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Radiation Safety
Published in W. David Yates, Safety Professional’s Reference and Study Guide, 2020
By placing an appropriate shield between the radioactive source and the employee, radiation is attenuated, and exposure may be completely eliminated or reduced to an acceptable level. The type and amount of shielding needed to achieve a safe working level vary with the type and quantity of radioactive material used. The half-value layer (HVL) may be used as a guide to the thickness of the shielding necessary to block the radiation. The HVL is the thickness of the shielding necessary to reduce the radiation dose rate to half of the original or unshielded dose rate. The HVL is expressed in units of distance (millimeters or centimeters). The HVL is inversely proportional to the attenuation coefficient. The attenuation coefficient is a quantity that characterizes how easily a material or medium can be penetrated by a beam of light, sound, particles, or other energy or matter.4 The HVL can be calculated using the following equation: HVL=0.693μ
Radiation Safety
Published in W. David Yates, Safety Professional’s, 2015
By placing an appropriate shield between the radioactive source and the employee, radiation is attenuated and exposure may be completely eliminated or reduced to an acceptable level. The type and amount of shielding needed to achieve a safe working level vary with the type and quantity of radioactive material used. The half-value layer (HVL) may be used as a guide to the thickness of the shielding necessary to block the radiation. The HVL is the thickness of the shielding necessary to reduce the radiation dose rate to half of the original or unshielded dose rate. The HVL is expressed in units of distance (millimeters or centimeters). The HVL is inversely proportional to the attenuation coefficient. The attenuation coefficient is a quantity that characterizes how easily a material or medium can be penetrated by a beam of light, sound, particles, or other energy or matter.4 The HVL can be calculated using the following equation: HVL=0.693μ,
The external radiation hazard
Published in Alan Martin, Sam Harbison, Karen Beach, Peter Cole, An Introduction to Radiation Protection, 2018
Alan Martin, Sam Harbison, Karen Beach, Peter Cole
The half-thickness or half-value layer (HVL) for a particular shielding material is the thickness required to reduce the intensity to one-half its incident value. Writing the HVL as t1/2, the previous equation becomes D1D0=0.5=exp(−μt1/2)
Bismuth (III) oxide decorated graphene oxide filled epoxy nanocomposites: thermo-mechanical and photon attenuation properties
Published in Advanced Composite Materials, 2023
Srilakshmi Prabhu, S. G. Bubbly, S. B. Gudennavar
Another important parameter, half value layer (HVL), is used widely to determine the thickness of the shielding material required to reduce the intensity of radiation to half of its initial value. Figure 14c displays the computed HVL values of epoxy composites at various energies and GO/BGO loadings. From the figure, we observe that HVL values of E15BGO composites are lowest among the studied samples. This is because HVL is inversely proportional to both linear attenuation coefficient (μ) and electron density of the interacting medium. We already know that the density of composites increases with BGO loading (Table 4), thus providing greater number of attenuator atoms in the path of incident radiation. Hence, with the increase in filler loading, thickness of the material required to provide adequate shielding also decreases. However, at a given loading, the HVL values increased with increase in the photon energy from 30.85 to 1332.50 keV. As lower values of HVL indicate better shielding ability, E15BGO nanocomposites are well suited for shielding applications.
Monte Carlo simulation for the interaction characteristics of gamma-rays with several tissues and water as a tissue substitute
Published in Radiation Effects and Defects in Solids, 2023
Urkiye Akar Tarim, Orhan Gurler, Latif Korkmaz
On the other hand, the special thickness of an absorber that attenuates the beam or radiation level to 50% is called as the half-value layer (HVL) and similarly, the other special thickness that attenuates the beam or radiation level to 10% is called as the tenth-value layer (TVL) (7). These parameters, which have great importance for nuclear diagnostics and medicine, radiation protection and dosimeters, gamma-ray fluorescence studies, radiation physics, radiation shields, security screening, etc., are related to the linear attenuation coefficient, as seen from following Equations (4) and (5).
Study of structural, physical, characteristics and radiation shielding parameters of Bi50-Pb40-Sn10 and Bi40-Pb40-Sn10-Cd10 alloys used for radiation therapy
Published in Radiation Effects and Defects in Solids, 2022
Mohamed Saad, Hussain ALMohiy, Mohammed S. Alqahtani, Abdulaziz A. Alshihri, Rizk Mostafa Shalaby
The present work aims to use of metallic alloys as a radiation shielding block material for gamma and x-rays. Radiation shielding blocks alloys are most widely and effectively used method for protecting correct living tissues from radiation hazards. Therefore, from a shielding perspective, it is important to study the interaction process with which radiation can interact with a material. The half-value layer (HVL) defined as the absorber's thickness, which is required to reduce the intensity of gamma radiations to half of its intensity. This parameter is obtained by using the following equation (18). HVL x1/2 = ln2/μ = 0.693/μ. The linear attenuation coefficient of radiation shielding block alloys is illustrated in Table 6, which influenced by the change in the microstructure. For a field size 5 × 5 cm2 and 6 MV photons and gamma rays, Bi-40Pb-10Sn has a linear attenuation coefficient higher than the alloy containing Cd. The attenuation curves of a 60Co gamma ray and 6 MV photon beam attenuated by shielding blocks of different thickness are given in Figure 3. The half-value layer (HVL or X1/2) is defined as that thickness of the shielding blocks that attenuates the 6 MV photon beam (or Gamma ray) intensity to 50% of its original value x1/2 = HVL = ln 2/µ, where µ is the linear attenuation coefficient that depends on photon energy and attenuator atomic number. The values of the HVL are listed in Table 6. Bi-40Pb-10Sn shows values lower than those containing the Cd alloy used in NCI. Therefore, alloy-free Cd is recommended as a radiation shielding block, instead of those containing the Cd alloy, to eliminate the cadmium toxicity during the fabrication of the blocks