JPH06331570A - High-speed neutron radiography and image recording body for high-speed neutron radiography - Google Patents

Abstract

PURPOSE:To obtain a clear image with a high resolution using a high-speed neutron. CONSTITUTION:An image recording body 5 where a film-shaped light emitting converter 3 and a sensitized film 4 are adhered is laid out at the rear of a subject 1, proton rays are applied from the front of the subject 1 toward a Be target 7 by a cyclotron 2, and high-speed neutrons discharged from the target 7 are applied, thus enabling the light emitting converter to emit light and sensitizing the sensitized film 4 and hence enabling the sensitized body to be sensitized with a high resolution and achieving an improved working efficiency.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fast neutron radiography method for obtaining a transmission image of an object using fast neutrons and an image recording body used for the method.

[0002]

2. Description of the Related Art Conventionally, a radiography method has been known in which low-speed neutrons (eV units) are used to image defects, internal properties, structures, etc. of a subject for nondestructive inspection. A fast neutron radiography method, in which the transparency is improved by utilizing faster neutrons (MeV unit), has been proposed and is being practically used. In this fast neutron radiography method, fast neutrons (0.1-1
By irradiating the subject with about 0 MeV) and irradiating the polymer material in the rear with neutrons that have passed through the subject, recoil proton tracks are generated in the polymer material. Since this track is very small and difficult to observe as it is, the procedure of enlarging the track by subjecting the polymer material to an etching treatment by immersing it in a strong alkaline solution, and transferring this track to a photographic film Is stepping on.

[0003]

However, in the above method, it is necessary to irradiate neutrons for a long time in order to surely generate a track on the polymer material. Further, after the tracks are formed, the work of etching and transfer to the photographic film is further required, which is a troublesome work and inefficient. Therefore, a thin plate or a film-like light emitting converter having a thickness of about 0.5 mm to several mm with a light emitting layer formed on the back surface is arranged behind the subject, and the light emitting state of the light emitting converter is recorded in a television camera or a light sensitive film. The method of exposing to light is performed.

However, the above-mentioned method using the luminescence converter has a problem that it has a low resolution and is not suitable for analysis of small defects and structures of an object. When high resolution is required, work efficiency is poor. However, there is a constraint that the above etching method, which has a good resolution, must be used. The present invention has as its basic object to solve the above problems, and an object thereof is to provide a fast neutron radiography method having a high resolution and excellent work efficiency, and an image recording body for the radiography.

[0005]

In order to solve the above problems, the fast neutron radiography method of the present invention provides an image recording body in which a film-like fast neutron emission converter and a photosensitive film are adhered to the back of a subject. The luminescent converter is arranged so that fast neutrons are irradiated from the front of the subject, and the luminescence converter is caused to emit light by the fast neutrons that have passed through the subject to expose the photosensitive film.

The image recording body for fast neutron radiography of the present invention is characterized in that a photosensitive film is brought into close contact with the neutron irradiation back side of the film-form fast neutron emission converter. The luminescence converter includes a neutron detector that produces recoil protons upon irradiation with neutrons, and a light emitter. For example, a film-shaped luminescence converter can be obtained by kneading a polymer material serving as a neutron detector and a light emitter material and curing the mixture. The film thickness of this light emitting converter is preferably 10 to 200 μm.

[0007]

In other words, according to the present invention, the fast neutrons applied to the subject are transmitted through the subject and applied to the luminescence converter. In the luminescence converter, recoil protons are generated, and the recoil protons cause the light-emitting body to emit light, which exposes the photosensitive film adhered to the back surface side. By forming the light emitting converter into a film, the light emission amount is reduced, but the resolution is dramatically improved. The reduction in the amount of light emission enables the photosensitive film to be sufficiently exposed to light because the photosensitive film is in close contact with the emission converter.

The thickness of this light emitting converter is 200 μm.
If it exceeds, the resolution is lowered and it becomes difficult to measure defects such as small dimensions. If the thickness is less than 10 μm, the amount of emitted light is insufficient and the photosensitive film cannot be sufficiently exposed.
It is desirable to set the range to. In addition, for the same reason, it is more preferable that the thickness is in the range of 30 to 100 μm.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the accompanying drawings. First, the radiography apparatus will be described. A cyclotron 2 that emits fast neutrons is arranged in front of a subject 1 that irradiates neutrons for non-destructive inspection, and behind the subject 1, a light emission with a film thickness of 40 μm. An image recording body 5 including a converter 3 and a photosensitive film 4 adhered to the back surface of the converter 3 is arranged. Image recording body 5
Are attached to the frame 6 for shape retention. The shape retention of the image recording body 5 is not limited to the one performed in a frame. The point is that it can hold the image recording material,
The structure does not matter.

