Transport container

Abstract

A transport container for helium, with an inner container for receiving the helium, a coolant container for receiving a cryogenic liquid (N.sub.2), an outer container, in which the inner container and the coolant container are contained, a thermal shield, in which the inner container is contained and which can be actively cooled with the aid of a liquid phase of the cryogenic liquid (LN.sub.2), the thermal shield having at least one first cooling line, in which the liquid phase of the cryogenic liquid can be received for actively cooling the thermal shield, and an insulating element, which is arranged between the outer container and the thermal shield and which can be actively cooled with the aid of a gaseous phase of the cryogenic liquid (GN.sub.2), the insulating element having at least one second cooling line, in which the gaseous phase of the cryogenic liquid can be received.

Claims

1. A transport container for helium comprising: an inner container for receiving the helium, a coolant container for receiving a cryogenic liquid, an outer container, wherein the inner container and the coolant container are contained within said outer container, a thermal shield, wherein the inner container is contained within said thermal shield, and said thermal shield can be cooled by a liquid phase of the cryogenic liquid from the coolant container, the thermal shield having at least one first cooling line which receives the liquid phase of the cryogenic liquid from the coolant container, and an insulating element arranged between the outer container and the thermal shield, wherein said insulating element can be cooled by a gaseous phase of the cryogenic liquid, the insulating element having at least one second cooling line which receives the gaseous phase of the cryogenic liquid, wherein the transport container further comprises a phase separator which separates the liquid phase of the cryogenic liquid from the gaseous phase of the cryogenic liquid, and said phase separator is arranged between said at least one first cooling line and said at least one second cooling line.

2. The transport container according to claim 1, wherein said at least one second cooling line receives the gaseous phase of the cryogenic liquid directly from said phase separator.

3. The transport container according to claim 1, wherein the at least one second cooling line is led through the insulating element.

4. The transport container according to claim 3, wherein the insulating element comprises multiple alternately arranged layers of a reflective film and a spacer and the at least one second cooling line is led through between the layers.

5. The transport container according to claim 4, wherein the insulating element has at least one heat conducting film to which the at least one second cooling line is connected in a thermally conducting manner, and the at least one heat conducting film is positioned between the layers of the reflective film and the spacer.

6. The transport container according to claim 5, wherein the at least one heat conducting film encloses the thermal shield.

7. The transport container according to claim 5, wherein the insulating element has multiple heat conducting films, and the layers of the reflective film and the spacer are arranged between the heat conducting films.

8. The transport container according to claim 7, wherein said transport container has a plurality of the second cooling lines, and each of the heat conducting film is assigned one of said second cooling lines and each of the heat conducting film is connected to the second cooling line assigned thereto in a thermally conducting manner.

9. The transport container according to claim 8, wherein the second cooling lines are in fluid connection with one another via pipe bends.

10. The transport container according to claim 5, wherein a thickness of the at least one heat conducting film is greater than a thickness of the reflective film.

11. The transport container according to claim 1, wherein the coolant container is arranged outside the thermal shield.

12. The transport container according to claim 11, wherein the thermal shield has a cover portion which is separate from the coolant container and is arranged between the inner container and the coolant container.

13. The transport container according to claim 4, wherein the reflective film is an aluminum foil and the spacer is glass paper.

14. The transport container according to claim 5, wherein the at least one heat conducting film is an aluminum or copper foil.

15. The transport container according to claim 13, wherein the at least one heat conducting film is copper foil.

16. The transport container according to claim 1, wherein the thermal shield comprises a cylindrical base portion having two ends which is closed at each end thereof by a cover portion, and one of the cover portions of said thermal shield is arranged between the inner container and the coolant container.

17. The transport container according to claim 1, wherein the thermal shield is spaced from the inner container to provide a first intermediate space, and the thermal shield is spaced from the outer container to provide a second intermediate space, and said thermal shield is fluid permeable so that said first intermediate space is in fluid communication with said second intermediate space.

18. The transport container according to claim 16, further comprising a further insulating element which encloses the inner container, said further insulating element comprising a copper layer which faces the thermal shield and a multilayer insulating layer arranged between the copper layer and the inner container, said insulating layer comprises multiple alternately arranged layers of a reflective film and a spacer.

19. The transport container according to claim 2, wherein the transport container has a plurality of second cooling lines and at least one of said plurality of second cooling lines is in direct fluid communication with the phase separator and at least another of said plurality of said second cooling lines is in direct fluid communication with the coolant container.

