A conventional container for radioactive materials typically includes a radiation-shielding body in which the radioactive material is received, and a radiation-shielding lid to be placed on the body to enclose the radioactive material in the container. Both the body and lid tend to be made of lead or lead alloy. In order to prevent radiation emanating from the radioactive material from leaking out of the container between the body and the lid, one of these parts usually includes an annular groove or recess having a substantially rectangular cross-section, while the other part includes a mating annular ridge. This particular design may be characterized as a complimentary stepped configuration of the respective contacting surfaces.
The stepped configuration of the interface between body and lid of the container generally includes one or more pairs of concentric and parallel contacting surfaces. For instance, a first pair of contacting surfaces may be formed by the edge of the body and the lid, and a second by the annular ridge and the groove. Due to manufacturing tolerances, the body and lid of the container may abut along only one of these pairs of contacting surfaces. This means that an undesired gap may be defined between the contacting surfaces of the other pair. Some may find the presence of such a gap disadvantageous, because, for example, the design of the contacting surfaces may not prevent radiation from entering into the gap, thus potentially reducing the container's ability to effectively prevent escape of radiation in some cases. Some may find the presence of such a gap disadvantageous, because, for example, an effective wall thickness of the container at that point may be reduced enough, in some cases, to enable radiation to get through the container at that point. As another possible detriment, some may find that various conventional containers fail to prevent radioactive material from moving about in the container to a location where radiation may be aligned with and/or concentrated near the gap between the contacting surfaces.
USPTO Backgrounds
USPTO Backgrounds