FR3060831A1 - DEVICE FOR PROTECTING AGAINST THE IONIZING RADIATION PRODUCED BY A CONTROL APPARATUS AND METHOD OF MANUFACTURING THE DEVICE - Google Patents

Abstract

The invention relates to a method of biological protection against radiation produced by an apparatus for imaging a radioactive waste package, in which substantially identical and joined radioactive waste packages are stacked and juxtaposed to form a barrier comprising two layers. nested over at least 360 degrees around the imaging device and the package to be controlled.

Description

Holder (s): COMMISSIONER OF ATOMIC ENERGY AND ALTERNATIVE ENERGIES Public establishment.

Extension request (s)

Agent (s): PAUL HERARD CONSEIL Limited liability company.

DEVICE FOR PROTECTION AGAINST IONIZING RADIATION PRODUCED BY A MONITORING APPARATUS AND METHOD FOR MANUFACTURING THIS DEVICE.

FR 3 060 831 - A1

The invention relates to a method of biological protection against radiation produced by an apparatus for imaging a package of radioactive waste, in which packages of substantially identical and contiguous radioactive waste are stacked and juxtaposed to form a barrier comprising two nested layers extending at least 360 degrees around the imaging device and the package to be inspected.

Device for protection against ionizing radiation produced by a monitoring device and method of manufacturing this device

TECHNICAL AREA

The present invention relates to a device and a method for protection against ionizing radiation produced by a control device, in particular for protection against X-rays, y rays (gamma) or neutrons produced by a control device. radioactive waste packages, in a storage facility for these packages.

STATE OF THE ART

The operation of nuclear sites, such as research reactors, laboratories, or nuclear facilities, generates nuclear waste.

We can distinguish radioactive waste according in particular to their level of radioactive activity per unit of mass, which can be measured in Becquerel per gram (Bq / g).

We can thus distinguish, for example, waste of very low radioactive activity whose activity level per unit of mass is less than one hundred (10 ² ) Bq / g, from low activity waste whose level of activity per unit of mass is at least equal to one hundred Bq / g and is less than one hundred thousand (10 ⁵ ) Bq / g, and intermediate level waste whose activity level per unit of mass is at least equal to one hundred thousand Bq / g and is less than one billion (10 ⁹ ) Bq / g. Waste is thus divided into categories, and is managed differently according to their level of activity.

Nuclear waste is packaged in packages, each package comprising waste, a matrix whose function is to confine the waste, and generally a container which contains the matrix. The matrix can essentially consist of concrete, a polymer material, or bitumen. The container is usually made of concrete or steel.

Such packages generally have the shape of a straight cylinder of circular section, a diameter which is of the order of approximately half a meter to approximately one and a half meters, a height which can reach approximately one and a half meters, and a mass which is generally in the range of about two hundred kilograms to about two tonnes.

Before leaving for final storage, these packages can be stored at a storage site dedicated to this type of package, and depending on their level of radioactive activity.

The existence of nuclear waste in the form of packages can result from the operation of sites for several years. Their contents generate variable radioactivity. They are very diverse in nature and sometimes not well known.

Information on this waste is however necessary in order to assign each package to the category which corresponds to it. Lack of information can lead to unnecessarily assigning waste to default categories and over-categorization (overvaluation of activity level) requiring more consistent and more expensive management procedures and resources.

The characterization of content requires heavy resources.

To characterize the content of one of these packages, one can use a control or imaging device comprising an accelerator producing ionizing radiation directed towards the package to be checked, in particular an X-ray or tomographic imaging device by transmission of X-rays (high energy), and subject the package to a beam of radiation produced by the apparatus, the beam possibly extending in an angular sector and / or in a determined plane (s).

To obtain sufficient penetration of the radiation into the package, the energy of the radiation must be sufficiently high, for example of the order of about ten million electron volts (MeV) approximately.

This results in radiation scattered (in particular by the package) in all directions, and / or leakage radiation from the control device, the dose rates of which are above acceptable standards for the exposure of humans. to these radiations.

This is why these devices are generally used in dedicated units, and they are equipped with biological protection means.