20. The transport container according to claim 4, wherein said transport container has a plurality of second cooling lines and the insulating element has at least a first and a second heat conducting film, and wherein one of said plurality of second cooling lines is connected to the first heat conducting film in a thermally conducting manner, another of said second cooling lines is connected to the second heat conducting film in a thermally conducting manner, and multiple layers of the reflective film and spacer are positioned between the first and second heat conducting films.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 shows a schematic view of one embodiment of a transport container;

(2) FIG. 2 shows a further schematic view of the transport container according to FIG. 1;

(3) FIG. 3 shows a further schematic view of the transport container according to FIG. 1;

(4) FIG. 4 shows a sectional view of the transport container according to the sectional line IV-IV of FIG. 3; and

(5) FIG. 5 shows a schematic view of a detail of the transport container according to FIG. 1.

(6) In the figures, elements that are identical or have the same function have been given the same reference signs, unless stated otherwise.

(7) FIG. 1 shows a greatly simplified schematic view of one embodiment of a transport container 1 for liquid helium He. FIGS. 2 and 3 show further schematic views of the transport container 1. In the following, reference is at the same time made to FIGS. 1 to 3.

(8) The transport container 1 may also be referred to as a helium transport container. The transport container 1 may also be used for other cryogenic liquids. Examples of cryogenic liquids, or cryogens for short, are the previously mentioned liquid helium He (boiling point at 1 bara: 4.222 K=−268.929° C.), liquid hydrogen H.sub.2 (boiling point at 1 bara: 20.268 K=−252.882° C.), liquid nitrogen N.sub.2 (boiling point at 1 bara: 7.35 K=−195.80° C.) or liquid oxygen O.sub.2 (boiling point at 1 bara: 90.18 K=−182.97° C.).

(9) The transport container 1 comprises an outer container 2. The outer container 2 is produced for example from high-grade steel. The outer container 2 may have a length L2 of for example 10 meters. The outer container 2 comprises a tubular or cylindrical base portion 3, which is closed at each of both the end faces with the aid of a cover portion 4, 5, in particular with the aid of a first cover portion 4 and a second cover portion 5. The base portion 3 may have a circular or approximately circular geometry in cross section. The cover portions 4, 5 are curved. The cover portions 4, 5 are oppositely curved, so that both cover portions 4, 5 are outwardly curved with respect to the base portion 3. The outer container 2 is fluid-tight, in particular gas-tight. The outer container 2 has an axis of symmetry or center axis M1, in relation to which the outer container 2 is constructed rotationally symmetrically.

(10) The transport container 1 also comprises an inner container 6 for receiving the helium He. The inner container 6 is likewise produced for example from high-grade steel. As long as the helium He is in the two-phase region, a gas zone 7 with evaporated helium He and a liquid zone 8 with liquid helium He may be provided in the inner container 6. The inner container 6 is fluid-tight, in particular gas-tight, and may comprise a blow-off valve for controlled pressure reduction. Like the outer container 2, the inner container 6 comprises a tubular or cylindrical base portion 9, which is closed on both end faces by cover portions 10, 11, in particular a first cover portion 10 and a second cover portion 11. The base portion 9 may have a circular or approximately circular geometry in cross section.

(11) The transport container 1 also comprises a cooling system 13 (FIG. 2) with a coolant container 14. The inner container 6 is completely enclosed by the outer container 2. Like the outer container 2, the inner container 6 is formed rotationally symmetrically in relation to the center axis M1. A gap or intermediate space 12 provided between the inner container 6, the coolant container 14 and the outer container 2 is evacuated. In the intermediate space 12 there may be arranged an insulating element which is not shown in FIGS. 1 to 3 and fills the intermediate space 12. The intermediate space 12 completely encloses the inner container 6 and the coolant container 14.

(12) A cryogenic liquid, such as for example nitrogen N.sub.2, is contained in the coolant container 14. The coolant container 14 comprises a tubular or cylindrical base portion 15, which may be constructed rotationally symmetrically in relation to the center axis M1. The base portion 15 may have a circular or approximately circular geometry in cross section. The base portion 15 is closed at each of the end faces by a cover portion 16, 17, in particular by a first cover portion 16 and a second cover portion 17. The cover portions 16, 17 may be curved. In particular, the cover portions 16, 17 are curved in the same direction. The coolant container 14 may also have a different construction. The coolant container 14 is arranged outside the inner container 6, but inside the outer container 2.

