GB2227186A

GB2227186A - Pressurized dissolving apparatus

Info

Publication number: GB2227186A
Application number: GB9001284A
Authority: GB
Inventors: Claude Guichard; Pierre Delorme
Original assignee: Commissariat a lEnergie Atomique CEA
Current assignee: Commissariat a lEnergie Atomique et aux Energies Alternatives CEA
Priority date: 1989-01-24
Filing date: 1990-01-19
Publication date: 1990-07-25
Anticipated expiration: 2010-01-19
Also published as: FR2642218B1; GB9001284D0; JPH02233129A; FR2642218A1; GB2227186B

Abstract

It comprises an internal container or bomb (1) formed by an upper cover (3) fitted to a cylindrical receptacle (2) having a hemispherical bottom (12), which is itself fitted in a base (4) having a hemispherical impression. The assembly is compressed in a metallic external container (17, 18), by means of spring (31). The special shape of the internal container (1) gives it an excellent mechanical strength and behaviour. Application to the dissolving of radioactive fuel residues. <IMAGE>

Description

Pressurized dissolving aPParatus.

DESCRIPTION.

The present invention relates to a pressurized dissolving apparatus.

The reprocessing of nuclear fuels requires the cutting up of rods into sectIons and the dissolving of the latter in a broiling nitric acid bath. Use is made for this purpose of large dissolvers essentially constituted by a vertical wheel partly immersed in the acid and carrying perforated buckets. However, these dissolvers are not completely satisfactory and are in particular unable to dissolve small fuel debris called "fines", which are highly radloactive. A more powerful dissolving process then has to be used according to which the acid is poured into a container, which is hermetically sealed after adding to it the fines to be dissolved. The container is then heated and the high temperature and pressure obtained make it possible to effect satisfactory dissolving.

The corrosive properties of the acid are greatly increased and therefore high demands are made on the container. A polymer material such as Teflon can be envisaged far the construction thereof. However, this material unfortunately has a relatively limited resistance to the mechanical stresses to which it is exposed.

The fundamental interest of the invention is based on a particular construction of the pressurized internal container and which leads to high strength. The adoption of secondary, but nevertheless advantageous characteristics of the invention make it possible to permit the performance of the dissolving process in a very easy manner by telemanipulation.

The invention more specifically relates to a pressurized dissolving apparatus for solids in an internal container constituted by a cylindrical receptacle and an upper cover fitted to the receptacle, characterized in that the receptacle has a hemispherical bottom with a constant thickness, in that the internal container comprises a base having an upper face in which is made a hemispherical impression for receiving the bottom and in that the apparatus also comprises an external container containing a recess for receiving the internal container and a spring for locking the receptacle between the cover and the base.

The external container is advantageously constituted by two cylindrical parts which can be screwed together.

The two parts of the external container can be provided with screwing stopping abutments. One of these parts is then tapped, the tap issuing in front of one end of the recess and receiving a screw for adjusting the locking of the spring. The adjusting screw and the tapped part of the external container can then be provided with abutments for stopping the screwing of said adjusting screw.

The invention is described in greater detail hereinafter relative to non-limitative embodiments and the attached drawings, wherein show: Fig. 1 a side view of the components of the apparatus.

Fig. 2 a view of the installed apparatus.

Fig. 3,4 and 5 the disassembly of the apparatus.

The fundamental component of the dissolving apparatus (fig.

1) consists of an internal container or bomb 1, which serves to contain under pressure the acid and the debris to be dissolved. The internal container 1 comprises a receptacle 2, a cover 3 fitted to the top of the receptacle 2 and a base 4 positioned below the receptacle 2. Cover 3 comprises a planar upper face 5. However, its lower face 6 has two concentric grooves 7,8 with a triangular cross-section, whilst the upper edge of the receptacle 2 is provided with two complementary ridges 10,11.

Receptacle 2 is generally cylindrical and comprises a hemis- pherical bottom 12, its thickness being the same throughout.

The base 4 comprises a planar lower face 13 and an upper face 14 having a hemispherical impression in which is precisely housed the bottom 12.

An external container, which is made from stainless steel, whereas the internal container 1 is of Teflon, is essentially constituted by an upper part 17 and a lower part 18, which are substantially cylindrical and can be screwed together by the engagement of a square-threaded nut end fitting 9 of the upper part 17 around the lower part 18. Once the two parts have been assembled, they form an extension of one another and define an internal recess 19 for containing inter alia the bomb 1.

A radial clearance is provided between the latter and the walls of parts 17,18 in order to take account of the greater thermal expansion of the Teflon. Circumferential collars 15,16 on the outside of the wall of receptacle 2 at different heights extend into said clearance in order to ensure the coaxial nature of internal container 1 and the external container.

Each of the parts 17 and 18 comprises an end wall 20,21 having a bore 22,23. Bore 22 on upper part 17 is in reality a squarethreaded tap, whereas the other bore 23 is smooth. The upper part 17 is provided on its upper face with radial slots 48 distributed over the entire circumference.

The lower part 18 is provided with gripping loops 24, which can be more easily seen in the other drawings and whereof one is extended upwards by an abutment 25 for contacting another abutment 26 on the bottom of the upper part 17 when the screwing of parts 17 and 18 has reached a certain limit. The stopping of screwing is ensured by contact between the vertical planar faces 37,38 of abutments 25,26, so that the height of recess 19 is known.

