Radiation Physics and Chemistry xxx (xxxx) xxx–xxx Contents lists available at ScienceDirect Radiation Physics and Chemistry journal homepage: www.elsevier.com/locate/radphyschem Determination of gamma ray shielding parameters of rocks and concrete Shamsan S. Obaid, Dhammajyot K. Gaikwad , Pravina P. Pawar ⁎ Department of Physics, Dr. Babasaheb Ambedkar Marathwada University, Aurangabad 431004, India A R T I C L E I N F O A B S T R A C T Keywords: Rocks Concrete Mass attenuation coefficient Effective atomic number Gamma shielding parameters such as mass attenuation coefficient (µ/ρ), effective atomic number (Zeff) and electron density (Neff) have been measured and calculated for rocks and concrete in the energy range 122–1330 keV. The measurements have been carried out at 122, 356, 511, 662, 1170, 1275, 1330 keV gamma ray energies using a gamma spectrometer includes a NaI(Tl) scintillation detector and MCA card. The atomic and electronic cross sections have also been investigated. Experimental and calculated (WinXCom) values were compared, and good agreement has been observed within the experimental error. The obtained results showed that feldspathic basalt, compact basalt, volcanic rock, dolerite and pink granite are more efficient than the sandstone and concrete for gamma ray shielding applications. 1. Introduction Study of the interaction of gamma radiations with matter is an important subject in the field of nuclear medicine, diagnostics, radiation protection and radiation physics and chemistry. The probability of radiation interacting with a material per unit path length is called the linear attenuation coefficient (µ), and is of great importance in radiation shielding. The mass attenuation coefficient (µ/ρ), which is defined as the µ per unit mass of the material, is the basic physical quantity characterizing the diffusion and penetration gamma radiations in the materials. Scattering and absorption of gamma radiations are related to the density and atomic numbers of the material, therefore knowledge of (µ/ρ), atomic cross section (σt), electronic cross section (σel), Zeff and Neff are of prime importance. The glass, concrete and rock are used in the radiation shielding technology because of its high attenuation crosssection for X-rays, Gamma ray photons and neutrons (Abdo, 2002; Singh et al., 2008). Typical applications of these materials are in the construction of hospitals (X-ray unit and therapy room), nuclear research laboratories, power stations, particle accelerators and radioactive waste disposal units. Investigation of the physical parameters such as (µ/ρ), σt, σel, Zeff and Neff of rocks and concretes is useful for understanding their physical properties. A comparison of predicted and experimental values of attenuation coefficients provides a check on the validity of physical parameters such as X-ray emission rates, fluorescence yields and jump ratio (Sitamahalakshmi et al., 2015). In composite materials, a single number cannot represent the atomic number uniquely in the entire energy region for photon interactions. This unique number for complex ⁎ materials is called Zeff, which is varying with energy. The effective atomic number is a convenient parameter for understanding the attenuation of X-rays and gamma photons in composites (Manohara et al., 2007). The accurate value of Zeff is very useful for medical radiation dosimetry, imaging and technological applications. Nowadays, radiations and radioisotopes are used in many diverse fields such as medical diagnosis, medicine, nuclear and food industry, scientific research. Therefore gamma ray shielding investigation of various material gains great attention. Tabulations of (µ/ρ) and the mass energy absorption coefficients for 40 elements and 45 mixtures and some compounds over the energy range from 1 keV to 20 MeV have been reported by Hubbell (1982). Chantler published tabulations of scattering cross-sections and quantities related to (µ/ρ). A computer