FR2662295A1 - CONTAINER DEVICE FOR STORING RADIOACTIVE OR TOXIC WASTE, AND FILLING METHOD THEREFOR. - Google Patents

Abstract

The container device makes it possible to store, over the long term, radioactive products of low and medium activity and suitable for the retention of cesium. The container (2) is lined inside a lower part (9) of a diffusion barrier, inside which the waste (10) is placed, embedded in a filling concrete (7). A cover (5) is placed beforehand on the container (2) before filling. Once the fill concrete (7) has been poured, an upper part (13) of the diffusion barrier is poured below, through and above the plug (5), this diffusion barrier entirely surrounding the filling concrete. (7). Application to the storage of weakly or moderately radioactive materials from nuclear power plants.

Description

-I

STORAGE CONTAINER DEVICE

RADIOACTIVE OR TOXIC WASTES,

AND ITS FILLING METHOD

DESCRIPTION

FIELD OF THE INVENTION

  The invention relates to the packaging of active waste, such as radioactive waste of low and medium activity or toxic waste, for their long-term storage. The materials used and the device built must respect the storage regulations

  and transport of radioactive products in force.

PRIOR ART

  Many devices for conditioning or blocking low and intermediate level radioactive waste, also called technological waste, have already been used for the long-term storage of this type of waste. French Patent Publication No. 2,624,301, describing a device for packaging radioactive or toxic waste containing borate ions and its process

Manufacturing.

  The container described in this document mainly comprises: a drum containing waste in the form of a dispersion of this waste in a mineral matrix; a layer of mortar disposed around the barrel; and an outer envelope surrounding the mortar layer. The latter is preferably made of sand, siliceous cement, silica fume and a smectic clay.

preferably concrete.

  However, most of the containers, used until now, do not offer the guarantees of retention of the radioelements required by the regulations in force, and more particularly by the specifications of surface storage defined by the ANDRA (National Agency for the management In particular, it is necessary that the biological protection constituted by the container and its different thicknesses be retained as a sufficient barrier against the diffusion of the radioelements. This entails that any contaminated technological waste is in contact with the inner wall. the container is considered as not being protected vis-à-vis

the environment of the package.

  One solution, overcoming this disadvantage, is to use a basket containing the waste to provide a sufficient thickness of concrete between the waste and the container.

  disadvantages inherent to this solution appear.

  Indeed, at the time of filling by the filling concrete, it may cause contamination to the inner wall of the container

in concrete.

  On the other hand, it is essential to respect the conditions relating to the external geometry of the containers, because the nuclear installations that use them are dimensioned accordingly. Modifications, resulting from different access, fixing or docking dimensions. , would have many disadvantages from the point of view of the safe and the financial point of view. However, various concrete formulations are known whose retention qualities vis-à-vis radioelements, such as cesium, have been improved In fact, they are sufficient to meet the conditions of surface storage

imposed by ANDRA.

  It is also known to use a prefabricated cap to close the container.

  allows the filling of the inside of the container.

  The advantage of such a prefabricated cap is that it biologically protects the container with its radioactive waste before the pouring operation of the concrete

blocking or filling.

  The object of the invention is to overcome the aforementioned drawbacks and to provide a container capable of meeting the current operating conditions of the nuclear installations and the transport regulations in force. Specifically, the objectives achieved by the container device according to the invention. are: Use current internal and external ratings of existing containers; maintain the same thicknesses of biological protection.

SUMMARY OF THE INVENTION

  One of the main objects of the invention is a low and medium activity or toxic radioactive waste storage container device comprising: a concrete container, inside which L must be placed the waste surrounded by filling concrete; and a prefabricated cap for closing the container and having at least one fill port through which the filling of the interior of the container by the filling concrete is to be carried out. According to the invention, there is used an integrated diffusion barrier, consisting of diffusion mortar, divided into a first lower part placed inside the container and by a second upper part placed inside and through

cap.

  The container device according to the invention is particularly effective when the thickness of the diffusion barrier is greater than or equal to

at 50 mm.

  Preferably, the plug is filled and covered with diffusion mortar thus forming an integral part of the upper part

of the diffusion barrier.

  In order to facilitate the filling and the disposal of the radioactive waste contained in the container, during the pouring of the filling concrete, the invention provides a horizontal grid, placed under the plug, to hold the waste in the middle of the concrete. if they have a lower density than the filling concrete, in which case they would tend to

to go back to the stopper.

  In order to completely cover the diffusion mortar plug, provision is made for a

  recess in the upper surface of the plug.

  To facilitate the filling operation of the interior of the container with the aid of the filling concrete, level probes are placed in

under the cap.

