Irradiation unit for the emission of nuclear radiation and corresponding method of manufacturing an irradiation unit

Abstract

This irradiation unit (10) for emitting nuclear radiation having an activity in the range of 9kCi to 15KCi, comprising: - a cylindrical irradiation vessel (18) forming a closed internal volume (22); and - a plurality of irradiation sources (20) located in the closed inner volume (22); wherein: - the irradiation sources (20) are essentially spherical; - the cylindrical irradiation vessel (18) is a single-walled vessel; and - the irradiation unit (10) further comprises a binder (21 ) arranged in the closed inner volume (22), wherein the irradiation sources (20) are embedded in the binder (21).

Description

[0001] Irradiation unit for the emission of nuclear radiation and corresponding method of manufacturing an irradiation unit

[0002] The invention relates to the field of irradiation units for the emission of nuclear radiation, for example for use in sterilisation systems. The invention also relates to a method of manufacturing such an irradiation unit.

[0003] For the production of irradiation units, it is generally known that irradiation sources are inserted in the form of cylinders into the core of a nuclear reactor in order to activate these sources. Reactors such as the CANDU reactor (from the abbreviation CANada Deuterium Uranium) are generally used for this purpose due to their high neutron flux.

[0004] Pressurised water reactors have a lower neutron flux than CANDU reactors, and the activation of known irradiation sources in this context is not sufficient to provide irradiation sources that meet the expectations of the irradiation unit market (i.e. about 12 kCi / irradiation unit).

[0005] Solutions have already been proposed to improve the activation of irradiation sources and thus provide more efficient irradiation units. One solution, for example, is to use zirconium layers between the layers to be activated during activation.

[0006] However, this solution is not entirely satisfactory, as the Zr material must be removed before the activated material can be used in the irradiation unit.

[0007] One aim of the invention is therefore to obtain an irradiation unit which is highly radioactive and can be easily manufactured without significant effects on the operation of nuclear reactors, e.g. from a PWR (Pressurised Water Reactor).

[0008] To this end, the invention relates to an irradiation unit for the emission of nuclear radiation with an activity in the range from 9kCi to 15KCi, comprising:

[0009] - a cylindrical irradiation vessel forming a closed internal volume; and

[0010] - a large number of irradiation sources located in the closed inner volume; where:

[0011] - the irradiation sources are essentially spherical;

[0012] - the cylindrical irradiation vessel is a single-walled vessel; and

[0013] - the irradiation unit further comprises a binder arranged in the closed inner volume, wherein the irradiation sources are embedded in the binder.

[0014] The use of essentially spherical irradiation sources is particularly advantageous as such irradiation sources have a small operational footprint on the nuclear reactor in which the sources are irradiated, while being particularly well activated due to the empty space between the sources. In addition, the use of a binder enables sufficient safety even with a single-walled irradiation vessel, which means that the number of irradiation sources accommodated in the irradiation vessel can be increased and the activity of the irradiation unit can be increased.

[0015] In a preferred embodiment, the irradiation unit according to the invention has one of the following features:

[0016] - the irradiation sources are made of Co-60 or a Co-60 alloy;

[0017] - an axial length of the irradiation vessel is between 200 mm and 500 mm and the internal diameter of the irradiation vessel is between 6 mm and 20 mm;

[0018] - a radius of the irradiation sources is smaller than 0.85 mm;

[0019] - the binder is a resin;

[0020] - the number of irradiation sources comprises between 2000 and 6000 irradiation sources;

[0021] - the irradiation sources fill between 30% and 70% of the volume of the closed internal volume; and

[0022] - the irradiation sources of the plurality of irradiation sources consist of different materials and / or have a different specific activity.

[0023] The invention also relates to a method of manufacturing an irradiation unit as described above, the method comprising the following steps:

[0024] - Introduction of a plurality of substantially spherical irradiation sources into at least one activation vessel to fill the activation vessel, the irradiation sources being in an inactivated state;

[0025] - Insertion of at least one filled activation vessel into a nuclear reactor;

[0026] - Activation of the radiation sources introduced in at least one activation vessel;

[0027] - Removal of at least one activation vessel from the nuclear reactor;

[0028] -Transfer of the activated irradiation sources from at least one activation vessel into a container of a cylindrical irradiation vessel;

[0029] - Filling the container of the cylindrical irradiation vessel with a binder so that the irradiation sources are embedded in the binding agent;

[0030] - Closing the container of the cylindrical irradiation vessel to form the irradiation unit.

