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Gamma ray shielding effectiveness of the Portland cement pastes doped with brass-copper: An experimental study
Radiation Physics and Chemistry 166 (2020) 108526
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Gamma ray shielding effectiveness of the Portland cement pastes doped with brass-copper: An experimental study
T
E. Kavaza,∗, S.R. Armooshb, U. Perişanoğlua, N. Ahmadic, M. Oltulub a
Ataturk University, Faculty of Sciences, Department of Physics, 25240, Erzurum, Turkey Ataturk University, Engineering Faculty, Department of Civil Engineering, 25240, Erzurum, Turkey c Department of Physics, Marand Branch, Islamic Azad University, Marand, Iran b
A R T I C LE I N FO
A B S T R A C T
Keywords: Cement paste Copper Brass Shielding Mass attenuation coefficient Buildup factor
This work focused to survey the radiation shielding properties of cement paste samples doped without and with Cu 10% and brass 5, 10, 15, 20% wt. Molar volume of the cement samples was determined by the densities obtained with the Archimedes principle. Transmission measurements of the samples were achieved using an Ultra Ge detector at 81, 276, 302, 356, 383 keV photon energies emitted from the Ba-133 radioactive point source. The essential parameters; mass attenuation coefficient ( μ/ ρ ), half value layer (HVL) and effective atomic number (Zeff ), for the cement samples were obtained experimentally and classed with the theoretical outcomes computed by using WinXCOM program. Zeff and effective electron density (Nel) were also assessed for cement samples in the energy range 1 keV-100 GeV by utilizing theoretical results. Additionally, a five parameter geometric progression (G-P) fitting approximation was used to estimate EBF at 0.015-15 MeV photon energies and penetration depths (up to 40 mfp). The results indicate that, smallest HVL and Nel and largest μ/ ρ values belong to 20% brass doped sample. The highest Zeff values were found for brass 20% containing sample, as undoped Portland cement possesses the lowest values of Zeff . The smallest EBF values are observed for high proportion of brass doped cement samples. It is concluded from the results that the cement paste samples containing brass have remarkable and comparable shielding competence.
1. Introduction The use of radiation in industry, medical applications, nuclear facilities and military motivations has attained wide and large dimensions. Radiation technology has brought many health problems related to exposure to radiation(Little, 2003). Protection precautions should be taken to minimize the danger of radiation. Sometimes, increasing distance or reducing exposure time cannot be possible. Therefore, the shielding materials are important for the protection from the destructive effects of ionizing radiation (Pomaro et al., 2019). Previously, Obaid et al. investigated gamma ray shielding parameters of some rocks and concrete in the 122–1330 keV photon energy range experimentally and theoretically (Obaid et al., 2018a). In another study, the experimental mass absorption coefficients of the same stone samples were compared with the results obtained with the GEANT4 and MCNPX simulation codes and calculated the exposure buildup factors(Obaid et al., 2018b). As one of the new generation radiation protectors, glass materials has a wide range of applications as a protective material in radiology, radiation oncology, nuclear medicine and imaging units,
∗
nuclear physics research laboratories. Many researchers have investigated radiation shielding features of glasses produced with different oxides(Gaikwad et al., 2019) (Issa et al., 2019)(Gaikwad et al., 2018). Heavy concrete is used in nuclear reactors, oncology hospitals, research laboratories and in defensive shelters against gamma and Xrays(Akkurt et al., 2006)(Gökçe et al., 2018). The radiation-prevention features of concrete depend primarily on the composition of the concrete. The additives used take in active role in altering the mechanical characteristics and radiation shielding ability(Abo-El-Enein et al., 2018). Cement, which is the most important concrete component, is preferred because of its high binding property, easily accessible, durability and it is the most economical building material (Kubiliute et al., 2018). Portland cement is a product that is produced by grinding the limestone and clay mixture raw materials and the so-called clinker material with very little gypsum. When combined with water, it becomes a hydraulic binder (Li et al., 2015). The durability of cement-based composites has a critical impact on the life of the concrete structure in the mixed environment. For this reason, doping materials such as metal, alloy
Corresponding author. E-mail addresses: [email protected], [email protected] (E. Kavaz).
https://doi.org/10.1016/j.radphyschem.2019.108526 Received 22 July 2019; Received in revised form 5 October 2019; Accepted 10 October 2019 Available online 15 October 2019 0969-806X/ © 2019 Elsevier Ltd. All rights reserved.
Radiation Physics and Chemistry 166 (2020) 108526
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Table 1 Chemical compositions and physical properties of cement. Chemical compositions % CaO SiO2 Al2O3 Fe2O3 MgO SO3 Na2O Ig. loss (%)
56.39 16.87 4.35 3.02 1.97 2.39 0.22 13.61
Physical properties Specific surface area (cm2/g) Density (g/cm3)
4801 2.91
powders and various minerals are added to increase the strengthening effects of cement paste(Lu et al., 2017)(Zhang et al., 2017). In addition, the presence of heavy additives in cement content increases the capability of radiation shielding. This study is focused on the effect of brass and copper additive to gamma ray shielding parameters of cement paste. It has recently been attracted attention for the investigation of the use of electrically conductive cement composites as self-heating materials (Chung, 2004). Previously Armoosh and Oltulu (2019) has reported that Cu, Fe metals and Brass (Cu–Zn) alloy with high electrical conductivity give self-heating property to cement. Considering the high atomic numbers and densities of Cu and Zn metals, it will be important to obtain cement paste, which is both self-heating and has high
Fig. 2. Transmission spectra for without sample and with Control and Brass 20% samples.
radiation shielding ability. For this purpose, we have investigated gamma-ray interaction parameters of five cement paste samples with Portland Cement (100-X)% - Cu 10% - Brass (X= 5, 10, 15, 20%) content. Density (ρ, g/cm3) of the samples were determined with Archimedes method and molar volumes were found using densities obtained. The experimental measurements were performed with transmission method using a HPGe detector at 81, 276, 302, 356, 383 keV
Fig. 1. Experimental setup and cement samples. 2
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doped cement paste samples. 2. Material and method 2.1. Preparation of cementitious composites Local Portland cement type CEM II/B-M 32,5 R was used to fabricate the cementitious composites. Its physical and chemical properties are presented in Table 1. Copper powder of particle sizes (0-50 μm, purity 99) and brass shavings sizes of (0-700 μm, purity +99.9%) were used. A hyper plasticizer was added to the mix of 0.5% of the cement’s weight to improve workability. The water to cement ratio (w/c) was 0.35 and it was kept constant for all specimens. In order to guarantee a proper metals dispersion in the mix, dry materials (cement and metal powders) were first mixed together for 1 min using a mechanical mixer. Later, water equivalent to 70% of the required water for the mix was added to the mixture and mixed for 2 min. Then, a hyper plasticizer was mixed with the rest of the required water, and they were added to the mix of the cementitious composite for another 2 min. The mixing time was kept short when the cement paste was mixed for a long time, as heavy metals would precipitate. Afterward, the mix was poured into oiled cube molds of (20x20x10 mm) and (10x10x10mm) and they were compacted using a table vibrator. The specimens were demolded after 24 h, and they were cured in water at room temperature of ± 20 °C for 28 days. The control sample consists of 10% copper and 90% Portland cement. We used the cubes of 10x10x10mm for transmission measurements (Fig. 1). Density (ρ, g/cm3) of the cement paste samples was obtained utilizing the Archimedes rule using water (ρ = 1 g/cm3) as the immersion
Fig. 3. Molar volume and density of the cement samples.
