US 3845315 A
The packaging is comprised from easily demountable and replaceable components, including a fluid-tight capsule for containing the radioactive materials, a liquid or gaseous coolant, a gamma ray shield and an outer pressure vessel. The latter has cooling elements on its lateral surface and contains a fluid capable of ensuring neutronic protection and evacuation of heat. The capsule and gamma ray shield are immersed in the fluid. The dimensions of the various components are such that the thickness of the fluid layer between the gamma ray shield and the outer pressure vessel provides adequate neutronic protection. Spacers maintain the components in position. A compressible material may be included in compartments between the outer container and the gamma ray shield.
Claims available in
Description (OCR text may contain errors)
United States Patent Blum PACKAGING FOR THE TRANSPORTATION OF RADIOACTIVE MATERIALS Inventor: Paul Blum, Saint-nom-La-Breteche,
France Assignee: Transnucleaire, Societe Pour Les Transports De L'Industries, Nucleaire, France Filed: Nov. 15, 1971 Appl. No.1 198,556
Foreign Application Priority Data Nov. 17, 1970 France 70.41201 Feb. 2, 1971 France 71.03499 U.S. CI 250/506, 250/507, 250/5I3 Int. Cl. GZlf 5/00 Field of Search 250/108 R, 506, 507, 515,
References Cited UNITED STATES PATENTS R6 ll/l963 Rogers 250/108 R 3.414,?27 12/1968 Bonilla ..25U/l0RR Primary Examiner-James W. Lawrence Assistant Examiner-Davis L. Willis Attorney, Agent, or Firm-Larson, Taylor and Hinds  ABSTRACT The packaging is comprised from easily demountable and replaceable components, including a fluid-tight capsule for containing the radioactive materials, a liquid or gaseous coolant, a gamma ray shield and an outer pressure vessel. The latter has cooling elements on its lateral surface and contains a fluid capable of ensuring neutronic protection and evacuation of heat. The capsule and gamma ray shield are immersed in the fluid. The dimensions of the various components are such that the thickness of the fluid layer between the gamma ray shield and the outer pressure vessel provides adequate neutronic protection. Spacers maintain the components in position. A compressible material may be included in compartments between the outer container and the gamma ray shield.
PAIENTEDnm 29 I974 SERIES n5 2 r. fur 7mm PAIENIEBIIWQ m4 3.845 315 NEH SM 5 The invention relates to packaging used for the shipping of radioactive materials, in particular of irradiated fuel elements requiring shielding against gamma rays and neutrons.
It is a particular object of the invention to place at the disposal of users a packaging which responds bettter to the various desiderata of practice than hitherto and which, especially,
have the smallest possible weight and greatest possible resistance to fire,
have great robustness, high resistance to accidental conditions and great insensitivity to climatic conditions,
facilitate the loading, unloading and decontamination,
remains suitable for the shipment of damaged elements or limits the consequences of any damage occurrring to the elements during this shipment,
is of a structure such that the quality controls are facilitated and that it is adapted to the construction of packaging of the type concerned having all possible dimensions.
Packaging according to the invention is characterised by the fact that it is constituted from easily dismountable and replaceable components among which are included:
at least one leak-tight inner container or capsule containing the radioactive materials. and a gaseous or liquid coolant,
a shield against gamma rays, independent of the inner container or forming part of the latter and placed around its lateral wall, means for shielding against gamma rays being also provided at the levels of the cover and of the bottom of the inner container, and
an outer container or pressure vessel, of high resistance to physical stresses, provided with cooling elements such as fins on it lateral surface and containing water (or another fluid able to ensure neutron shielding and heat transfers) in which the capsule and its surrounding gamma shields are immersed,
the respective dimensions of these various components of the packaging being such that the thickness of the layer of water comprised between the gamma shield and the pressure vessel is sufficient to ensure the neutron shielding, spacing means being provided to maintain the said components ofthe packaging in predetermined respective positions.
