RU2779257C2 - Radiation source for non-destructive testing, and method and device for its production - Google Patents

Abstract

FIELD: testing equipment.

SUBSTANCE: target for irradiation is made in the form of a sphere. The spherical target for irradiation may consist of metal iridium containing natural or enriched iridium-191. A radiation source of the present invention can be manufactured by the production of a spherical target for irradiation, placement of the spherical target for irradiation in a rotating capsule, and rotation of an impeller of an axial flow by a descending flow of a primary heat carrier of a reactor, due to which the rotating capsule is rotated.

EFFECT: this radiation source provides an improved image of non-destructive testing, having high geometrical resolution, and does not have anisotropy of the radiation source, as well as has high suitability of a target to recycling.

5 cl, 6 dwg

Description

FIELD OF TECHNOLOGY TO WHICH THE INVENTION RELATES

[0001] The present invention relates to a radiation source for non-destructive testing, and a method and apparatus for its production. In particular, the present invention relates to a non-destructive testing radiation source that can obtain an image having a high geometric resolution through non-destructive testing, and that can ensure source intensity uniformity from target to target and is easily regenerated, and a method and apparatus for producing the same.

BACKGROUND OF THE INVENTION

[0002] Japanese Patent Application Laid-Open No. 2010-127825 describes a method for producing non-destructive testing radiation sources (hereinafter, simply referred to as radiation sources) using a nuclear reactor.

SUMMARY OF THE INVENTION

Technical problems to be solved

[0003] However, since three to four disc-shaped targets having, for example, a diameter of 1.5 mm × a thickness of 0.2 mm are traditionally stacked to form a cylindrical radiation source, the radiation emitted from the top and bottom surfaces and the side surface radiation source was anisotropic. In addition, there are problems such as non-uniform source intensity from target to target, low geometric resolution of the non-destructive testing image (e.g. images), difficulty in establishing the assigned source intensity during re-emission due to changes in source intensity from target to target, and insufficient target suitability. to processing.

[0004] The present invention is intended to solve the aforementioned conventional problems, and its object is to provide a non-destructive testing radiation source that provides a non-destructive testing image having high geometric resolution and no radiation source anisotropy, uniform source intensity from target to target, and high usability. target for processing, and a method and device for its production.

Troubleshooter

[0005] The present invention solves the above problems by forming a target for irradiating a radiation source for non-destructive testing in the form of a small sphere with a diameter of about 0.5 to 1.5 mm.

[0006] The spherical target for irradiation may be composed of metallic iridium containing natural or enriched iridium-191.

[0007] The present invention also solves the above problems by a method for producing a radiation source for non-destructive testing, including manufacturing a spherical irradiation target, placing the spherical irradiation target in a rotating capsule, and rotating the axial flow impeller with the downward flow of the primary reactor coolant, whereby the rotating capsule rotates.

[0008] In this case, a spherical target for irradiation can be made by dropping molten iridium into a liquid.

[0009] Alternatively, the spherical target for irradiation may be machined.

[0010] A plurality of spherical targets for irradiation can be loaded into a rotating capsule in several layers.

[0011] The present invention also solves the aforementioned problems by an apparatus for manufacturing a radiation source for non-destructive testing, including a rotating capsule housing a spherical target for irradiation, and an axial flow impeller that is rotated by the downward flow of the primary reactor coolant, and the rotating capsule is driven in rotational movement of the axial flow impeller.

Positive results of the invention

[0012] According to the present invention, a small sphere-shaped irradiation target can improve the geometric resolution of an NDT image compared to a disk-shaped one. In addition, the anisotropy of the radiation source can be eliminated. In addition, the smaller the change in source intensity, the higher the reusability of the target, which makes it possible to economically use scarce resources to reduce material costs. Homogeneous radiation sources for non-destructive testing can be efficiently manufactured for increased cost efficiency. Radiation sources can be easily manufactured at low cost because the capsule is rotated by using the downward flow of the reactor's primary coolant without the capsule being rotated by a motor driven by an external power source. These and other features of the novelty and advantages of the present invention will appear from the following detailed description of the preferred embodiments.

