Gamma Radiation Shielding Evaluation

To evaluate the interaction between gamma radiation and incident matter, the linear attenuation coefficient (μ) is a key parameter and can be calculated by Beer–Lambert’s Law [18 (link)] as follows: $\mathsf{\mu }=\frac{1}{\mathrm{x}}\ln \left(\frac{\mathrm{I}}{{\mathrm{I}}_0}\right)$
where I₀ is the intensity of incident γ-ray photon while I is transmitted γ-ray photons through a target of absorber thickness x. I and I₀ were calculated by determining the peak count rate in the presence and absence of the bentonite sample, respectively.
The mass attenuation coefficient (μ/ρ) was calculated to check the ability of the studied materials as shielding to rays without depending on the density of the material, by dividing the experimental calculated (μ) for a given material by its density (ρ). The (μ/ρ) can also be calculated theoretically using Equation (2) [19 (link)]: $\frac{\mathsf{\mu }}{\mathsf{\rho }}={\displaystyle \sum }_{\mathrm{i}}{\mathrm{w}}_{\mathrm{i}}{\left(\frac{\mathsf{\mu }}{\mathsf{\rho }}\right)}_{\mathrm{i}}$
where (μ/ρ)_i and (w_i) are the mass attenuation and the weight-fraction of the ith constituent element in the sample, respectively.
The half-value layer (HVL) is an important parameter when making a siutable radiation protecting material. This factor is the absorption thickness required to decrease the incident radiation to 50% of its initial value and is evaluated using Equation (3) [20 (link)]: $\mathrm{HVL}=\frac{\ln 2}{\mathsf{\mu }}$
When the photons pass through the sample, they travel a certain distance; the middle distance that a radiation travels between two consecutive interactions is known as the MFP and is described by Equation (4) [21 (link)]: $\mathrm{MFP}=\frac{1}{\mathsf{\mu }}$
When designing and selecting the shielding material, the EBF and EABF should be taken into account to correct the attenuation calculations due to the buildup of secondary photons generated by Compton scattering [22 (link)]. The minimum value of the buildup factor is 1 (BF ≥ 1); in this case, the absorption ratio of the buildup photons is 100%, and the greater the buildup factor more than one, the higher the scattering ratio of the buildup photons. Both exposure and energy absorption buildup factor can be estimated by phy-x software depending on the chemical composition of sample and its density [23 (link)].