In a preferred embodiment there is provided, between the pressure vessel and the gamma shield, open compartments filled with a compressible material to limit the risk of water pressure build-up.
In another preferred embodiment, the abovesaid packaging comprises several inner containers or capsules.
In another advantageous embodiment, when the packaging comprises several capsules, each of the latter is provided with an individual leak tight lid which is not shielded.
In a further advantageous embodiment, the capsules are connected at their extremity by welding to a common fluid tight flange cooperating with a flanged cover.
In another advantageous embodiment of the said packaging the said capsules are connected at their lower end by a structure similar to that which connects them at the level of their upper end, this structure cooperating with a common botton, possibly removable.
Again according to a preferred embodiment of the abovesaid packaging the removable common cover and bottom of the abovesaid capsules have a hollow struc ture reinforced by ribs, the said covers and bottom comprising a peripheral flange which is applied, with the interposition of a gasket, against the peripheral flange formed by the plate which connects the capsules.
Again according to a preferred embodiment, the flange of the cover and that of thebottom, when the latter is removable, comprises a rim parallel to the axis of the capsules and forming respectively with the cover and the wall of these capsules a peripheral cavity adapted to hold water.
The invention consists, apart from the abovesaid features, of certain other features which are used preferably, at the same time, and which will be more explicitly considered below.
And it will in any case be well understood with the aid of the complement of description which follows, as well as of the accompanying drawings, given purely by way of illustrative but nonlimiting example, wherein:
FIG. 1 shows in axial cross section one embodiment of a packaging according to the invention;
FIG. 2 is a partial section along the line IIII, of FIG.
FIG. 3 shows, in radial section, a portion of a second embodiment according to the invention;
FIGS. 4 and 5 show respectively in partial axial section and in radial section, two further embodiments of a packaging according to the invention;
FIGS. 6 and 7 are views in partial axial section showing details ofthe abovesaid packaging corresponding to other embodiments, FIG. 8 being a section along the line VIII-VIII of FIG. 7;
FIG. 9 shows in partial axial section another embodiment of a packaging according to the invention;
FIG. 10 is a partial radial section along the line X -X of FIG. 9;
FIG. 1] shows in partial section, a variation of the structure shown in FIG. 10; and
FIG. I2, lastly, shows in partial axial section, a portion of the packaging of FIG. 9 arranged according to a further preferred embodiment.
According to the invention and, more especially, according to those of its methods of application as well as according to those of its methods of production of its various parts, to which it would appear that preference should be given, in order to construct a packaging of the type concerned, procedure is as follows or in analogous manner.
It will be recalled firstly that radioactive materials which it is proposed to transport by means of packaging according to the invention are fuel elements irradiated in nuclear plants and having generally an elongated prismatic shape. These elements are withdrawn normally from the reactor at very spaced intervals in batches of about fifty and must then, as soon as possible, be shipped to a reprocessing plant in order to recover certain of their highly valuable constituents.
They are arranged, by means of stainless steel casings, spacers or other ordering means inside the abovesaid packaging which are constituted from the easily dismountable and replaceable components which will be described below.
Among these components there is at least one leaktight inner container or capsule l which is filled with gas or coolant medium. It is immersed in water contained inside an outer container or pressure vessel 2 which comprises means for heat dissipation 3 outside its lateral surface and, in the case of rather small packaging, thermal insulation 4 at its extremities. Of course, it is possible to provide such an insulation even in the case of larger packaging.
The abovesaid coolant medium may be a gas, for example air, argon or helium or a liquid, for example water.
A shield 5, for protection against gamma rays, is placed around the lateral wall of the capsule l, and protective means against gamma rays, that is to say shields 6 and 7, of constitution generally similar to that of the shield 5, are placed next to the bottom and the lid of the capsule l.
The shield 5 can be either independent of the capsule I, or form part of the latter. In the description which follows, these two embodiments are described and their advantages mentioned.