BRIEF DESCRIPTION OF THE DRAWINGS

[0013] FIG. 1 is a diagram showing the first half of the 192 ( ¹⁹² Ir) iridium production procedure according to an embodiment of the present invention;

fig. 2 is a diagram showing its second half;

fig. 3 is a diagram showing the radioactivity of iridium targets obtained by enriching iridium-191 ( ¹⁹¹ Ir) to describe the principle of the present invention;

fig. 4A is a diagram showing the effect (self-shielding effect) of the ¹⁹¹ Ir reaction cross section for the same purpose;

fig. 4B is a diagram showing the rate of generation of ¹⁹² Ir in outer spheres for the same purpose;

fig. 4C is a diagram showing the rate of generation of ¹⁹² Ir in inner spheres for the same purpose;

fig. 5 is a diagram showing the result of evaluating the rotatability of a rotating capsule by means of a reactor primary coolant for the same purpose; and

fig. 6 is a diagram showing a sectional view of a rotating ¹⁹² Ir generation capsule useful in the above embodiment.

DESCRIPTION OF EMBODIMENTS

[0014] An embodiment of the present invention will be described in detail below with reference to the drawings. It should be noted that the present invention is not limited to the description of the following embodiment or practical examples. The components of the following embodiment and practical examples include those that are readily available to those skilled in the art that are substantially identical and within the so-called equivalence range. The components disclosed in the following embodiment and practical examples may be combined as needed and may be selectively used as needed.

[0015] FIG. 1 schematically shows the first half of the ¹⁹² Ir generation procedure according to an embodiment of the present invention.

[0016] As shown in steps A and B in FIG. 1, iridium (Ir) microspheres 12 with a diameter of 1 mm, with a diameter tolerance of ±0.02 mm and a mass of 12 mg, etc. are made, for example, from metallic iridium (Ir) 10, consisting of enriched iridium (Ir), which is, for example, ¹⁹¹ Ir enriched up to 80%.

[0017] The production uses a method of melting metallic iridium. Ir microspheres 12 can be made by dropping molten iridium into a liquid (eg water).

[0018] Alternatively, the Ir microspheres 12 may be machined using finish turning as the machining method.

[0019] Then, as shown in step C in FIG. 1, 28 Ir microspheres 12 are loaded in layers at an appropriate spacing of, for example, 2 mm along the inner periphery of a 20 mm diameter cylindrical aluminum heat pipe 14 having a diameter of, for example, 25 mm. As shown in step D in FIG. 1, for example, eight such layers are loaded by stacking vertically at appropriate distances to provide, for example, a total of approximately 220 radiation targets.

[0020] Then, as shown in step E in FIG. 1, eight layers of heat pipes 14 loaded with Ir microspheres 12 that are targets for irradiation are sealed in a rotating capsule 20 (also referred to as an irradiation ampoule). As shown in step F in FIG. 1 (= step A in FIG. 2), the spinning capsule 20 is inserted into the reactor 40 and irradiated with neutrons while spinning with the downward flow of the reactor's primary coolant. The reason why the rotating capsule 20 is not fixed but rotates is because of the need for uniform neutron irradiation. In the present embodiment, a downward flow of the primary reactor coolant is used, which eliminates the need for an electric motor for rotation, an external power supply, a connecting cable between them, and the like, thereby reducing costs. In addition, installation operations are simple and easy, since the cable-free rotating capsule 20 is simply placed in the primary reactor coolant channel.

[0021] Then, as shown in step B in FIG. 2, the irradiated rotating capsule 20A removed from the reactor 40 is disassembled. As shown in step C in FIG. 2, the irradiated heat pipes 14A including the irradiated Ir microspheres 12A are removed. Then, as shown in step D in FIG. 2, approximately 220 Ir-irradiated 12A microspheres are recovered. Then, as shown in step E in FIG. 2, each of the Ir-irradiated microspheres 12A is loaded into the container 50. As shown in step F in FIG. 2, container 50 is measured and tested for a predetermined dose of γ-radiation (eg, 13 Ci). As shown in step G in FIG. 2, container 50 is sealed. As shown in step H in FIG. 2, sealed containers 50A are transported in a shipping container 52.

[0022] FIG. 3 shows the Ir radioactivity of targets containing enriched ¹⁹¹ Ir according to the present invention.

[0023] To generate ¹⁹² Ir, a thermal neutron flux density of approximately 1 to 2×10 ¹⁴ (1/cm ² ) is required, regardless of the need to enrich ¹⁹¹ Ir. For example, in the case of transport once every two months, the exposure time can be 40 days.

[0024] Then, in FIG. 4 shows the result of monitoring the effect (self-shielding effect) of the ¹⁹¹ Ir reaction cross section also according to the present invention.