program XCOM was developed by the Berger and Hubbell (1987), which calculates attenuation coefficients and photon cross sections for elements compounds and mixtures in the energy range 1 keV to 100 GeV. This widely used program transformed to windows platform called WinXCOM (Gerward, 2001). Using XCOM and WinXCOM, many attempts have been made to calculate attenuation coefficients for different elements, compounds and mixtures. Kaewkhao et al. (2010) determined the (µ/ρ) experimentally and theoretically for borate-bismuth glass system. Un and Demir (2013) calculated (µ/ρ), Zeff and Neff of heavy-weight and normal-weight concrete, and observed that iron, barium and calcium concentration of the concretes is more capable for X- or gamma radiation shielding. Demir and Keles (2006) performed a narrow beam transmission experiment using Am-241 and Ba-133 for concrete containing boron waste, and found out that (µ/ρ) is increased with increasing boron concentration in the concrete. Medhat (2009) Corresponding author. E-mail addresses: [email protected] (S.S. Obaid), [email protected] (D.K. Gaikwad), [email protected] (P.P. Pawar). http://dx.doi.org/10.1016/j.radphyschem.2017.09.022 Received 23 January 2017; Received in revised form 21 August 2017; Accepted 19 September 2017 0969-806X/ © 2017 Elsevier Ltd. All rights reserved. Please cite this article as: Obaid, S.S., Radiation Physics and Chemistry (2017), http://dx.doi.org/10.1016/j.radphyschem.2017.09.022 Radiation Physics and Chemistry xxx (xxxx) xxx–xxx S.S. Obaid et al. Table 1 Chemical composition as weight fraction in percentage (w%) of rocks and concrete. Sample O (w%) Na (w%) Mg (w%) Al (w%) Si (w%) P (w%) K (w%) Ca (w%) Ti (w%) Mn (w%) Fe (w%) S (w%) H (w%) C (w%) Feldspathic basalt Compact basalt Volcanic rock Pink granite Sandstone Dolerite Concrete 0.44352 0.02923 0.02404 0.06711 0.23944 0.00172 0.00769 0.07866 0.01408 0.00132 0.09321 – – – 0.44537 0.434257 0.487639 0.526674 0.43996 0.45558 0.03282 0.038852 0.03831 0.000108 0.02976 0.04176 0.02058 0.02455 0.000019 0.000021 0.02287 0.02967 0.06329 0.061466 0.054954 0.028128 0.06466 0.04176 0.24496 0.222114 0.358348 0.437027 0.22981 0.12205 0.00238 0.00372 0.000249 0.000169 0.00152 – 0.00833 0.01166 0.041024 0.000043 0.00259 0.01934 0.06438 0.08656 0.004965 0.00218 0.07076 0.24957 0.01699 0.021733 0.00103 0.000702 0.02251 0.00024 0.0013 0.002072 0.000242 0.000064 0.00167 – 0.0996 0.093016 0.01322 0.004883 0.1139 0.01602 – – – – – 0.00215 – – – – – 0.0087 – – – – – 0.0256 Fig. 1. Schematic view of experimental setup. determined the (µ/ρ) for the building materials using a high-resolution HPGe spectrometer detector, and showed that a brick covered with cement can shield about 49–67% more radiations than brick itself. In recent years, A great number of researchers reported (µ/ρ), Zeff and Neff in different materials such as concretes (Akkurt et al., 2012; Medhat, 2012; Oto et al., 2015, 2016), alloys (Singh et al., 2014; Kaewkhaoa et al., 2008), compound and mixtures (Awasarmol et al., 2017a, 2017b; Bhosale et al., 2016a, 2016b; Gaikwad et al., 2016; Pawar and Bichile, 2013; Un and Sahin, 2011) and glasses (Matori et al., 2017; Singh et al., 2014). Oto et al. (2016) calculated Zeff and effective removal crosssections of magnetite concrete for gamma and fast neutron shielding. In this paper, mass attenuation coefficients (µ/ρ) of some rocks and a concrete have been measured in the energy range 122–1330 keV and calculated using the computer code WinXCom. Then atomic and electronic cross sections, effective atomic number and electron density have been determined using (µ/ρ) for same energies. This work also includes a comparison of attenuation coefficients of rocks with concrete. Present results could be very useful in radiation shielding applications for construction of nuclear power plants, X-ray and radiotherapy units. Fig. 2. The measured mass attenuation coefficients at 122–1330 keV. 2. Experimental details Concrete has been