[0031] According to a preferred embodiment, a plurality of activation vessels were used in the process steps.

[0032] Further features and advantages of this invention are apparent from the following description with reference to the accompanying drawings, which show a non-limiting example. In these figures:

[0033] - Figure 1 is a cross-sectional view of an irradiation unit according to the invention;

[0034] - Figure 2 is a further cross-sectional view of the irradiation unit from Figure 1 , perpendicular to the cross-sectional view from Figure 1 ; - Figure 3 is a flowchart of the steps of the method for manufacturing an irradiation unit according to the invention; and

[0035] - Figure 4 is a schematic representation of a step in the manufacture of the irradiation unit and of such a unit located in an irradiation facility.

[0036] Figure 1 shows a cross-section of an irradiation unit 10.

[0037] As explained later, such an irradiation unit 10 is manufactured using a nuclear reactor 12 and is configured for use in an irradiation facility 14, for example, as shown in Figure 4.

[0038] The irradiation unit 10 is designed to emit nuclear radiation with an activity in the range from 9kCi to 15KCi. In other words, the irradiation unit 10 is radioactive and configured to have an activity in the range of 9kCi to 15KCi.

[0039] As shown in Figures 1 and 2, the irradiation unit 10 comprises a cylindrical irradiation vessel 18, a plurality of irradiation sources 20 and a binder 21 .

[0040] The irradiation vessel 18 is essentially cylindrical and defines, for example, a longitudinal axis L-L'.

[0041] As shown in Figures 1 and 2, the irradiation vessel 18 forms a closed internal volume 22. The closed internal volume 22 is cylindrical, for example.

[0042] The irradiation vessel 18 is single-walled, i.e. it comprises a single wall 24 which separates the closed inner volume 22 from an environment 26 of the irradiation unit 10.

[0043] The irradiation vessel 18 is moulded, for example, from a radiation-permeable material and is made of stainless steel, for example.

[0044] An axial length L of the irradiation vessel 18, i.e. a length, for example an inner length, of the irradiation vessel 18 along the longitudinal axis L-L', is for example between 200 mm and 500 mm.

[0045] An internal diameter D of the irradiation vessel 18, i.e. a diameter of the internal volume 22, measured radially to the longitudinal axis L-L', is for example between 6 mm and 20 mm.

[0046] As shown in Figure 2, the irradiation vessel 18 comprises, for example, a container 28 and a lid 30, wherein the container 28 and the lid 30 define the closed internal volume 22. The container 28 is single-walled and the lid 30 is also single-walled, for example.

[0047] The container 28 and the lid 30 are movable relative to each other, for example. The container 28 and the lid 30 then form the irradiation vessel 18, for example, when the lid 30 is attached to the container 28.

[0048] As shown in Figures 1 and 2, the plurality of irradiation sources 20 are located in the closed inner volume 22, that is, in the irradiation vessel 18. The plurality of irradiation sources 18 comprises, for example, between 2000 and 6000 irradiation sources 20. In other words, between 2000 and 6000 irradiation sources 20 are located in the closed inner volume 22.

[0049] For example, the radius R of each irradiation source is smaller than 0.85 mm. For example, the radius of each irradiation source is identical.

[0050] The irradiation sources 20 emit radioactive radiation, in particular gamma radiation. In particular, the irradiation sources 20 are formed from a material that was activated in the nuclear power plant, as will be described in more detail later.

[0051] The irradiation sources 20 consist, for example, of Co-60 or a Co-60 alloy. Alternatively, the radiation sources 20 consist of any other radioactive alloy.

[0052] In a particular embodiment, each irradiation source 20 of the plurality of irradiation sources is made of the same material and has, for example, a similar activity.

[0053] Alternatively, the irradiation sources 20 of the plurality of irradiation sources 20 consist of different materials and / or have a different specific activity.