photons energies for μ/ ρ values of the samples. μ/ ρ , Zeff and HVL calculated theoretically by using WinXCOM and experimentally obtained. Also some staminal factors for gamma-ray shielding nominately half and tenth value layer (HVL and TVL), mean free path (MFP) and effective atomic number (Zeff ) and effective electron density (Nel) in wide energy range of 1 keV-100 GeV were calculated utilizing μ/ ρ values. Exposure Buildup Factor (EBF) which is a very significant parameter for radiation shielding studies at energies between 0.015-15 MeV were determined for particular penetration depths from 1 to 40 mfp for
Table 2 Theoretically and experimentally obtained values of μ/ρ, Zeff and HVL of the cement samples. Energy (MeV)
theo.
expt.
theo.
Control
μ/ρ (cm /g)
expt.
theo.
0.081 0.276 0.302 0.356 0.383
0.262 0.115 0.110 0.103 0.100
Brass 5 %
μ/ρ (cm2/g)
0.081 0.276 0.302 0.356 0.383 Brass 10 %
0.335 0.115 0.110 0.103 0.099 μ/ρ (cm2/g)
0.332 0.117 0.114 0.101 0.101
± ± ± ± ±
0.008 0.002 0.002 0.002 0.002
16.179 16.589 16.606 16.581 16.604 Ζeff
16.038 16.851 17.137 16.331 16.894
± ± ± ± ±
0.400 0.421 0.428 0.408 0.422
0.081 0.276 0.302 0.356 0.383
0.360 0.115 0.111 0.102 0.099
0.364 0.117 0.110 0.106 0.101
± ± ± ± ±
0.009 0.002 0.002 0.002 0.002
16.920 17.393 17.411 17.383 17.410
17.105 17.630 17.322 17.983 17.740
± ± ± ± ±
0.427 0.440 0.433 0.448 0.443
Brass 15 %
μ/ρ (cm2/g)
0.081 0.276 0.302 0.356 0.383
0.385 0.116 0.111 0.102 0.099
Brass 20 %
μ/ρ (cm2/g)
0.081 0.276 0.302 0.356 0.383
0.410 0.116 0.111 0.102 0.099
Ζeff
2
0.257 0.111 0.106 0.100 0.096
± ± ± ± ±
0.006 0.002 0.002 0.002 0.002
HVL
14.007 14.131 14.144 14.132 14.139
13.746 13.696 13.600 13.739 13.610
± ± ± ± ±
0.343 0.342 0.340 0.343 0.340
Ζeff
± ± ± ± ±
0.009 0.003 0.002 0.002 0.002
± ± ± ± ±
0.009 0.003 0.002 0.002 0.002
1.071 2.479 2.597 2.752 2.867
± ± ± ± ±
0.026 0.061 0.064 0.068 0.071
0.667 1.940 2.023 2.179 2.251 HVL
0.673 1.910 1.960 2.213 2.213
± ± ± ± ±
0.016 0.047 0.049 0.055 0.055
0.523 1.632 1.703 1.838 1.900
0.517 1.610 1.712 1.777 1.864
± ± ± ± ±
0.012 0.040 0.042 0.044 0.046
0.462 1.437 1.514 1.629 1.745
± ± ± ± ±
0.011 0.035 0.037 0.040 0.043
0.404 1.344 1.414 1.521 1.596
± ± ± ± ±
0.010 0.033 0.035 0.038 0.039
HVL
17.693 18.212 18.231 18.198 18.231
16.993 18.735 18.616 18.664 18.049
± ± ± ± ±
0.424 0.468 0.465 0.466 0.451
Ζeff 0.399 0.121 0.114 0.106 0.101
1.051 2.403 2.496 2.676 2.759 HVL
Ζeff 0.372 0.119 0.113 0.105 0.098
expt.
0.444 1.479 1.545 1.671 1.728 HVL
18.456 19.019 19.039 19.002 19.040
3
17.943 19.688 19.596 19.690 19.455
± ± ± ± ±
0.448 0.492 0.489 0.492 0.486
0.393 1.391 1.456 1.576 1.631
Radiation Physics and Chemistry 166 (2020) 108526
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Fig. 4. The variation of mass attenuation coefficients of cement samples with photon energy.
liquid with a digital balance of sensitivity 10−4g. Density of the samples under examination was computed following relation (Han et al., 2018);
ρ=
Wair ρ . Wair − Wwater water.
Vm =
M ρ
(2)
where M denotes the molar mass of the composite and ρ is the density of composite sample(Çelikbilek et al., 2013).
(1)
where Wair and Wwater refer the weights of the cement paste sample in air and water, respectively. The molar volumes of the samples were stated by employing the density of the composites.
2.2. Transmission measurements The aim of the work is to designate the shielding qualities of cement paste including brass (5, 10, 15, 20%) and copper (10%) produced. The 4
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Fig. 4. (continued)
experimental set up is given in fig. 1. In the experiments, the Ultra Ge detector was utilized to specify the gamma transmission values (I/I0) of cement pastes. To irradiate the composites, 81, 276, 302, 356 and 383 keV gamma photon energies emitted from 3 Ci 133Ba radioactive point source were preferred. The experiments were repeated several times (average error is around 2.5%) to reduce the errors. The computer software MAESTRO (6.08 version) was used to attained the transmission spectra. The resulting spectra were evaluated in the Origin 9.0 program and peak areas were found. The transmission spectrum obtained is given by way of example in Fig. 2. 2.3. Calculations The term of mass attenuation coefficient (μρ) for selected sample is expressed using following Lambert-Beer law,
I = I0 e−(μ / ρ) t
(3)
where I and I0 are the intensity with absorber, intensity without absorber, respectively. t, g/cm2, is the thickness of the sample and μ , cm2/ g, is the mass attenuation coefficient. In addition, the μ/ ρ values of the cement paste samples under study were also obtained theoretically by WinXCOM software(Gerward et al., 2004). The mean free path (MFP) is the average distance taken by moving particle between two consecutive collusion MFP values can be obtained by the following equation(Matori et al., 2017);
MFP = (1/ μ)
Fig. 5. The half value layer of the cement samples versus the brass content (a) and photon energy (b).
Zeff =
j
(7)
Nel (electron/g) were computed using Eq.(Oto et al., 2019);
Nel = NA
(5)
Zeff ⟨A⟩
.