These protective means can be, for example, a concrete “pillbox” several meters thick.

Given the technical, financial and risk difficulties of transporting packages, it is highly desirable that these characterization means be deployed on the package storage site, in various environments such as hangars or covered warehouses.

The movement to the storage site of these characterization devices must be accompanied by the movement or creation of means of biological protection also called shields.

There are several shielding solutions.

Permanent construction can be envisaged on the site. For example, a pillbox can be built at each storage site. This solution is interesting for long-term measurement campaigns, on the order of a year or several years. It is equivalent to building a dedicated room within the site. One drawback of this solution is that it takes a long time to implement, often requiring prior authorizations. In addition, it is expensive. It can generate radioactive waste, especially when it is dismantled. And it is not modular.

Alternatively, temporary and / or removable protection can be sought.

Protection in a block (monolithic) is hardly possible given its high weight and volume, and difficulties in transporting this protection with conventional means of transport.

Lead protection screens can be used, as described for example in US Pat. No. 5,903,623, to protect human beings from the radiation produced by the imaging device, the package being placed between the imaging device which contains the source. of radiation, and the screen.

Such a screen provides protection only against direct radiation from the imaging device, and it remains necessary to provide protection against the radiation scattered by the screen in particular, which is complementary to that provided by the screen.

The problem with these means of protection is that they require the installation of many screens, according to an arrangement to be determined as a function of the beam scattering angles. They are not easy to implement. And they require setting up means for holding these screens.

In addition, this requires significant transport operations between outside and inside the site, with the inherent risks. And to transport these screens, it is necessary to have means of transport adapted to their geometry.

In addition, there is a risk that these screens - and their means of transport - may be contaminated by radioactive pollution and generate nuclear waste themselves.

Finally, these means have a significant cost.

STATEMENT OF THE INVENTION

An object of the invention is to provide a device for protection against radiation produced by a control device, which remedies, in part at least, the shortcomings or disadvantages of known protection devices.

In particular, a device for protection against radiation produced by a radioactive waste package monitoring device is sought, which is modular and simple to implement, which generates the minimum of additional nuclear waste, which minimizes the transport operations between the outside and inside the parcel storage site, as well as the assembly and disassembly operations of the device, and which can be adapted to different packages, especially on different sites.

Another object of the invention is to propose a method of protection against radiation produced by a control device, which is improved and / or which remedies, in part at least, the shortcomings or disadvantages of known methods of protection against radiation produced by a recording device.

According to one aspect of the invention, there is proposed such a device which comprises:

- first level radioactive waste packages resting on their bases on at least one substantially flat and horizontal support; such as a concrete slab, and

- second level radioactive waste packages, each based by its base on one of the first level packages;

in which the first level radioactive waste packages include, as well as the second level radioactive waste packages:

- first packages of radioactive waste, the first packages being of substantially cylindrical shape with circular section and vertical axis, of substantially identical dimensions, and being arranged substantially regularly spaced along a contour extending over at least 360 degrees around the control device and the radioactive waste package to be checked,

- second packages of radioactive waste, the second packages being of substantially identical shape and dimensions to those of the first packages, of vertical axis, which are arranged, for example substantially regularly spaced, along said contour, each second package being substantially in contact with two adjacent first packages, and in which the ratio of the distance separating two adjacent first packages, with the diameter common to the first and second packages, is situated in a range going from 0 (zero) to approximately 0.5.

Consequently, the angle oc between a horizontal segment joining the traces of the respective axes of two adjacent second packages (neighbors), and a horizontal segment joining the axis of a first package disposed substantially joined with the two second packages adjacent and the trace of the axis of one of the two adjacent second packages is located in a range from approximately 45 ° to approximately 60 °, so that the first and second packages are substantially joined two by two and staggered , and form a biological protection barrier against the radiation emitted by the control device and diffused in particular by the waste package controlled using the control device.

