Classifications

• • G—PHYSICS
  • G21—NUCLEAR PHYSICS; NUCLEAR ENGINEERING
  • G21F—PROTECTION AGAINST X-RADIATION, GAMMA RADIATION, CORPUSCULAR RADIATION OR PARTICLE BOMBARDMENT; TREATING RADIOACTIVELY CONTAMINATED MATERIAL; DECONTAMINATION ARRANGEMENTS THEREFOR
  • G21F5/00—Transportable or portable shielded containers
  • G21F5/06—Details of, or accessories to, the containers
• • G—PHYSICS
  • G21—NUCLEAR PHYSICS; NUCLEAR ENGINEERING
  • G21F—PROTECTION AGAINST X-RADIATION, GAMMA RADIATION, CORPUSCULAR RADIATION OR PARTICLE BOMBARDMENT; TREATING RADIOACTIVELY CONTAMINATED MATERIAL; DECONTAMINATION ARRANGEMENTS THEREFOR
  • G21F5/00—Transportable or portable shielded containers
  • G21F5/06—Details of, or accessories to, the containers
  • G21F5/08—Shock-absorbers, e.g. impact buffers for containers
• • G—PHYSICS
  • G21—NUCLEAR PHYSICS; NUCLEAR ENGINEERING
  • G21F—PROTECTION AGAINST X-RADIATION, GAMMA RADIATION, CORPUSCULAR RADIATION OR PARTICLE BOMBARDMENT; TREATING RADIOACTIVELY CONTAMINATED MATERIAL; DECONTAMINATION ARRANGEMENTS THEREFOR
  • G21F7/00—Shielded cells or rooms
  • G21F7/015—Room atmosphere, temperature or pressure control devices
• • G—PHYSICS
  • G21—NUCLEAR PHYSICS; NUCLEAR ENGINEERING
  • G21F—PROTECTION AGAINST X-RADIATION, GAMMA RADIATION, CORPUSCULAR RADIATION OR PARTICLE BOMBARDMENT; TREATING RADIOACTIVELY CONTAMINATED MATERIAL; DECONTAMINATION ARRANGEMENTS THEREFOR
  • G21F1/00—Shielding characterised by the composition of the materials
  • G21F1/02—Selection of uniform shielding materials
  • G21F1/08—Metals; Alloys; Cermets, i.e. sintered mixtures of ceramics and metals
  • G21F1/085—Heavy metals or alloys

Definitions

• the present invention relates to a packaging for transporting and / or storing radioactive material such as a radioactive source emitting highly energetic ionizing radiation.
• radioactive material such as a radioactive source emitting highly energetic ionizing radiation.
• ionizing radiations such as gamma radiation, should be attenuated when the radioactive material is housed in the transport and / or storage packaging in order to reduce the exposure of individuals to ionizing radiation.
• the invention relates to the transport and / or storage of radioactive sources, such as radium, the application of which is preferably an application in the medical field, for a therapeutic purpose.
• the regulatory limit for the transport of radioactive material for DED at any point on the outer surface of the package is set at 2 mSv / h.
• DED Another regulatory requirement that the package must meet is DED at a distance of 1 meter from the outer surface of the package, this DED must be less than 0.1 mSv / h. However this last criterion is significantly easier to check for point or near point radioactive sources. The criterion of maximum DED on the surface is thus predominant.
• the packaging loaded with the radioactive source must meet regulatory mechanical tests including a free fall test of 1.2 meters in height. At the end of this test, the DED must not undergo an increase of more than 20%.
• the packaging must be strong enough not to undergo significant deformation of its wall.
• packaging for radioactive sources for medical applications essentially comprises a radiological protection structure designed to attenuate the DED by exploiting the shielding effect of the ionizing radiation emitted by the radioactive source.
• This shielding effect is then obtained using high density materials such as lead, tungsten.
• This radiological protection structure delimits a cavity intended to house the radioactive source.
• the package is a source holder to be fixed in a teletherapy device.