(8)
To compute the correct quantity for attenuation for a given shielding material, the build-up factors are utilized. EBF for cement paste samples is derived by substituting G-P fitting parameters in the equations 8–10. The equivalent atomic number (Zeq ) is found by determining the ratio of the interaction coefficients of the substance to (μ/ρ)Compton /( μ/ρ) Total ) the element having the ratio of the interaction coefficients corresponding to this in the same energies. The geometric progression parameters for exposure build-up factors (EBF) can be calculated using an interpolation procedure. G-P fitting parameters are obtained from the standard reference database ANSI/ANS-6.4.3. Then, the G-P fitting parameters are used exposure buildup factors from the G-
where μ (cm−1) denotes linear attenuation coefficient which is determined by the multiplication of the mass attenuation coefficient value ( μ/ ρ ) and density of the sample (ρ) . Tenth-value layer (TVL) symbolizes the thickness of the material that declines the radiation passing by a factor of one tenth of the initial level.
TVL = (2.303/ μ)
Aj
∑j f j Z (μρ ) j
(4)
Half value of layer (HVL) of the materials is the thickness which reduce the incident photon intensity to fifty percent. The equation (4) is utilized to determine the HVL for the material(Shamshad et al., 2017).
HVL = (0.693/ μ)
∑i fi Ai (μρ )i
(6)
where μ is the linear attenuation coefficient. The effective atomic number (Zeff) of the samples were determined by Eq. (6) (Sayyed et al., 2017); 5
Radiation Physics and Chemistry 166 (2020) 108526
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Fig. 6. Variation of effective atomic number and electron density with photon energy for cement samples. Table 3 Equivalent atomic numbers of the cement samples for the energy range 0.015–15 MeV. Energy (MeV)
5%
10%
15%
%20
Control
0.015 0.02 0.03 0.04 0.05 0.06 0.08 0.1 0.15 0.2 0.3 0.4 0.5 0.6 0.8 1 1.5 2 3 4 5 6 8 10 15
18.284 18.558 18.854 19.024 19.152 19.247 19.381 19.470 19.603 19.685 19.779 19.830 19.862 19.883 19.898 19.901 16.747 16.429 15.987 15.877 15.829 15.798 15.762 15.744 15.721
19.093 19.371 19.679 19.855 19.982 20.082 20.226 20.319 20.458 20.541 20.636 20.691 20.721 20.743 20.760 20.760 18.656 17.237 16.747 16.623 16.565 16.531 16.491 16.471 16.446
19.873 20.140 20.453 20.631 20.760 20.860 21.010 21.104 21.245 21.328 21.422 21.474 21.505 21.527 21.543 21.545 19.550 18.045 17.515 17.373 17.307 17.270 17.226 17.204 17.176
20.618 20.874 21.183 21.363 21.491 21.590 21.733 21.828 21.982 22.063 22.154 22.203 22.234 22.255 22.270 22.273 20.401 18.841 18.284 18.126 18.059 18.022 17.964 17.944 17.910
15.620 15.806 15.991 16.107 16.190 16.252 16.328 16.380 16.456 16.502 16.553 16.580 16.597 16.606 16.616 16.614 14.731 14.017 13.777 13.722 13.693 13.675 13.660 13.647 13.632
Fig. 7. Variation of equivalent atomic numbers of the cement samples as a function of photon energy.
3. Results and discussion The molar volume and density of the cement pastes were visualized in Fig. 3. The densities of the samples were varied depending on the proportion of additives. The density and molar volume of cement pastes are increased with increment in brass percentage. The density of the cement samples varies between 2.5 and 4.3 g/cm3. The high density of a material is important not only for the attenuation of photon radiation, but also for reducing the thickness of the shielding material. The mass attenuation coefficient ( μ/ ρ ) of the cement samples were measured for 81, 276, 302, 356, 383 keV photon energies experimentally and calculated by using WinXCOM program theoretically. It is seen from Table 2 and Fig. 4a that experimental and WinXCOM results of μ/ ρ for selected energies are in concordance with each other. 20% brass added cement sample have the highest values of μ/ ρ while lowest values belong to control sample. It is obvious from Fig. 4 that the values
P fitting formula(Kavaz, 2019) (Singh et al., 2008);
B(E,X) = 1+
b− 1 x (K − 1) for K≠ 1 K− 1
B(E,X) = 1+ ( b− 1)x for K= 1.
(9) (10)
where,
K(E,x)= cx a + d
tanh(x/Xk − 2) − tanh(− 2) for x≤ 40mfp 1 − tanh(−2)
(11)
where E is the incident photon energy, x is the penetration depth in mfp (cm), a,b,c,d and Xk are the G-P fitting parameters and at the same time b is the buildup factor at 1 mean free path (mfp). 6
Radiation Physics and Chemistry 166 (2020) 108526
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Fig. 8. (a–e). The exposure buildup factors in the energy region 0.015-15 MeV at 1–40 mfp for cement samples.
Fig. 9. (a–c). The EBF for cement samples up to 40 mfp at 0.15, 1.5, 15 MeV.
effective at intermediate energies. μ/ ρ values of the cement pastes are almost constant and zero due to the linear dependence of cross-section of Compton scattering with atomic number Z (See Fig. 4b). HVL enables us to obtain in an easy way a material’s shielding ability. Fig 5 (a and b) represents HVL values versus the incident photon
of μ/ ρ depend on both photon energy and chemical composition of samples. In low energy region, since photoelectric cross section changes proportional with Z4 and inversely proportional with the incident photon energy as E3.5, μ/ ρ values of the cement samples were decreased rapidly up to 0.275 MeV. Beyond 0.2 MeV, Compton scattering becomes 7
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parameters were obtained theoretically and experimentally for 81, 276, 302, 356 and 383 keV photon energies. The highest μρ values were observed at 82 keV, ie low energies, for all the samples. The μρ and Zeff values of 20% brass doped cement pastes were maximum while HVL and Nel values were lowest among the investigated cement pastes. It is concluded that 20% Brass doped Cement sample transmitted the incoming photons far less. EBF values of the samples were also determined at 0.015-15 MeV up to 40 mfp. The smallest EBF values are found for 20% brass doped cement sample. The outcomes indicate that the insertion of Cu and brass affects positively the photon shielding parameters of cement samples. It can be concluded that those cement samples can be evaluated for further gamma protection applications.