produced using the ordinary Portland cement (PC 42.5) and normal sand. A constant water (w) to cement (c) ratio (w/c = 50%) and 25% normal sand concentration was selected for concrete preparation. Rocks and produced concrete samples were ground separately and sieved with 400 mesh. These samples were heated (at 60 °C) Fig. 3. Experimental (µ/ρ) versus theoretical (µ/ρ). Table 2 Mass attenuation coefficients (cm2/g) of rocks and concrete samples. Energy (keV) 122 356 511 662 1170 1275 1330 Feldspathic basalt Compact basalt Volcanic rock Pink granite Sandstone µ/ρ exp. µ/ρ theo. µ/ρ exp. µ/ρ theo. µ/ρ exp. µ/ρ theo. µ/ρ exp. µ/ρ theo. µ/ρ exp. µ/ρ theo. µ/ρ exp. µ/ρ theo. µ/ρ exp. µ/ρ theo. 0.182 0.101 0.087 0.078 0.059 0.056 0.056 0.172 0.100 0.086 0.078 0.058 0.056 0.055 0.181 0.098 0.087 0.078 0.059 0.057 0.056 0.172 0.099 0.086 0.078 0.058 0.056 0.055 0.180 0.110 0.089 0.080 0.059 0.056 0.056 0.173 0.101 0.086 0.078 0.058 0.056 0.055 0.167 0.110 0.089 0.080 0.060 0.057 0.056 0.158 0.101 0.087 0.078 0.059 0.056 0.056 0.151 0.099 0.086 0.077 0.056 0.054 0.053 0.156 0.010 0.087 0.079 0.059 0.056 0.056 0.175 0.099 0.084 0.077 0.056 0.055 0.054 0.174 0.099 0.086 0.078 0.058 0.055 0.055 0.154 0.102 0.087 0.078 0.058 0.057 0.055 0.153 0.100 0.086 0.077 0.059 0.057 0.055 2 Dolerite Concrete Radiation Physics and Chemistry xxx (xxxx) xxx–xxx S.S. Obaid et al. Table 3 Atomic cross sections (barn/atom) of rocks and concrete samples. Energy (keV) 122 356 511 662 1170 1275 1330 Feldspathic basalt Compact basalt Volcanic rock Pink granite Sandstone Dolerite Concrete exp. theo. exp. theo. exp. theo. exp. theo. exp. theo. exp. theo. exp. theo. 26.74 14.67 12.85 11.52 8.70 8.25 8.22 25.22 14.62 12.68 11.45 8.55 8.16 8.13 26.56 14.42 12.79 11.45 8.64 8.30 8.24 25.21 14.58 12.66 11.41 8.54 8.14 8.11 24.57 15.08 12.15 10.89 8.06 7.64 7.61 23.62 13.87 11.81 10.66 7.96 7.59 7.57 20.53 13.58 10.93 9.84 7.34 6.97 6.88 19.46 12.48 10.66 9.63 7.21 6.87 6.84 15.15 9.89 8.58 7.68 5.58 5.40 5.27 15.63 9.99 8.71 7.87 5.90 5.63 5.61 25.10 14.64 12.51 11.35 8.33 8.12 7.99 25.80 14.73 12.77 11.53 8.61 8.21 8.18 15.19 10.06 8.56 7.70 5.72 5.62 5.43 15.10 9.87 8.50 7.58 5.82 5.52 5.41 Table 4 Electronic cross sections (barn/atom) of rocks and concrete. Energy (keV) 122 356 511 662 1170 1275 1330 Feldspathic basalt Compact basalt Volcanic rock Pink granite Sandstone Dolerite concrete exp. theo. exp. theo. exp. theo. exp. theo. exp. theo. exp. theo. exp. theo. 2.356 1.292 1.132 1.015 0.767 0.726 0.724 2.222 1.288 1.118 1.009 0.754 0.719 0.716 2.295 1.246 1.105 0.990 0.746 0.717 0.712 2.178 1.260 1.094 0.986 0.737 0.703 0.701 2.130 1.307 1.053 0.944 0.699 0.662 0.659 2.047 1.203 1.024 0.924 0.690 0.658 0.656 1.971 1.304 1.05 0.944 0.704 0.669 0.661 1.869 1.198 1.024 0.924 0.693 0.659 0.657 1.504 0.982 0.852 0.763 0.554 0.536 0.524 1.552 0.992 0.865 0.782 0.585 0.559 0.557 2.243 1.263 1.079 0.980 0.719 0.701 0.689 2.226 1.271 1.102 0.995 0.743 0.709 0.706 1.446 0.958 0.813 0.732 0.544 0.535 0.517 1.436 0.939 0.808 0.721 0.554 0.525 0.515 in a muffle furnace for 48 h. The chemical contents of the concrete and rock samples were measured by X- ray fluorescence spectrometer (XRF, SPECTRO XEPOS, AMETEK), are tabulated in Table 1. SPECTRO XEPOS instrument was controlled by a menu based X-LAB pro software computer. This instrument characteristics included; 50 W end-window Xray tube, up to eight polarization and secondary targets, automatic sample changer, SSD detection system. The attenuation coefficient measurements were performed using the gamma spectrometer that includes a NaI(Tl) scintillation detector coupled to 8k MCA card. The mass attenuation coefficients of the samples were measured at photon energies of 122, 356, 511, 662, 1170, 1275 and 1330 keV obtained from 57Co, 133Ba,137Cs,60Co and 22Na gamma ray sources, respectively. A schematic view of the good geometry transmission experiment is shown in Fig. 1. The distance (30 cm ≤ d ≤ 50 cm) has been kept