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Mn binary alloys
Journal of Alloys and Compounds 815 (2020) 152484
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Journal of Alloys and Compounds journal homepage: http://www.elsevier.com/locate/jalcom
The influence of gallium (Ga) additive on nuclear radiation shielding effectiveness of Pd/Mn binary alloys H.O. Tekin a, b, *, O. Kilicoglu b, c a
Uskudar University, Vocational School of Health Services, Radiotherapy Department, Istanbul, 34672, Turkey Uskudar University, Medical Radiation Research Center (USMERA), Istanbul, 34672, Turkey c Uskudar University, Department of Nuclear Technology and Radiation Protection, Istanbul, 34672, Turkey b
a r t i c l e i n f o
a b s t r a c t
Article history: Received 29 July 2019 Received in revised form 14 September 2019 Accepted 27 September 2019 Available online 28 September 2019
The aim of this investigation was to present the gamma-ray and neutron shielding properties of different type of Ga additive Pd/Mn binary alloys. Therefore, mass attenuation coefficient (mm) values of different types of Pd-Mn-Ga alloys were calculated using the MCNPX simulation code in the 0.02e15 MeV energy region. Afterwards, the obtained mm values have been utilized for determination of HVL, TVL, MFP and Zeff gamma shielding parameters for evaluation of the gamma radiation shielding abilities of alloy P samples. Moreover, effective removal cross-sections ( R) of investigated alloy samples have been calculared. The results showed that both mm and Zeff values are increased as the Ga concentration increases. Thus, the study is indicates that 25Ga alloy sample owns distinguished protection ability to attenuate the gamma-ray radiation. The results also showed that 0Ga alloy sample which containing %0 of Ga has the P highest R value as a most effective alloy sample among the other samples for fast neutron shielding. To observe the shielding paerformance of superior sample, we have compared our results with previous available investigations in literature. It can be concluded that Ga additive for this type of binary alloys can help to increase the shielding gamma-ray performance. © 2019 Elsevier B.V. All rights reserved.
Keywords: Pd/Mn alloys Gamma-ray shielding Monte Carlo method MCNPX
1. Introduction The extensive utilizations with ionizing radiation in different areas of medical applications such as diagnostic imaging, radiation therapy, nuclear medicine is increasing day-by-day. Moreover, it has been using in various industrial application areas such as food preservative and sterilization [1]. The possible effect of ionizing radiation such as gamma ray and x-ray on living cells require strong radiation protection efforts [2]. Therefore, protection requirements of radiation workers and radiation exposed patients is critical to decrease the radiation effects and to avoid radiation risk. The term of radiation protection is set on ALARA principle namely As Low As Reasonably Achievable, which means that even the very low dose should be avoided if it is not necessary. ALARA can be applied through three basic parameters namely time, distance and shielding [3,4]. Among the those three basic rules, the term of shielding is defined as a reduction of scatter radiation by using high atomic
* Corresponding author. Uskudar University, Vocational School of Health Services, Radiotherapy Department, Istanbul, 34672, Turkey. E-mail address: [email protected] (H.O. Tekin). https://doi.org/10.1016/j.jallcom.2019.152484 0925-8388/© 2019 Elsevier B.V. All rights reserved.
number material [5]. In addition, the parameters determined for the shielding material are pre-determined properties that should be considered according to the radiation type and source energy. This material should be able to absorb the radiation energy and prevent it from passing and possible interactions with living organ and tissues. It is well-known that the most used material in diagnostic imaging facilities is lead for aprons as well as for personal shielding equipment. However, using of lead accompany with several effects and limitations, such as, toxicity, weight, inflexibility as well as the cost and installation [6]. As a result, many studies and researches were conducted to find out alternative materials to overcome limitations of lead as well as improve shielding efficiency in medical and industrial fields. Among the investigated alternative materials for radiation fields, alloys, composites and glasses have been introduced as suitable shielding material as environmental friendly, non-toxic compare to the lead [7e15]. Among the alternative radiation shielding materials, alloy materials have gained a major importance in the literature [9,11]. It is well-known that an alloy material is a combination of different types of metals. On the other hand, it can be also combination of a metal with a nonmetalic element. Providing such a combination also allows the
