O-ring 39 serves as a seal between the head and the body. The locking ring 34 is used to lock the head 31 on the body 30 and also allows the handling of the assembly. An indexing screw 49 positions and immobilizes

  the locking ring after it has pressed against the stop system 50.

  The two pins 43 are welded after the lifting ring has been placed on the

head.

  The screen is made of perforated sheet. A full sheet metal inclined at 45 can serve as a deflector (cone portion). A captive screw allows the

mounting and dismounting on the head.

  The supply hose 38 is connected to the supply reel 29 for supplying the device. The hose reel is used for both feeding and handling the device. The retractor is maneuvered, for example, using a pneumatic remote-controlled key which acts on a worm gear 28 to modify the altitude of the device of the invention on request. The reel

  29 can either be placed on the decking or held on the deck.

  Given the simplicity of mounting the device of the invention, it is possible to mount on the head 31 (standard) bodies 30 of

  different geometries adapted to specific situations.

  The physical phenomena involved in the aspiration are the same in the invention and in the cited document. However, the implementation of technical means are different. In the invention, compressed air is injected, making it possible to operate dry in the installations, unlike the cited document which uses pressurized water and which is therefore intended to be

used in swimming pools.

  Furthermore, the invention does not use a "disposable" filter but a means for receiving radioactive materials provided with a strainer or filter 36

  to stop the materials.

  Finally, the originality of the invention consists in the means for injecting the compressed air with its two nozzles 47 and the two nozzles 35. In an exemplary embodiment, the device of the invention consists of: a cylindrical body 30 of length 1000 mm and of diameter mm with a useful volume of 8.5 liters; with in the lower part, a suction tube 32 of diameter 48 mm, and length 765 mm); - A cylindrical head 31 comprising on the top a tube 37 for air supply with a telemanipulable connector 44, two nozzles 35 in tube, the upper part 46 of which is screened to prevent any intrusion of an object; and in the lower part, two discharge nozzles 47; the two nozzles 47 located at a distance of 52 mm under the flange 40; - a sieve 36 made of perforated sheet (diameter 3) with a full sheet

  inclined at 450 serving as a deflector.

  The head 31 is micro-blasted except for the interior of the nozzles 35 which is mirror polished. The body 30 and the screen 36 are passively pickled. All

is made of stainless steel.

  The entire device of the invention then has a space requirement of: - total height: 1,355 mm;

- maximum diameter: 170 mm.

  The working fluid is compressed air with the following characteristics: - pressure approximately 7 bars;

- flow 5000 I / min.

  For the handling of the device of the invention in boxes and dissolving tubes, there is monitoring throughout the descent and

  the climb using an intervention camera.

  The device of the invention is emptied by

  separating the head from the body. The shells contained in the store of this one

  these are then emptied into a bucket.

  The conditions of use of the device of the invention are as follows: suction can only be carried out on rinsed shells. The device of the invention should not be used for the recovery of oxide or

  shells in the internal shear frame or in the rotary distributor.

  The possible suction zones are as follows: - dissolving boxes; - the hydraulic guards for the inlet sealing plugs of the dissolving tubes; - the bottom grids of dissolving tubes;

- the bottoms of dissolving tubes.

Claims (14)

  1. Suction device at the bottom of a tank of a nuclear installation, characterized in that it comprises a body (30) comprising a suction tube (32) and a receiving barrel (33), a head (31), ensuring the depressurization of the body, comprising at least two nozzles (35) and at least two discharge nozzles (47), a retaining screen (36), a flexible hose (38) for supplying compressed air , and an O-ring (39) sealing between the body (30) and the head (31), and a locking means (34), for the   joining of the body and the head.   2. Device according to claim 1, characterized in that the body (30) is of cylindrical sheet metal shape with the tube in the lower part   suction (32) and in the upper part a flange (34).   3. Device according to claim 2, characterized in that it   comprises several centralizers (42) welded on the periphery of the body (30).   4. Device according to claim 2, characterized in that it   includes a pin serving as a key to the positioning of the head (31).   5. Device according to claim 2, characterized in that it comprises two rotary axes (43) used for locking the body (30) on the head (31) by action on the locking means (34) 6. Device according to claim 1, characterized in that the head (31) is of cylindrical shape comprising on the top a tube (37) for air supply with a connector (44) and the two nozzles (35) in tube terminated by a cone, the upper part (46) of which is closed by a welded mesh   to avoid any intrusion of objects.   7. Device according to claim 6, characterized in that it   comprises two delivery nozzles (47) coaxial with the nozzles.   8. Device according to claim 7, characterized in that the   delivery nozzles are at a determined distance from the flange (40).   9. Device according to claim 6, characterized in that it   includes a pin serving as a key for setting up the sieve.   10. Device according to claim 1, characterized in that the sieve is made of perforated sheet.   11. Device according to claim 1, characterized in that it   includes a full sheet metal inclined at 45 serving as a deflector.   12. Device according to claim 1, characterized in that the supply hose (38), connected to the supply reel, serves both to   feeding and handling said device.   13. Device according to claim 12, characterized in that the supply hose (38) is connected to a reel (29).   14. Device according to any one of the claims   above, characterized in that it is used at the bottom of the dissolver.