between a source and a detector. The rocks and concrete samples under investigation were pellets formed. The mass and diameter of the pellet were used to determined mass per unit area in each case. For given µ/ρ, the pellets thickness (mass per unit area) in the range of 0.200–0.540 g/ cm2 was selected. Experimental procedure followed for measuring attenuation coefficients has been discussed with details in previous work (Pawar and Bichile, 2013, Awasarmol et at, 2017a,b; Bhosale et al., 2016a, Gaikwad et al., 2017). Photon intensities I and Io, which are with and without the sample, respectively, were measured for a sample of thickness t (cm). The linear attenuation coefficient values of the rocks and concrete are determined by the following relation: Fig. 4. Atomic cross section versus photons energy. I = exp (−µ t ) I0 (1) Where µ (cm−1) is the linear attenuation coefficient of a material and I0 and I are the without attenuated and attenuated photon intensity, respectively. The mass attenuation coefficients for the given materials are determined by using the following mixture rule (Hubbell and Seltzer, 1995): µ = ρ Fig. 5. Electronic cross section versus photons energy. ∑ Wi ⎛ ρ ⎞ ⎜ i µ ⎟ ⎝ ⎠i (2) Where ρ is the density of the material, Wi and (µ/ρ)i are weight fraction mass attenuation coefficients of the ith constituent element, respectively. For chemical compound, Wi is given by 3 Radiation Physics and Chemistry xxx (xxxx) xxx–xxx S.S. Obaid et al. Table 5 Effective atomic numbers (Zeff) of rocks and concrete samples. Energy (keV) 122 356 511 662 1170 1275 1330 Feldspathic basalt Compact basalt Volcanic rock Pink granite Sandstone exp. theo. exp. theo. exp. theo. exp. theo. exp. theo. exp. theo. exp. theo. 14.00 13.23 12.96 12.72 12.32 12.25 12.20 13.94 13.13 12.87 12.68 12.28 12.22 12.20 13.97 13.12 12.89 12.72 12.30 12.21 12.14 13.79 12.10 12.74 12.56 12.17 12.11 12.08 13.97 13.22 12.95 12.77 12.38 12.30 12.24 14.20 13.36 13.09 12.90 12.49 12.42 12.39 12.63 11.95 11.72 11.55 11.27 11.21 11.19 12.53 11.86 11.64 11.48 11.15 11.10 10.66 12.12 11.42 11.20 11.01 10.65 10.59 10.52 12.00 11.38 11.18 11.04 10.73 10.68 10.66 14.37 13.50 13.11 12.90 12.45 12.33 12.30 14.29 13.44 13.17 12.97 12.56 12.50 12.47 12.64 11.98 11.75 11.59 11.24 11.19 11.17 12.63 11.95 11.73 11.57 11.24 11.19 11.16 ni Ai ∑i ni Ai (3) Where Ai is the atomic weight of the ith element and ni is the number of formula units. Theoretical (µ/ρ) for the given samples were calculated by WinXCom Code (Gerward, 2001). A detailed information about the calculation of the atomic cross section, electronic cross section and the effective atomic number has been given in our previous work (Pawar and Bichile, 2013; Gaikwad et al., 2016). The effective electron density, Neff, which is expressed as in number of electron per unit mass can be found from Neff = NA Zeff N ∑ ni = (µ/ ρ) σel Concrete in this work are given in Table 1. The values of (µ/ρ) for the rocks and a concrete have been measured at gamma energies from 122 to 1330 keV and calculated using WinXCom, are shown in Table 2. Fig. 2 shows the trends of measured (µ/ρ) values for all samples at photon energies from 122 to 1330 keV. It is clearly seen from this figure that (µ/ρ) depends on the gamma-ray energy. It is obviously seen from Fig. 2 that the values of (µ/ρ) decrease with increasing photon energies. It can also be seen from the same figure that the (µ/ρ) values of feldspathic basalt, compact basalt, volcanic rock, dolerite and pink granie are higher than sandstone and concrete. The measured results are compared with calculated values in Table 2. It can be seen that the results of (µ/ρ) show good agreement between experimental and calculated results. For a better view of the comparison between experiment and theory, theoretical line with the values of experimental (µ/ρ) is plotted versus corresponding calculated (µ/ρ) in Fig. 3 where it can be seen that almost all experimental data lie within the experimental