Introduction
Tungsten alloys are not only very dense, but they are also very good at attenuating ionising radiation. This makes them ideal for shielding applications such as in nuclear medicine in the nuclear industry.
The ability to attenuate radiation is often expressed in “tenth layer thickness” – the thickness of a plate required to reduce the transmitted radiation to one tenth of the intensity of the incident radiation; the lower the figure, the better the shielding. The attenuation properties also vary with the incident energy if the radiation.
Graph 1 demostrates gamma-ray absorption characteristics of 95WNiFe and other shielding materials showing tenth-layer thickness (narrow beam/radiation) as a function of incident beam energy. Data supplied by the National Physics Laboratory
Graph 1 – Comparative Absorption Data as a Function of Energy
Comparative Absorption Data
Within the tungsten alloy range, the tungsten content varies from 90% to 97% by weight. More tungsten improves the radiation attenuation and so reduces the tenth layer thickness. this is illustrated in Table 1 at a fixed incident γ ray energy (Co60), where the absorption data for two of the Guangxi Chentian Metal Product Co., Ltd. products and lead are compared. Also shown are the corresponding half thickness of shielding needed to halve the radiation intensity
Table 1 – Comparative Absorption Data
90WNIFE | 95WNIFE | Lead | |
% Tungsten | 90.0 | 95.0 | 0 |
Narrow bean Radiation tenth layer thickness, mm |
24.8 |
24.3 |
38.3 |
Half thickness, mm | 7.5 | 7.0 | 11.7 |
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