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development and improvement of different material properties. An important material property worth investigating is the nuclear radiation shielding performance for medical, industrial fields as well as personal use. The absolute composition of a alloy material may changes to meet certain applications requirements. Thus, some additional materials can be added into the alloy material to change the certain properties. A good example can be given by zinc (Zn) and copper (Cu) alloy namely Brass. Although copper and zinc alone have different types of material properties, the Brass alloy obtained from them has far superior material properties [16]. On the other hand, any structural modifications in alloys can cause some certain effects to mechanical, physical as well as chemical features [17]. One of the well-known alloy types is Pd-Mn-Ge alloys that have been investigated by different researchers to determine the various properties. For example, Yapav et al., have investigated the formation of icosahedral AleGaePdeMn alloys and provided a useful surface characteristic for scientific attention in operative sight of quasicrystals [18]. In another study, Pugaczowa-Michalska has investigated the supercell approach and obtained results showed that the disordered Pd2MnGe can be predicted as a mixture of different supercells [19]. Bonifacich et al., have determined the influence of thermal treatments in Fe-Pd-Mn alloys and investigated the effects in mechanical features [20]. So far, no large-scale nuclear radiation shielding investigation has been studied for PdMn-based alloys in the literature. This has encouraged us to conduct a large-scale investigation to investigate whether Pd-Mnbased alloys are shielding material that can be used in medical and industrial fields. It was aimed to observe the multiple effects Ga additive on nuclear radiation shielding performance of Pd50Mn50 binary alloys against to gamma-ray and neutron radiation. Previously, Ito et al., have investigated the martensitic transformation behaviors, microstructures, magnetic properties, and the shape memory effect SME for Pd50Mn50-xGax alloys [21] and further details about the fabricated alloys can be obtained from literature elsewhere [21]. The Pd50Mn50-xGax (denoted as xGa hereafter) alloys were fabricated by repeated arc melting in an argon atmosphere with high purity elements (99.9%). This available literature work has encouraged us the perform the recent continuation research on those fabricated alloy samples for determination of their nuclear radiation shielding performances. Therefore, a wide range gamma-ray and neutron shielding properties as well as gamma-ray transmission factors (TF) have been determined for six different types of Pd-Mn-Ga alloys with different Ga additive amounts. In the present investigation, Monte Carlo method by using MCNPX (v-2.6.0) has been utilized for the determination of mass attenuation coefficients (m/r) of Pd-Mn-Ga alloy samples. The obtained mass attenuation coefficients have been employed to determination of remaining important gamma-ray shielding parameters namely half value layer (HVL), mean free path (mfp), tenth value layer (TVL), effective electron number (Neff), effective atomic number (Zeff), respectively. Simultaneously, effective removal cross P section ( R) values for fast neutrons have been also calculated. The outcomes obtained from the recent investigation can provide a better understanding of the impact mechanism of Ga on nuclear radiation shielding performance of Pd-Mn alloys and can bring a different perspective to the wide-ranging researches on Ga additive. 2. Materials and methods 2.1. Gamma-ray and neutron shielding parameters The chemical structure of the selected alloys has been given in the Table 1. To investigate applicability of these binary alloys to radiation shielding applications as attenuator material, the gamma-
Table 1 Chemical compositions of investigated alloy samples (%wt). Sample ID
Pd
Mn
Ga
Pd50Mn50 (0Ga) Pd50Mn45Ga5 (5Ga) Pd50Mn40Ga10 (10Ga) Pd50Mn35Ga15 (15Ga) Pd50Mn30Ga20 (20Ga) Pd50Mn30Ga20 (25Ga)
0,512 0,506 0,504 0,502 0,508 0,500
0,488 0,442 0,390 0,340 0,284 0,245
0 0,052 0,106 0,158 0,208 0,255
ray and neutron attenuation properties for the 0Ga, 5Ga, 10Ga, 15Ga, 20Ga and 25Ga samples are studied. One of these attenuation properties is known as MAC (mass attenuation coefficients) (m/r), which basically refers the ability of the given materials to absorb radiation per unit of its mass. Atomic numbers of the given material and the energy level applied to that material are two important factors that effects MAC values. Thus, at different levels of energies yield differences in Mac values. Same is true for different atomic numbers. MAC values can be derived from the following formula.
mm ¼
X
wi ðm=rÞi
(1)
i
where wi denotes the weight fraction and ðm=rÞi is the mass attenuation coefficient of i.th element. These data derived from MCNPX Monte Carlo code and WinXcom program (Table 2). The ratio of thickness per unit is a significant factor effecting the attenuation properties of the given materials. Form this fact, values like HVL, TVL and LAC become important values to evaluate the applicability of any material for radiation shielding purposes. Linear attenuation coefficient (LAC, m (cm1)) refers the ability of the given material to absorb photons per unit thickness and the following formula gives us the LAC values:
m ¼ mm r
(2)
where mm and r denote the MAC value and the density of the material respectively. Half Value Layer (HVL, cm) is another important factor in evaluating the shielding effectiveness of the material with respect to its thickness per unit. HVL denotes the thickness that attenuates half of the radiation passing through the material. The HVL is derived from the following formula:
HVL ¼
ln2
m
(3)
In a similar way, the tenth value layer (TVL, cm) symbolises the thickness of the material that decreases the radiation passing by a factor of one tenth of the initial level. The equation for the calculation of TVL is the following:
TVL ¼
ln10
m
(4)
where m corresponds to the total linear attenuation coefficient. Another factor effecting the quality of attenuation I, radiation shielding is mean free path (MFP, cm), which is basically the average distance taken by moving particle between two consecutive collusion. MFP is derived from the formula below:
MFP ¼
1
m
(5)
To determine the result of the interaction of energy and material, effective atomic number (Zeff) is an important parameter. Zeff
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Table 2 Mass attenuation coefficients (m/r) of alloy samples obtained from MCNPX version 2.6.0 and WinXcom. Energy (MeV)
0Ga (m/r)
5Ga (m/r)
10Ga (m/r)
MCNPX (2.6.0)
WinXcom
MCNPX (2.6.0)
WinXcom
MCNPX (2.6.0)
WinXcom
0,02 0,02 0,03 0,04 0,05 0,06 0,08 0,10 0,15 0,20 0,30 0,40 0,50 0,60 0,80 1,00 1,50 2,00 3,00 4,00 5,00 6,00 8,00 10,00 15,00
44,21474 20,18660 22,36843 9,95446 5,78567 3,45841 1,54248 0,87225 0,36579 0,22394 0,13013 0,10281 0,08855 0,07855 0,06924 0,05924 0,04871 0,04236 0,03725 0,03412 0,03300 0,03285 0,03292 0,03351 0,03598
43,55157 19,71843 21,22424 9,80793 5,36653 3,28125 1,52883 0,86917 0,35161 0,21266 0,12897 0,10103 0,08675 0,07766 0,06605 0,05851 0,04735 0,04162 0,03616 0,03387 0,03287 0,03251 0,03272 0,03348 0,03581
46,25170 21,00874 22,45244 9,97452 5,82476 3,46820 1,55639 0,88241 0,36897 0,22458 0,13157 0,10293 0,08801 0,07824 0,06818 0,05835 0,04566 0,04181 0,03698 0,03421 0,03357 0,03297 0,03298 0,03359 0,03607
45,45528 20,62250 21,35390 9,86307 5,39454 3,29725 1,53542 0,87245 0,35250 0,21298 0,12902 0,10101 0,08672 0,07762 0,06600 0,05846 0,04731 0,04159 0,03616 0,03388 0,03290 0,03255 0,03279 0,03356 0,03592
48,56981 22,25175 23,78547 9,99501 5,84217 3,47851 1,56247 0,89221 0,37004 0,22569 0,13217 0,10307 0,08783 0,07814 0,06799 0,05791 0,04513 0,04157 0,03651 0,03434 0,03390 0,03317 0,03314 0,03398 0,03619
47,37668 21,53814 21,60491 9,97518 5,45381 3,33221 1,55051 0,88026 0,35480 0,21392 0,12926 0,10108 0,08672 0,07760 0,06596 0,05842 0,04727 0,04157 0,03616 0,03391 0,03295 0,03262 0,03288 0,03368 0,03608
Energy (MeV)
15Ga (m/r)
0,02 0,02 0,03 0,04 0,05 0,06 0,08 0,10 0,15 0,20 0,30 0,40 0,50 0,60 0,80 1,00 1,50 2,00 3,00 4,00 5,00 6,00 8,00 10,00 15,00
20Ga (m/r)
MCNPX (2.6.0)
WinXcom
MCNPX (2.6.0)
WinXcom
MCNPX (2.6.0)
WinXcom
50,21700 23,82476 23,94710 10,25774 5,85221 3,48700 1,57024 0,89621 0,37112 0,22623 0,13310 0,10314 0,08754 0,07751 0,06714 0,05766 0,04501 0,04124 0,03614 0,03457 0,03399 0,03353 0,03350 0,03404 0,03457
49,22789 22,42028 21,84459 10,08218 5,51036 3,36557 1,56490 0,88770 0,35700 0,21482 0,12948 0,10114 0,08672 0,07757 0,06592 0,05837 0,04723 0,04154 0,03617 0,03394 0,03300 0,03269 0,03298 0,03379 0,03624
51,24017 23,99854 24,24770 10,59854 5,87142 3,51225 1,61250 0,90998 0,37951 0,22891 0,13541 0,10390 0,08761 0,07784 0,06701 0,05750 0,04487 0,04100 0,03607 0,03461 0,03404 0,03374 0,03371 0,03424 0,03471
50,90389 23,22504 22,29298 10,28779 5,62126 3,43201 1,59418 0,90310 0,36171 0,21682 0,13006 0,10135 0,08680 0,07759 0,06590 0,05833 0,04719 0,04152 0,03619 0,03399 0,03308 0,03280 0,03313 0,03398 0,03648
53,58701 25,01175 24,65221 10,71005 5,87541 3,51498 1,61571 0,91014 0,37850 0,22862 0,01339 0,10381 0,08734 0,07781 0,06681 0,05734 0,04463 0,04095 0,03601 0,03495 0,03412 0,03385 0,03386 0,03459 0,03486
52,65838 24,05631 22,33929 10,30421 5,62819 3,43529 1,59511 0,90338 0,36167 0,21675 0,12999 0,10129 0,08675 0,07754 0,06585 0,05829 0,04716 0,04149 0,03618 0,03400 0,03310 0,03282 0,03317 0,03403 0,03655
refers the average atomic number derived from the weighted atomic numbers of the constituent atoms and the formula below is used to calculate the Zeff values [22,23]:
Zeff ¼
sa se
(6)
The macroscopic effective removal cross section (SR) (cm1) is important for the attenuation of fast neutrons in materials. The following formula gives SR values, which are calculated from the value of their constituent elements:
X
R¼
25Ga (m/r)
X X . R r Wi
i
(7)
P where R=r (cm2/g) denotes mass removal cross section of the ith constituent while Wi is the partial density (g/.cm3), which is derived from the following formula:
Wi ¼ r:wi
(8)
WinXcom a web-based database to compute photon cross sections for scattering, total attenuation coefficients, pair production and photoelectric absorption for any mixture, compound or element (Z 100), at energies from 1 keV to 100 GeV.