(13) A gas zone 18 with evaporated or gaseous nitrogen GN.sub.2 and a liquid zone 19 with liquid nitrogen LN.sub.2 may be provided in the coolant container 14. The coolant container 14 is arranged next to the inner container 6 when viewed in an axial direction A of the inner container 6. The axial direction A is positioned parallel to the center axis M1. The axial direction A may be oriented from the first cover portion 4 of the outer container 2 in the direction of the second cover portion 5 of the outer container 2. A gap or intermediate space 20, which may be part of the intermediate space 12, is provided between the inner container 6, in particular between the second cover portion 11 of the inner container 6, and the coolant container 14, in particular the first cover portion 16 of the coolant container 14. That is to say that the intermediate space 20 is likewise evacuated.

(14) The transport container 1 also comprises a thermal shield 21 assigned to the cooling system 13. The thermal shield 21 is arranged in the evacuated intermediate space 12 provided between the inner container 6 and the outer container 2. The thermal shield 21 can be actively cooled or is actively cooled with the aid of the liquid nitrogen LN.sub.2. Active cooling should be understood in the present case as meaning that, for cooling the thermal shield 21, the liquid nitrogen LN.sub.2 is passed through the latter or along it. The thermal shield 21 is thereby cooled to a temperature that corresponds approximately to the boiling point of the nitrogen N.sub.2.

(15) The thermal shield 21 comprises a cylindrical or tubular base portion 22, which is closed on both sides by a cover portion 23, 24 closing it off at the end face, in particular a first cover portion 23 and a second cover portion 24. Both the base portion 22 and the cover portions 23, 24 are actively cooled with the aid of the nitrogen N.sub.2. The base portion 22 may have a circular or approximately circular geometry in cross section. The thermal shield 21 is preferably likewise constructed rotationally symmetrically in relation to the center axis M1. The second cover portion 24 of the thermal shield 21 is arranged between the inner container 6, in particular the second cover portion 11 of the inner container 6, and the coolant container 14, in particular the first cover portion 16 of the coolant container 14.

(16) The second cover portion 24 of the thermal shield 21 is a component that is separate from the coolant container 14. That is to say that the first cover portion 23 is not part of the coolant container 14. When viewed in the axial direction A, the second cover portion 24 of the thermal shield 21 is arranged between the inner container 6, in particular the second cover portion 11 of the inner container 6, and the coolant container 14, in particular the first cover portion 16 of the coolant container 14. The intermediate space 12 completely encloses the thermal shield 21.

(17) The first cover portion 23 of the thermal shield 21 is facing away from the coolant container 14. The first cover portion 23 of the thermal shield 21 is arranged between the first cover portion 4 of the outer container 2 and the first cover portion 10 of the inner container 6. The thermal shield 21 is in this case self-supporting. That is to say that the thermal shield 21 is not supported on either the inner container 6 or the outer container 2. For this purpose, the thermal shield 21 may be provided with a carrying ring, which is suspended from the outer container 2 by supporting bars, in particular tension bars. The inner container 6 may also be suspended from the carrying ring by further supporting bars, in particular tension bars. The heat input through the mechanical supporting bars is partially realized by the carrying ring. The carrying ring has pockets, which allow the supporting bars to be of the greatest possible thermal length. The coolant container 14 may comprise bushings for the mechanical supporting bars.

(18) The thermal shield 21 is fluid-permeable. That is to say that a gap or intermediate space 25 between the inner container 6 and the thermal shield 21 is in fluid connection with the intermediate space 12. As a result, the intermediate spaces 12, 25 can be evacuated at the same time. The intermediate space 25 completely encloses the inner container 6. A further insulating element that is not shown in FIGS. 1 to 3 may be arranged in the intermediate space 25. Bores, apertures or the like may be provided in the thermal shield 21, in order to allow evacuation of the intermediate spaces 12, 25. The thermal shield 21 is preferably produced from a high-purity aluminum material.

(19) The second cover portion 24 of the thermal shield 21 shields the cooling container 14 completely from the inner container 6. That is to say that, when looking in the direction from the inner container 6 toward the coolant container 14, that is to say when looking in the axial direction A, the coolant container 14 is completely covered by the second cover portion 24 of the thermal shield 21. In particular, the thermal shield 21 in this case completely encloses the inner container 6. That is to say that the inner container 6 is arranged completely inside the thermal shield 21, while, as already mentioned above, the thermal shield 21 is not fluid-tight.