• the radiological protection structure comprises a shielding portion of radiological protection material, with a density greater than 10, helping to define the cavity and intended to house the radioactive source, enclosed in two concentric stainless steel boxes forming a double-walled assembly.
• radioactive material packages are known from, for example, US 7,276,715, US 2,912,591, US 5,442,186.
• D D 0 .e - ( with D 0 , the DED on one side of the radiological protection material, on the side where the radioactive source is housed, D, the DED on the other side of the radiological protection material, which corresponds to the external surface of the packaging, ⁇ , the attenuation coefficient whose value depends on the nature of the radiological protection material and the radiation energy of the radioactive source. It may be noted that when the radiation is of the gamma type, the attenuation coefficient of the radiological protection material is then all the higher as its density is important.
• a third disadvantage of these packages is related to hygiene constraints inherent in the medical sector.
• the purpose of the present invention is precisely to propose a packaging for transporting and / or storing radioactive material that does not have the drawbacks mentioned above.
• the packaging according to the invention satisfies the mass and DED criteria and the free fall tests.
• Another object of the invention is to provide a transport packaging and / or storage of radioactive material that meets a DED criterion measured in contact with the outer surface of the package, more ambitious than that imposed by the regulations. .
• Another object of the invention is to provide a package that can be cleaned and disinfected to meet the current hygiene constraints imposed in medicine.
• the idea is, in addition to the use of the shielding part, to exploit the effect distance or removal with a part of the packaging having a much lower average density than that of the radiological protection material.
• it is sought to reduce the thickness of the shielding portion.
• the attenuation of the DED by this distance effect is reflected for a point or quasi-point radioactive source in the following manner: the dose rate at a point is inversely proportional to the square of the distance separating this point from the point or quasi-point radioactive source .
• the present invention relates to a packaging for transporting and / or storing radioactive material
• a radiological protection structure comprising a shielding part vis-à-vis ionizing radiation emitted by the radioactive material, having a surface internal which delimits a cavity for housing the radioactive material.
• the average density of the shielding portion is greater than 8 and the average density of the effecting portion is less than 0.5.
• the cavity preferably has a larger dimension which is smaller than the thickness e of the radiological protection structure.
• the average density of the remote effect portion is less than 0.3. It should be noted that the attenuation of the DED obtained by virtue of the shielding effect of the remote effect part is then negligible.
• the shielding part is preferably made of lead, tungsten, depleted uranium or their alloys and its average density is greater than 10.
• the armor part has two half-shells intended to be contiguous.
• the shielding portion comprises a central portion and two end portions on either side of the central portion, the central portion being thickened relative to the end portions.
• the remoteness portion has a volume fully filled by contiguous filler elements having a density of less than 0.5. In this first embodiment, the remote effect portion therefore has no empty space between the adjacent filler elements.
• one or more of these filler elements are made of a material whose density is less than 0.5 such as wood, polyurethane foam, phenolic foam.
• one or more of these filler elements have a cellular honeycomb type structure, corrugated cardboard type.
• the filling elements always have a density lower than
• the material of which they are made may have a density greater than 0.5, such as aluminum or cardboard.
• the filling elements of the first alternative can be described as more massive than those of the second alternative.
• the filling elements of these two alternatives may take the form of a hollow member for accommodating the shielding portion and a plugging plug for closing a portion of the hollow member.
• the hollow element may be doubled externally with an outer sheath in the form of a pot, and the wedging plug may be doubled with a cover which locks on the outer sheath, this outer sheath and this cover forming part of the solid elements of the part with the effect of removal.
• the remoteness portion includes structural elements and air. This has more than about 70% of the overall volume of the remote effect part.
• the structural elements can be made from polyethylene and more particularly from high density polyethylene. These materials have the advantage of being easily cleaned and disinfected, in particular to meet the current hygiene constraints imposed in medicine.
• the structural members may include a pair of wedging members of the shielding portion with an inner wedging element and an outer wedging element, mounted in one another and separated by air.