2.2. MCNPX Monte Carlo code The quantity of researches on the shielding performance of
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different types of new-generation shielding materials such as alloys, glassy systems, concretes and compounds to be used in nuclear radiation fileds is increasing day-by-day. This condition also increases the frequency of the type of study methods. A Monte Carlo simulation code substantially models the possible interaction scenario based on simulation principles. In this study, we used MCNPX (Monte Carlo N-Particle Transport Code System-extended) code for investigation of broad range nuclear shielding performance of different types of Pd-Mn binary alloys. The definition of binary alloy samples has been done by considering the chemical compositions of each alloy sample. Previously, different studies have been focused on MCNPX code application on evaluation of nuclear shielding abilities of different types of alloys for various aims [9,11]. In the present investigation, MCNPX (Monte Carlo NParticle Transport Code System-extended) code was used to calculate mass attenuation coefficients of alloy samples by applying the basis of Lambert-Beer rule. Fig. 1 presents the 2-D view of gamma-ray attenuation setup of MCNPX with main simulation equipment. To detect the attenuated photons thru the alloy attenuator sample, a 3 3 inch NaI(Tl) scintillation detector has been modeled considering the basic parameters and dimensions [24]. The 3-D view of modeled detector can be seen in Fig. 2. At last, gamm-ray transmission factors of investigated binary alloy samples have been calculated using MCNPX code. In order to measure the quantity of primary gamma-ray from the source and secondary and attenuated gamma-ray after passing through the sample, two detection areas (F4 Tally Mesh) have been defined, separately. It is to be noted that examined alloy samples was designed as circular geometry with a thickness of 1 cm and a diameter of 5 cm. The 3-D cross-sectional structure of transmission factors calculations obtained from MCNPX Visual Editor (VE X_22S) is also presented in Fig. 3. Finally, it is to be noted that some variance reduction techniques such as energy cut-off and optimum size of simulation mother volume has been defined in input file. To avoid from the unnecessary particle tracking, we have defined the value of energy cut-off as 1 keV. It means that no photon tracking has been done above 1 keV.
3. Results and discussion MAC (mm) of the binary alloys are estimated at various photon energies through derived from through MCNPX simulation code. These samples are initially derivative of Pd-Mn based alloys. The Fig. 1 gives the corresponding MAC values between 0.02 MeV and 15 MeV. From this figure, it can be seen that the MAC values sharply decrease while the photon energy increases to 0.511 MeV. The cross
Fig. 2. MCNPX Visual Editor (VE X_22S) Screenshot of modeled 3 3 inch NaI(Tl) detector.
section of the photoelectric absorbing effect is a function of the atomic number as Z45 in low energy region, where most of the interaction between the alloy samples and the photons occurs. MAC values becomes smaller after 0.511 MeV and almost constant for all selected samples, and that result of the linear dependence between cross-section of Compton scattering and the atomic number. The pair production mechanism becomes the dominant process in the higher energy region, and it yields a small increase in the mm values. From Fig. 4, it is seen that the MAC has the maximum values for 25Ga. From that figure, it can be seen that both energy and chemical structure of the alloys samples are vital for the values of mm. The values of mm are higher in the low energy regions, even though their structures consist of Ga. The photoelectric effect becomes dominant in the low energy regions yielding an inverse relations between mm values and energy levels. The photoelectric cross section changes proportionally with Z45 and an inversely proportional incident photon energy is given as E3.5. However, at higher energy regions, the pair production dominates the process while Z2 at higher energies is related to the cross section for this process. Similar behaviors have been observed by Shams et al., in the same photon energy regions for mentioned radiation-matter einteractions [25]. With regard to the of chemical composition of alloys samples, as 25Ga contain more Ga elements than the other samples, photon energy is high for them while low for 0Ga and 5Ga.
Fig. 1. The appearance of simulation setup and position of equipment obtained from MCNPX Visual Editor (VE X_22S).
H.O. Tekin, O. Kilicoglu / Journal of Alloys and Compounds 815 (2020) 152484
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Fig. 5. Half value layer (HVL) of the binary alloys samples.
Fig. 3. MCNPX Visual Editor (VE X_22S) Screenshot of modeled setup for gamma-ray transmission factors (TF) simulations.
These two are the reference samples and depicted in the Fig. 4. In the medium level energies from 0.511 MeV upward Compton scattering grows into dominant process. Thus, the mm values of the alloys decline gradually and become constant under 1 MeV due to the linear correlation of the atomic number Z and cross-section of Compton scattering. Small TVL, HVL, and MFP are vital parameters determining the ability of radiation attenuation of the given materials. The variation in the TVL and HVL values with respect to changing energy graphically depicted in the Fig. 5 and Fig. 6, respectively. It can be clearly seen from the Figs. 5 and 6 that the TVL and HVL are proportional to the photon energy contrary to the
Fig. 4. Mass attenuation coefficient of the selected binary alloys with photon energy 0.02 MeVe15 MeV.
MAC. Thus, as the energy rises, the TVL and HVL values increase as well. Fig.s 5 and 6 reveal that TVL, HVL, and MFP (Fig. 7) values initially increase as the photon energy increase and then stay stable with 5 MeV and upper level energy levels. As the energy values increase, the photon energy the HVL values rapidly increase and maximum HVL is observed at 5 MeV for all alloy samples. The behavior of HVL with energy can be clarified similarly to the aforementioned discussion of mm. The behaviors of HVL, TVL and MFP are directly depend on linear attenuation coefficients of alloy samples (see the equations (2)e(5)). The linear attenuation coefficient (m) is directly related with material density. Therefore, densities of the investigated alloys have influenced the obtained HVL, TVL and MFP values. For example, with higher density 0Ga and 5Ga alloy samples have bigger TVL and HVL values with regards to other. For these five binary alloys, the MFP (1/m) values are also assessed for the energy region of 0.015 MeVe15 MeV as given Fig. 7. MFP values of 0Ga, 5Ga, 10Ga, 15Ga, 20Ga and 25Ga are in the range of 0.0025e2.9948 cm, 0.0024e2.9974 cm, 0.0023e3.0149 cm, 0.0022e3.0369 cm, 0.0022e3.0587 cm and 0.0021e3.0967, respectively. As in the TVL and HVL, 20 Ga and 25Ga are the samples with the minimum MFP. Zeff values are also proporational to photon energy. As it shown in Fig. 8. we can see that Zeff has decline swiftly in the low energy region below 0.356 MeV, where photoelectric absorption dominates the process and variation in Zeff values are large. This can be due to that samples of binary alloys have no heavy
Fig. 6. Tenth value layer (TVL) of the binary alloys samples.