According to embodiments:

- Said ratio can be situated in a range going from approximately 0.35 to approximately 0.45, being in particular substantially equal to 2 °> ⁵ (V2) minus one, or approximately 0.414, which corresponds to a value of said angle oc of 45 degrees (°) approximately, and which makes it possible to limit the number of packages to be moved to form the barrier by approximately 25 percent compared to the case where the value of said angle oc is 60 degrees;

- the vertical axes of the first and second waste packages can be arranged, in plan view, at the vertices of a broken line trace (sawtooth) which extends along and on either side of said contour ;

- Said outline may include at least four rectilinear segments sharing two by two (connected two by two by) a common end, so that the outline has (in plan view) a form of angular spiral (or angular spiral);

- Each pair of adjacent rectilinear segments of the outline can form a substantially right angle, so that the outline has a square or rectangular spiral shape.

In particular when the radiation emitted by the device forms a beam, the protection device preferably comprises a screen for protection against direct radiation, which is arranged so as to intercept the beam, and the first and second packages form a protective barrier extending (360 degrees) around the screen, the recording device (and a package to be checked).

When the route (said outline) of the protective barrier formed by the waste packages is open, the route delimits an opening in the barrier, the width of the opening being sufficient to allow the passage of a package of radioactive waste to control and an appliance or means of transport of this package, such as a forklift, and the waste package to be checked can be transported to the control appliance, by passing this package through this opening.

When the route (said outline) of the barrier is closed, a package of waste to be inspected can be transported to the control device, by passing this package over the barrier. A lifting device - such as a lifting bridge - can then be used to transport the waste package to be checked.

Parcels of the barrier can delimit a passage corridor for the package to be checked and the transport device for this package, in particular a bent corridor or forming a baffle.

Thus, an open path of the barrier can be arranged to prevent the passage, through an opening provided in the barrier, of radiation produced by the control device which has not undergone at least two successive diffusions by the screen, the package to be checked, and / or the barrier packages, in particular radiation produced by the monitoring device which have not undergone at least three successive diffusions, so as to ensure a minimum level of attenuation of the radiation passing through the opening provided in the barrier.

The device may comprise first juxtaposed packages resting on a first substantially planar and horizontal support, such as a concrete slab, and may comprise second packages resting on a second substantially planar and horizontal support, which extends to a dimension ( height) different from that of the first support, so as to avoid a leak of radiation by the interface between two first packages stacked one on the other, the leakage radiation then being intercepted and / or diffused by one of the second packages which is juxtaposed with these first two packages.

This difference in dimension may be a fraction of the height common to packages, in particular a fraction of the order of a tenth or a twentieth. The difference between these two dimensions can for example be in a range from about five centimeters to about 10 centimeters

The second support can be produced by at least one raised part placed under the second first level packages or else under the first first level packages.

The packages forming the biological protection barrier may have an activity level per unit mass which is less than one billion (10 ⁹ ) Bq / g, in particular an activity level less than one hundred thousand (10 ⁵ ) Bq / g, in particular an activity level below one hundred (10 ² ) Bq / g ·

According to another aspect of the invention, a method of biological protection against radiation produced by an apparatus for imaging a package of radioactive waste is proposed, in which one stacks (on at least two levels) and juxtaposes radioactive waste packages included in a matrix, which are substantially identical and contiguous and form a barrier comprising two layers of nested packages, extending over at least 360 degrees around the imaging device and the package to be inspected.

A protection device can be constructed as described and defined in the present application.

For this purpose, one can if necessary build a platform near a site - or on a site - for storing radioactive waste packages, and place on the platform the imaging device, if necessary a screen of protection against direct radiation produced by the device, as well as the packages forming the biological protection barrier.

We can then transport a package of waste to be inspected to the imaging device, by passing the package to be inspected above the barrier or through an opening provided in the barrier.

To check the level of attenuation of ionizing radiation by the package barrier, the dose rate received outside the barrier formed by the waste packages can be measured, while the imaging device emits ionizing radiation. , and check that the measured dose rate does not exceed a determined value, for example a value of the order of 2 milli sievert per hour (mSv / h) for a dose rate measured one meter from the barrier, in particular before transport a package to be checked to the imaging device.

When the imaging device emits a beam located in a - or extending a short distance from a - horizontal plane, there are preferably at least some of the packages juxtaposed so that their base or their summit extends to a distance from the beam plane which is preferably within a range from about 2 centimeters to about 10 centimeters.