  As regards the materials used, the filling concrete preferably has the following constitution by weight: at 30% CPA Z 45 cement; 11 to 16% water;

57 to 62% sand.

  The diffusion mortar preferably has the following constitution by weight: cement CLC 45, at a rate of about 847 kg / m 3; bayous sand (05 mm) at a rate of about 1,152 kg / m 3; water, at a rate of about 245 l / m 3;

  "Pozzolith 450" at a rate of about 16.9 l / m 3.

  A second main object of the invention is a method of filling the container device,

which has just been summarized.

  According to the invention, this method consists in: placing the waste inside the lower part of the diffusion barrier; place the cap on the container; fill the interior volume of the diffusion barrier in which the waste is located, by means of a filling concrete, up to the level of the grid, so as to leave a free space under the plug; filling said free space with diffusion mortar, until the filling holes are

completely clogged.

  Preferably, the diffusion mortar completely fills the recess provided on the upper surface of the plug to form a layer

of cleanliness.

  A third object of the invention is a method of manufacturing the container device,

previously described.

  According to the invention, it comprises the following phases: development of the concrete container; placing the lower part of the diffusion barrier by casting a diffusion mortar by means of a mold whose shape of the outer surface corresponds to the shape of the inner surface of the lower part of the diffusion barrier; drying, with the mold, of this molded lower part of the diffusion barrier during a

  duration between 10 and 20 hours.

  During drying, this process is advantageously completed by regular wetting with water or oil of the upper surface of the part

  lower molded diffusion barrier.

LIST OF FIGURES

  The invention and its different features will be better understood when reading

  of the description that follows It is completed by

  several figures which respectively represent: FIG. 1, a section of the container device according to the invention, filled with waste and hermetically sealed; FIGS. 2A and 2B, two phases of manufacturing processes of the container device according to the invention; FIGS. 3A to 3D, four phases of the filling process of the container device

according to the invention.

DETAILED DESCRIPTION OF A MODE OF

PRODUCTION

  FIG. 1 shows the container device according to the invention containing radioactive waste, in particular of low and medium activity, and hermetically closed, ready to be transported and stored for a long time. All the constituent elements of the container device are described.

in this figure.

  In known manner, it comprises a container 2 made of conventional concrete The formulation of the latter may be based on sand and gravel rolled and crushed, the latter being divided into four granular classes ranging from 0 to 25 mm,

and HPR cement.

  A more precise formulation of a filling concrete is as follows: at 30% CPA Z45 cement; 11 to 16% water;

57 to 62% sand.

  The quality of the filling concrete composition can be achieved by the use of a dry load, which is a load whose elements are already measured and mixed by the manufacturer. The outer shape of the container 2 is preferably cylindrical An internal volume has been

  arranged during the development of this container 2.

  This internal volume is preferably also cylindrical In the upper part of the outer surface 3 of the container 2, can be embedded a hollow annular profile 4, adapted to the device for handling and handling of this type of container. The container 2 is closed by a prefabricated cap 5, the material used can also be the same concrete as that used for the container 2 The cap 5 is placed on an upper support surface 11 of the container 2 It comprises in known manner at least a filling orifice 6, but preferably, several orifices 6 These are vertical and are intended for filling the internal volume of the container device inside which the waste 10 is placed Indeed, these are coated completely with a filling concrete 7 intended to hold them in place and to cooperate in their radioactive confinement The filling orifices 6 thus completely pass through the plug 5. In order to facilitate the filling of the inside of the container device, leakage orifices 8 These vents are intended to allow air to be forced out of the concrete inside the container device to escape and to avoid i The presence of air pockets at

The inside of the container.

  The invention, the whole consisting of waste 10 embedded in the filling concrete 7, is surrounded by a diffusion barrier consisting of a first lower portion 9 pressed against the inner wall of the container 2 and defining the The lower part 9 stops at its upper end at the level of the bearing surface 11 of the container 2, on the lacquer L The plug 5 takes

support.

  It can be seen that in this FIG. 1, the coating of filling concrete 7 does not completely fill the volume defined by the lower part 9 of the diffusion barrier. Indeed, there remains a part between this concrete filling coating 7 and the lower surface 12 of the plug 5 This space is filled by the upper part 13 of the diffusion barrier The assembly formed by the filling concrete 7, coating the waste 10, is thus completely closed by the

diffusion barrier.

  The upper part 13 of the diffusion barrier is preferably extended inside the filling orifices 6 of the cap 5 to overflow on the upper surface 14 of the lid. To facilitate this overflow of the upper portion 13 of the diffusion barrier, the thickness of the plug 5 is provided, so that once placed, the plug 5 forms in cooperation with the upper part of the container 2 a recess to inside which the upper part 13 of

  the diffusion barrier can take place.