The respective dimensions of the different components of the packaging are selected so that the thickness of the water layer comprised between the shield 5 and the outer container or pressure vessel 2 is sufficient to ensure neutron shielding.
Lastly, spacing means 8 are provided to maintain the different components of the packaging in the predetermined suitable positions.
These spacers may be connected to the shield 5, to the pressure vessel 2, or constitute an independent structure such as will be seen below.
To avoid neutron beaming, there is provided, as described below, between the pressure vessel 2 and the shield S compartments filled with a compressible material.
It is also possible, according to the invention, to provide in a same packaging several capsules 1, these capsules being, connected or not to the shield S, and in contact or not with the water filling the pressure vessel 2.
In the embodiment illustrated in FIG. 1, the shield S is independent of the capsule I.
This capsule is made generally of stainless steel and the shield 5, which is in the form of a sleeve, is constituted of a core 9 of heavy metal such as lead and uranium surrounded by a sheath I0 of stainless steel.
As seen in FIG. 1, the shield 6 forms directly the bottom of the capsule I (it comprises a core 9 of lead or uranium), whilst the shield 7 forms a cover with a core 9 sheathed with stainless steel which. by means of a flange II, is fastened to the flange 13 of the capsule I by means such as bolts 12. Leaktightness between the facing flanges II and I3 is obtained by a gasket 14 which is made, for example, of silicon rubber. It is advantageous to shape the flange 13 so that it comprises an annular shield 15 of similar constitution to that of the shields 6 and 7, which constitution is apparent from the FIG. I. This annular shielding protects in particular the gasket I4. During shipping, the capsule I and the shield 5 are rigidly fixed to one another, by means such as bolt 13a, spacers 16 being provided between the capsule l and the shield 5. for example at the places indicated in the drawing, to enable water, which fills the pressure vessel 2, to circulate by convection between the shield 5 and the fluid tight capsule 1.
Inside the pressure vessel 2, the shield 5 is held in place by the abovesaid spacing means 8 which can be constituted by ribs oriented parallel to the axis of the pressure vessel as seen in the FIG. I.
Preferably, all the spacing means are perforated, as shown in FIG. 1, to facilitate water convection.
The edge of the spacing ribs which are in contact with the capsule I or with the shield 5 and which are thus most exposed to wear are constituted, preferably, of stainless steel. In addition, in a general way, the inner wall of the pressure vessel which can, if necessary, be made of carbon steel, is protected against corrosion by stainless steel plating, painting, chemical nickel plating, or any other similar means.
These spacers 8 act as shock absorbers in case of a crash.
They can also be borne by the shield 5 or be in the form of a removable structure which appears in FIGS. 6, 7, and 8.
This structure is a kind of basket constructed of ribs 8a parallel to the axis of the packaging and perpendicular rings 8b, said ribs advantageously comprising holes SC for the passage of the water. As seen in FIGS. 7 and 8 the rings 8b can be smaller in width than the ribs 80. They can also be constituted as shown in FIG. 5.
The pressure vessel 2 itself is constituted generally by two flanged elements, namely a sleeve 20 on which is fixed permanently, generally by welding, a convex bottom 2b of which the shape is clear from the Figure, and a convex cover 24: of which the shape also is evident from the Figure, which are fastened together, generally by bolts 120. A gasket I7 is inserted between the flanges 2d and 2e.
The insulation 4 which has been considered above and which covers in the case of packagings of small size and, ifdesired, also in packagings oflarge size, the convex bottom and cover 212 and 2c, --it also protects preferably the flanges 2d and 2e--, may be constituted for example of an expanded material 4a covered with a heat-proof coating 4b. This insulating coating plays also a damping role in the ease of a fall, in the same manner as the spacing elements 8.
