FAST-NEUTRON FLUX RADIATING DEVICE WITH AN IMPROVED SUPPORT FOR A TARGET OF RADIATIONS AND RADIATING METHOD THEREOF

Abstract

Radiating device (1) comprising at least one vacuum chamber (2), an electrostatic accelerator or laser of high power and high frequency (5) for producing at least one primary beam inside the vacuum chamber (2), and an active material layer (4) carried by a support (3) into the vacuum chamber (2) to generate an intense neutron flux when the active layer is struck by the primary beam, and at least one target (6) comprising a material, with the target (6) disposed on the same side of the electrostatic accelerator or power laser (5) as the active material layer (4).

Claims

1. A radiating device (1) comprising: at least one vacuum chamber (2), a first generator of a primary energy beam (5) for producing a first primary energy beam inside the vacuum chamber (2), and an active material layer (4) carried by a support (3) into the vacuum chamber (2), thereby generating an intense neutron flux when a nuclear fusion reaction is triggered on the active material via the energy of said beam, and at least one target (6) comprising a material to be irradiated in the vacuum chamber (2), in which the at least one target (6) is disposed on the same side of an origin of the primary beam with respect to the active material layer (4).

2. The radiating device according to claim 1, wherein the at least one target (6) comprises a cavity and is arranged so that, in use, the primary beam passes through the cavity and reaches the active layer (4).

3. The radiating device of claim 1, wherein the support (3) is movable and the layer of active material (4) is applied on the support along a path such that, while the support is in motion, the primary beam intercepts a portion of the active material layer to generate the neutron flux.

4. The radiating device of claim 1, further comprising a cooling circuit configured to remove heat from the support and arranged so that the active material layer and the primary beam are on the same side with respect to the cooling circuit so that the neutron flux does not pass through the circuit as it reaches the at least one target (6).

4. The radiating device of claim 3, wherein the support is hollow and rotatable and comprises a central body (10) with inclined side walls (11) diverging towards a head flange (12) which carries the active layer (4) and the cooling circuit comprises a first cooling fluid sealed inside the support (3) to reach the head flange (12) and a second cooling fluid arranged in heat exchange with the first cooling fluid through the inclined side walls (11).

6. The radiating device of claim 4, further comprising: a second generator of a second primary energy beam, a further active material layer applied on the support, and a further target, wherein optionally the further target is arranged on an opposite side of the said first generator of a primary energy beam, active layer and target with respect to a plane passing through said support, said second generator of the second primary energy beam being configured to generate a second primary energy beam to hit the further active material layer and to generate a further flow of fast neutrons for the further target.

7. The radiating device of claim 1, wherein the active layer (4) comprises Tritium or Lithium and the at least one target (6) or the further target comprises one of molybdenum-100, copper-65, zinc-64 or tin-112.

8. A method for generating radiation in a vacuum chamber inside which there is a support (3) and an active layer (4) carried by the support (3), comprising the steps of: facing a target (6) having a cavity on the active layer (4) emitting a primary energy beam 5 directed on the active layer (4) through the cavity; triggering a nuclear fusion reaction on the active layer (4) by means of the primary energy beam comprising accelerated deuterons (D+) or lasers, so that a flux of produced neutrons intercepts the target (6) in a non-degraded way in energy and intensity.

9. The method of claim 8, wherein the active layer (4) comprises tritium (T), deuterium and tritium or lithium-7.

10. The method of claim 8, wherein the vacuum chamber, support (3) and active layer (4) are contained in a radiating device of claim 1.

11. The method of claim 8, wherein the active layer (4) when struck by the primary energy beam generates a flux of fast neutrons.

12. The method of claim 11, wherein the flux of fast neutrons have an energy of energy 2.45 MeV or 14.1 MeV.

13. The method of claim 8, wherein the active layer 4 is arranged orthogonally to the direction of the primary energy beam 5.

14. The radiating device of claim 1, wherein the active layer 4 is arranged orthogonally to the direction of the primary energy beam 5.

15. The radiating device of claim 1, wherein the at least one target 6 comprises a concave surface.

16. The radiating device of claim 1, wherein the target 6 comprises a cylinder coaxial with the direction of the primary beam, having a through hole 8 of adequate area to allow the passage of the beam itself without obstruction.

17. The method of claim 8, wherein an operator uses a sample holder 7 to replace material to be irradiated at the end of an operation.

18. The method of claim 17, wherein the target 7 is positioned as close to the layer 4 as possible but, in the case of a rotating support 3, without hindering the rotation that is necessary in high power systems to dissipate thermal energy.