• the outer wedging member may include a sidewall and a stopper protruding internally from the sidewall to wedge the central portion of the shield portion while providing a thickness of air between the side wall of the external wedging element and the shielding portion.
• the inner wedging element bears on the shielding part when the latter is in abutment against the stop of the external wedging element.
• the structural members may include an additional wedging member mounted around the wedge pair with a wall and an abutment projecting internally from the side wall to wedge the outer chock member of the pair of chocks.
• the additional wedging member may further include a guide ring that projects internally from its sidewall to substantially maintain the pair of wedging members in the additional wedging member.
• the structural members further include a stopper for wedging the wedging members of the pair relative to each other at one of their ends.
• the stopper may extend to the additional shoe member to wedge it relative to the pair of wedging members.
• the structural elements also comprise two additional elements materialized by an outer sheath-shaped pot and a lid that locks on the pot to accommodate all other structural elements.
• FIG. 1A, 1B respectively show in longitudinal section and three-dimensional view cut away a first embodiment of a packaging according to the invention
• 2A1, 2A2, 2B1, 2B2, 2C1, 2C2, 2D1, 2D2 show in longitudinal section and in cross section a plurality of packages of the prior art and according to the invention
• Fig. 3 is a graph for selecting the thickness of the shield portion and the package to meet the mass and dose rate criteria;
• Figure 4 shows in longitudinal section another embodiment of the package according to the invention.
• the objective of the invention is to optimize the mass of the package while satisfying the dose rate criterion at any point on its external surface and at the tests. provided by current regulations for the transport of radioactive material.
• the idea underlying the invention is to place the radioactive material in a cavity delimited by a radiological protection structure which comprises a shielding part, this shielding part being surrounded directly by an external part designed to attenuate the ionizing radiation. generated by the radioactive material by an effect of removal of the radioactive material vis-à-vis the outer surface of the packaging.
• This outer part should be as light as possible to not significantly increase the weight of the package, while being strong enough not to undergo significant deformation at the end of regulatory freefall tests.
• FIGS. 1A, 1B show a first exemplary embodiment of a packaging for transporting and / or storing radioactive material according to the invention.
• a radioactive source 1 housed in a cavity 2 of the packaging 3 that is the subject of the invention.
• the radioactive source 1 has an elongated shape and may be formed of a charged tube of radioactive material such as radium 224. Other types of radioactive sources 1 could be employed. It is considered that the radioactive source 1 is point or quasi-point and that the cavity 2 can house only a point or quasi-point radioactive source.
• quasi-point source is meant the configuration for which the ratio between the largest dimension of the source and the thickness of the radiological protection structure is strictly less than 1.
• the packaging 3, object of the invention comprises a radiological protection structure 4 which contributes to define the cavity 2 and which protects the external environment of the package 3 vis-à-vis the ionizing radiation produced by the radioactive source 1.
• the ionizing radiation is gamma radiation.
• radiological protection structure Another function of the radiological protection structure is to ensure a setting and a mechanical protection of the radioactive source 1.
• a package 3 loaded with the radioactive source 1 must not undergo excessive mechanical deformation in the event of a fall which could lead to an increase in the maximum DED of more than 20%.
• the radiological protection structure 4 has a shielding portion 5 with respect to the ionizing radiation generated by the radioactive source 1.
• the shielding portion 5 has an interior surface which delimits the cavity 2.
• the cavity 2 has a shape and dimensions that are slightly greater than those of the radioactive source 1 so that the radioactive source 1 once installed in the cavity is immobilized. This cavity 2 can be likened to an impression of the radioactive source 1.
• the shielding part 5 can be broken down into two substantially identical half-shells 5.1, 5.2 which, when contiguous as in FIGS. 1A, 1B, delimit the cavity 2 intended to house the radioactive source 1.
• the radioactive source 1 is represented as a global volume of revolution built around an axis 6, said longitudinal axis.
• the shielding part 5 also has a global shape of revolution of longitudinal axis 6 when the radioactive source 1 is housed in the cavity 2.