error evidencing a good agreement. The overall error in the measured experimental (µ/ρ) is estimated to be ≤ 2%. The total experimental error in (µ/ρ) was calculated from errors in intensities I0 (without attenuation) and I (with attenuation), mass per unit area measurements and counting statistics (< 1%). The errors for the intensities measurements influence the measured data were estimated to be ≤ 1%. The errors in the mass per unit area measurement were within 0.5%. Experimental and theoretical atomic (σt) and electronic cross sections (σel) for the rocks and a concrete are given in Tables 3, 4, respectively. The typical plots of experimental σt against the gamma ray energies and σel against the gamma ray energies for all the samples are shown in Figs. 4 and 5, respectively. It is depicted that the trends of σt and σel with photon energies are identical to mass attenuation coefficient. Experimental and theoretical effective atomic numbers of all the samples determined at gamma ray energies from 122 to 1330 keV are given in Table 5. Trends of Zeff values with energy are also shown graphically in Fig. 6. It is clearly seen from the figure and table that the values of Zeff for present samples vary with the range of atomic numbers. As depicted in Fig. 6, Zeff values of each sample decreased with increasing gamma ray energy. This result supports the statement made by Hine (1952), who commented that Zeff varies with energy. Results of Neff for all samples were determined using (µ/ρ) and atomic cross section and given in Table 6. Also, experimental Neff values for all samples Fig. 6. Effective atomic number versus photons energy. Wi = Dolerite (4) Where NA is the Avogadro's number, ∑i ni Ai = N is the atomic mass of materials and σel is the electronic cross-section. 3. Results and discussions The chemical composition of a concrete and the rock samples used Table 6 Effective electron densities (*1024 electrons/g) of rock and concrete. Energy (keV) 122 356 511 662 1170 1275 1330 Feld spathic basalt Compact basalt Volcanic rock Pink granite Sandstone theo. exp. theo. exp. theo. exp. theo. exp. theo. exp. theo. exp. theo. exp. 0.363 0.341 0.335 0.33 0.319 0.318 0.317 0.364 0.344 0.337 0.331 0.32 0.318 0.317 0.362 0.341 0.334 0.33 0.319 0.318 0.317 0.367 0.345 0.338 0.334 0.323 0.321 0.319 0.363 0.342 0.335 0.33 0.319 0.318 0.317 0.357 0.338 0.331 0.327 0.317 0.315 0.313 0.359 0.34 0.333 0.329 0.32 0.318 0.305 0.362 0.342 0.336 0.331 0.323 0.321 0.321 0.357 0.339 0.332 0.328 0.32 0.318 0.317 0.361 0.34 0.334 0.328 0.317 0.315 0.313 0.363 0.342 0.335 0.33 0.319 0.318 0.317 0.365 0.343 0.333 0.328 0.317 0.313 0.312 0.359 0.340 0.333 0.329 0.319 0.318 0.317 0.359 0.340 0.334 0.329 0.320 0.318 0.318 4 Dolerite Concrete Radiation Physics and Chemistry xxx (xxxx) xxx–xxx S.S. Obaid et al. Berger, M.J., Hubbell, J.H., 1987. XCOM Photon Cross Section on a Personal Computer NBSIR. 87. NIST, pp. 3597. 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Conclusion Gamma rays shielding properties of the rocks and concrete have been studied. Results of the (µ/ρ), σt and σel increase with decreasing incident gamma ray energy. It is noticed that Zeff and Neff depend on elements of the materials and incoming photon energies. The mass attenuation coefficient of feldspathic basalt, compact basalt, volcanic rock, dolerite and pink granite is higher than sandstone and concrete. This means that the feldspathic basalt, compact basalt, volcanic rock, dolerite and pink granite are good candidates for gamma ray shielding applications. The results of this work will be helpful in the development of radiation shielding technology. Acknowledgement One of the authors DKG would like to thank University Grant Commission, New Delhi for providing RGNF. References Abdo, A. El-Sayed, 2002. Calculation of the cross-sections for fast neutrons and gammarays in concrete shields. Ann. Nucl. Energy 29, 1977–1988. 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