(20) As FIG. 2 also shows, the thermal shield 21 comprises at least one first cooling line 26 for actively cooling it. The first cooling line 26 is assigned to the cooling system 13. Preferably, multiple such first cooling lines 26 are provided, for example six such first cooling lines 26. However, there can be any number of first cooling lines 26. The first cooling line 26 may comprise two vertical portions 27, 28, running in a direction of gravitational force g, and two sloping portions 29, 30. The vertical portions 27, 28 may be provided on the cover portions 23, 24 and/or on the base portion 22 of the thermal shield 21. The sloping portions 29, 30 may likewise be provided on the cover portions 23, 24 and/or on the base portion 22.

(21) The first cooling line 26 is connected to the thermal shield 21 in a material-bonding manner. In the case of material-bonding connections, the parts being connected are held together by atomic or molecular forces. Material-bonding connections are non-releasable connections, which can only be separated by destroying the connecting means or the parts being connected. Material-bonding connections can be produced for example by adhesive bonding, soldering, welding or vulcanizing. Preferably, the first cooling line 26 or the first cooling lines 26 is/are welded, soldered or adhesively bonded to the thermal shield 21.

(22) The first cooling line 26 is in fluid connection with the coolant container 14 by way of a connection line 31, so that the liquid nitrogen LN.sub.2 is forced from the coolant container 14 into the first cooling line 26. The connection line 31 opens out into a distributor 32, from which the portion 27 and the portion 30 branch off. The portion 29 and the portion 28 meet at a manifold 33, from which a connection line 34 leads to a phase separator 35 arranged outside the outer container 2. The phase separator 35 may also be positioned inside the outer container 2. The phase separator 35 is designed to separate gaseous nitrogen GN.sub.2 from liquid nitrogen LN.sub.2. With the aid of the phase separator 35, the gaseous nitrogen GN.sub.2 may also be removed from the first cooling line 26.

(23) As mentioned above, the first cooling line 26 or the first cooling lines 26 is/are provided both on the base portion 22 and on the cover portions 23, 24 of the thermal shield 21. Alternatively, the cover portions 23, 24 are connected to the base portion 22 as one part in terms of the material, in particular in a material-bonding manner. For example, the cover portions 23, 24 are welded to the base portion 22. The fact that the cover portions 23, 24 are connected to the base portion 22 as one part in terms of the material, that is to say in a material-bonding manner, means that the cooling of the cover portions 23, 24 can take place by heat conduction.

(24) The first cooling line 26, and in particular the sloping portions 29, 30 of the first cooling line 26, has/have a gradient with respect to a horizontal H, which is arranged perpendicularly to the direction of gravitational force g. In particular, the portions 29, 30 form an angle α of greater than 3° with the horizontal H. The angle α may be 3 to 15° or even more. In particular, the angle α may also be exactly 3°. In particular, the portions 29, 30 have a positive gradient in the direction of the phase separator 35, so that gas bubbles rise up to the phase separator 35.

(25) The inner container 6 comprises an insulating element 36 that is shown in FIG. 4. The insulating element 36 completely encloses the inner container 6, that is to say that the insulating element 36 is provided both on the base portion 9 and on the cover portions 10, 11 of the inner container 6. The insulating element 36 encapsulates the inner container 6. The insulating element 36 is arranged between the inner container 6 and the thermal shield 21, in the intermediate space 25, and partially fills the latter. The insulating element 36 has a highly reflective copper layer 37 on the outer side, that is to say facing the thermal shield 21. The copper layer 37 is metallically bright. That is to say that the copper layer 37 does not have a surface coating or oxide layer. The copper layer 37 may be for example a copper foil or an aluminum foil with a vapor-deposited copper coating.

(26) The actual thermal damping of the inner container 6 with respect to the temperature level of the liquid nitrogen LN.sub.2 of the thermal shield 21 is provided by the copper layer 37. Preferably, the copper layer 37 is a smooth film of high-purity bright copper, which is drawn tightly and without creases around a multilayer insulating layer 38 arranged between the copper layer 37 and the inner container 6. The insulating layer 38 comprises multiple alternately arranged layers of a reflective film and a spacer. The reflective film may be a perforated and embossed aluminum foil or a metallized plastic film. The spacer may for example comprise glass paper or glass fabric. The reflective film serves as a reflector and the spacer keeps the layers of reflective film spaced apart from one another and serves as damping in the event of a breakdown of the vacuum between the reflective films.

