Patent Number: 051130785
Section: description

DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below with reference to FIG. 1. A radiation shielding panel 1, which constitutes the radiation shielding structure of the present invention, comprises a lead transparent plate 2, for example, a transparent lead acrylic resin plate, lead glass plate, etc., and a thin nonlead transparent plate 3, for example, a transparent acrylate resin plate, glass plate, etc., which is laminated on at least one side of the lead transparent plate 2. Thus, lead that is contained in the lead transparent plate 2 shields radioactive rays, while the nonlead transparent plate 3 prevents oxidation of the lead in the lead transparent plate 2 by air or chemicals, for example, nitric acid, which oxidation would otherwise form an oxide film on the panel surface and make the panel 1 opaque. It is preferable from the viewpoint of mechanical strength and machinability to employ a lead acrylic resin plate as the lead transparent plate 2 and an acrylate resin plate as the nonlead transparent plate 3, which is laminated on the lead acrylic resin plate. The outer peripheral edge of the radiation shielding panel 1 is formed with a taper 4 that serves as a guide when the panel 1 is mounted, and the inner peripheral edge of a panel mounting portion 6 of a box frame 5 is also formed with a taper 7 as a guide for mounting, so that the radiation shielding panel 1 is fitted into the panel mounting portion 6 by being guided by the tapers 4 and 7. In addition, the outer peripheral edge of the radiation shielding panel 1 is provided with a gasket fitting recess 8 which is in the form of a groove, and a positioning projection 10 that is integrally formed on the inner peripheral edge of the gasket 9 is fitted into the gasket fitting recess 8, thereby enabling the gasket 9 to be attached to the radiation shielding panel 1. The outer peripheral edge of the gasket 9 is provided with a plurality of contact projections 11 having an acute triangle-shaped cross-section with a view to enhancing the adhesion between the gasket 9 and the panel mounting portion 6 and thereby improving the airtightness. The gasket 9 further has a buffer portion 12, as an integral part thereof, which is interposed between the radiation shielding panel 1 and a retaining plate 14 (described later) to prevent the radiation shielding panel 1 from being damaged by the retaining plate 14. A plurality of bolts 13 are attached to the peripheral edge of the panel mounting portion 6 by means, for example, of welding. The retaining plate 14 is pierced with the bolts 13 and brought into contact with the boundary between the radiation shielding panel 1 and the panel mounting portion 6, and the radiation shielding panel 1 is secured to the panel mounting portion 6 through the retaining plate 14 and the buffer portion 12 of the gasket 9 by nuts 15 that are screwed onto the bolts 13. Although in this embodiment the bolts 13 and the nuts 15 are employed as fastening means for securing the radiation shielding panel 1 through the retaining plate 14, any other fastening means may be employed, as a matter of course. This embodiment, arranged as described above, functions as follows. In the radiation shielding panel 1, lead that is contained in the lead transparent plate 2 shields radioactive rays, while the nonlead transparent plate 3, which is laminated on at least one side of the lead transparent plate 2, prevents oxidation of the lead in the lead transparent plate 2 by air or chemicals, which oxidation would otherwise form an oxide film on the panel surface and make the panel opaque. Since the work face comprises only the radiation shielding panel 1, the radiation shielding structure of the present invention is free from the problem of lowering in the transparency due to the moisture or suspended dust in the gap between two panels of the conventional double-panel structure, and it is also free from the problem of leakage of radioactive rays through the gap between the two panels of the prior art. In addition, it is possible to improve the efficiency of the panel mounting operation. Since the radiation shielding panel 1 is fitted into the panel mounting portion 6 by being guided by the tapers 4 and 7, the efficiency of the panel mounting operation improves and the panel 1 can be mounted even more stably. Since the positioning projection 10 of the gasket 9 is fitted into the gasket fitting recess 8 in the radiation shielding panel 1, displacement of the gasket 9 is prevented. Since the contact projections 11 of the gasket 9 come into close contact with the inner peripheral edge of the panel mounting portion 6, the airtightness improves. In addition, since the buffer portion 12 of the gasket 9 is interposed between the retaining plate 14 and the radiation shielding panel 1, there is no danger of the radiation shielding panel 1 being damaged by the retaining plate 14. The present invention provides the following advantages: (1) In the radiation shielding panel, lead that is contained in the lead transparent plate shields radioactive rays, while the nonlead transparent plate, which is laminated on at least one side of the lead transparent plate, prevents oxidation of the lead in the lead transparent plate, which would otherwise form an oxide film on the panel surface and make the panel opaque. Since the lowering in the transparency due to such oxidation can be eliminated by the radiation shielding panel only, the radiation shielding structure of the present invention is free from the problem of lowering in the transparency due to the moisture or suspended dust in the gap between two panels of the conventional double-panel structure, and it is also free from the problem of leakage of radioactive rays through the gap between the two panels of the prior art. In addition, since the radiation shielding panel alone needs to be mounted, the panel mounting operation improves. (2) Since the radiation shielding panel is fitted into the panel mounting portion by being guided by the tapers, the efficiency of the panel mounting operation improves and the panel can be mounted even more stably. (3) Since the positioning projection of the gasket is fitted into the gasket fitting recess in the radiation shielding panel, displacement of the gasket is prevented. (4) Since the contact projections of the gasket come into close contact with the panel mounting portion, the airtightness improves. (5) Since the buffer portion of the gasket is interposed between the radiation shielding panel and the retaining plate, the radiation shielding panel is prevented from being damaged by the retaining plate.