Patent Application
20050205794
The present invention relates to a radioactivity measuring apparatus adaptable to objects to be measured having a variety of curved surfaces. More specifically, the present invention relates to a radioactivity measuring apparatus comprising a plurality of elongated plate-shaped radioactivity detection units arranged in the width direction and connected together using connecting fittings, each of which is formed in such a way that it is bent at angles between surfaces of parts thereof on which the respective radioactivity detection units are mounted corresponding to the shape of the surface to be measured, thereby constructing a radiation detection section so as to be adaptable to a variety of shapes of surfaces to be measured such as curved surfaces with different curvatures.
Nuclear power related facilities, etc., produce many articles to be taken out and waste of various shapes. The former includes apparatuses, equipment, scaffolding, etc. which were used in a controlled area, and the latter includes waste produced when the aging facilities are remodeled or dismantled. It is mandatory to classify these articles and waste according to their radioactivity levels so that they are subjected to predetermined processing such as disposal or storage. For this purpose, the presence/absence and the level of radioactive contamination of waste are measured using various radioactivity measuring apparatuses. In this case, a radioactivity measuring apparatus (a surface contamination survey meter) is widely used to measure surface contamination by measuring the entire surface of an object to be measured.
Most of conventional surface contamination survey meters have a flat detection surface. Therefore, when the surface of an object to be measured is flat (plank, etc.), there is no big problem, but in the case of curved surfaces (pipes and drums, etc.), measurements take time and trouble or there are cases where measurements are even not possible. Therefore, when the object to be measured has a curved surface such as a cylindrical shape, and when measuring α-rays having a short range in particular, a method of remodeling the detection surface into a shape conforming to the shape of the surface to be measured has been adopted so far. For example, Japanese Patent Laid-Open Specification No. 9-159769/1997 discloses an example of changing the shape of a detection surface according to the object to be measured.
However, even if a conventional surface contamination survey meter remodels the detection surface in conformity with the shape of the object to be measured, it cannot handle different objects to be measured and it is necessary to prepare many types of surface contamination survey meters having a variety of shapes of detection surfaces, which is not realistic. Therefore, in measurements of waste, etc., the object to be measured is cut (e.g., a pipe is cut longitudinally) in most cases so as to make the shape of the detection surface flat to facilitate measurements and enable measurements.
The problems to be solved by the present invention include problems that the conventional system is unable to directly measure surface contamination of objects to be measured having curved surfaces such as inner or outer surfaces of pipes without cutting pipes longitudinally, thus taking time in preprocessing and measurements, which results in very poor efficiency in survey work.
According to the present invention, there is provided a radioactivity measuring apparatus adaptable to the shape of a surface to be measured, comprising a radioactivity detection section and a radioactivity measuring section arranged separately and connected together via cables, wherein the radioactivity detection section has a structure in which a plurality of elongated plate-shaped radioactivity detection units are arranged in the width direction and connected together in a detachable manner using connecting fittings, each of the connecting fittings being formed in such a way that it is bent at angles between surfaces of parts thereof on which the respective radioactivity detection units are mounted corresponding to the shape of the surface to be measured.
Here, each of the connecting fittings preferably has a structure in which holes and/or notches for insertion of screws are formed in a strip metal sheet which is bent at necessary angles between the mounting surfaces, the connecting fittings being fixed by screws at two locations on the front end side and base end side of the respective radioactivity detection units. When the shape of the surface to be measured is flat, the connecting fitting has a plate-shape. When the shape of the surface to be measured is curved surface, the connecting fitting is bent at a predetermined angle at a position between the neighboring mounting surfaces.
Since the radioactivity measuring apparatus according to the present invention has the radioactivity detection section with a plurality of elongated plate-shaped radioactivity detection units connected in the width direction using connecting fittings, it is possible to select connecting fittings having necessary angles between mounting surfaces and thereby arrange and hold the respective radioactivity detection units according to the surface shape of the object to be measured even in the case of inner or outer surfaces of pipes and drums having different diameters. Therefore, it is possible to directly measure surface contamination on inner or outer surfaces of pipes and drums having different diameters. Furthermore, since no preprocessing such as longitudinal cutting of pipes for measurements is required, it is also possible to significantly improve the efficiency in overall survey work.
The respective radioactivity detection units used in the present invention have an elongated, plate-shape and can have a flat detection surface, and consequently a commercially available radiation source can be used as a standard radiation source for calibration. Therefore, while being a radioactivity measuring apparatus adaptable to various curved surfaces, it can be easily calibrated using a radiation source in a procedure similar to that for a general surface contamination survey meter.
As shown in
The radioactivity measuring apparatus can have an arbitrary structure, but preferably combines a radioactivity detection section provided with a scintillator and a radioactivity measuring section provided with a photomultiplier, both of which are connected together using wavelength conversion optical fiber cables so that a measurement signal (optical signal) of α-rays detected by the radioactivity detection section is directly transmitted to the radioactivity measuring section using the optical fiber cables. This is because this structure allows the relatively bulky photomultiplier to be incorporated in the radioactivity measuring section, making it possible to design the shape of the radioactivity detection unit relatively freely and thereby drastically reduce the size and make the apparatus more elongated and thinner (e.g., a thickness of approximately 10 mm or less). For this purpose, an array structure using connecting fittings is particularly effective and it is possible to easily measure contamination on inner and outer surfaces of objects to be measured of a curved shape such as pipes and drums.
Each of the connecting fittings 18 is formed so that angles between mounting surfaces correspond or conform to the shape of the surface to be measured (180 degrees, that is, plate-shape in this example). As shown in
The structure shown in
As being understood from the foregoing, by replacing connecting fittings 18, it is possible to arrange the respective radioactivity detection units 16 along an arbitrary curved surface in close contact therewith, and measure inner or outer surfaces of pipes and drums of different diameters along the curved surfaces. This also allows efficient measurements of surface contamination of pipes, scaffolding pipes, drums and equipment, etc.
The above illustrated examples show the case where three radioactivity detection units are connected, but when the area of the detection surface should be widened (especially when measuring a flat surface), more radioactivity detection units can be connected. The bending angles of the connecting fittings may be freely set and the lengths thereof may also be changed as appropriate. With regard to the mounting structure, a method of tightening using screws is preferable but other methods using clamps, etc., may also be used. With regard to screw insertion holes and notches, only holes or only notches may be used, but using holes in the center and notches at both sides thereof can produce advantages of facilitating provisional holding with holes and detachment/attachment with notches.
In the respective radioactivity detection units of this example, α-rays emitted from a radioactivity material pass through a light-shielding film, reach a ZnS(Ag) scintillator layer and generate scintillation light. The scintillation light generated propagates directly or inside a light guide to reach a wavelength conversion optical fiber, is converted to a wavelength appropriate for photoreception or transmission, propagates through the wavelength conversion optical fiber, passes through the wavelength conversion optical fiber cable and reaches the photomultiplier of the radioactivity measuring section 12. The circuit structure for measuring radiation by the radioactivity measuring apparatus can be similar to that of a conventional apparatus.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2004-54923 | Feb 2004 | JP | national |