The cooling elements 3, which have been considered above and which line the outer surface of the sleeve 2a, are preferably constituted by fins of the type of those which form the subject of applicants copending US. Pat. Application Ser. No. 63,529, filed 13 Aug. I970, now allowed.
It will be recalled that these fins are obtained,
by fixing by welding, along an axis parallel to the sleeve 20, on the outer surface of the latter, blades ofa material selected for its good thermal conductivity, especially of copper,
by dividing on these blades, by incision perpendicular to the axis of the sleeve 2a, such incisions stopping at a short distance from the surface of the sleeve and by twisting at right angle the successive teeth thus formed on the said blades, to give them an orienta tion substantially perpendicular to the axis of the sleeve and able to facilitate the circulation of air and, consequently, the cooling.
It is advantageous to provide, at the base ofthe cooling elements 3, a layer 18 of the material of the plaster or cement type with a thickness of only a few centimeters and of which the role is to increase the protection in the case of fire by its cooling action.
To facilitate the handling of the packaging thus constituted, means may be provided such as base plates 19a for example on the portion 26, trunnions 19b for tilting on the part 20, and positioning rim 20 on the part 212.
The invention gives a solution for this problem by providing between the pressure vessel and the shield for example attached to the spacing structure as shown in FIGS. 7 and 8 open compartments C containing bladders or a compressible expanded material C, such as rubber or plastic foam, the volume of previous expanded material being sufficient to avoid simultaneously neutron beaming and the risk of pressure build up, as the pressure vessel can be filled up with the neutron absorbing liquid (water) and the thermal expansion of said liquid balanced by the compression of the expanded material. In practice, the volume of the compartments C represents about l percent of the available volume in the pressure vessel. The compartments C are distributed so as to reduce local neutron beaming. They can be in the form of tubes parallel to the axis of the packaging and borne by elements 8b as shown.
To limit the pressure in the case of unusually prolonged fire, there may be provided a valve 24 and, to enable the elimination of the hydrogen formed by radi olysis, a permeable plug" 25 constituted, for example, by a sheet of palladium, may be used.
In a general way, all these valves and other accessories are protected against shock by mechanical guards and against variations in temperature by the choice of their position (thus the abovesaid valves are protected by the insulating covers).
There results from the constitution of the packaging which has just been described, the possibility, after lifting the cover 2c, of transferring, in the loading or unloading area (pool or hot cell), only the assembly constituted by the capsule l and the shield 5, in this respect there are provided handling means 27 borne by the shield thus the other constituents, in particular the finned pressure vessel 2, does not risk to be contaminated during its stays in the loading or unloading area.
Due to this possibility, only a portion of the constituents of the packaging have to be handled at the moment of loading or unloading, which enables recourse to be had to smaller handling apparatus.
Of course, there must then be provided means en abling the packaging to be brought from the horizontal shipping position to the vertical loading or unloading position. These means can advantageously comprise tilting jacks and bearings attached to the transporting chassis and with which the trunnions 19!) indicated above cooperate. In other words, the pressure vessel is then associated with the transporting chassis by these tilting mechanisms.
Naturally, like the the pressure vessel 2, the capsule l comprise a filling valve 29 which this time is advantageously provided with a dip tube 30 for level control,
an expansion valve 31,
a vent valve 32, and
a permeable plug" 33 permeable to hydrogen but tight to gases and radioactive vapors.
Here again, mechanical means, not shown, are provided to ensure protection of these members against mechanical shock.
In the case of capsules filled with a gas as coolant there may be provided, valves or connections not shown enabling the draining and drying of the capsule while in the loading pool.
In FIG. 2 have been shown the partitions 35 used inside the capsule l for spacing the fuel elements 36. Certain constituents of these partitions which are usually made of stainless steel have another composition in order to be an efficient neutronic poison able to prevent criticality.