The invention facilitates the in situ characterization of radioactive waste packages, in particular by avoiding the transport of construction materials from a biological protection barrier which are heavy and bulky, to a package storage site. radioactive waste that we want to control.

The invention makes it possible to minimize the number of packages stored on a site which must be moved to form the protective barrier.

Other aspects, characteristics, and advantages of the invention appear in the following description which refers to the appended figures and illustrates, without any limiting character, embodiments of the invention.

BRIEF DESCRIPTION OF THE FIGURES

Figure 1 schematically illustrates, in plan view, a biological protection barrier extending continuously along a rectangle and surrounding a waste package control device.

FIG. 2 schematically illustrates, in section view in a vertical plane, part of the protection device illustrated in FIG. 1, and is a view along II-II of FIG. 1.

FIG. 3 schematically illustrates, in plan view, a biological protection barrier delimiting a passage for the movement of a waste package to the control device.

FIG. 4 schematically illustrates, in section view in a vertical plane, an alternative embodiment of the protection device illustrated in FIG. 1.

Each of Figures 5 and 6 schematically illustrates, in plan view, five juxtaposed packages forming part of a biological protection barrier.

FIG. 7 schematically illustrates, in plan view, a biological protection barrier which surrounds a device for checking waste packages, and has an opening and a baffled corridor allowing the passage of a package to be checked and of a device transport of this package.

FIGS. 8 and 9 are graphs representing the attenuation capacity of X-rays by juxtaposed packages according to the respective configurations of FIGS. 5 and 6.

DETAILED DESCRIPTION OF THE INVENTION

Unless expressly or implicitly indicated otherwise, identical or similar elements or bodies - structurally or functionally - are designated by identical references in the various figures.

With reference to FIGS. 1 to 4 and 7 in particular, the device 10 serves to protect people approaching an imaging device 13 producing ionizing radiation, radiation 11 directly coming from the device, as well as radiation 12 resulting from the scattering of radiation 11 by objects located near the device 13.

The invention applies in particular to devices 13 producing a beam of radiation 11 extending substantially in a horizontal plane which corresponds to the plane of FIGS. 1, 3 and 7 and is marked 32 in FIG. 2.

The protection of persons against direct radiation 11 can be ensured, at least in part, by a screen 14 disposed near the device 13, so as to intercept and strongly attenuate the beam 11 of direct radiation.

The device 13 and the screen 14 are installed on the surface 41 of a platform 40 in a site for storing packages of radioactive waste (see FIG. 4). A screen support (not shown) can be provided for this purpose.

The radiation 11 produced by the device 13 is used to determine the nature of the waste 16 included in a matrix 17 of a package 31 of radioactive waste stored on the storage site.

To this end, the package 31 to be checked is placed between the device 13 and the screen 14, on the platform 40, 41, where it rests by means of a support 33 allowing for example to lift the package 31 so to successively expose horizontal "sections" of this package to the beam 11, when this beam and the device 13 are stationary.

The protection of people against scattered radiation 12 is provided by a barrier 100, 100a to 100g, made up of packages 15, 20, 25, 30 juxtaposed with radioactive waste, this barrier surrounding the device 13, screen 14 on 360 degrees. , and package 31 to be checked.

As illustrated in FIGS. 1 to 7, the packages 15, 20, 25, 30 of the barrier 100 are of circular horizontal section and rest (by their respective circular bases) on the platform 40 to 42, on another package 25, 30, or on a support 70.

In FIG. 3, the barrier 100 is formed of five barrier elements or “walls” 100a to 100e, each barrier element comprising first packages (or “internal” packages) 15, 25 stacked and arranged substantially contiguous (joined) two in pairs along a first straight segment, and comprising second packages (or “external” packages) 20.30 stacked, arranged substantially contiguous two by two along a second straight segment parallel to the first straight segment, the second packages being substantially in contact with the first packages.

The five segments corresponding respectively to these five elements are orthogonal two by two and form an angular spiral delimited by a rectangular contour.