(27) The insulating layer 38 may for example comprise ten layers. The layers of reflective film and spacer are applied on the inner container 6 without any gaps, that is to say are pressed. The insulating layer 38 may be what is known as an MLI (multilayer insulation). On the outer side, that is to say facing the thermal shield 21, the inner container 6 and also the insulating element 36 are approximately at a temperature corresponding to the boiling point of the helium He. During the mounting of the insulating layer 38, it is ensured that the layers of reflective film and spacer have the greatest possible mechanical pressing, to achieve the effect that all of the layers of the insulating layer 38 are as isothermal as possible. The insulating element 36 may be referred to as the first insulating element 36.

(28) Provided between the insulating element 36 and the thermal shield 21 is the intermediate space 25, running completely around the inner container 6. The intermediate space 25 is also provided between the insulating element 36 and the cover portions 23, 24 of the thermal shield 21. The intermediate space 25 has a gap width which is preferably 5 to 15 millimeters, more preferably 10 millimeters. With the aid of the intermediate space 25, the thermal shield 21 is arranged peripherally spaced apart from the copper layer 37 of the insulating element 36 of the inner container 6 and is not in contact with it. As a result, the heat input by radiation is reduced to the minimum physically possible. Heat is only transferred from the surfaces of the inner container 6 to the thermal shield 21 by radiation and residual gas conduction.

(29) A further, in particular a second, insulating element 39 is provided between the thermal shield 21 and the outer container 2, that is to say in the intermediate space 12. The insulating element 39 preferably completely fills the intermediate space 12 in the region of the inner container 6, so that there the insulating element 39 contacts the thermal shield 21 on the outer side and the outer container 2 on the inner side. The insulating element 39 encloses the thermal shield 21 apart from its second cover portion 24, that is to say it encloses the first cover portion 23 and the base portion 22. Furthermore, the cylindrical base portion 15 and the second cover portion 17 of the coolant container 14 are enclosed by the insulating element 39. The insulating element 39 is preferably likewise a so-called MLI.

(30) The insulating element 39 is provided both between the respective base portions 3, 15, 22 of the outer container 2, of the coolant container 14 and of the thermal shield 21 and between the first cover portion 23 of the thermal shield 21 and the first cover portion 4 of the outer container 2 and also between the second cover portion 17 of the coolant container 14 and the second cover portion 5 of the outer container 2. The insulating element 39 may consequently also enclose the coolant container 14. The insulating element 39 comprises alternately arranged layers of a reflective film 40, in particular an aluminum foil or metallized plastic film, and a spacer 41, in particular glass paper. There can be any number of layers. Apart from glass paper, the spacer 41 may also comprise glass silk, glass mesh fabric or the like.

(31) As a difference from the insulating element 36 described above of the inner container 6, the layers of reflective film 40 and spacer 41 are introduced loosely into the intermediate space 12. Loosely means here that the layers of reflective film 40 and spacer 41 are not pressed, so that an embossing and perforation of the reflective film 40 allows the insulating element 39, and consequently the intermediate space 12, to be evacuated without any problem.

(32) The insulating element 39 comprises at least one second cooling line 42 to 46, with the aid of which the insulating element 39 can be actively cooled with the gaseous nitrogen GN.sub.2. Active cooling should be understood in the present case as meaning that, for cooling the insulating element 39, the gaseous nitrogen GN.sub.2 is passed through the latter or along it. There can be any number of second cooling lines 42 to 46. For example, as shown in FIG. 3, five such second cooling lines 42 to 46 may be provided. It is also possible for three second cooling lines 42 to 46 to be provided. The second cooling lines 42 to 46 are in fluid connection with one another with the aid of pipe bends 47 to 49. The second cooling lines 42 to 46 may be arranged such that they run around both the base portion 22 and the first cover portion 23 of the thermal shield 21. The second cooling lines 42 to 46 may also run around the coolant container 14. The second cooling lines 42 to 46 are assigned to the cooling system 13.