[0025] The cross section for the reaction of Ir with neutrons is greater than for uranium, and Ir microspheres in front section neutrons (self-shielding). Let us assume that, as shown on the left in Fig. 4A, neutrons arrive in one direction (in the diagram, left), and Ir microspheres are arranged on the inner circle and the outer circle, as shown in the sectional view shown on the right in FIG. 4A. In such a case, the amount of generation of ¹⁹² Ir is non-uniform, as shown in FIG. 4B ( ¹⁹² Ir generation rate in outer spheres) and FIG. 4C (rate of generation of ¹⁹² Ir in the inner spheres). The rotation makes the generation volume uniform, since the Ir microspheres are irradiated with neutrons in all directions. Note that it is desirable to load the Ir microspheres only on the outer circumference, since the generation volume differs between the inner circumference and the outer circumference.

[0026] In addition, in FIG. 5 shows the result of evaluating the rotatability of a rotating capsule with a reactor primary coolant, also according to the present invention.

[0027] Since the flow velocity in the gap portion is 1000 or more times the rotational speed, the flow on the surface of the cylindrical container passes through the gap portion without rotation. Therefore, a mechanism is needed to convert the axial flow into a vortex flow. Thus, in this system, the excess axial force, as shown in FIG. 5 occurs due to the loss of flow impinging on the cylindrical container and the loss occurring at the gap portion. In such a case, it turns out that in order to rotate the cylindrical container, it is necessary to use a thrust bearing that can withstand an axial force (an axial load of approximately 50 N or more for a gap of 7 mm).

[0028] In FIG. 6 shows a state in which the ¹⁹² Ir generation rotating capsule is inserted into a primary coolant passage vertically extending inside the reactor 40.

[0029] The inner capsule 30, made of, for example, A5052, where the rotating capsule 20 is located, is located in the outer tube 22, made of, for example, A6063. The inner capsule 30 is then inserted into the primary coolant channel of the reactor. The axis of the inner capsule 30 is rotatably supported in the outer tube 22 from above and below by bearings 26 made of, for example, SUS304 and bearing holders 24 made of, for example, A5052. The axle is additionally provided with an axial flow impeller 32 similarly made from A5052. In the diagram, reference numeral 34 denotes a mesh made of, for example, SUS304, and reference numeral 36 denotes a mesh holder made of, for example, A5052. Thus, the axial flow impeller 32 is rotated by the downward flow of the primary reactor coolant, whereby the inner capsule 30 and the rotating capsule 20 therein also rotate.

[0030] The above radiation source has a dose of, for example, 13 Ci due to the fact that the assigned amount of radioactivity after unloading from the reactor is 10 Ci. However, due to the need in the future, a 39 Ci radiation source can be manufactured, i.e. 1.3 times greater than 30 Ci.

[0031] In the above embodiment, the radioactive isotope is described as iridium Ir-192. However, the type of radioactive isotope is not limited to this, and other radioactive isotopes such as cobalt Co-60, cesium Cs-127, ytterbium Yb-169, selenium Se-75 and thulium Tm-170 can be used. The size and number of layers of the heat conductor 14, the number of microspheres, etc. are also not limited to the above embodiment.

LIST OF REFERENCES

[0032]

10 ... metallic iridium (Ir)

12, 12A … iridium (Ir) microsphere

14, 14A … heat pipe

20 ... rotating capsule

30 … inner capsule

32 … axial flow impeller

40 ... nuclear reactor

50, 50A … container

52 ... shipping container

Claims (5)

1. A radiation source for non-destructive testing, containing a target for irradiation in the form of a small sphere with a diameter of 0.5 to 1.5 mm, and the spherical target for irradiation is a metallic iridium containing natural or enriched iridium-191, and the spherical target for irradiation made by dripping molten iridium into a liquid. 2. Method for the production of a radiation source for non-destructive testing, containing the steps in which: make a spherical target for irradiation; placing a spherical target for irradiation in a rotating capsule; and rotating the axial flow impeller with the downward flow of the primary reactor coolant, whereby the rotating capsule rotates. 3. The method for manufacturing a radiation source for non-destructive testing according to claim 2, wherein the spherical target for irradiation is made by dropping molten iridium into a liquid. 4. The method for producing a radiation source for non-destructive testing according to claim 2, wherein a plurality of spherical targets for irradiation are loaded into a rotating capsule in a plurality of layers. 5. A device for the production of a radiation source for non-destructive testing, containing: a rotating capsule, which houses a spherical target for irradiation; and an axial flow impeller which is rotated by the downward flow of the primary reactor coolant, whereby the rotating capsule is rotated by the axial flow impeller.

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