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Photon Shielding Characterization of SiO2-PbO-CdO- TiO2 Glasses for Radiotheraphy Shielding Application

In this study, photon attenuation parameters of (30-x) SiO2–15PbO–10CdO-xTiO2, with x = 0, 2, 4, 6, 8 and 10% mol, were determined and their application as shielding material were discussed. The WinXCOM software was used to determine the mass attenuation coefficient of the studied glasses for the energy range (0.015-15MeV). The mass attenuation coefficient of the glass samples first decline up to 0.09 MeV and slightly increase abruptly and then declined uniformly for all the glasses to approximately zero after about 10 MeV. The effective atomic number (Zeff) was also calculated for the glass samples and were observe to raise from 0.015 to 0.02 MeV and then decreased between 0.02-5 MeV. On account of the dominance of the photoelectric effect in the low energy region, there was a sudden increase in Zeff at about 0.08 MeV close to the absorption edge of the Pb (0.088 MeV). The rapid increment was observed at 0.1–1.5 MeV by transcending typical Compton scattering interaction at intermediate energies for Zeff'’s and began to decrease in the same form again. The lower Zeff values were found in low and high energy region for all SPCT Original Research Article Mustapha et al.; AJR2P, 4(4): 32-38, 2021; Article no.AJR2P.72356 33 glasses. The calculated mean free path, half value layer and tenth value layer values were observe to decline as the TiO2 doping of the glasses increased which accounts for the three photon interaction mechanisms effectiveness in the variation of MFP and HVL values with energy. It can be concluded that SPCT glasses may be considered an alternative material for radiation shielding practices.


INTRODUCTION
The increased demand of ionizing radiation in many areas of endeavor such radiotherapy is one of the most concerning subjects in regard to use of medical radiation [1,2]. In the medical radiation facilities, technicians, doctors, and nurses are experiencing radiation exposure every day which could potentially lead to effects that is detrimental. The evaluation of the radiation exposure of the clinical personnel is important and numerous publications have been analyzed this subject with common target the safe application of the exposure [2,3,4]. Several protection procedures are currently implemented in everyday practice, including radiation protection apparels, personalized radiation monitoring devices and exposure-decreasing operational techniques [1,3]. However, the basic protection of the medical radiation fields is the correct and complete shielding of the room which is capable of ensuring the safety of the personnel and population [5,6]. The term of ionizing radiation transmission through matter is basic of the shielding studies for medical radiation fields. The selection of the shielding material requires some pre-decided parameters such as attenuation performance, structural properties and thermal properties considering the radiation type, energy and source type [1,7]. Radiation shielding serves a number of functions. Foremost among these is reducing the radiation exposure to persons in the vicinity of radiation sources. Shielding used for this purpose is named biological shielding [8,9].
In different areas of ionising radiation application photons (gamma rays) are of major concern to medical physicist and engineers when designing radiation shield. This is due to their abilities to penetrate deeper into any given medium. Traditionally, materials for photon attenuation are required to be of high density.
Obviously, effective shielding of photons is very important because it is the primary product of a radiotherapy unit [10]. One of the parameters than can be used to describe the photon shielding effectiveness of a medium is the mass attenuation coefficient. The mass attenuation coefficient is a quantity that describes how much photon is absorbed or transmitted by a medium [2,4,11]. Therefore, this study aimed to determine the gamma shielding parameters Tin oxide added glasses.
Theoretical mass attenuation coefficients μ m of the glass mixtures were calculated for the chemical composition of the glass mixtures (S1 to S6) using winXCOM software. The XCOM code is a database for calculating mass attenuation coefficients at different photon energies [1,2,12]. Theoretical linear attenuation coefficients were calculated by multiplying the obtained theoretical mass attenuation coefficients by the density of the mortar mixtures. The linear attenuation coefficients (µ) which are a measure of the shielding capacity of the material against radiation is investigated for many materials both theoretically and experimentally. The linear attenuation coefficient (μ) is related to the mass attenuation coefficient (μ m ) as [1,10]: where ρ represents the density of the absorbing medium. It has the dimensions of area per unit mass (cm 2 /g).
The other important related shielding parameters were calculated by applying the linear attenuation coefficient (μ) results of each glass mixtures. The HVL and MFP reflect the necessary thickness that should be used to attenuate gamma rays or x-rays by half and a factor of e, respectively. They were calculated using [1,2,12]: The Z eff values of materials have a strong energy dependence, which differs from the Z (atomic number) of individual elements (for example, Z is constant with changing E). In this study, the equations 4 was used to calculate the Z eff of the investigated glasses mixtures [2,10,12]: where Z i ,f i , and A i , are the atomic number, molar fraction, and atomic mass of the elements inside the glass specimens, respectively.

RESULTS AND DISCURSIONS
The mass attenuation coefficient (µ m ) values obtained in the 0.015-15 MeV range using the WinXCOM program is shown in Fig. 1. The chemical compositions and densities of the investigated glasses are summarized in Table 1. The linear attenuation coefficient ( ) was calculated from µ m and the density ( ) of the glass sample as a function of energy as depicted in Fig. 2. The vary with energy in similar way as µ m . The increase in density of the glass mixture (S1-S6) greatly affect the attenuation capability.
A vital parameter to consider a material to be substituted for radiation shielding is the effective atomic number (Z eff ). The fluctuation of Z eff with respect to photon energy is depicted in Fig. 3. Initially, Z eff values were raised from 0.015 to 0.02 MeV and then decreased between 0.02-5 MeV. On account of the dominance of the photoelectric effect in the low energy region, there was a sudden increase at about 0.08 MeV close to the absorption edge of the Pb (0.088 MeV). The rapid increment was observed at 0.1-1.5 MeV by transcending typical Compton scattering interaction at intermediate energies for Z eff' 's and began to decrease in the same form again. The lower Z eff values were found in low and high energy region for all SPCT glasses. Observation of the larger Z eff values in the high energy region compared to the lower energies is due to the fact that the cross-section of pair production mechanism is less dependent on the energy and atomic number [1]. The addition of TiO 2 to the SPCT glass systems has also increased the Z eff values.  Tenth Value Layer (cm) The mean free path (MFP), half value layer (HVL) and tenth value layer (TVL) which are the most commonly used transmission thickness for gamma rays [1,10,11], are given in Fig. 4, 5, and 6 respectively. The MFP, HVL and TVL values were declined as the TiO 2 doping of the glasses increased. As we explained for µ m values, it is seen that the three photon interaction mechanisms is effective in the variation of MFP and HVL values with energy.

CONCLUSION
This study investigates the gamma attenuation parameters of (30-x) SiO 2 -15PbO-10CdO-xTiO 2 glass, with x = 0, 2, 4, 6, 8 and 10% mol. Mass attenuation coefficient of the glass exposed to gamma radiation decline up to a certain value and increases abruptly within a short energy range and decreases thereafter as the photon energy increases. The mean free path, half value layer and tenth value layer were observed to decline as the TiO 2 doping of the glasses increased. The addition of TiO 2 and enhancement of SiO 2 reduction in the glasses increases the radiation attenuation capability of the glasses. The fluctuation of these parameters with energy is due to the three photon interaction mechanisms (photoelectric effect, Compton scattering and pair production). The addition of TiO 2 to the glass mixture has a significant effect to evolve the gamma shielding properties of the studied glass.
HO. The impact of Cr2O3 additive on nuclear radiation shielding properties of LiF-SrO- B2O3