In the embodiment illustrated in FIG. 3, the capsule I is fonned by the part ofthe sheath 10 of stainless steel ofthe shield 5 which is directed toward the inside of the packaging. In this embodiment, the capsule l and the shield 5 form a top-opened container of which the Iateral wall and bottom are made of heavy metal sheathed with stainless steel.
The closing of this container is achieved in similar manner to that described in the embodiment according to FIG. I.
Here, it is not possible in consequence to extract the capsule I alone from the packaging. For loading and unloading operations, the shield 5 is therefore necessarily withdrawn.
To remedy as far as possible the absence of the cooling effect as obtained in the preceding embodiment as a result of the circulation of water between the capsule l and the shield 5, it is advantageous to provide channels 37 for the circulation of water obtained for example by welding partition 38 (FIG. 3) against the inner surface of the sheath 10 of the shield 5.
Of course, as in the embodiment of FIG. 1, there is not mixing between the liquid which surrounds the radioactive elements transported inside the packaging and that which is contained between the shield 5 and the pressure vessel 2 (and which circulates also in the channels 37).
Again in the embodiment of FIG. 3, there is shown the shield S which is not of revolution Such contours can be advantageous for housing the largest number of elements 36.
Apart from the particular aspects which have just been described with regard to the embodiment of FIG. 3, the packaging according to this embodiment has the same characteristics as that according to the embodiment of FIG. 1. There is no need to detail the common characteristics, which, to the extend that they are shown in FIG. 3, are designated by corresponding ref erence numerals.
In the two embodiments respectively illustrated by FIGS. 4 and 5, the packaging according to the invention comprises several capsules 1 instead of a single one.
In the case of the embodiment of FIG. 4, there are provided four capsules 1 arranged inside the cavity denoted by C and formed by the shield 5. As seen in the Figure, the means of protection 6 provided at the level of the bottom of the capsules 1 are this time constituted by a cover of constitution similar to that of the shield 5. The shielding means 7 are constituted by a cover of identical shape to the cover of the bottom but pierced with four holes of which the shape is apparent from the Figure and in which are fitted the upper ends of the capsules I. To close each of the capsules 1, there are provided plugs 70, of constitution similar to that of the shielding 5, bolted onto the said capsules; leaktightness s ensured by a gasket 14, for example of silicon rubber.
A plate K, for example of steel, is provided to tighten the capsules and their plugs 7a, by applying them against the cover 7.
To enable circulation of the coolant, for example water, the cavity C towards the outside of the shield 5, there are provided spacing means such as stops 16 at the places indicated in the drawing.
As regards the other constituents of the packaging which have just been described, they have either not been shown in order to avoid spoiling the clarity of the drawing, or they are referred to by the same reference numerals as in FIG. 1.
As a result of the constitution of this packaging it is possible to withdraw from the pressure vessel 2 the assembly constituted by the shield and the capsules 1 or again, under the conditions described above with re gard to the embodiment of FIG. 4, one only or several at a time of the capsules 1 closed with their plugs 70.
Now as regards the embodiment of FIG. 5, there is also provided a plurality of capsules 1, in this instance seven as is apparent from the Figure, instead ofa single one, but this time the said capsules form part of the shielding 5 and it is necessary to withdrawn at the same time the said shielding and the said capsules for the op eration of loading and unloading.
The various other parts of this embodiment will not be further described as they are similar to those of the preceding embodiments and which have been shown using same reference numerals.
It will be noted however that in this embodiment, contrary to that of FIG. 3, there have not been provided channels 37 for water contained in the space comprised between the pressure vessel 2 and the shielding 5.
ln the embodiments of FIGS. 1, 3 and 4, the heat generated by the fuel elements transported is transmitted by convection of the coolant circulating in contact with the capsule and between the shield and the pressure vessel [or in the channels 37 ofthe embodiment of HO. 3 as well as through the shield 5 in this ease) up to the pressure vessel from which it is dissipated by means of copper fins borne by the latter. ln the case of the embodiment of FIG. 5, the heat is transmitted through the shield 5.
ln the embodiment illustrated by FIG. 6, each ofthe capsules l is provided with an individual leak-tight lid such as a blind flange fixed, for example, by means of screws. An upper common shield 5b in the form of a cover is provided at the upper part of the packaging.