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Fig. 7. Mean free path (MFP) of the binary alloys samples.
Fig. 8. Effective atomic numbers of the binary alloys samples with photon energy.
elements in their compositions. That is the main factor yielding the sudden declines in the Zeff values. While Compton scattering become the dominant processes in the medium energies between 0.511 MeV < E < 1.33 MeV, Zeff values reach the lowest level. 20 Ga and 25Ga are two alloys with the highest Zeff values of 32.75e35.83and 32.94e36,01respectively. Pair production becomes dominating processes in the high energy region between 5 MeV and 20 MeV and Zeff grows slowly due to a weaker Z2 dependence in this region. The variations of Zeff with regard to changing photon energy can be seen in the Fig. 8. From the figure, we see that the Zeff decreases in low energy region (E < 1 MeV) for all of the selected alloys with the increasing photon energies. That result derives from decreasing mm values as the photon energy rises. Larger atomic number in Ga element cause increasing Zeff values. For example, 20 Ga and 25Ga, alloys, which have larger portion of Ga in their composition, have larger Zeff values than other materials do. The Fig. 4 shows that 20Ga and 25Ga have highest Zeff values respectively. For almost all of the alloy samples, Zeff values stay explicitly constant in medium energy level since the changes in Z and cross section of the Compton process. As shown in Fig. 9 the gamma-ray transmission factors of alloy samples changed with changing Ga concentration from % 0 to % 0,255% (wt). Among the binary alloy samples examined, the highest Ga-containing sample, unlike other alloy samples, provied the lowest gamma-ray transmission, which means having the highest m value. Similar relationship between Sb2O3 and WO3 and effects on transmission factors of various amorphous materials have been reported previously by Sayyed et al., [26]. The effective removal cross-section (SR) has generated for Ga containing alloys by the means of Equations (10) and (11). It is fair to claim that there is a negative correlation between increasing Ga in the binary alloys. Minor variations in the SR values deriving from density of the alloys samples can be observed. The highest SR value belongs to the 0Ga sample (Fig. 10). The term of effective removal cross-section can be obtained with the information of elemental weigth fractions in sample (%) and (SR)i of each element. It can be seen from the Table 1, 0Ga sample is the sample with highest amount of Mn additive. Among the investigated alloy samples, Mn constituent has the higest SR with 0.0203 [27]. Since the effective removal cross-section is directly
Fig. 9. Gamma-ray transmissions of investigated alloy samples.
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energy region. This can be due to differences between density and elemental mass fractions of 25Ga and Ag92.5/Cu7.5 samples. The differences between obtained mass attenuation coefficients have been decreased up to 500 keV. The differences between the mass attenuation coefficients have been gradually decreased above 500 keV energy. 4. Conclusion
Fig. 10. Effective removal cross-section values of the binary alloys with density.
The term of alloy is a well-known material type in terms of radiation equipment. Due to their advanced material properties, alloys can provide direct solutions for the radiation shielding and collimation of radiation beam. Some of the well-known alloys for radiation facilities are Tungsten alloys and Lead Alloys. Their potenital in the radiation sciences and lack in the literature have encouraged us to investigate the nuclear shieldnig abilities of Pd/ Mn binary alloys and impact og Ga additive. The aim of this study was to present the gamma-ray and neutron shielding properties of different type of Ga additive Pd/Mn binary alloys. The mm values were calculated by using the MCNPX simulation code in the 0.02e15 MeV energy region. By using the obtained mm values, HVL, TVL, MFP and Zeff gamma shielding parameters were calculated for the investigated alloy samples to determine the gamma radiation shielding ability. The results underlined that both mm and Zeff values are increased as the Ga concentration increases. Thus, the study is indicates that 25Ga alloy sample owns distinguished protection ability to attenuate the photon and proton radiations. The outcomes of the recent investigation has underlined the status of 25Ga sample for radiation shielding application. The wide-range of basic shielding parameters of Pd/Mn binary alloys with Ga additive can be useful for advanced investigations on those samples with their own chemical structure. It can be concluded that effect of Ga can be investigated in terms of another materials properties and rest of the nuclear shielding properties for future applications. Declaration of competing interest None. Acknowledgements None.