The assembly contained in recess 19 comprises, from bottom to top, a lower plug 27 having a part 28 partly filling the lower bore 23, washers 29 regulating, if need be, the base 4, the receptacle 2, the cover 3, an intermediate plug 30, a helical spring 31 and an upper plug 32, which bears on the end wall 20 of lower part 17. Helical spring 31 is compressed between plugs 30,32 and itself compresses the internal container 1, preventing the raising of cover 3.

The locking tension of spring 31 can be produced by the screwing of parts 17 and 18 of the external container and adjusted by washers 29. However, there is a more precise adjustment with the aid of screw 33, which enters the bore 22 so as to force back the upper plug 32. Screw 33 is provided with an abutment 34 radially projecting over the screw head in order to come into contact with an abutment 35 at the top of the upper part 17. The screwing of screw 33 into tap 22 is then interrupted and further compression of spring 31 is impossible.

The internal container 1 is then exposed to forces due to the internal pressure and to compressive forces due to the spring 31. The separation of the base 4 and the receptacle 2 and the construction of a hemispherical bottom 12 to a significant extent break down these stresses and in particular prevent excessive stress concentrations in the bottom 12, which significantly increases the mechanical strength of the bomb 1, which is able to resist a pressure of several hundred bars. The radial clearance between bomb 1 and the external container makes it possible to accept the thermal expansion differences, e.g. at 2400C, between the Teflon and the steel.

The aforementioned assembly is used in an enclosure provided with telemanipulating tools and placed in a case for assembly or disassembly (fig. 2).

Reference is now made to figs. 3 and 4. The case 41, attached to a wall 42, receives the assembly in an impression open at the top and whose height is roughly the same as that of the lower part 18. Vertical grooves 44 are made from the top of the case 41 to permit the passage to the outside of loops 24.

Case 41 is provided on its bottom with a tapped end fitting 45 in which engages a square-threaded screw 46 completed at its lower end by a swivel 47. Screw 46 is located in front of the lower bore 23.

The disassembly of the assembly from the state of fig. 2 firstly takes place by positioning the screw 33 on a bushing 49 having six flats surmounted by radial tubes 50. A tool 51 constituted by a rod 52 having at its end a cylindrical termination 53 is approached by bushing 49 by a telemanipulated fork 58, whose fingers 57 are engaged in hoods 54 fixed to rod 52. The termination 53 is introduced into the tubes 50 in order to unscrew screw 33. Spring 31 is then almost relaxed.

Bushing 49 is removed and the termination 53 of tool 51 is introduced into slots 48 of the upper part 17 in order to unscrew the latter from the lower part 18 and remove it, together with the spring 31 and the adjacent plugs. The loops 24 prevent the rotation of the lower part 18.

The following stage consists of turning swivel 47. Screw 46 enters the lower bore 23 and raises the lower plug 27. Receptacle 2 and cover 3 then appear above the lower part 18. Another tool 60 (fig. 4) constituted by a gripping hood 54, to which is attached a variable diameter clip 55, whose tightening is regulated by a screw 56 is then approached. The clip 55 is tightened around the receptacle 2 which can be removed from the lower part 18. It is then possible to raise the latter and the rest of its content out of the case 41 through the gripping of loops 24 by a fork 59 (fig. 5).

The reassembly of the assembly takes place under the same conditions with the reverse operations.

Claims

1. Pressurized dissolving apparatus for solids in an internal container (1) constituted by a cylindrical receptacle and an upper cover (3) fitted to the receptacle (2), character ized in that the receptacle has a hemispherical bottom (12) with a constant thickness, in that the internal cont ainer comprises a base (4) having an upper face (14) In which is made a hemispherical impression for receiving the bottom and in that the apparatus also comprises an external container containing a recess (19) for receiving the internal container (1) and a spring (31) for locking the receptacle (2) between the cover (3) and the base (4).

2. Pressurized dissolving apparatus according to claim 1, characterized in that the external container is constituted by two cylindrical parts (17,18), which can be screwed together.

3. Pressurized dissolving apparatus according to claim 2, characterized in that the two parts of the external cont ainer are provided with screwing stopping abutments (25,26) and one of the parts (17) is tapped (22), the tap issuing in front of one end of the recess (19) and receiving a screw (33) for adjusting the locking of spring (31).

4. Pressurized dissolving apparatus according to claim 3, characterized in that the adjusting screw (33) and the tapped part (17) of the external container are provided with other abutments (34,35) stopping the screwing of the adjusting screw.

5. Pressurized dissolving apparatus according to any one of the claims 2 to 4, characterized in that one of the parts (18) of the external container is provided with loops (24).

6. Pressurized dissolving apparatus according to claim 5, characterized in that it comprises a case (41) for receiving the external container, the case being notched parallel to an introduction direction of the external container into the envelope, so that the loops (24) project towards the outside of the case.

7. Pressurized dissolving apparatus according to either of the claims 5 or 6, characterized in that that part of the external container not provided with loops (17) is provided with radial bores (48) positioned along a circumference.

8. Pressurized dissolving apparatus according to any one of the claims 1 to 7, characterized In that the internal cont ainer is made from a polymer materIal.

9. Pressurized dissolving apparatus according to claim 8, characterized in that the container is provided in the recess with external centering excrescences (15,16).