There is given here by way of example and to establish ideas the dimensional characteristics of a packaging according to the first embodiment of the invention:
height of the capsule 4,550 mm inner diameter of the capsule I.l20 mm thickness of the wall of the capsule I5 mm thickness of the shields 5, 6, 7, (lead) I35 mm thickness of the water layer comprised between the capsule and the shield 5 [0 mm thickness of the water layer com prised between the shield and the pressure vessel 2 200 mm thickness of the pressure vessel 2 mm dimensions of the copper fins 200 mm X 2 mm X 5 mm outer dimensions of the packaging diameter 2.440 mm length 5,600 mm weight of the empty capsule l,000 kg weight of the shield 40,000 kg total weight of the loaded packaging 90,000 kg In the following, there will be indicated several advantages offered by the packaging according to the invention and some of the possibilities offered due to its structural characteristics.
Firstly, it is emphasized that by their structure dismountable into essential components (capsules, shield, centering structures of the shield, pressure vessel, casing for holding the radioactive contents, ect.), the packaging according to the invention offers great flexibility and economy of operation.
ln fact, the possibility of insepcting and quick replacing in the case of defect one of the components reduces to the minimum the time of immobilization of the packaging.
Moreover, the invention enables safe and rather economical shipment of irradiated fuel elements with defective, cracked or corroded cladding.
Another advantage resulting from this possibility of only withdrawing the capsule with its contents from the packaging is that the masses handled at the time of loading and unloading operations are much smaller than the total packaging weight, thus enabling the use of overcranes and other lifting apparatus of reduced capacity.
The removable capsules being loadable in advance or replaceable in a case of abnormal contamination on arrival, the duration of the loading or unloading operations of the packaging are reduced to a considerable extent.
Due to the construction of the packaging as provided by the invention, the amount of coolant, especially contaminated water which is confined within the capsules, is reduced to a minimum, and, due also to this structure, the amount of hydrogen formed by radiolysis and by corrosion is reduced in considerable proportions.
Due to the rather simple outer shapes of the capsules and ofthe shield S, which, in general, are the only elements of the packaging to be handled in the contaminated areas, it is evident that decontamination is very easy. Furthermore, as the pressure vessel remains outside the contaminated areas, one may rely upon the cooling fins described above in spite of the fact they are rather difficult to decontaminate to take advantage of their characteristics concerning heat dissipation, weight and ability to absorb energy in case of crash.
Transfer of the heat generated by the transported fuel elements, which is hence done by convection of the coolant inside the packaging and convection of air at the level of the fins outside the packaging, does not require any auxiliary device (such as thermosyphon or condenser) and is reliable asit is improved at higher temperature by acceleration of the convection The efficiency of the abovesaid fins used according to the invention is such that it is possible to cover with then, only a relatively small portion of the surface of the packaging.
The packaging according to the invention remains leak-tight under normal and accidental conditions of use, and the thickness and shape of the pressure vessel 2 confer on it a special resistance to shock and enable it to withstand high pressures.
The presence of the insulation at the places not provided with the cooling fins protects the packaging from climatic influences and improves the resistance to fire.
Moreover, the position of the neutron shield (water) outside the main gamma shield and its lack of local reduction due to the use of the compartments C results in an economy of weight, the water layer contributing besides, by its high heat capacity. to protection in case of fire.
Lastly, and this is an additional advantage, the structure of the packaging according to the invention enables the construction also of packaging of great size as well as small packaging, which is important since use of large sized packagings reduces the number of shipments, and use of small sized ones provide the possibility ofcompleting the shipment of one batch without immobilising and oversized packaging. This constitutes considerable progress since, on the one hand packaging containing water already known had necessarily to be of rather heavy weight to resist the accidental conditions of fire, and on the other hand there was no possibility hitherto of constructing a dry" packaging of large size.