The elements 100a and 100e, which are parallel and partly facing each other, delimit an opening 36 and a corridor 101 of width 38 allowing the introduction of a package to be checked, inside the rectangular space delimited by the package of elements 100a to 100d.

For this purpose, the width 38 is chosen to allow the passage of a forklift transporting a package to be checked, between the elements 100a and 100e of the barrier, through the opening 36, to the device 13 of control.

In the variant embodiment illustrated in FIG. 7, the barrier 100 further comprises two additional barrier elements 100f and 100g which, with the elements 100a and 100e, delimit a passage 101 for the passage of a vehicle carrying a package to be checked, which has several bends and forms a baffle. The wall 100f extends substantially in the extension of the wall 100b, and the wall 100g extends from the wall 100f, parallel to the walls 100a and 100e, along a rectilinear segment 37.

These two configurations make it possible in particular to prevent the passage, through the opening 36, of radiation produced by the device 13 which has not undergone at least three successive diffusions 12 by the screen 14, the package 31 to be checked. , and / or the barrier packages, as schematically illustrated in Figures 3 and 7.

In FIG. 1, the barrier 100 is formed of packages 15, 20, 25, 30 arranged contiguously (joined) along a rectangle 35, continuously, without delimiting an opening.

In the various embodiments shown, each package of the barrier 100 is arranged so as to be substantially joined, along vertical generatrixes of the package, to at least two packages of the barrier which are adjacent (neighbors) to the package in question, so as to avoid the escape of ionizing radiation between two adjacent packages.

In the embodiment illustrated in FIG. 6 in particular, the barrier portion 100 illustrated comprises a first series of aligned packages 15 whose traces of the respective vertical axes 58 extend along a rectilinear segment 56, which are spaced two by two from a distance 52, and thus form a first row (or a first "layer") 50 of packages.

The barrier portion 100 illustrated in FIG. 6 comprises a second series of aligned packages 20 whose traces of the respective vertical axes 59 extend along a rectilinear segment 57, which are spaced two by two by a distance 53, and form thus a second row (or a second “layer”) 51 of packages.

The distances 52 and 53 being equal to and less than the diameter common to packages 15, 20, and the segments 56, 57 being separated by a distance less than the diameter (reference 60 in figure 5) common to packages 15, 20, both rows or layers are nested and the packages are joined in pairs and staggered.

Thus, in this configuration of the barrier 100, three successive vertices of a line 18 in broken line connecting the traces of the respective vertical axes 58, 59 of the packages 15, 20 in a horizontal plane (the plane of Figure 6), form the vertices of an isosceles triangle whose angle at the top is greater than sixty degrees, and whose length 54 of the two smallest sides is substantially equal (very little greater) to the diameter of packages 15, 20.

In this configuration, the angle oc between a horizontal segment joining the traces of the respective axes 59 of two adjacent second packages 20 (neighbors), and a horizontal segment joining the trace of the axis 58 of a first package 15 disposed contiguous with the two second packages 20 considered and the trace of the axis 59 of one of the two adjacent second packages 20 is of the order of 45 to 50 degrees.

When the angle oc is equal to 45 degrees, the ratio of the distance separating the traces or "centers" 58 of two first adjacent packages 15 of the first row 50 of packages, with the common diameter 60 of the packages, is equal to t2 (2 °> ⁵ ), and the ratio of the distance separating the traces or “centers” 59 of two adjacent second packages 20 of the second row 51 of packages, to the common diameter of the packages, is equal to the same value.

In the more compact configuration of the barrier portion 100 illustrated in FIG. 5, the packages 15 of the layer 50 are joined in pairs, and the packages 20 of the layer 51 are also joined in pairs.

In this configuration, the traces of the axes of the packages in a horizontal plane (the plane of FIG. 5) form a broken line 18 and are spaced two by two by a distance 54 substantially equal to the common diameter 60 of the packages 15, 20, so that three successive vertices of this broken line form an equilateral triangle.

In this configuration, the angle oc is equal to 60 degrees.

In the configurations illustrated in FIGS. 5 and 6 in particular, the trace 58 of the axis of a first package 15 is located on the perpendicular bisector of the segment connecting the traces 59 of the axes of two successive / neighboring second packages 20 and, in the same way , the trace 59 of the axis of a second package 20 is located on the perpendicular bisector of the segment connecting the traces 58 of the axes of two successive / neighboring first two packages 15.