energy and brass content for 0.081-0.383 MeV photon energies. In contrast to μ/ ρ values, HVL values are enhanced as the photon energy increases. The HVL values also depend on the density of the sample in inverse proportion. 20% brass including cement sample have smaller HVL values comparing with other samples due to its higher density (4.29 g/cm3). Firstly, values of HVL were raised with increment in photon energy up to 0.275 MeV, then tended to rise slowly and remain stable. At low energies, HVL is less dependent from the content of the material. Moreover Fig. 5 a presents the variation of HVL values based on brass content for the experimental photon energies studied. It is clear that as the photon energy increases, the HVL values are increased and the HVL values are declined as the brass ratio in the Portland cement samples increases. The changes of Zeff and Nel with photon energy for the cement paste samples have been indicated in Fig. 6. For the samples used, different partial photon interaction processes are dominated by Zeff's variation with photon energy. Zeff values initially decrease slowly, but as mentioned above, sudden increments occur at 0.04 and 0.01 keV due to Ca, Cu and Zn K-shell absorption edges. Zeff starts to increase with photon energy beyond 0.02 MeV and creates a spherical peak in the mid-energy region. According to Fig. 6, the highest Zeff was for 20% brass added sample since Cu and Zn have higher effective atomic cross section. The Zeff values of the samples at intermediate energies are virtually stable because of Compton scattering cross section differs linearly with the Z. For all photon interaction processes, the variation of effective electron density (Nel) in the samples with photon energy is analogous to that of Zeff. Because there is an inverse relationship between Nel and Zeff. The control sample with the lowest effective atomic weight has the highest electron density (Fig. 6). Table 3 and Fig. 7 provide equivalent atomic numbers (Zeq) of the cement samples with photon energy. It is clear from Fig. 7 that Zeq values vary between 13-23. The Zeq and G-P fitting parameters are manipulated to obtain the Exposure Buildup Factor (EBF) up to 40 mfp penetration in the 0.015-15 MeV energy range. As shown in the Fig. 8(a–e), EBF values are increase with increasing photon energy and reach the maximum value of 0.2-0.3 MeV, and then decrease with the increment of photon energy up to 15 MeV. The EBF of the cement samples indicate minimum values in the low-energy region where photoelectric absorption is dominant. EBF values are raised with increasing photon energy due to Compton scattering at middle energies. In the high-energy region, where the pair production begins to dominate, the EBF values enter a decreasing curve. Brass doped samples possess the lowest values of EBF while EBF of the control sample, ordinary Portland cement were maximum for all the penetration depths. Fig. 9a-c shows the EBF values depending on the penetration depth up to 40 mfp for selected energies (0.15, 1.5 and 15 MeV). At 0.15 MeV, which is the low energy region, it yields wide EBF variations for the samples. EBF chiefly depends on chemical composition at 0.15. The 20% brass doped sample has lowest EBF. It is also seen that for control sample with low equivalent numbers (Zeq) the values of EBF are larger while the EBF values of brass added samples with higher equivalent numbers are relatively small. At 1.5 MeV, Compton scattering becomes dominant, therefore, the commitment to the composition of the material is reduced. However, for this energy, the doped cements have lower EBF values. EBF values for brass doped cement samples are found to be the highest at 15 MeV, due to the basis of dominance of pair production in this higher energy region. So, the samples with higher Zeq has higher probability to undergo pair-production.
Declaration of competing interest There are no conflicts of interest to declare. References Abo-El-Enein, S.A., El-Hosiny, F.I., El-Gamal, S.M.A., Amin, M.S., Ramadan, M., 2018. Gamma radiation shielding, fire resistance and physicochemical characteristics of Portland cement pastes modified with synthesized Fe 2 O 3 and ZnO nanoparticles. Constr. Build. Mater. 173, 687–706. https://doi.org/10.1016/j.conbuildmat.2018. 04.071. Akkurt, I., Basyigit, C., Kilincarslan, S., Mavi, B., Akkurt, A., 2006. Radiation shielding of concretes containing different aggregates. Cement Concr. Compos. 28(2), 153–157. https://doi.org/10.1016/j.cemconcomp.2005.09.006. Armoosh, S.R., Oltulu, M., 2019. Self-heating of electrically conductive metal-cementitious composites. J. Intell. Mater. Syst. Struct. 30(15), 2234–2240. https://doi.org/ 10.1177/1045389X19862373. Çelikbilek, M., Ersundu, A.E., Aydin, S., 2013. Preparation and characterization of TeO2WO3-Li 2O glasses. J. Non-Cryst. Solids 378, 247–253. https://doi.org/10.1016/j. jnoncrysol.2013.07.020. Chung, D.D.L., 2004. Self-heating structural materials. Smart Mater. Struct. 13(3), 562–568. https://doi.org/10.1088/0964-1726/13/3/015. Gaikwad, D.K., Obaid, S.S., Sayyed, M.I., Bhosale, R.R., Awasarmol, V.V., Kumar, A., Shirsat, M.D., Pawar, P.P., 2018. Comparative study of gamma ray shielding competence of WO3-TeO2-PbO glass system to different glasses and concretes. Mater. Chem. Phys. 213, 508–517. https://doi.org/10.1016/j.matchemphys.2018.04.019. Gaikwad, D.K., Sayyed, M.I., Botewad, S.N., Obaid, S.S., Khattari, Z.Y., Gawai, U.P., Afaneh, F., Shirshat, M.D., Pawar, P.P., 2019. Physical, structural, optical investigation and shielding featuresof tungsten bismuth tellurite based glasses. J. NonCryst. Solids 503, 158–168. https://doi.org/10.1016/j.jnoncrysol.2018.09.038. Gerward, L., Guilbert, N., Jensen, K.B., Levring, H., 2004. WinXCom—a program for calculating X-ray attenuation coefficients. Radiat. Phys. Chem. 71, 653–654. https:// doi.org/10.1016/j.radphyschem.2004.04.040. Gökçe, H.S., Öztürk, B.C., Çam, N.F., Andiç-Çakır, Ö., 2018. Gamma-ray attenuation coefficients and transmission thickness of high consistency heavyweight concrete containing mineral admixture. Cement Concr. Compos. 92, 56–69. https://doi.org/ 10.1016/j.cemconcomp.2018.05.015. Han, D., Kim, W., Lee, S., Kim, H., Romero, P., 2018. Assessment of gamma radiation shielding properties of concrete containers containing recycled coarse aggregates. Constr. Build. Mater. 163, 122–138. https://doi.org/10.1016/j.conbuildmat.2017. 12.078. Issa, S.A.M., Tekin, H.O., Erguzel, T.T., Susoy, G., 2019. The effective contribution of PbO on nuclear shielding properties of xPbO-(100 −x) P2O5 glass system: a broad range investigation. Appl. Phys. A 125(9), 640–648. https://doi.org/10.1007/s00339-0192941-x. Kavaz, E., 2019. An experimental study on gamma ray shielding features of lithium borate glasses doped with dolomite, hematite and goethite minerals. Radiat. Phys. Chem. 160, 112–123. https://doi.org/10.1016/j.radphyschem.2019.03.032. Kubiliute, R., Kaminskas, R., Kazlauskaite, A., 2018. Mineral wool production waste as an additive for Portland cement. Cement Concr. Compos. 88, 130–138. https://doi.org/ 10.1016/j.cemconcomp.2018.02.003. Li, H., Jiang, Z., Yang, X., Yu, L., Zhang, G., Wu, J., Liu, X.Y., 2015. Sustainable resource opportunity for cane molasses: use of cane molasses as a grinding aid in the production of Portland cement. J. Clean. Prod. 93, 56–64. https://doi.org/10.1016/j. jclepro.2015.01.027. Little, M.P., 2003. Risks associated with ionizing radiation: environmental pollution and health. Br. Med. Bull. 68(1), 259–275. https://doi.org/10.1093/bmb/ldg031. Lu, L., Xiang, C., He, Y., Wang, F., Hu, S., 2017. Early hydration of C3S in the presence of Cd2+, Pb2+ and Cr3+ and the immobilization of heavy metals in pastes. Constr. Build. Mater. 152, 923–932. https://doi.org/10.1016/j.conbuildmat.2017.07.026. Matori, K.A., Sayyed, M.I., Sidek, H.A.A., Zaid, M.H.M., Singh, V.P., 2017. Comprehensive study on physical, elastic and shielding properties of lead zinc phosphate glasses. J. Non-Cryst. Solids 457, 97–103. https://doi.org/10.1016/j.jnoncrysol.2016.11.029. Obaid, S.S., Gaikwad, D.K., Pawar, P.P., 2018a. Determination of gamma ray shielding parameters of rocks and concrete. Radiat. Phys. Chem. 144, 356–360. https://doi. org/10.1016/j.radphyschem.2017.09.022. Obaid, S.S., Sayyed, M.I., Gaikwad, D.K., Tekin, H.O., Elmahroug, Y., Pawar, P.P., 2018b.