[0054] The irradiation sources 20 fill between, for example, 30% and 70% of the volume of the closed inner volume 22. The remainder of the volume of the closed inner volume 22 is filled, for example, by the binder 21 .

[0055] As shown in Figures 1 and 2, the binder 21 is arranged in the closed inner volume 22. In particular, the binder 21 is arranged in the closed interior in such a way that the radiation sources 20 are embedded in the binder 21 .

[0056] The binder 21 is preferably radiolucent. The binder 21 is created, for example, by curing a liquid material. The binder 21 is a resin, for example.

[0057] On the right-hand side of Figure 4, an irradiation system 14 is shown, which comprises an irradiation unit 10 as described above. For example, the irradiation system 14 comprises a receiving area 32 configured to receive the irradiation unit 10. The use of an irradiation unit 10 as described above is particularly advantageous due to the high activity of the irradiation unit 10, which makes the irradiation system 14 particularly efficient.

[0058] With reference to Figure 3, a method 100 for manufacturing the irradiation unit 10 is now described.

[0059] As already mentioned, an irradiation unit 10 is manufactured as described above with the aid of at least one nuclear reactor 12.

[0060] As shown in Figure 4, the nuclear reactor 12 comprises, for example, at least one introduction channel 34. The nuclear reactor 12, for example, is a pressurised water reactor (or PWR reactor).

[0061] For example, the insertion channel 34 is configured such that it can accommodate at least one activation vessel 36. In the example of Figure 4, the nuclear reactor 12 comprises two introduction channels 34, each of the introduction channels 34 being configured to receive an activation vessel 36. In alternatives, a plurality of nuclear reactors 12 each comprise an insertion channel 34 configured to receive an activation vessel 36.

[0062] In an introduction step 110, a plurality of irradiation sources 20 are introduced into at least one activation vessel 36 to fill the activation vessel 36.

[0063] For example, the activation vessel 36 is completely or partially filled with the plurality of irradiation sources 20. For example, the activation vessel 36 is configured to hold 1000 to 4000 irradiation sources 20.

[0064] In the example of Figure 4, the plurality of irradiation sources 20 in the introduction step 110 are introduced into two different activation vessels 36 in the introduction step 110.

[0065] The irradiation sources 20 introduced into the activation vessel 36 are as described above, except that they are not yet activated. In other words, the irradiation sources 20 are in an inactivated state in the introduction step 110.

[0066] The non-activated irradiation sources 20 consist, for example, of Co-59 or a Co-59 alloy.

[0067] In an insertion step 120, at least one filled activation vessel 36 is inserted into a nuclear reactor 12, for example into the core of a nuclear reactor. In the example of Figure 4, the two filled activation vessels 36 are introduced into the reactor, for example each into a separate introduction channel 34.

[0068] In an activation step 130, the irradiation sources 20 arranged in the activation vessels 36 are activated. The irradiation sources 20 are activated by the radiation generated by the operation of the nuclear reactor 12.

[0069] For example, the irradiation sources 20 are fully activated after an irradiation time of between 2 and 6 years in the nuclear reactor.

[0070] In a removal step 140, at least one activation vessel 36 is then removed from the nuclear power plant. In the example in Figure 4, the two activation vessels 36 are removed.

[0071] The removal step 140 takes place when the irradiation sources 20 are activated.

[0072] In a transfer step 150, the activated irradiation sources 20 are transferred from at least one activation vessel 36 to the container 28 of the cylindrical irradiation vessel 18. In the example of Figure 4, the activated irradiation sources 20 are transferred from the two activation vessels 36 into the container 28 of the cylindrical irradiation vessel 18.

[0073] In a filling step 160, the container 28 of the cylindrical irradiation vessel 18 is filled with a binder. The container is filled in such a way that the irradiation sources 20 are embedded in the binder. The filling step 160 is followed, for example, by a solidification step (not shown), in which the binder 21 is solidified if necessary.

[0074] In a sealing step 170, the container 28 containing the irradiation sources 20 and the binder 21 is sealed, for example by placing the lid 30 on top. The container 28 sealed in this way then forms the irradiation unit 10.