The configuration of the packages of the barrier illustrated in FIG. 5 corresponds substantially to those illustrated in FIGS. 1, 3, and 7 in which most of the packages, with the exception of certain packages located in the corners of the contour 35 and those located at the free ends. walls 100a, 100e, and 100g are joined with the four packages closest to the package in question.

In FIGS. 8 and 9, the abscissa axis corresponds to a distance measured along the rows 50, 51 of packages 15, 20, and the ordinate axis corresponds to a calculated level of attenuation of X-rays.

FIG. 8 illustrates the attenuation capacity 61 of X-rays by packages juxtaposed according to the configuration of FIG. 5 which have a diameter of 0.59 meters and a density of 0.82, by comparison with the attenuation capacity 62 X-ray radiation from a wall with a thickness of 0.38 meters and a density of 2.25.

In this configuration, the minimum levels 63 of attenuation by the packages are higher than the level of attenuation provided by the wall.

FIG. 9 illustrates the attenuation capacity 64 of X-rays by juxtaposed packages according to the configuration of FIG. 6 which also have a diameter of 0.59 meters and a density of 0.82, by comparison with the attenuation capacity 62 of X-rays by a wall which also has a thickness of 0.38 meters and a density of 2.25.

In this configuration, the minimum levels 63 of attenuation by the packages are substantially equal to the level of attenuation provided by the wall.

With reference to FIG. 4, the “internal” layer 50 of the barrier 100 comprises first juxtaposed packages 25 resting on the surface 41 of a concrete slab 40 also receiving the device 13 and the screen 14, and comprising first packages 15 juxtaposed resting (stacked) on the first packages 25.

The “external” layer 51 of the barrier comprises second packages 30 juxtaposed and substantially contiguous with the first packages 25 and resting on a second surface 42 which extends above the surface 41, and comprises second packages 20 juxtaposed resting on the second packages 25.

This allows, packages 25 and 30 having the same height, to avoid the free propagation of leakage radiation likely to pass through an interstice separating the first packages 15 and 25 superimposed, the difference 43 in dimension between the tops of the packages 25 and 30 corresponding to that existing between the surfaces 41, 42 of the support slab 40.

In the variant illustrated in FIG. 2, this difference in dimension results from the presence of a part 70 (for example in the form of a disc) inserted between the platform 40 and the base of the second packages 30.

Claims (18)