4. Conclusion This study is aimed to research gamma ray shielding parameters of the fabricated brass and copper inserted cement paste samples. Density and molar volume of cement samples were calculated. It is found that brass and copper additives increased cement density and molar volume. The μρ , Zeff and HVL values which are the significant gamma absorption 8
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1016/j.jallcom.2016.11.160. Shamshad, L., Rooh, G., Limkitjaroenporn, P., Srisittipokakun, N., Chaiphaksa, W., Kim, H.J., Kaewkhao, J., 2017. A comparative study of gadolinium based oxide and oxyfluoride glasses as low energy radiation shielding materials. Prog. Nucl. Energy 97, 53–59. https://doi.org/10.1016/j.pnucene.2016.12.014. Singh, P.S., Singh, T., Kaur, P., 2008. Variation of energy absorption buildup factors with incident photon energy and penetration depth for some commonly used solvents. Ann. Nucl. Energy 35(6), 1093–1097. https://doi.org/10.1016/j.anucene.2007.10. 007. Zhang, G., Yan, Y., Hu, Z., Xiao, B., 2017. Investigation on preparation of pyrite tailingsbased mineral admixture with photocatalytic activity. Constr. Build. Mater. 138, 26–34. https://doi.org/10.1016/j.conbuildmat.2017.01.134.
Photon attenuation coefficients of different rock samples using MCNPX, Geant4 simulation codes and experimental results: a comparison study. Radiat. Eff. Defects Solids 173(11-12), 900–914. https://doi.org/10.1080/10420150.2018.1505890. Oto, B., Gulebaglan, S.E., Madak, Z., Kavaz, E., 2019. Effective atomic numbers, electron densities and gamma rays buildup factors of inorganic metal halide cubic perovskites CsBX3 (B = Sn, Ge; X = I, Br, Cl). Radiat. Phys. Chem. 159, 195–206. https://doi. org/10.1016/j.radphyschem.2019.03.010. Pomaro, B., Gramegna, F., Cherubini, R., De Nadal, V., Salomoni, V., Faleschini, F., 2019. Gamma-ray shielding properties of heavyweight concrete with Electric Arc Furnace slag as aggregate: an experimental and numerical study. Constr. Build. Mater. 200, 188–197. https://doi.org/10.1016/j.conbuildmat.2018.12.098. Sayyed, M.I., Qashou, S.I., Khattari, Z.Y., 2017. Radiation shielding competence of newly developed TeO2-WO3glasses. J. Alloy. Comp. 696, 632–638. https://doi.org/10.
9
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Radiation Physics and Chemistry journal homepage: www.elsevier.com/locate/radphyschem
Gamma ray shielding effectiveness of the Portland cement pastes doped with brass-copper: An experimental study
T
E. Kavaza,∗, S.R. Armooshb, U. Perişanoğlua, N. Ahmadic, M. Oltulub a
Ataturk University, Faculty of Sciences, Department of Physics, 25240, Erzurum, Turkey Ataturk University, Engineering Faculty, Department of Civil Engineering, 25240, Erzurum, Turkey c Department of Physics, Marand Branch, Islamic Azad University, Marand, Iran b
A R T I C LE I N FO
A B S T R A C T
Keywords: Cement paste Copper Brass Shielding Mass attenuation coefficient Buildup factor
This work focused to survey the radiation shielding properties of cement paste samples doped without and with Cu 10% and brass 5, 10, 15, 20% wt. Molar volume of the cement samples was determined by the densities obtained with the Archimedes principle. Transmission measurements of the samples were achieved using an Ultra Ge detector at 81, 276, 302, 356, 383 keV photon energies emitted from the Ba-133 radioactive point source. The essential parameters; mass attenuation coefficient ( μ/ ρ ), half value layer (HVL) and effective atomic number (Zeff ), for the cement samples were obtained experimentally and classed with the theoretical outcomes computed by using WinXCOM program. Zeff and effective electron density (Nel) were also assessed for cement samples in the energy range 1 keV-100 GeV by utilizing theoretical results. Additionally, a five parameter geometric progression (G-P) fitting approximation was used to estimate EBF at 0.015-15 MeV photon energies and penetration depths (up to 40 mfp). The results indicate that, smallest HVL and Nel and largest μ/ ρ values belong to 20% brass doped sample. The highest Zeff values were found for brass 20% containing sample, as undoped Portland cement possesses the lowest values of Zeff . The smallest EBF values are observed for high proportion of brass doped cement samples. It is concluded from the results that the cement paste samples containing brass have remarkable and comparable shielding competence.