[0075] As shown on the right in Figure 4, such an irradiation unit 10 can then be introduced into an irradiation facility 14, for example into the receiving area 32 of such an irradiation facility 14, in particular for the irradiation of goods to be irradiated.

[0076] The use of spherical irradiation sources 20 is particularly advantageous, since the inherent gaps when stacking such irradiation sources 20 lead to very good activation of these irradiation sources 20.

[0077] In addition, the use of a binder 21 enables the safe use of a single-walled irradiation vessel 18, which leads to an optimisation of the usable space for the irradiation sources 20 and to a high output of the irradiation unit 10.

[0078] The use of Co-60 or a Co-60 alloy for the irradiation sources is particularly advantageous for the emission of gamma rays used for the irradiation system14. The dimensions of the irradiation vessel 18 also allow good integration into such irradiation systems 14.

[0079] The dimensions of the irradiation sources 20, their density in the inner volume 22 and their number are particularly favourable for fast and effective activation and for forming an effective irradiation unit 10.

[0080] The use of resin as a binder 21 ensures that the radioactive emission is not disturbed and at the same time makes it easy to manufacture the irradiation unit 10.

[0081] The use of irradiation sources 20 made of different materials and / or with different specific activities ensures that the irradiation unit 10 is optimally adapted to the needs of the irradiation system 14 in which it is integrated.

Claims

CLAIMS1 An irradiation unit (10) for emitting nuclear radiation having an activity in the range of 9kCi to 15KCi, comprising:- a cylindrical irradiation vessel (18) forming a closed internal volume (22); and- a plurality of irradiation sources (20) located in the closed inner volume (22); wherein:- the irradiation sources (20) are essentially spherical;- the cylindrical irradiation vessel (18) is a single-walled vessel; and- the irradiation unit (10) further comprises a binder (21 ) arranged in the closed inner volume (22), wherein the irradiation sources (20) are embedded in the binder (21 ).2.- The irradiation unit (10) according to claim 1 , wherein the irradiation sources (20) consist of Co-60 or of a Co-60 alloy.3.- The irradiation unit (10) according to claim 1 or 2, wherein an axial length of the irradiation vessel (18) is between 200 mm and 500 mm and wherein an inner diameter (D) of the irradiation vessel is between 6 mm and 20 mm.4.- The irradiation unit (10) according to one of the preceding claims, wherein a radius of the irradiation sources (20) is smaller than 0.85 mm.5.- The irradiation unit (10) according to any one of the preceding claims, wherein the binder (21) is a resin.6.- The irradiation unit (10) according to any one of the preceding claims, wherein the plurality of irradiation sources (20) comprises between 2000 and 6000 irradiation sources (20).7.- The irradiation unit (10) according to any one of the preceding claims, wherein the irradiation sources (20) fill between 30% and 70% of the volume of the closed inner volume (22).8.- The irradiation unit (10) according to any one of the preceding claims, wherein the irradiation sources (20) of the plurality of irradiation sources are made of different materials and / or have different specific activity.9.- A method (100) of manufacturing an irradiation unit (10) according to any one of claims 1 to 8, the method comprising the steps of:- Introducing (110) a plurality of substantially spherical irradiation sources (20) into at least one activation vessel (36) to fill the activation vessel (36), wherein the irradiation sources (20) are in an inactivated state;- Insertion (120) of the at least one filled activation vessel (18) into a nuclear reactor (12);- Activation (130) of the irradiation sources (20) introduced into the at least one activation vessel (18);- Removal (140) of the at least one activation vessel (18) from the nuclear reactor (12);- T ransfer (150) of the activated irradiation sources (20) from the at least one activation vessel (36) into a container (28) of a cylindrical irradiation vessel (18);- Filling (160) the container (28) of the cylindrical irradiation vessel (18) with a binder (21 ), so that the irradiation sources (20) are embedded in the binder (21);- Closing (170) the container (28) of the cylindrical irradiation vessel (18) to form the irradiation unit (10).10.- A method (100) of manufacturing an irradiation unit according to claim 9, wherein a plurality of activation vessels (36) are used in the method steps.

Images