Fig. 11. A comparison between mass attenuation coefficients of 25Ga (this study) and Ag92.5/Cu7.5 [28] samples.
proportional to SR, decreasing of Mn amount in the alloy samples has caused to reduction of effective removal cross-section of alloy samples. Finally, to compare the shielding performances of investigated alloy samples with previous investigations, mass attenuaation coefficients have been calculated in the photon energy range of 81e1333 keV. Previously, Akman et al., have investigated the shielding performances of four (Ag92.5/Cu7.5, Ag72/Cu28, Pd94/ Cr6 and Pd60/Cu40) different types of alloys [28]. Among the investigated alloy samples, Ag92.5/Cu7.5 sample has been reported as superior shielding material against to gamma-ray. Similar to their study, we have calculated mass attenuation coefficients of 25Ga sample (superior gamma shielding sample of the present investigation) in the photon energy range of 81e1333 keV. Next, we have compared the obtained mass attenuation coefficients (see Fig. 11). It can be seen from the Fig. 11 that slight differences have been occured in the low energy region. The sample encoded Ag92.5/Cu7.5 has showed better shielding performance in the low-
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H.O. Tekin, O. Kilicoglu / Journal of Alloys and Compounds 815 (2020) 152484 projected range (PR) andnuclear radiation shielding abilities of silicate glasses, Results. Phys. 14 (2019) 102424. https://doi.org/10.1016/j.rinp.2019.102424. O. Agar, M.I. Sayyed, F. Akman, H.O. Tekin, M.R. Kacal, An extensive investigation on gamma ray shielding features of Pd/Ag-based alloys, Nucl. Eng. Technol. (2018). Available Online 21 December, https://doi.org/10.1016/j.net. 2018.12.014. H.O. Tekin, E. Kavaz, E.E. Altunsoy, M. Kamislioglu, O. Kilicoglu, O. Agar, M.I. Sayyed, N. Tarhan, Characterization of a broad range gamma-ray and neutron shielding properties of MgO-Al2O3-SiO2-B2O3 and Na2O-Al2O3SiO2 glass systems, J. Non-Cryst. Solids 518 (2019) 92e102. https://doi.org/ 10.1016/j.jnoncrysol.2019.05.012. F. Akman, M.I. Sayyed, M.R. Kacal, H.O. Tekin, Investigation of photon shielding performances of some selected alloys by experimental data, theoretical and MCNPX code in the energy range of 81 keV-1333 keV, J. Alloy. Comp. 772 (2019) 516e524, 25 January, https://doi.org/10.1016/j.jallcom. 2018.09.177. Shamsan S. Obaid, et al., Attenuation coefficients and exposure buildup factor of some rocks for gamma ray shielding applications, Radiat. Phys. Chem. 148 (2018) 86e94. https://doi.org/10.1016/j.radphyschem.2018.02.026. Ashok Kumar, et al., Experimental studies and Monte Carlo simulations on gamma ray shielding competence of (30þ x) PbO10WO3 10Na2O- 10MgO(40-x) B2O3 glasses, Prog. Nucl. Energy (2019) 103047. Shamsan S. Obaid, et al., Photon attenuation coefficients of different rock samples using MCNPX, Geant4 simulation codes and experimental results: a comparison study, Radiat. Eff. Defects Solids 173 (11e12) (2018) 900e914. S. Kobayashi, N. Hosoda, R. Takashima, Tungsten alloys as radiation protection materials, Nucl. Instrum. Methods Phys. Res. 390 (1997) 426e430. https://doi. org/10.1016/S0168-9002(97)00392-6. Taranjot Kaur, Jeewan Sharma, Tejbir Singh, Review on scope of metallic alloys in gamma rays shield designing, Prog. Nucl. Energy 113 (2019) 95e113. https://doi.org/10.1016/j.pnucene.2019.01.016. L.N. Shiganov, S.V. Shakov, L.V. Tarasenko, A.L. Plokhikh, Examination of the effect of the speed of laser welding on structure and properties of aluminium alloys alloyed with lithium and scandium, Weld. Int. 19 (2005) 982e986. T.P. Yadav, Devinder Singh, Rohit R. Shahi, M.A. Shaz, R.S. Tiwari, O.N. Srivastava, Synthesis of quasicrystalline film of AleGaePdeMn alloy, Thin Solid Films 534 (2013) 265e269. https://doi.org/10.1016/j.tsf.2013.03. 012. M. Pugaczowa-Michalska, Magnetic moment of Mn in disordered Pd2MnGe Heusler alloy as studied by CPA and supercell modelling, J. Magn. Magn.
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Contents lists available at ScienceDirect
Journal of Alloys and Compounds journal homepage: http://www.elsevier.com/locate/jalcom
The influence of gallium (Ga) additive on nuclear radiation shielding effectiveness of Pd/Mn binary alloys H.O. Tekin a, b, *, O. Kilicoglu b, c a
Uskudar University, Vocational School of Health Services, Radiotherapy Department, Istanbul, 34672, Turkey Uskudar University, Medical Radiation Research Center (USMERA), Istanbul, 34672, Turkey c Uskudar University, Department of Nuclear Technology and Radiation Protection, Istanbul, 34672, Turkey b
a r t i c l e i n f o
a b s t r a c t
Article history: Received 29 July 2019 Received in revised form 14 September 2019 Accepted 27 September 2019 Available online 28 September 2019
The aim of this investigation was to present the gamma-ray and neutron shielding properties of different type of Ga additive Pd/Mn binary alloys. Therefore, mass attenuation coefficient (mm) values of different types of Pd-Mn-Ga alloys were calculated using the MCNPX simulation code in the 0.02e15 MeV energy region. Afterwards, the obtained mm values have been utilized for determination of HVL, TVL, MFP and Zeff gamma shielding parameters for evaluation of the gamma radiation shielding abilities of alloy P samples. Moreover, effective removal cross-sections ( R) of investigated alloy samples have been calculared. The results showed that both mm and Zeff values are increased as the Ga concentration increases. Thus, the study is indicates that 25Ga alloy sample owns distinguished protection ability to attenuate the gamma-ray radiation. The results also showed that 0Ga alloy sample which containing %0 of Ga has the P highest R value as a most effective alloy sample among the other samples for fast neutron shielding. To observe the shielding paerformance of superior sample, we have compared our results with previous available investigations in literature. It can be concluded that Ga additive for this type of binary alloys can help to increase the shielding gamma-ray performance. © 2019 Elsevier B.V. All rights reserved.