1. Introduction The use of radiation in industry, medical applications, nuclear facilities and military motivations has attained wide and large dimensions. Radiation technology has brought many health problems related to exposure to radiation(Little, 2003). Protection precautions should be taken to minimize the danger of radiation. Sometimes, increasing distance or reducing exposure time cannot be possible. Therefore, the shielding materials are important for the protection from the destructive effects of ionizing radiation (Pomaro et al., 2019). Previously, Obaid et al. investigated gamma ray shielding parameters of some rocks and concrete in the 122–1330 keV photon energy range experimentally and theoretically (Obaid et al., 2018a). In another study, the experimental mass absorption coefficients of the same stone samples were compared with the results obtained with the GEANT4 and MCNPX simulation codes and calculated the exposure buildup factors(Obaid et al., 2018b). As one of the new generation radiation protectors, glass materials has a wide range of applications as a protective material in radiology, radiation oncology, nuclear medicine and imaging units,
∗
nuclear physics research laboratories. Many researchers have investigated radiation shielding features of glasses produced with different oxides(Gaikwad et al., 2019) (Issa et al., 2019)(Gaikwad et al., 2018). Heavy concrete is used in nuclear reactors, oncology hospitals, research laboratories and in defensive shelters against gamma and Xrays(Akkurt et al., 2006)(Gökçe et al., 2018). The radiation-prevention features of concrete depend primarily on the composition of the concrete. The additives used take in active role in altering the mechanical characteristics and radiation shielding ability(Abo-El-Enein et al., 2018). Cement, which is the most important concrete component, is preferred because of its high binding property, easily accessible, durability and it is the most economical building material (Kubiliute et al., 2018). Portland cement is a product that is produced by grinding the limestone and clay mixture raw materials and the so-called clinker material with very little gypsum. When combined with water, it becomes a hydraulic binder (Li et al., 2015). The durability of cement-based composites has a critical impact on the life of the concrete structure in the mixed environment. For this reason, doping materials such as metal, alloy
Corresponding author. E-mail addresses: [email protected], [email protected] (E. Kavaz).
https://doi.org/10.1016/j.radphyschem.2019.108526 Received 22 July 2019; Received in revised form 5 October 2019; Accepted 10 October 2019 Available online 15 October 2019 0969-806X/ © 2019 Elsevier Ltd. All rights reserved.
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Table 1 Chemical compositions and physical properties of cement. Chemical compositions % CaO SiO2 Al2O3 Fe2O3 MgO SO3 Na2O Ig. loss (%)
56.39 16.87 4.35 3.02 1.97 2.39 0.22 13.61
Physical properties Specific surface area (cm2/g) Density (g/cm3)
4801 2.91
powders and various minerals are added to increase the strengthening effects of cement paste(Lu et al., 2017)(Zhang et al., 2017). In addition, the presence of heavy additives in cement content increases the capability of radiation shielding. This study is focused on the effect of brass and copper additive to gamma ray shielding parameters of cement paste. It has recently been attracted attention for the investigation of the use of electrically conductive cement composites as self-heating materials (Chung, 2004). Previously Armoosh and Oltulu (2019) has reported that Cu, Fe metals and Brass (Cu–Zn) alloy with high electrical conductivity give self-heating property to cement. Considering the high atomic numbers and densities of Cu and Zn metals, it will be important to obtain cement paste, which is both self-heating and has high
Fig. 2. Transmission spectra for without sample and with Control and Brass 20% samples.
radiation shielding ability. For this purpose, we have investigated gamma-ray interaction parameters of five cement paste samples with Portland Cement (100-X)% - Cu 10% - Brass (X= 5, 10, 15, 20%) content. Density (ρ, g/cm3) of the samples were determined with Archimedes method and molar volumes were found using densities obtained. The experimental measurements were performed with transmission method using a HPGe detector at 81, 276, 302, 356, 383 keV
Fig. 1. Experimental setup and cement samples. 2
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doped cement paste samples. 2. Material and method 2.1. Preparation of cementitious composites Local Portland cement type CEM II/B-M 32,5 R was used to fabricate the cementitious composites. Its physical and chemical properties are presented in Table 1. Copper powder of particle sizes (0-50 μm, purity 99) and brass shavings sizes of (0-700 μm, purity +99.9%) were used. A hyper plasticizer was added to the mix of 0.5% of the cement’s weight to improve workability. The water to cement ratio (w/c) was 0.35 and it was kept constant for all specimens. In order to guarantee a proper metals dispersion in the mix, dry materials (cement and metal powders) were first mixed together for 1 min using a mechanical mixer. Later, water equivalent to 70% of the required water for the mix was added to the mixture and mixed for 2 min. Then, a hyper plasticizer was mixed with the rest of the required water, and they were added to the mix of the cementitious composite for another 2 min. The mixing time was kept short when the cement paste was mixed for a long time, as heavy metals would precipitate. Afterward, the mix was poured into oiled cube molds of (20x20x10 mm) and (10x10x10mm) and they were compacted using a table vibrator. The specimens were demolded after 24 h, and they were cured in water at room temperature of ± 20 °C for 28 days. The control sample consists of 10% copper and 90% Portland cement. We used the cubes of 10x10x10mm for transmission measurements (Fig. 1). Density (ρ, g/cm3) of the cement paste samples was obtained utilizing the Archimedes rule using water (ρ = 1 g/cm3) as the immersion
Fig. 3. Molar volume and density of the cement samples.
photons energies for μ/ ρ values of the samples. μ/ ρ , Zeff and HVL calculated theoretically by using WinXCOM and experimentally obtained. Also some staminal factors for gamma-ray shielding nominately half and tenth value layer (HVL and TVL), mean free path (MFP) and effective atomic number (Zeff ) and effective electron density (Nel) in wide energy range of 1 keV-100 GeV were calculated utilizing μ/ ρ values. Exposure Buildup Factor (EBF) which is a very significant parameter for radiation shielding studies at energies between 0.015-15 MeV were determined for particular penetration depths from 1 to 40 mfp for
Table 2 Theoretically and experimentally obtained values of μ/ρ, Zeff and HVL of the cement samples. Energy (MeV)
theo.
expt.
theo.
Control
μ/ρ (cm /g)
expt.
theo.
0.081 0.276 0.302 0.356 0.383
0.262 0.115 0.110 0.103 0.100
Brass 5 %
μ/ρ (cm2/g)
0.081 0.276 0.302 0.356 0.383 Brass 10 %
0.335 0.115 0.110 0.103 0.099 μ/ρ (cm2/g)
0.332 0.117 0.114 0.101 0.101
± ± ± ± ±
0.008 0.002 0.002 0.002 0.002
16.179 16.589 16.606 16.581 16.604 Ζeff
16.038 16.851 17.137 16.331 16.894
± ± ± ± ±
0.400 0.421 0.428 0.408 0.422
0.081 0.276 0.302 0.356 0.383
0.360 0.115 0.111 0.102 0.099
0.364 0.117 0.110 0.106 0.101
± ± ± ± ±
0.009 0.002 0.002 0.002 0.002
16.920 17.393 17.411 17.383 17.410
17.105 17.630 17.322 17.983 17.740
± ± ± ± ±
0.427 0.440 0.433 0.448 0.443
Brass 15 %
μ/ρ (cm2/g)
0.081 0.276 0.302 0.356 0.383
0.385 0.116 0.111 0.102 0.099
Brass 20 %
μ/ρ (cm2/g)
0.081 0.276 0.302 0.356 0.383
0.410 0.116 0.111 0.102 0.099
Ζeff
2
0.257 0.111 0.106 0.100 0.096
± ± ± ± ±
0.006 0.002 0.002 0.002 0.002
HVL
14.007 14.131 14.144 14.132 14.139
13.746 13.696 13.600 13.739 13.610
± ± ± ± ±
0.343 0.342 0.340 0.343 0.340
Ζeff
± ± ± ± ±
0.009 0.003 0.002 0.002 0.002
± ± ± ± ±
0.009 0.003 0.002 0.002 0.002
1.071 2.479 2.597 2.752 2.867
± ± ± ± ±
0.026 0.061 0.064 0.068 0.071
0.667 1.940 2.023 2.179 2.251 HVL
0.673 1.910 1.960 2.213 2.213
± ± ± ± ±
0.016 0.047 0.049 0.055 0.055
0.523 1.632 1.703 1.838 1.900
0.517 1.610 1.712 1.777 1.864
± ± ± ± ±
0.012 0.040 0.042 0.044 0.046
0.462 1.437 1.514 1.629 1.745
± ± ± ± ±
0.011 0.035 0.037 0.040 0.043
0.404 1.344 1.414 1.521 1.596
± ± ± ± ±
0.010 0.033 0.035 0.038 0.039
HVL
17.693 18.212 18.231 18.198 18.231
16.993 18.735 18.616 18.664 18.049
± ± ± ± ±
0.424 0.468 0.465 0.466 0.451
Ζeff 0.399 0.121 0.114 0.106 0.101
1.051 2.403 2.496 2.676 2.759 HVL
Ζeff 0.372 0.119 0.113 0.105 0.098
expt.