• the cavity 2 also has this overall shape of revolution of longitudinal axis 6. It ends with substantially half spherical ends.
• the letter G represents its center of gravity.
• the position of the center of gravity G depends solely on the geometry of the cavity 2.
• the shielding part 5 is made of material whose density is greater than 8.
• the shielding part 5 is formed of several of these materials and is, for example, multilayered. The density we are talking about is an average density. In this context, the average density of the shielding part is the ratio of the mass of the shielding part to its volume.
• the shielding portion 5 preferably comprises, longitudinally, a succession of three portions, two end portions 5.10 enclosing a central portion 5.11.
• the central portion 5.11 has a transverse thickness greater than that of the end portions 5.10.
• the thickness is the gap that exists between the inner surface and the outer surface of each of the portions. These surfaces are substantially parallel to the level where the difference is measured.
• the thickening of the central portion 5.11 has several advantages, it enhances the attenuation of the ionizing radiation produced by the radioactive material opposite the radioactive source 1, it facilitates the handling of the shielding portion 5 and facilitates its setting.
• the radiological protection structure 4 further comprises a part 7 designed for an effect of moving the radioactive source 1 away from the outside of the package 3. This part is subsequently called part of 7. It directly surrounds the shielding part 5. This means that it is directly adjacent to the shielding part 5.
• This remote effect part 7, unlike the shielding part 5, is realized from elements whose average density is less than 0.5.
• This remote-effect part 7 may be formed, in a first embodiment, only contiguous filling elements as in Figures 1A, 1B. In a second embodiment, it may be formed of alternating structural elements with air so as to reduce the overall mass without weakening the mechanical strength of the package 3, as in FIG. 4.
• one or more of these filler elements are made of a material whose density is less than 0.5 such as wood, polyurethane foam, phenolic foam. Balsa has a density of about 0.1.
• one or more of these filler elements have a honeycomb-like honeycomb structure of corrugated cardboard type.
• the elements always have a density less than 0.5, but the material of which they are made may have a density greater than 0.5, such as aluminum or cardboard.
• first filling elements of the remote effect part 7 take the form of a hollow element 7.1 intended to house the shielding part 5 and a blocking plug 7.2 intended to to seal a part of the hollow element 7.1.
• the hollow element instead of being monolithic, is subdivided into several sub-elements stacked on each other for example.
• the hollow element 7.1 has a side wall 7.10 substantially shaped cylinder of revolution associated with a 7.11 bottom.
• the side wall 7.10 and the bottom 7.11 delimit a housing 7.12 for the shielding portion 5.
• the housing 7.12 has a shape and dimensions chosen to wedge laterally the shielding part 5 when it rests on the bottom 7.11.
• the thickened central portion 5.11 of the shielding portion 5 contributes to this wedging because it thus rests on a step 7.15 shaped in the side wall 7.10.
• the side wall 7.10 ends with an end 7.13 which delimits an opening 7.14 for inserting the shielding portion 5 into the hollow element 7.1.
• the stopper 7.2 closes the housing 7.12 at the opening 7.14. It has an end intended to come against the armor part 5 and whose geometry is conjugated to that of the shielding part so as to wedge in translation the shielding portion 5 in the housing 7.12.
• first filling elements 7.1, 7.2 previously described within the remote effect part 7, that it comprises second filling elements 7.3, 7.4 taking the form of an outer sheath 7.3 configured as a pot and lid 7.4 which locks on the outer sheath 7.3.
• the first filling elements 7.1, 7.2 are housed in the outer sheath 7.3 before locking the cover 7.4.
• This outer sheath 7.3 and its cover 7.4 may have a role of protecting the first filling elements 7.1, 7.2 vis-à-vis the external environment including moisture, friction, etc..
• the outer sheath 7.3 and the lid 7.4 assembled to each other have an outer surface which defines the outer surface of the distancing portion. This outer surface also constitutes the outer surface of the package at which DED is measured.