Keywords: Pd/Mn alloys Gamma-ray shielding Monte Carlo method MCNPX
1. Introduction The extensive utilizations with ionizing radiation in different areas of medical applications such as diagnostic imaging, radiation therapy, nuclear medicine is increasing day-by-day. Moreover, it has been using in various industrial application areas such as food preservative and sterilization [1]. The possible effect of ionizing radiation such as gamma ray and x-ray on living cells require strong radiation protection efforts [2]. Therefore, protection requirements of radiation workers and radiation exposed patients is critical to decrease the radiation effects and to avoid radiation risk. The term of radiation protection is set on ALARA principle namely As Low As Reasonably Achievable, which means that even the very low dose should be avoided if it is not necessary. ALARA can be applied through three basic parameters namely time, distance and shielding [3,4]. Among the those three basic rules, the term of shielding is defined as a reduction of scatter radiation by using high atomic
* Corresponding author. Uskudar University, Vocational School of Health Services, Radiotherapy Department, Istanbul, 34672, Turkey. E-mail address: [email protected] (H.O. Tekin). https://doi.org/10.1016/j.jallcom.2019.152484 0925-8388/© 2019 Elsevier B.V. All rights reserved.
number material [5]. In addition, the parameters determined for the shielding material are pre-determined properties that should be considered according to the radiation type and source energy. This material should be able to absorb the radiation energy and prevent it from passing and possible interactions with living organ and tissues. It is well-known that the most used material in diagnostic imaging facilities is lead for aprons as well as for personal shielding equipment. However, using of lead accompany with several effects and limitations, such as, toxicity, weight, inflexibility as well as the cost and installation [6]. As a result, many studies and researches were conducted to find out alternative materials to overcome limitations of lead as well as improve shielding efficiency in medical and industrial fields. Among the investigated alternative materials for radiation fields, alloys, composites and glasses have been introduced as suitable shielding material as environmental friendly, non-toxic compare to the lead [7e15]. Among the alternative radiation shielding materials, alloy materials have gained a major importance in the literature [9,11]. It is well-known that an alloy material is a combination of different types of metals. On the other hand, it can be also combination of a metal with a nonmetalic element. Providing such a combination also allows the
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H.O. Tekin, O. Kilicoglu / Journal of Alloys and Compounds 815 (2020) 152484
development and improvement of different material properties. An important material property worth investigating is the nuclear radiation shielding performance for medical, industrial fields as well as personal use. The absolute composition of a alloy material may changes to meet certain applications requirements. Thus, some additional materials can be added into the alloy material to change the certain properties. A good example can be given by zinc (Zn) and copper (Cu) alloy namely Brass. Although copper and zinc alone have different types of material properties, the Brass alloy obtained from them has far superior material properties [16]. On the other hand, any structural modifications in alloys can cause some certain effects to mechanical, physical as well as chemical features [17]. One of the well-known alloy types is Pd-Mn-Ge alloys that have been investigated by different researchers to determine the various properties. For example, Yapav et al., have investigated the formation of icosahedral AleGaePdeMn alloys and provided a useful surface characteristic for scientific attention in operative sight of quasicrystals [18]. In another study, Pugaczowa-Michalska has investigated the supercell approach and obtained results showed that the disordered Pd2MnGe can be predicted as a mixture of different supercells [19]. Bonifacich et al., have determined the influence of thermal treatments in Fe-Pd-Mn alloys and investigated the effects in mechanical features [20]. So far, no large-scale nuclear radiation shielding investigation has been studied for PdMn-based alloys in the literature. This has encouraged us to conduct a large-scale investigation to investigate whether Pd-Mnbased alloys are shielding material that can be used in medical and industrial fields. It was aimed to observe the multiple effects Ga additive on nuclear radiation shielding performance of Pd50Mn50 binary alloys against to gamma-ray and neutron radiation. Previously, Ito et al., have investigated the martensitic transformation behaviors, microstructures, magnetic properties, and the shape memory effect SME for Pd50Mn50-xGax alloys [21] and further details about the fabricated alloys can be obtained from literature elsewhere [21]. The Pd50Mn50-xGax (denoted as xGa hereafter) alloys were fabricated by repeated arc melting in an argon atmosphere with high purity elements (99.9%). This available literature work has encouraged us the perform the recent continuation research on those fabricated alloy samples for determination of their nuclear radiation shielding performances. Therefore, a wide range gamma-ray and neutron shielding properties as well as gamma-ray transmission factors (TF) have been determined for six different types of Pd-Mn-Ga alloys with different Ga additive amounts. In the present investigation, Monte Carlo method by using MCNPX (v-2.6.0) has been utilized for the determination of mass attenuation coefficients (m/r) of Pd-Mn-Ga alloy samples. The obtained mass attenuation coefficients have been employed to determination of remaining important gamma-ray shielding parameters namely half value layer (HVL), mean free path (mfp), tenth value layer (TVL), effective electron number (Neff), effective atomic number (Zeff), respectively. Simultaneously, effective removal cross P section ( R) values for fast neutrons have been also calculated. The outcomes obtained from the recent investigation can provide a better understanding of the impact mechanism of Ga on nuclear radiation shielding performance of Pd-Mn alloys and can bring a different perspective to the wide-ranging researches on Ga additive. 2. Materials and methods 2.1. Gamma-ray and neutron shielding parameters The chemical structure of the selected alloys has been given in the Table 1. To investigate applicability of these binary alloys to radiation shielding applications as attenuator material, the gamma-
Table 1 Chemical compositions of investigated alloy samples (%wt). Sample ID
Pd
Mn
Ga
Pd50Mn50 (0Ga) Pd50Mn45Ga5 (5Ga) Pd50Mn40Ga10 (10Ga) Pd50Mn35Ga15 (15Ga) Pd50Mn30Ga20 (20Ga) Pd50Mn30Ga20 (25Ga)
0,512 0,506 0,504 0,502 0,508 0,500
0,488 0,442 0,390 0,340 0,284 0,245
0 0,052 0,106 0,158 0,208 0,255
ray and neutron attenuation properties for the 0Ga, 5Ga, 10Ga, 15Ga, 20Ga and 25Ga samples are studied. One of these attenuation properties is known as MAC (mass attenuation coefficients) (m/r), which basically refers the ability of the given materials to absorb radiation per unit of its mass. Atomic numbers of the given material and the energy level applied to that material are two important factors that effects MAC values. Thus, at different levels of energies yield differences in Mac values. Same is true for different atomic numbers. MAC values can be derived from the following formula.