In the embodiment illustrated by FIG. 9, the shield 5 comprises an open container 50 and a cover 5!) of identical constitutions, these two elements being connected to one another, for example by bolts 5c.
In this embodiment, according to the invention, the capsules l are united at their upper end by welding to a plate 40 comprising holes 400 at the place of fixing each capsule and forming a peripheral flange 40b, which cooperates with a leak-tight common cover 41 provided with a flange 41b, leak-tightness between the flanges 40b and 41b is ensured by means ofa gasket 44 made for example of silicon rubber.
Preferably, to resist pressure better, the cover 41 has a hollow structure such as is seen from FIGS. 9 and I2 and it is reinforced by ribs 43 delimiting voids 42 which extend the capsules.
To ensure cooling of the gasket 44 in case of prolonged immobilisation during handling in air, the flange 41b is provided with a rim 45 parallel to the axis of the capsules 1 and forming, in cooperation with the cover 4], as seen in FIGS. 9 and I I, a peripheral cavity 46 capable of holding water due to the presence of which the gasket 44 is kept at a sufficiently low temperature.
To enable fllling of the cavity 46 on such an immobilisation, there may be provided through the cover 51) a piping shaped to avoid radiation beaming.
In the case of the embodiment of FIG. 9, each ofthe capsules comprises an individual bottom and is held at a suitable distance from neighboring capsules by means of welded spacers not shown, which gives a sufficient rigidity to the assembly and keeps in position the neutronic poison plates diagrammatically represented at P (FIGS. II and 12) and used to prevent criticality.
In a preferred embodiment, the capsules 1 are united at their lower end by a structure similar to that which unites their upper end, that is to say by a plate 47 comprising holes 47a, and a peripheral flange 47b. The lower end of the capsules 1 is closed by a common bottom 49 comprising a peripheral flange 4911 which is applied against the flange 47b.
To enable this bottom 49 to resist pressure, it is advantageous to give it a hollow structure, similar to that of the cover 4], and comprising consequently a series of ribs 49c and voids 49a facing the capsules as seen in FIG. 12. Communicating orifices 49d between the different voids 490 are provided through the ribs 490.
There is provided between the peripheral flanges 47b and 49b a gasket 50, constituted for example of the same material as the gasket 44. It is also possible to fix the bottom 49 by welding. In this case, the gasket 50 is eliminated.
To ensure the cooling of the gasket 50 during handling in air, it is advantageous to provide a rim 51, similar to that provided at the level of the cover 41, in order to form a cavity 52 which can be filled with water.
Of course, the fixing of the cover 41 and that of the bottom 49, when it is removable, can be ensured by any suitable means, for example by bolts such as 53 acting on the flanges 40b and 41b and on the flanges 47b and 49/).
As has already been indicated above, the capsules 1 are filled with a gaseous or liquid coolant.
To facilitate remote draining and air drying of the capsules, there is provided a syphon-drain, diagrammatically indicated at 54, and a vent not shown, situated at the level of the common lid 41.
As shown above, the capsules 1 as well as their shield 5 are immersed in the water filling the pressure vessel 2.
To facilitate the circulation by convection of this water between the outside and the inside of the shield 5, according to the present invention, the container 5a is made to comprise a plurality of conduits 55 which pass through it and of which the shape is such that it prevents radiation beaming. For example, the conduit 55 can be bent as seen in FIGS. 10 and 11.
Preferably these conduits 55 are arranged in the vicinity of the lower an upper generatrices of the packaging in the horizontal position of transportion.
The total cross-section of the conduits at lower and upper levels are about the same.
To compensate the lack of shielding against gamma rays at the level of the bent conduits 55, bosses 56 are provided on the said shield 5 at these levels, these bosses being directed towards the inside of the shield (FIG, 10), or towards the outside (FIG. 11).