  It can thus be seen that the waste is surrounded by a diffusion barrier developed in several phases, but consisting of a single pocket

homogeneous and waterproof.

  The thicknesses of this diffusion barrier are preferably greater than or equal to

at 50 mm.

  In order to facilitate the maintenance of the waste 10 during the pouring of the filling concrete 7, provision is made, beneath the cap 5, of a holding grid 15 which is horizontal and positioned at a distance greater than the thickness of the upper part 13 of the barrier of

diffusion, below the plug 5.

  Still to facilitate the filling of the filling concrete 7, probes may be arranged at the level of the grid 15 to detect the level of the filling concrete 7, when the latter

reaches the level of the grid.

  Additional indications concerning the dimensions and the positioning of the different elements of the container device according to the invention will now be given by way of example and

  to concretize the feasibility of the invention.

  The two filling orifices 6 may be cylindrical or conical. Nevertheless, their

  minimum diameter must be 50 mm.

  The grid 15 preferably has a mesh of 25 mm It is fixed at a minimum distance of 150 mm from the lower surface 12 of the plug 5, this corresponds to a thickness equal to the attenuation thickness "1/10 C 0. The vents 8 are provided in number of six They preferably have a diameter equal to 20 mm They promote the evacuation of the air located under the plug during the filling of the part upper 13 of the diffusion barrier They also facilitate the mechanical connection between the diffusion mortar and the conventional concrete of which

is constituted the plug 5.

  It is possible to add a probe device in some of the vents 8 It is thus possible to have an additional indication 1 1 concerning the level of the filling concrete,

  especially when it reaches grid 15.

  The manufacture of the container device, according to the invention, is now described, with reference to FIGS. 2A and 2B. The preparation of the concrete container 2 is made conventionally using the

formulation cited above.

  The development of the lower part 9 of the diffusion barrier is obtained by pouring the diffusion mortar. To define the volume that this lower part 9 must occupy, a mold is placed inside the volume defined by the inner wall of the container. This mold 20 has a shape complementary to the inner wall of the container 2, that is to say a cylindrical or slightly conical shape. The diameter of the mold 20, at each height, is at least 100 mm smaller than the diameter of the mold.

the inner wall of the container 2.

  To be correctly positioned relative to the container 2 the mold 20, shown in phantom in Figure 2 A, is suspended by a suspension system 21 bearing on the upper part of the container 2 so that the mold 20 is centered accurately the suspension system 21 is fixed rigidly to the mold and has a circular centering stopper 22 coaxial with the mold 20, and whose inner diameter is equal to the outer diameter of the upper part of the container 2 The depth of the mold 20 corresponds to at the height of the container 2, less the thickness of the bottom of the latter and the bottom thickness of the future lower part 9 of the barrier

of diffusion.

  It can then proceed to casting the diffusion mortar in the space left free

  between the mold 20 and the container 2.

  It can be specified that the container 2, having external dimensions identical to the current containers, is provided with internal dimensions

  less the thickness of the diffusion barrier.

  The usual internal reinforcement of such a container

is not, however, modified.

  The formulation of the diffusion mortar is, in a first embodiment, based on specified sand, in this case two sands whose grain sizes are defined, of siliceous cement based on smoke, and possibly a fluidifying agent. formulation is used for its retention capacity with respect to radioelements,

especially cesium.

  Another formulation of the diffusion mortar has the following composition: cement CLC 45, at a rate of about 847 kg / m 3, "Bayeux" sand 0-1 mm, at a rate of about 1150 kg / m 3; water, at a rate of about 254 l / m 3;

  "Pozzolith 450" at a rate of about 16.9 l / m 3.

  This operation is followed by a drying time of between 10 and 20 hours, preferably 12 to 14 hours. For this to be effective, the upper surface 23 of the lower part 9 of the diffusion barrier must be wetted regularly. preferably every hour, to avoid a phenomenon of faiençage of the surface This wetting can be made using

  water or oil, to prevent evaporation of water.

  To improve the casting and distribution of the diffusion mortar, it is possible to use a needle, but this additional operation

is not necessary.

  The product obtained is shown schematically in FIG. 2B, showing the container 2 and the lower part 9 of the diffusion barrier, ready

  to receive the waste and the filling concrete.

  The method for using the device

  container according to the invention is now described.

  As shown in Figure 3A, the first phase consists of placing the radioactive waste inside the lower 9 of the

diffusion barrier.