0.444 1.479 1.545 1.671 1.728 HVL
18.456 19.019 19.039 19.002 19.040
3
17.943 19.688 19.596 19.690 19.455
± ± ± ± ±
0.448 0.492 0.489 0.492 0.486
0.393 1.391 1.456 1.576 1.631
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Fig. 4. The variation of mass attenuation coefficients of cement samples with photon energy.
liquid with a digital balance of sensitivity 10−4g. Density of the samples under examination was computed following relation (Han et al., 2018);
ρ=
Wair ρ . Wair − Wwater water.
Vm =
M ρ
(2)
where M denotes the molar mass of the composite and ρ is the density of composite sample(Çelikbilek et al., 2013).
(1)
where Wair and Wwater refer the weights of the cement paste sample in air and water, respectively. The molar volumes of the samples were stated by employing the density of the composites.
2.2. Transmission measurements The aim of the work is to designate the shielding qualities of cement paste including brass (5, 10, 15, 20%) and copper (10%) produced. The 4
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Fig. 4. (continued)
experimental set up is given in fig. 1. In the experiments, the Ultra Ge detector was utilized to specify the gamma transmission values (I/I0) of cement pastes. To irradiate the composites, 81, 276, 302, 356 and 383 keV gamma photon energies emitted from 3 Ci 133Ba radioactive point source were preferred. The experiments were repeated several times (average error is around 2.5%) to reduce the errors. The computer software MAESTRO (6.08 version) was used to attained the transmission spectra. The resulting spectra were evaluated in the Origin 9.0 program and peak areas were found. The transmission spectrum obtained is given by way of example in Fig. 2. 2.3. Calculations The term of mass attenuation coefficient (μρ) for selected sample is expressed using following Lambert-Beer law,
I = I0 e−(μ / ρ) t
(3)
where I and I0 are the intensity with absorber, intensity without absorber, respectively. t, g/cm2, is the thickness of the sample and μ , cm2/ g, is the mass attenuation coefficient. In addition, the μ/ ρ values of the cement paste samples under study were also obtained theoretically by WinXCOM software(Gerward et al., 2004). The mean free path (MFP) is the average distance taken by moving particle between two consecutive collusion MFP values can be obtained by the following equation(Matori et al., 2017);
MFP = (1/ μ)
Fig. 5. The half value layer of the cement samples versus the brass content (a) and photon energy (b).
Zeff =
j
(7)
Nel (electron/g) were computed using Eq.(Oto et al., 2019);
Nel = NA
(5)
Zeff ⟨A⟩
.
(8)
To compute the correct quantity for attenuation for a given shielding material, the build-up factors are utilized. EBF for cement paste samples is derived by substituting G-P fitting parameters in the equations 8–10. The equivalent atomic number (Zeq ) is found by determining the ratio of the interaction coefficients of the substance to (μ/ρ)Compton /( μ/ρ) Total ) the element having the ratio of the interaction coefficients corresponding to this in the same energies. The geometric progression parameters for exposure build-up factors (EBF) can be calculated using an interpolation procedure. G-P fitting parameters are obtained from the standard reference database ANSI/ANS-6.4.3. Then, the G-P fitting parameters are used exposure buildup factors from the G-
where μ (cm−1) denotes linear attenuation coefficient which is determined by the multiplication of the mass attenuation coefficient value ( μ/ ρ ) and density of the sample (ρ) . Tenth-value layer (TVL) symbolizes the thickness of the material that declines the radiation passing by a factor of one tenth of the initial level.
TVL = (2.303/ μ)
Aj
∑j f j Z (μρ ) j
(4)
Half value of layer (HVL) of the materials is the thickness which reduce the incident photon intensity to fifty percent. The equation (4) is utilized to determine the HVL for the material(Shamshad et al., 2017).
HVL = (0.693/ μ)
∑i fi Ai (μρ )i
(6)
where μ is the linear attenuation coefficient. The effective atomic number (Zeff) of the samples were determined by Eq. (6) (Sayyed et al., 2017); 5
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Fig. 6. Variation of effective atomic number and electron density with photon energy for cement samples. Table 3 Equivalent atomic numbers of the cement samples for the energy range 0.015–15 MeV. Energy (MeV)
5%
10%
15%
%20
Control
0.015 0.02 0.03 0.04 0.05 0.06 0.08 0.1 0.15 0.2 0.3 0.4 0.5 0.6 0.8 1 1.5 2 3 4 5 6 8 10 15
18.284 18.558 18.854 19.024 19.152 19.247 19.381 19.470 19.603 19.685 19.779 19.830 19.862 19.883 19.898 19.901 16.747 16.429 15.987 15.877 15.829 15.798 15.762 15.744 15.721
19.093 19.371 19.679 19.855 19.982 20.082 20.226 20.319 20.458 20.541 20.636 20.691 20.721 20.743 20.760 20.760 18.656 17.237 16.747 16.623 16.565 16.531 16.491 16.471 16.446
19.873 20.140 20.453 20.631 20.760 20.860 21.010 21.104 21.245 21.328 21.422 21.474 21.505 21.527 21.543 21.545 19.550 18.045 17.515 17.373 17.307 17.270 17.226 17.204 17.176
20.618 20.874 21.183 21.363 21.491 21.590 21.733 21.828 21.982 22.063 22.154 22.203 22.234 22.255 22.270 22.273 20.401 18.841 18.284 18.126 18.059 18.022 17.964 17.944 17.910
15.620 15.806 15.991 16.107 16.190 16.252 16.328 16.380 16.456 16.502 16.553 16.580 16.597 16.606 16.616 16.614 14.731 14.017 13.777 13.722 13.693 13.675 13.660 13.647 13.632
Fig. 7. Variation of equivalent atomic numbers of the cement samples as a function of photon energy.