To gain weight, the core 9 of the shield 5 can comprise parts of lead and others of uranium, the latter being then arranged preferably at the level of the corners. Of course, for reasons of ease of construction, the conduit 55 will be buried in the lead.
To gain space, the cross-section of the capsules 1 is preferably similar to that of the fule elements to be transported; these elements being often right angle prisms with square bases, the cross-section of the cap sules is frequently square, as seen in FIGS. I0 and I1.
To gain weight. it is also advantageous to confer on the shield such a cross-section that the volume of water which surrounds the capsules 1 is reduced to the minimum. Thus the shield 5 may be made for example in the manner indicated in FIG. 1].
It is of course understood that the package thus constituted comprises filling, draining and safety devices similar to those which have been described above.
Of course, the packaging according to this embodiment, as well as the others described above, may include the improvements described with respect to FIGS. 6 to 8.
The packaging thus constituted has its own advantages, especially:
same temperature for all the fuel elements as their capsules are all equally dipped in water and cooled by convection (effect realised also in the case of the em bodiment of FIG. 4),
simple structure of the capsule assembly which can withstand pressure in spite ofthin walls, due to reduced section ofthe said capsules and the particular structure of the cover and bottom,
possibility to avoid overheating of the gaskets in case of delays during handling in air.
1. Packaging for the shipment and storage of irradiated materials. comprising:
an outer container forming a pressure vessel having a high resistance to physical stresses and having cooling elements on its outer surface.
a gamma ray shield located in the pressure vessel and spaced inwardly from the inside wall of the pressure vessel to define therebetween a space, a liquid in said space, the thickness ofthe space being large enough such that the liquid therein ensures neutronic protection and evacuation of heat from the gamma ray shield through to the pressure vessel, said gamma ray shield being readily mountable in and removable from said pressure vessel,
at lease one leak-tight inner container adapted to contain the irridiated material and a fluid coolant therein, said inner container being easily mountable in and removable from the interior of said gamma ray shield,
spacing means in said space for fixing the position of the gamma ray shield when it is in the pressure vessel and means securely positioning said inner container when located within the gamma ray shield such that the orientation of the pressure vessel, the gamma ray shield and the inner container remains the same regardless of the orientation of the pres sure vessel, whereby the packaging is operable for properly carrying the gamma ray shield and its contents in either a horizontal or a vertical position.
2. Packaging according to claim 1 wherein the coolant is air.
3. Packaging according to claim 1 wherein the coolant is helium.
4. Packaging according to claim 1, wherein the coolant is water.
5. Packaging according to claim 1, comprising antineutronic poison plates arranged between the inner containers.
6. Packaging according to claim 1. Comprising. between the outer container and the gamma ray shield, compartments containing a compressible material.
7. Packaging according to claim 1, comprising means ensuring communication between (a) the space inside the shield and surrounding the one or more inner containers and (b) the space outside the gamma ray shield.
8. Packaging according to claim 1, wherein the spacing means are constituted by a structure in the form of a removable basket.
9. Packaging according to claim 8, comprising an insulating and shock-abosrbing covering for the places without cooling means.
10. Packaging according to claim 9, wherein the pressure vessel is composed of a sleeve on which has been attached a convex bottom and which is closed at the other end by means of a convex cover, by the cooperation of two flanges provided on these two component elements and the interposition of a leak-tight gasket.
11. Packaging according to claim 10 and comprising several inner containers, wherein the inner containers are united at least at one of their ends to a common leak-tight flange cooperating with a cover.
12. Packaging according to claim 11, wherein the cover has a hollow structure reinforced by ribs.
13. Packaging according to claim 12, wherein the common peripheral flange of the cover comprises a rim parallel to the axis of the inner containers and forming a peripheral cavity adapted to hold water.
i i I!