(33) Preferably, the second cooling line 42 is in fluid connection with the phase separator 35 with the aid of a feed line 50. The feed line 50 is used to feed the gaseous nitrogen GN.sub.2, which has been separated from the liquid nitrogen LN.sub.2 with the aid of the phase separator 35, to the second cooling lines 42 to 44. A discharge line 51 can be used to send the heated gaseous nitrogen GN.sub.2 to the surroundings. The phase separator 35 is in fluid connection with the coolant container 14 with the aid of the first cooling line 26. In this case, the phase separator 35 is arranged between the first cooling line 26 and the second cooling line 42.

(34) Optionally, a number of second cooling lines 45, 46 may be connected directly to the coolant container 14. In this case, the phase separator 35 is not arranged upstream of the second cooling lines 45, 46. This allows what is known as boil-off gas of the coolant container 14, that is to say gaseous nitrogen GN.sub.2, to be fed to the second cooling lines 45, 46 by way of a feed line 52. Provided on a discharge line 53 of the second cooling lines 45, 46 to the surroundings is a pressure-maintaining valve 54 of the coolant container 14, which gives off the heated gaseous nitrogen GN2 to the surroundings.

(35) As shown in FIG. 4, the second cooling lines 42 to 46 are led through the insulating element 39. The insulating element 39 has in addition to the layers of reflective film 40 and spacer 41 a multiplicity of heat conducting films 55 to 57. There can be any number of heat conducting films 55 to 57. The heat conducting films 55 to 57 are preferably formed as high-purity aluminum or copper foils. The heat conducting films 55 to 57 run around the thermal shield 21. In particular, the thermal shield 21 is arranged within a third heat conducting film 57, the third heat conducting film 57 is arranged within a second heat conducting film 56 and the second heat conducting film 56 is arranged within a first heat conducting film 55.

(36) Layers of the reflective film 40 and the spacer 41 are respectively arranged between the heat conducting films 55 to 57. For example, four layers of reflective film 40 and spacer 41 are provided between the thermal shield 21 and the third heat conducting film 57. Furthermore, for example, ten layers of reflective film 40 and spacer 41 may be provided between the third heat conducting film 57 and the second heat conducting film 56. Twelve layers of reflective film 40 and spacer 41 may be provided between the second heat conducting film 56 and the first heat conducting film 55 and, for example, fourteen layers of reflective film 40 and spacer 41 may be provided between the first heat conducting film 55 and the outer container 2. There can however be any number of layers in each case.

(37) Preferably, each second cooling line 42 to 46 is assigned such a heat conducting film 55 to 57. For example, the second cooling line 42 is assigned the third heat conducting film 57, the second cooling line 43 is assigned the second heat conducting film 56 and the second cooling line 44 is assigned the first heat conducting film 55. Furthermore, the optional second cooling lines 45, 46 may also be assigned such heat conducting films 55 to 57. The heat conducting films 55 to 57 preferably have in each case a greater thickness than the reflective films 40. For example, the heat conducting films 55 to 57 have in each case a thickness of 0.5 to 1.5 millimeters. The thickness of the heat conducting films 55 to 57 may vary along the second cooling lines 42 to 46.

(38) Preferably, the second cooling lines 42 to 46 are connected to the heat conducting films 55 to 57 assigned to them in a material-bonding manner. For example, the second cooling lines 42 to 46 are adhesively bonded to the respective heat conducting film 55 to 57. For the case where the heat conducting films 55 to 57 are produced from copper, the second cooling lines 42 to 46 are soldered to them. For the case where the heat conducting films 55 to 57 are produced from aluminum, the second cooling lines 42 to 46 are adhesively bonded to them. In this way, a good heat transfer between the respective second cooling line 42 to 46 and the heat conducting film 55 to 57 assigned to it is ensured.

(39) As shown in a view of a detail in FIG. 5, the heat conducting films 55 to 57 take the form of sheets and have a width b of, for example, 1 meter. As viewed in the axial direction A, a spacing a is respectively provided between two adjacent third heat conducting films 57 or first or second heat conducting films 55, 56. That is to say that the heat conducting films 55 to 57 are arranged spaced apart from one another in the axial direction A and run peripherally around the thermal shield 21. The sheets of the heat conducting films 55 to 57 may also in each case overlap one another. The spacing a may be for example 0.1 to 1 meter. The heat conducting films 55 to 57 are wrapped peripherally around the thermal shield 21 while incorporated in the insulating element 39.