Claims 1 - Device (10) for protection against radiation (11,12) produced by an apparatus (13) for monitoring a package (31) of radioactive waste (16), characterized in that it comprises: - Packages (25, 30) of first level radioactive waste resting on their bases on at least one support (41, 42, 70) substantially planar and horizontal; and - packages (15, 20) of second level radioactive waste each resting by its base on one of the packages (25, 30) of first level; in which the packages (25, 30) of first level radioactive waste include, like the packages (15, 20) of second level radioactive waste: - first packages (15, 25) of radioactive waste, the first packages being of substantially cylindrical shape with circular section and vertical axis (58), of substantially identical dimensions, and being arranged substantially regularly spaced along a contour (35, 37) extending over at least 360 degrees around the monitoring device (13) and the package (31) of radioactive waste (16) to be checked, - second packages (20, 30) of radioactive waste, the second packages being of shape and dimensions substantially identical to those of the first packages, with a vertical axis (59), and arranged along said outline (35, 37), each second package (20, 30) being substantially in contact with two adjacent first packages (15, 25), and in which the ratio of the distance (52) separating two adjacent first packages (15, 25), to the diameter (60) common to the first and second packages (15, 20, 25, 30), is located in a range from 0 (zero) to about 0.5. 2 - Device according to claim 1 wherein said ratio is located in a range from about 0.35 to about 0.45, being in particular substantially equal to k2 minus one. 3 - Device according to claim 1 or 2 wherein said outline (35, 37) is open, and the packages (15, 20, 25, 30) of juxtaposed waste form a protective barrier (100, 100a, 100b, 100c) biological comprising an opening (36) whose width (38) is sufficient to allow the passage of the package (31) of radioactive waste to be checked and of a means of transport of this package, such as a forklift. 4 - Device according to any one of claims 1 to 3 wherein the packages (15, 20, 25, 30) of juxtaposed waste delimit a passageway (101) for the package (31) to be checked and for a means of transport of this package, in particular a bent corridor or forming a baffle. 5 - Device according to any one of claims 1 to 4 wherein the packages (15, 20, 25, 30) of juxtaposed waste are arranged to prevent passage, through an opening (36) provided in the barrier ( 100, 100a, 100b, 100c) formed by the packages (15, 20, 25, 30), of radiation (11) produced by the recording equipment which have not undergone at least two successive diffusions (12) per l screen, the package (31) to be checked, and / or the packages (15, 20, 25, 30) of the barrier, in particular of radiation produced by the monitoring device which have not undergone at least three diffusions successive. 6 - Device according to claim 1 or 2 wherein said outline (35, 56, 57) is closed. 7 - Device according to any one of claims 1 to 6 wherein said outline (35, 37) comprises at least four rectilinear segments (37, 56, 57) sharing two by two (connected two by two by) a common end, each pair of adjacent rectilinear segments of the contour preferably forming a substantially right angle. 8 - Device according to any one of claims 1 to 7 which comprises first packages (25) juxtaposed resting on a first support (41) substantially planar and horizontal, such as a concrete slab, and comprises second packages (30 ) resting on a second support (42, 70) substantially planar and horizontal, which extends to a dimension (height) different (43) from that of the first support (41). 9 - Device according to claim 8 wherein the difference in dimension (43) is a fraction of the height common to packages (15, 20, 25, 30), in particular a fraction of the order of a tenth or one twentieth. 10 - Device according to claim 8 or 9 which comprises a part (70) of elevation disposed under the second packages (30) or under the first packages (25). 11 - Device according to any one of claims 1 to 10 wherein, the radiation emitted by the device forming a beam (11), the protection device comprises a screen (14) for protection against direct radiation (11) emitted by the apparatus, which is arranged so as to intercept the beam, and in which the first packages (15, 25) and the second packages (20,30) form a protective barrier (100, 100a, 100b, 100c) s 'extending over at least 360 degrees around the screen (14), the package (31) to be checked, and the checking device (13). 12 - Method of biological protection against radiation produced by an apparatus (13) for imaging a package (31) of radioactive waste, characterized in that packages (15, 20, 25, are stacked and juxtaposed) 30) of substantially identical and contiguous radioactive waste to form a barrier (100, 100a, 100b, 100c) comprising two overlapping layers (50, 51) extending over at least 360 degrees around the imaging device and the package (31) to be checked. 13 - Method according to claim 12 wherein a device is constructed according to any one of claims 1 to 11. 14 - The method of claim 12 or 13, wherein there is the device (13) for imaging, a screen (14) for protection against direct radiation (11) produced by the device, the package (31) to check, as well as the juxtaposed packages (15, 20, 25, 30) forming the barrier (100, 100a, 100b, 100c) of biological protection, on a platform (40 to 42) extending near a site - or on a site - storage of 5 packages (15, 20, 25, 30, 31) of radioactive waste. 15 - Process according to any one of claims 12 to 14 in which a package (31) of waste to be checked is transported to the imaging device, by passing the package to be checked over the barrier ( 100, 100a, 100b, 100c) or through an opening (36) 10 provided or formed in the barrier. 16 - Method according to any one of claims 12 to 15 in which the dose rate received outside the barrier formed by the waste packages is measured, while the imaging device emits ionizing radiation, and we check that the dose rate measured 15 does not exceed a determined value. 17 - Method according to any one of claims 12 to 16 wherein, the imaging device emitting a beam (11) located in a - or extending a short distance from a - plane (32) horizontal, it has at least some of the packages (15, 20, 25, 30) juxtaposed so 20 that their base or their summit extends at a distance from the plane (32) which is situated in a range going from approximately 2 centimeters to approximately 10 centimeters. 1/7