• the outer sheath 7.3 and the cover 7.4 will preferably be made of one of the plastic materials mentioned above, rather than in cardboard or aluminum.
• the average density is the ratio of the total mass of the remote effect part to its total volume.
• the total mass is the mass of all its filling elements and the total volume is defined by the space between the inner and outer surfaces of the remote effect part, as defined above.
• the cavity 2 of the package according to the invention can accommodate only a radioactive source 1 point or quasi point.
• the cavity 2 has a large dimension d which is smaller than the thickness e of the radiological protection structure 4.
• the thickness e of the radiological protection structure 4 belongs to a line segment S connecting a point B of the outer surface of the package at the center of gravity G of the cavity 2. This thickness e satisfies the relation (1):
• e el + e2 with the thickness of the shielding part 5 and e2 the thickness of the remote effect part 7.
• These thicknesses e1 and e2 belong to the line segment S.
• el corresponds to the part of the straight segment S extending in the shield portion 5
• e2 corresponds to the portion of the line segment S which extends into the remote effect portion 7.
• the condition on the thickness e of the radiological protection structure 4 and on the thicknesses e1, e2 of the two parts 5, 7 of the radiological protection structure 4 will now be defined.
• the geometric dimensions of the radiological protection structures 4 are adjusted. two parts 5, 7 of the radiological protection structure 4 so that on the one hand the dose equivalent dose rate in contact with the packaging is met and that the mass is reduced compared to the prior art.
• FIGS. 2A1, 2A2, 2B1, 2B2, 2C1, 2C2, 2D1, 2D2 show partial and transverse longitudinal sections of packages of the prior art or according to the invention.
• the thicknesses e1 and e2 were determined so that the equivalent dose rate in contact with the packaging is identical and four times lower than that which is prescribed. Its value must therefore be less than or equal to 0.5 mSv / h. The proportions between the different elements are respected.
• the radioactive source is not present in the cavity.
• the estimate of the DED has been made by neglecting the attenuation by shielding effect of the remote effect part.
• the average density of the distancing part is considered solely for the calculation of the mass of the package which is made considering that the packaging takes a general shape similar to that of Figure 1B.
• the radiological protection structure 4 is limited only to the shielding part 5.
• the cavity 2 for the radioactive source 1 delimited by the part of shielding 5 is shown in the center, extending around the longitudinal axis 6.
• the shielding portion is made of tungsten (density 19.3). Its thickness el opposite the radioactive source 1 and therefore the cavity 2 is 50 mm.
• the cavity 2 has a diameter of 10 mm.
• the weight of the package is 45 kg, which does not meet the mass criterion that the package of the invention must meet.
• the thickness el is measured on the line segment S which goes from the cross to the center of gravity G of the cavity.
• the thickness e1 of the shielding portion 5 corresponds to the gap between the inner surface and the outer surface of the shielding portion because the straight line segment S is substantially perpendicular to the longitudinal axis 6.
• the surfaces inner and outer portions of the shielding portion are substantially parallel.
• the radiological protection structure further comprises a remote-effect part 7 which directly surrounds the shielding part 5.
• the two parts are directly adjacent, they are in contact with each other .
• the remoteness effect portion 7 has an average density of 0.2. This average density is used only for calculating the mass of the package. It could be the far-end part of the first embodiment or the second embodiment which will be described later in connection with FIG. 4.
• the shielding portion has a thickness of 35 mm and the distance effect portion has a thickness e2 of 60 mm.
• the radiological protection structure also comprises the remote-effect part 7 directly contiguous to the shielding part 5.
• the remote-effect part 7 has an average density of 0.2.
• the shielding portion 5 has a thickness el of 25 mm and the distance effect part has a thickness e2 of 125 mm.
• the weight of the package is 21 kg and is in accordance with the mass criterion that has been set.
• the largest dimension d of the cavity 2 is equal to 100 mm and is therefore smaller than the thickness e of the radiological protection structure.