3. Results and discussion The molar volume and density of the cement pastes were visualized in Fig. 3. The densities of the samples were varied depending on the proportion of additives. The density and molar volume of cement pastes are increased with increment in brass percentage. The density of the cement samples varies between 2.5 and 4.3 g/cm3. The high density of a material is important not only for the attenuation of photon radiation, but also for reducing the thickness of the shielding material. The mass attenuation coefficient ( μ/ ρ ) of the cement samples were measured for 81, 276, 302, 356, 383 keV photon energies experimentally and calculated by using WinXCOM program theoretically. It is seen from Table 2 and Fig. 4a that experimental and WinXCOM results of μ/ ρ for selected energies are in concordance with each other. 20% brass added cement sample have the highest values of μ/ ρ while lowest values belong to control sample. It is obvious from Fig. 4 that the values
P fitting formula(Kavaz, 2019) (Singh et al., 2008);
B(E,X) = 1+
b− 1 x (K − 1) for K≠ 1 K− 1
B(E,X) = 1+ ( b− 1)x for K= 1.
(9) (10)
where,
K(E,x)= cx a + d
tanh(x/Xk − 2) − tanh(− 2) for x≤ 40mfp 1 − tanh(−2)
(11)
where E is the incident photon energy, x is the penetration depth in mfp (cm), a,b,c,d and Xk are the G-P fitting parameters and at the same time b is the buildup factor at 1 mean free path (mfp). 6
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Fig. 8. (a–e). The exposure buildup factors in the energy region 0.015-15 MeV at 1–40 mfp for cement samples.
Fig. 9. (a–c). The EBF for cement samples up to 40 mfp at 0.15, 1.5, 15 MeV.
effective at intermediate energies. μ/ ρ values of the cement pastes are almost constant and zero due to the linear dependence of cross-section of Compton scattering with atomic number Z (See Fig. 4b). HVL enables us to obtain in an easy way a material’s shielding ability. Fig 5 (a and b) represents HVL values versus the incident photon
of μ/ ρ depend on both photon energy and chemical composition of samples. In low energy region, since photoelectric cross section changes proportional with Z4 and inversely proportional with the incident photon energy as E3.5, μ/ ρ values of the cement samples were decreased rapidly up to 0.275 MeV. Beyond 0.2 MeV, Compton scattering becomes 7
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parameters were obtained theoretically and experimentally for 81, 276, 302, 356 and 383 keV photon energies. The highest μρ values were observed at 82 keV, ie low energies, for all the samples. The μρ and Zeff values of 20% brass doped cement pastes were maximum while HVL and Nel values were lowest among the investigated cement pastes. It is concluded that 20% Brass doped Cement sample transmitted the incoming photons far less. EBF values of the samples were also determined at 0.015-15 MeV up to 40 mfp. The smallest EBF values are found for 20% brass doped cement sample. The outcomes indicate that the insertion of Cu and brass affects positively the photon shielding parameters of cement samples. It can be concluded that those cement samples can be evaluated for further gamma protection applications.
energy and brass content for 0.081-0.383 MeV photon energies. In contrast to μ/ ρ values, HVL values are enhanced as the photon energy increases. The HVL values also depend on the density of the sample in inverse proportion. 20% brass including cement sample have smaller HVL values comparing with other samples due to its higher density (4.29 g/cm3). Firstly, values of HVL were raised with increment in photon energy up to 0.275 MeV, then tended to rise slowly and remain stable. At low energies, HVL is less dependent from the content of the material. Moreover Fig. 5 a presents the variation of HVL values based on brass content for the experimental photon energies studied. It is clear that as the photon energy increases, the HVL values are increased and the HVL values are declined as the brass ratio in the Portland cement samples increases. The changes of Zeff and Nel with photon energy for the cement paste samples have been indicated in Fig. 6. For the samples used, different partial photon interaction processes are dominated by Zeff's variation with photon energy. Zeff values initially decrease slowly, but as mentioned above, sudden increments occur at 0.04 and 0.01 keV due to Ca, Cu and Zn K-shell absorption edges. Zeff starts to increase with photon energy beyond 0.02 MeV and creates a spherical peak in the mid-energy region. According to Fig. 6, the highest Zeff was for 20% brass added sample since Cu and Zn have higher effective atomic cross section. The Zeff values of the samples at intermediate energies are virtually stable because of Compton scattering cross section differs linearly with the Z. For all photon interaction processes, the variation of effective electron density (Nel) in the samples with photon energy is analogous to that of Zeff. Because there is an inverse relationship between Nel and Zeff. The control sample with the lowest effective atomic weight has the highest electron density (Fig. 6). Table 3 and Fig. 7 provide equivalent atomic numbers (Zeq) of the cement samples with photon energy. It is clear from Fig. 7 that Zeq values vary between 13-23. The Zeq and G-P fitting parameters are manipulated to obtain the Exposure Buildup Factor (EBF) up to 40 mfp penetration in the 0.015-15 MeV energy range. As shown in the Fig. 8(a–e), EBF values are increase with increasing photon energy and reach the maximum value of 0.2-0.3 MeV, and then decrease with the increment of photon energy up to 15 MeV. The EBF of the cement samples indicate minimum values in the low-energy region where photoelectric absorption is dominant. EBF values are raised with increasing photon energy due to Compton scattering at middle energies. In the high-energy region, where the pair production begins to dominate, the EBF values enter a decreasing curve. Brass doped samples possess the lowest values of EBF while EBF of the control sample, ordinary Portland cement were maximum for all the penetration depths. Fig. 9a-c shows the EBF values depending on the penetration depth up to 40 mfp for selected energies (0.15, 1.5 and 15 MeV). At 0.15 MeV, which is the low energy region, it yields wide EBF variations for the samples. EBF chiefly depends on chemical composition at 0.15. The 20% brass doped sample has lowest EBF. It is also seen that for control sample with low equivalent numbers (Zeq) the values of EBF are larger while the EBF values of brass added samples with higher equivalent numbers are relatively small. At 1.5 MeV, Compton scattering becomes dominant, therefore, the commitment to the composition of the material is reduced. However, for this energy, the doped cements have lower EBF values. EBF values for brass doped cement samples are found to be the highest at 15 MeV, due to the basis of dominance of pair production in this higher energy region. So, the samples with higher Zeq has higher probability to undergo pair-production.
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4. Conclusion This study is aimed to research gamma ray shielding parameters of the fabricated brass and copper inserted cement paste samples. Density and molar volume of cement samples were calculated. It is found that brass and copper additives increased cement density and molar volume. The μρ , Zeff and HVL values which are the significant gamma absorption 8
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