19. The radiating device of claim 1, wherein the target 6 comprises copper-natural or zinc-natural.

20. The method of claim 8, wherein the target 6 comprises copper-natural or zinc-natural to generate a reaction generating Cu-65(n,2n)Cu-64 or Zn-64(n,p)Cu-64 for the production of copper-64 (Cu-64).

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0022] The invention is described below on the basis of non-limiting examples illustrated by way of example in the following figures, which refer respectively to:

[0023] FIG. 1 a schematic view of a radiating device according to the present invention; and

[0024] FIG. 2 is a schematic section of a preferred embodiment of an element of FIG. 1.

DETAILED DESCRIPTION OF THE INVENTION

[0025] The present invention relates to the positioning, relative to a source of fast, quasi-monochromatic neutrons e.g. of energy about 14.1 MeV, and the specific geometrical configuration of a target to be subjected to neutron irradiation to obtain high neutron fluxes under effective conditions, i.e., with the right energy and not degraded in intensity and, consequently, allowing for high yields of the produced activity. According to an embodiment example, neutrons are obtained from the reaction .sup.3H(d,n).sup.4He (D-T), but can also be extended to fast neutrons of energy 2.45 MeV obtained from the reaction .sup.2H(d,n).sup.3H (D-D) or fast neutrons of energy 13.36 MeV obtained from reaction .sup.2H(.sup.7Li,n).sup.8Be (D-Li) or fast neutrons that have a continuous energy spectrum and can be used for material activation or other applications. The present invention applies to the general field of irradiation of a target by a neutron flux and, based on the energy of the neutrons, the applications of the irradiated target are varied. For example, when the energy is a little over 10 MeV the application of the target is also in the field of nuclear medicine and when the energy is a few, e.g. 2.45, MeV, there may be various applications in laboratories for the study of irradiated materials for both basic and applied sciences.

[0026] According to the preferred example in FIG. 1, the radiating device 1 of the present invention comprises a vacuum chamber 2, with pressure inside between 10.sup.−5 and 10.sup.−9 bar , a rotatable and cooled support 3 inside the vacuum chamber 2, an active material layer 4, e.g. Tritium adsorbed on a support, and at least one electrostatic accelerator 5 or laser of sufficient power to constitute a high-energy primary beam, in use, the accelerated ions define a high-energy primary beam that intercepts the active material layer 4 so as to generate a neutron flux that propagates spherically, i.e. equiprobably over the entire solid angle. The device 1 further comprises a target 6 comprising a material to be irradiated, e.g. Molybdenum 100, held by a sample holder 7 at a position facing the active material layer 4. Preferably, the target 6 is shaped taking into account area and profile of the primary beam normal section as well as the size of the vacuum chamber, so as to maximize the fraction of neutrons that can be intercepted. As an example, a cylindrically shaped target 6 having height H and internal hole of radius R, collects the fraction, f, of secondary beam approximately equal to f=(2*π*H*R−π*R2)/(4*π*H2). For appropriate values of H and R (with H>2*R), the fraction therefore of intercepted neutrons approaches 50% of the total available neutrons.

[0027] According to the invention, the target 6 is arranged in the half-space from which the charged particle beam or laser beam (primary beam) originates, but without interfering with the same. There are numerous possible configurations in terms of arrangements and geometries that can be used. In any case, the target 6 defines a central hole to allow the passage of the accelerated charged particle beam (primary beam) directed towards the active material layer 4. In addition, the target 6 defines a hollow i.e. concave surface exposed to the neutron source, in order to uniformly collect as many neutrons emitted from the active material layer as possible, limiting dispersions. With these prescriptions, the simplest form for the target 6 is that of a cylinder coaxial with the direction of the primary beam, having a through hole 8 of adequate area to allow the passage of the beam itself without obstruction. However, one cannot exclude, e.g., hemi-spherical and/or hemi-toroidal geometries, which may increase the fraction of neutrons intercepted by the target 6 approaching the value of 50% of the entire neutron flux produced, i.e., neutrons are released both towards the target 6 and towards the support 3 and neutrons that are directed in the latter direction quickly lose energy due to obstacles encountered, e.g., the support itself, the cooling circuit etc. Therefore, the value of 50% is a limiting value that, due to the through-hole of the target, will never be reached. In use, the accelerated beam of charged particles (primary beam), consisting of deuterons (D+), directed toward the active material layer 4 on which tritium (T) is implanted, crosses, without being disturbed, the target 6 located near to layer 4. The D-T reaction produces neutrons at about 14 MeV energy. The use of Lithium-7 on the active layer involves, instead, D-Li7 reactions with production of neutrons from 13.36 MeV energy starting from a material, i.e. Li, not radioactive and therefore easier to treat especially in plants intended for the production of radioisotopes for nuclear medicine and not used in research on nuclear fusion. The use of Deuterium implanted on the active layer involves D-D reactions with neutron production from 2.45 MeV. The target 6, which can e.g. also have a concave shell shape with a through-hole, with an axis coincident with the direction of the accelerated deuteron beam. By means of the sample holder 7 an operator can replace the material to be irradiated at the end of the operation. The target 7 is preferably positioned as close to the layer 4 as possible but, in the case of a rotating support 3, without hindering the rotation that is necessary in high power systems to dissipate thermal energy.