  With reference to FIG. 3B, this operation is immediately followed by the positioning of the stopper on the container 2, and more precisely on the support surface 11 of the latter. The stopper then provides a biological protection before the pouring of the IL fill concrete. obviously supplements the biological protection afforded by the container 2. The third operation consists in filling the volume defined by the internal wall of the lower part 9 of the diffusion barrier of a filling concrete. This operation is carried out through at least one orifice 6 of the plug 5 As shown in FIG. 3C, the pouring concrete thus cast completely drowns the radioactive waste 10 In the case where some of them have a density lower than the density of this filling concrete 7, the grid 15 prevents their rise above it The probes 16 placed at the level of it can detect the level of the concrete of

  filling 7 and stop the casting of the latter.

  The waste 10 is then completely coated.

  It is necessary to provide a free space above the filling concrete 7 and below the lower surface 12 of the cap This volume is intended for the neck of the party

  upper 13 of the diffusion barrier.

  As shown in FIG. 3D, this free space is then filled with diffusion mortar by means of the filling orifices 6, the vents 8 allowing the air to escape and thus facilitating the homogeneous and total distribution of the diffusion mortar. in the space left free by the concrete

filling 7.

  Preferably, this operation continues until the holes 6 are completely filled

broadcast mortar.

  To facilitate the end of this operation, it is expected that the upper surface 14 of the cap 5 is at a lower level of the part.

  upper container 2 for recessing.

  The pouring of the diffusion mortar can then be prolonged so that it fills the recess provided by the upper surface 14, then acting as an overflow.

to be made.

Claims (13)

  1 Container for storing low-level or intermediate-level or toxic radioactive waste comprising: a concrete container (2) inside which waste (10) surrounded by filling concrete (7) must be placed; a prefabricated plug (5) for closing the container (2) and having at least one filling opening (6) through which the filling inside the container (2) by the filling concrete (7) is to take place, characterized in that it comprises an integrated diffusion mortar barrier consisting of a first lower part (9) placed inside the container (2) and a second upper part   (13) placed inside the plug (5).   2 Device according to claim 1, characterized in that the integrated barrier has a   thickness equal to or greater than 50 mm.   3 Device according to claim 1 or 2, characterized in that the cap (5) is covered and filled with a layer of diffusion mortar forming part of the part   upper (13) of the diffusion barrier.   4 Device according to any one of   preceding claims, characterized in that   comprises a grid (15) horizontal, placed under the plug (5), to maintain the waste (10)   in the middle of the filling concrete (5).   5 Device according to claim 3, characterized in that it comprises a recess on the upper surface (14) of the plug (5), so as to allow the overflow of the diffusion mortar when filling the lid.   6 Device according to claim 4, characterized in that it comprises level probes (16), placed on the grid (15) below the plug (5), to detect the level of filling of the concrete filling (7).   7 Device according to any one of   preceding claims, characterized in that   the filling concrete has the following formulation, by weight: at 30% CPA Z 45 cement; 11 to 16% water; 57 to 62% sand.   8 Device according to any one of   preceding claims, characterized in that   that the diffusion mortar has the following formulation: cement CLC 45, at a rate of about 847 kg / m 3; bayous sand (0-5 mm) at a rate of about 1,152 kg / m 3; water, at a rate of about 254 L / m 3;   "Pozzolith 450" at a rate of about 16.9 L / m 3.   9 Method of filling a device   container according to claims 4 and 5, characterized   in that it comprises the following steps: placing the waste (10) inside the lower part (9) of the diffusion barrier; placing the cap (5) on the container (2); filling the inner volume of the lower part (9) of the diffusion barrier, in which the waste (10), filling concrete (7) is located, up to the level of the grid (15), so as to leave a free space under the plug (5); filling said free space with diffusion mortar, until the filling orifices (6) are completely plugged, so as to constitute the second upper part (13) of the diffusion barrier. Process according to Claim 9, characterized in that the diffusion mortar completely fills the recess above the plug (5)   to form a clean layer (17).   11 A method of manufacturing the container device according to revendi cation 1, characterized in that it comprises the following phases: development of a concrete container (2); placing the lower part (9) of the diffusion diffusion molding mortar barrier by means of a mold (20) whose shape the outer surface corresponds to the shape of the inner surface of the lower part (9) of the diffusion barrier; drying with the mold for a period of time between 10 and 20 hours.   12 Process according to claim 11, characterized in that, during the drying phase, a wetting with water is regularly carried out on the upper surface (23) of the lower part   (9) molded diffusion barrier.   Process according to Claim 10, characterized in that, during the drying stage, an oil wetting is carried out regularly on the upper surface (23) of the lower part   (9) molded diffusion barrier.