Gamma Radiation Shielding of Silicone Rubber

A ready-made RTV2 silicone rubber in liquid form was purchased from a local store in Egypt, with its stiffener made in China, in addition to purchasing micro-magnesium oxide from El-Gomhouria Chemicals Company in Cairo, Egypt, with a purity of 97.8% and an average particle size of 60 ± 4 μm. Nano-magnesium oxide was purchased from Nano Tech Company, Egypt, with a purity of 99.8% and an average particle size of 20 ± 5 nm. The nanoparticles were prepared chemically and their purity was confirmed using EDX analysis. Samples were photographed using a transmission electron microscope (TEM) to confirm their size.
The mixing process was manually carried out until it became a single mixture that had no lumps or voids, after which it was poured into molds until dried. The samples were mixed in the same proportions as listed in Table 1, with 2 grams of hardener added to every 50 grams of silicone rubber, then adding either micro- or nano-MgO and mixing well until homogeneous. Then they were poured into molds and left for 24 h.
First, the density was measured using the law of mass per volume; the sample was weighed for mass and the volume was measured by the thickness and the sample radius. Then, a system was designed, as shown in Figure 1, to measure the attenuation coefficient of the existing samples using three radioactive sources (Co-60, Cs-137, and Am-241) and a HPGe detector at the Environmental and Radiation Measurements Laboratory, Institute of Graduate Studies and Research, Alexandria University, Alexandria, Egypt.
The measurement was made in the presence and absence of the absorbed sample to determine the intensity of gamma ray photons in both cases. Genie 2000 software was used to analyze the resulting spectrum and determine the intensity of the photons in the presence of the silicon rubber sample (N) and in the absence of the silicon rubber sample (N₀). The linear attenuation coefficient (LAC) was experimentally determined using Equation (1) [18 (link),19 (link),20 (link),21 (link),22 (link)]: $$LAC=\frac{1}{d} ln\frac{N_0}{N}$$
where d is the thickness of the sample. From LAC, we can determine the half-value layer (HVL) by the following Equation (2) [23 (link),24 (link),25 (link),26 (link),27 (link),28 (link),29 (link),30 (link)]: $$HVL=\frac{LN \left(2\right)}{LAC}$$
The mean free path (MFP) is calculated using Equation (3): $$MFP=\frac{1}{LAC}$$
The radiation absorption ratio (RAR) is an useful quantity for estimating the efficacy of shielding materials and given by Equation (4) [31 (link),32 (link),33 (link),34 (link)].
$$RAR\left(\%\right)=\left(1-\frac{N}{N_0}\right)\times 100$$