• the radiological protection structure also comprises the remote-effect part 7. As before, it has a mean density equal to 0.2.
• the shielding portion 5 has a thickness el of 15 mm and the remote effect part 7 has a thickness e2 of 200 mm.
• the weight of the packaging increases again to reach 29 kg, but it remains acceptable for the package to be handled by a single operator.
• the mass of the remoteness part has increased considerably with the increase of its thickness e2, making the package heavier.
• FIG. 3 shows, on the one hand, the variation of the mass of the vacuum packaging as a function of the thickness of the shielding part and, on the other hand, of the outside diameter of the packaging as a function of the thickness of the shielding part.
• the diameter of the package is equal to the sum of the diameter of the cavity and twice the thickness of the radiological protection structure e of Figures 2A to 2D.
• the graphics are obtained for a DED in contact with the constant packaging. These graphs make it easy to choose the thickness of the shielding part (between 15 and 25 mm) so that the weight of the packaging is less than 30 kg. It is also assumed here that the diameter of the cavity is 10 mm.
• the shielding portion 5 is similar to that described in Figures 1A, 1B. It will not be described again.
• the remoteness part is now referenced 70. It has structural elements and air.
• the air preferably represents at least 70% of the overall volume of the far-end portion 70.
• the overall volume of the far-end portion is understood as the total volume of the far-end portion, as previously defined.
• the structural elements are made, for example, of polyethylene and more particularly HDPE high density polyethylene (density 0.94).
• a pair of wedging elements 71, 72 mounted one inside the other and separated by the air 90.
• the outer wedging element 71 is of tubular shape, the other referenced 72 and qualified interior may also be tubular or be full. In Figure 4, it is shown tubular and is filled with air 90.
• the outer wedging element 71 is open at at least one of its ends. It comprises a side wall 71.1 and a stop 73 which protrudes internally from the side wall 71.1. In this embodiment, the stop 73 takes the form of a recessed tray. The stop 73 serves to wedge in translation the central portion 5.11 of the shielding portion 5.
• One of the end portions 5.10 of the shielding portion 5 passes through the recess of the plate 73 when the shielding portion 5 is mounted in the external wedging element 71.
• An air thickness 90 is present between the lateral wall 71.1 of the outer wedging element 71 and the shielding part 5 except at the stop 73.
• Both ends of the outer wedging element 71 can be opened.
• the inner wedging element 72 bears against the shielding part 5 at its other end portion 5.10. It is without contact with the outer wedging element 71 of the pair. It contributes to keeping the shielding portion 5 locked in translation abutting against the hollow plate 73 when assembling the different parts of the radiological protection structure.
• a first stopper 74 is also provided for holding in position the two wedging elements 71, 12 of the pair, this first stopper 74 being placed opposite the shielding portion 5 with respect to the inner locking element 72.
• the structural elements may also include an additional structural element which is an additional wedging element 76 of tubular shape, mounted coaxially around the pair of wedges 71,72 but remotely, so that air 90 separates them laterally at least locally.
• This additional wedging element 76 has a side wall 76.1 which ends with at least one open end 76.2, the latter being on the side of an open end of the outer wedging element 71 of the pair.
• This additional wedging element comprises a stop 77 which projects internally from the side wall 76.1 to wedge the external wedging element 71 of the pair of wedging elements. It is further provided to provide the additional wedging member 76 with a guide ring 78 which projects internally from its side wall 76.1 to maintain substantially centered the pair of wedging elements 71, 72 in the additional wedging element 76.
• the first stopper 74 extends laterally to the open end 76.2 of the additional wedging element 76. It closes it.
• the additional wedging element 76 has a second open end 76.3.
• a second stopper 75 is provided which closes the second open end 76.2.
• wedging elements 71, 72, 76 may be externally cylinders of revolution or prisms, but other forms are possible. In the example of FIG. 4, the wedging elements are longer and longer as they move from the inside of the package to the outside, which allows the radioactive source to be sufficiently far away from any point in the package. the outer surface of the package.

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• 2012
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