The above-mentioned luminescence converter 3 was manufactured by dissolving MMA polymer as a neutron detector in an organic solvent, mixing ZnS as a luminescent material in this liquid, and drying the mixture to remove the organic solvent. The ZnS content was adjusted to 60 wt%. Also, for comparison, a comparative device was prepared in which a polymer resin plate that causes a recoiled proton track was disposed behind the subject as an image recording body. Further, as another comparative example, the above MMA polymer is 2 mm
An image recording body was prepared in which a thin thin plate was formed, and ZnS was applied to the back surface of the thin plate to form a light emitting layer, and an apparatus was prepared in which the image recording body was placed behind the subject in the same manner as described above.

Explaining the operation of the apparatus of the embodiment, the proton beam accelerated to 16 MeV by the cyclotron 2 is Be.
The target 1 was irradiated, and the fast neutron beam 7a having an energy distribution of 0 to 2 MeV emitted from the target 7 was irradiated to the subject 1. The fast neutrons passed through the subject 1 and irradiated the image recording body 5. In the image recording body 5, the luminescence converter 3 emits light by the irradiation of neutrons,
Photosensitive film 4 was exposed. When this photosensitive film 4 was developed and the recorded image was observed, a hole having a diameter of 0.5 mm in the subject 1 was clearly identified as an image.

On the other hand, in the comparative example by the etching method, although a resolution similar to that of the above-mentioned embodiment was obtained, it took five times as long as that in the above-mentioned embodiment until a necessary track was formed on the image recording material. Needed Further, since the etching process and the transfer work to the photographic film were required thereafter, the work efficiency was extremely poor. Further, in the comparative example using the thin plate image recording body, it was almost difficult to identify the 0.5 mm hole in the subject 1 on the image, and the resolution was insufficient.

[0013]

As described above, according to the fast neutron radiography method of the present invention, an image recording body in which a film-like fast neutron emission converter and a photosensitive film are closely attached is arranged behind the subject, Irradiate fast neutrons from the front of the, to sensitize the photosensitive film by emitting light from the luminescence converter with the fast neutrons that have passed through the subject, so that the film-like luminescence converter is sufficiently lit, at a high resolution,
The photoconductor can be exposed to light. Moreover, since special work such as etching is not required, there is an effect that radiography can be performed efficiently. Further, according to the image recording body for fast neutron radiography of the present invention, since the photosensitive film was adhered to the neutron irradiation back surface side of the film-form fast neutron luminescence converter, by using in the above method, it is clear at high resolution. There is an effect that various recorded images can be easily obtained.

[Brief description of drawings]

FIG. 1 is a schematic view showing an embodiment of the present invention.

[Explanation of symbols]

 1 Subject 2 Cyclotron 3 Emission Converter 4 Photoreceptor 5 Image Recorder 7a Fast Neutron Beam

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification number Reference number within the agency FI Technical display location H05H 13/00 9014-2G (72) Inventor Koji Yoshii 2-Shirahone Shirane, Tokai-mura, Naka-gun, Ibaraki Prefecture 22 Inside the Nuclear Engineering Research Facility, Faculty of Engineering, University of Tokyo (72) Inventor Hiroteru Hasegawa 1-1 Sadamu Sakai-cho, Sakai-gun, Fukui Prefecture Fukubi Kagaku Kogyo Co., Ltd. Sakai Plant

Claims (3)

[Claims] 1. An image recording body in which a film-form luminescence converter for fast neutrons and a photosensitive film are closely attached to the back of a subject, fast neutrons are irradiated from the front of the subject, and fast neutrons passing through the subject Fast neutron radiography method characterized by exposing a photosensitive film by causing an emission converter to emit light 2. An image recording body for fast neutron radiography, characterized in that a photosensitive film is adhered to the neutron irradiation back surface side of a film-form luminescence converter for fast neutrons. 3. The film thickness of the luminescence converter for fast neutrons is 1
The image recording medium for fast neutron radiography according to claim 2, wherein the image recording medium has a thickness of 0 to 200 μm.