[0028] In the half-space opposite to that of origin of the primary beam, with respect to the active surface, it is possible, compatibly with the encumbrance materials used to cool the same, to place, always in the vacuum chamber 2, an additional target 6′. In this way the conditions are realized for which the neutrons, emitted at 4π in the nuclear fusion reaction, D-T, D-7Li, or D-D, which takes place on the active surface, are used in the maximum condition of geometric efficiency. Finally, it becomes clear that modifications or variations can be made to the fast neutron radiating device described and illustrated herein without departing from the scope of protection as defined by the appended claims.

[0029] It is possible to make targets of various materials, such as copper-natural or even better zinc-natural on which to induce reactions such as Cu-65(n,2n)Cu-64 or Zn-64(n,p)Cu-64 for the production of copper-64 (Cu-64) which is a radioisotope theranostic. It should be noted that Zn-64 is widespread and obtainable commercially in discrete quantities since, for example, it can be obtained from natural zinc, in which it is present in percentages close to 50%. By means of the present invention, it is possible to process quantities of a few kilograms e.g. 10 kg, in order to obtain a production of radioisotopes e.g. for radiotherapeutic use capable of satisfying the growing market related to the development of nuclear medicine.

[0030] The advantage of using neutrons at 14 MeV to produce Cu-64, which is also produced with cyclotrons (reactions n, p on nickel-64), is that you do not have to use nickel that is very expensive and has an extremely localized extraction and production and therefore subject to constraints.

[0031] For example, even indium-111 (In-111), which is another radioisotope used in nuclear medicine, can be obtained from a generator of tin-111 (Sn-111) in turn produced by reaction Sn-112(n,2n)Sn-111 with neutrons at 14 MeV. In this case, as is the case for Mo-99/Tc-99m, the presence of the generator allows the radioisotope of interest (In-111) to be used far from the production center.

[0032] The target 6 may have additional shapes with a cavity arranged to allow the primary energy beam to reach the active layer 4. For example, the target may have a U-shaped cross-section, despite the fact that in this case the yield is lower than having a through-hole that is closed in the circumferential direction. The fusion reaction and the energy beam that initiates it generate a large amount of heat and, particularly when multiple primary beams are present, a cooling assembly of the radiating device 1 includes an on-board cooling fluid carried by the support 3 and a second cooling fluid in heat exchange with the first cooling fluid through the walls of the support 3.

[0033] For example, the support 3 is hollow and sealed. The support also has a central body 10 with inclined walls 11 and a flange 12 protruding from the inclined walls and on which the active layer 4 is disposed. When the support 3 is rotated by a motor, e.g., a rotary motor driving a gearing pinion in a gear wheel 13 attached to the support 3, the coolant rises by the action of centrifugal force along the inclined walls toward the flange 12.

[0034] Thus, the primary energy beam initiates the nuclear fusion reaction.

[0035] Once this reaction is initiated, the thermal power released on the active layer 4 causes the first phase change of the first cooling fluid and the first fluid, preferably water, evaporates. In particular, the vapor and the still-liquid refrigerant generate a pressure gradient between a head 14 of the support 3, toward which the side walls 11 diverge and where the flange is located, and a bottom 15 of the support 3.

[0036] Then, the pressure difference moves the generated vapor toward the bottom 15, causing the second phase change, i.e., condensation of the vapor. In particular, the vapor, by impacting on the side surface 11 and preferably on a base 16, accomplishes the second phase change. In more detail, the vapor, by condensation, exchanges heat with the second coolant maintained at a lower temperature.

[0037] After the second phase change, the first coolant fluid migrates back to the head flange 12 driven by the centrifugal force due to the rotation of the support 3. Advantageously, the perfectly sealed hollow support 3 allows for replacement of the hollow support itself, if necessary, avoiding leakage to the external environment of radioactive products possibly contained in the first fluid. In particular, in the case where the first coolant fluid is water, the sealed hollow support 3 prevents leakage of tritium water produced during operation of the device 1.

[0038] The central body 10 is immersed at least partially in a tank 17 within which the second fluid cools the first fluid. The vacuum chamber 2 may contain all or a large part of the central body 10 or, by means of suitable seals, contain only the part of the support 3 on which the active layer 4 and the target 6 are located.