(40) The functioning mode of the transport container 1 will be explained below. Before the filling of the inner container 6 with helium He, first the thermal shield 21 is cooled down with the aid of cryogenic, initially gaseous and later liquid, nitrogen N.sub.2 at least almost or right up to the boiling point (1.3 bara, 7.95 K) of the liquid nitrogen LN.sub.2. The inner container 6 is in this case not yet actively cooled. During the cooling down of the thermal shield 21, the residual vacuum gas still located in the intermediate spaces 12, 20, 25 is frozen out on the thermal shield 21. In this way it can be prevented when filling the inner container 6 with the helium He that the residual vacuum gas freezes out on the outer side of the inner container 6 and thereby contaminates the metallically bright surface of the copper layer 37 of the insulating element 36 of the inner container 6. As soon as the thermal shield 21 and the coolant container 14 have cooled down completely and the coolant container 14 is again completely filled with nitrogen N.sub.2, the inner container 6 is filled with the helium He.

(41) The transport container may then be transferred onto a transporting vehicle, such as for example a truck or a ship, for transporting the helium He. This involves cooling the thermal shield 21 continuously with the aid of the liquid nitrogen LN.sub.2. The liquid nitrogen LN.sub.2 is thereby used and boils in the first cooling line 26 or in the first cooling lines 26. Gas bubbles produced in the process are fed to the phase separator 35 arranged highest in the cooling system 13 with respect to the direction of gravitational force g. As soon as the gaseous nitrogen GN.sub.2 has been removed from the cooling system 13 with the aid of the phase separator 35, liquid nitrogen LN.sub.2 flows into the phase separator 35. The gaseous nitrogen GN.sub.2 is fed to the second cooling lines 42 to 44 by way of the feed line 50. In addition, gaseous nitrogen GN.sub.2 may be fed to the second cooling lines 45, 46 directly from the coolant container 14.

(42) The fact that the thermal shield 21 is also arranged between the coolant container 14 and the inner container 6 means that it can be reliably ensured that the inner container 6 is sufficiently cooled even when there is a falling filling level or liquid level of nitrogen N.sub.2 in the coolant container 14. The fact that the inner container 6 is completely surrounded by the thermal shield 21 means that it is ensured that the inner container 6 is only surrounded by surfaces that are at a temperature corresponding to the boiling point (1.3 bara, 79.5 K) of nitrogen N.sub.2. In this way, there is only a small difference in temperature between the thermal shield 21 (79.5 K) and the inner container 6 (4.2 to 6 K). This extends the holding time for the helium He.

(43) Furthermore, the fact that the insulating element 39 arranged between the thermal shield 21 and the outer container 2 is actively cooled with the aid of the gaseous nitrogen GN.sub.2 means that the holding time for the helium He can be extended further. In comparison with known transport containers, the holding time for the helium He can consequently be extended significantly. Heat is in this case only transferred from the inner container 6 to the thermal shield 21 by radiation and residual gas conduction. The transport container 1 has in particular a holding time for the helium He of over 60 days, there also being no restrictions on the natural surrounding temperature.

(44) Although the present invention has been described using exemplary embodiments, it can be modified in various ways.

REFERENCE SYMBOLS USED

(45) 1 Transport container 2 Outer container 3 Base portion 4 Cover portion 5 Cover portion 6 Inner container 7 Gas zone 8 Liquid zone 9 Base portion 10 Cover portion 11 Cover portion 12 Intermediate space 13 Cooling system 14 Coolant container 15 Base portion 16 Cover portion 17 Cover portion 18 Gas zone 19 Liquid zone 20 Intermediate space 21 Thermal shield 22 Base portion 23 Cover portion 24 Cover portion 25 Intermediate space 26 Cooling line 27 Portion 28 Portion 29 Portion 30 Portion 31 Connection line 32 Distributor 33 Manifold 34 Connection line 35 Phase separator 36 Insulating element 37 Copper layer 38 Insulating layer 39 Insulating element 40 Reflective film 41 Spacer 42 Cooling line 43 Cooling line 44 Cooling line 45 Cooling line 46 Cooling line 47 Pipe bend 48 Pipe bend 49 Pipe bend 50 Feed line 51 Discharge line 52 Feed line 53 Discharge line 54 Pressure-maintaining valve 55 Heat conducting film 56 Heat conducting film 57 Heat conducting film a Spacing A Axial direction b Width g Direction of gravitational force GN.sub.2 Nitrogen H Horizontal He Helium LN.sub.2 Nitrogen L2 Length N.sub.2 Nitrogen M1 Center axis α Angle