mm ¼
X
wi ðm=rÞi
(1)
i
where wi denotes the weight fraction and ðm=rÞi is the mass attenuation coefficient of i.th element. These data derived from MCNPX Monte Carlo code and WinXcom program (Table 2). The ratio of thickness per unit is a significant factor effecting the attenuation properties of the given materials. Form this fact, values like HVL, TVL and LAC become important values to evaluate the applicability of any material for radiation shielding purposes. Linear attenuation coefficient (LAC, m (cm1)) refers the ability of the given material to absorb photons per unit thickness and the following formula gives us the LAC values:
m ¼ mm r
(2)
where mm and r denote the MAC value and the density of the material respectively. Half Value Layer (HVL, cm) is another important factor in evaluating the shielding effectiveness of the material with respect to its thickness per unit. HVL denotes the thickness that attenuates half of the radiation passing through the material. The HVL is derived from the following formula:
HVL ¼
ln2
m
(3)
In a similar way, the tenth value layer (TVL, cm) symbolises the thickness of the material that decreases the radiation passing by a factor of one tenth of the initial level. The equation for the calculation of TVL is the following:
TVL ¼
ln10
m
(4)
where m corresponds to the total linear attenuation coefficient. Another factor effecting the quality of attenuation I, radiation shielding is mean free path (MFP, cm), which is basically the average distance taken by moving particle between two consecutive collusion. MFP is derived from the formula below:
MFP ¼
1
m
(5)
To determine the result of the interaction of energy and material, effective atomic number (Zeff) is an important parameter. Zeff
H.O. Tekin, O. Kilicoglu / Journal of Alloys and Compounds 815 (2020) 152484
3
Table 2 Mass attenuation coefficients (m/r) of alloy samples obtained from MCNPX version 2.6.0 and WinXcom. Energy (MeV)
0Ga (m/r)
5Ga (m/r)
10Ga (m/r)
MCNPX (2.6.0)
WinXcom
MCNPX (2.6.0)
WinXcom
MCNPX (2.6.0)
WinXcom
0,02 0,02 0,03 0,04 0,05 0,06 0,08 0,10 0,15 0,20 0,30 0,40 0,50 0,60 0,80 1,00 1,50 2,00 3,00 4,00 5,00 6,00 8,00 10,00 15,00
44,21474 20,18660 22,36843 9,95446 5,78567 3,45841 1,54248 0,87225 0,36579 0,22394 0,13013 0,10281 0,08855 0,07855 0,06924 0,05924 0,04871 0,04236 0,03725 0,03412 0,03300 0,03285 0,03292 0,03351 0,03598
43,55157 19,71843 21,22424 9,80793 5,36653 3,28125 1,52883 0,86917 0,35161 0,21266 0,12897 0,10103 0,08675 0,07766 0,06605 0,05851 0,04735 0,04162 0,03616 0,03387 0,03287 0,03251 0,03272 0,03348 0,03581
46,25170 21,00874 22,45244 9,97452 5,82476 3,46820 1,55639 0,88241 0,36897 0,22458 0,13157 0,10293 0,08801 0,07824 0,06818 0,05835 0,04566 0,04181 0,03698 0,03421 0,03357 0,03297 0,03298 0,03359 0,03607
45,45528 20,62250 21,35390 9,86307 5,39454 3,29725 1,53542 0,87245 0,35250 0,21298 0,12902 0,10101 0,08672 0,07762 0,06600 0,05846 0,04731 0,04159 0,03616 0,03388 0,03290 0,03255 0,03279 0,03356 0,03592
48,56981 22,25175 23,78547 9,99501 5,84217 3,47851 1,56247 0,89221 0,37004 0,22569 0,13217 0,10307 0,08783 0,07814 0,06799 0,05791 0,04513 0,04157 0,03651 0,03434 0,03390 0,03317 0,03314 0,03398 0,03619
47,37668 21,53814 21,60491 9,97518 5,45381 3,33221 1,55051 0,88026 0,35480 0,21392 0,12926 0,10108 0,08672 0,07760 0,06596 0,05842 0,04727 0,04157 0,03616 0,03391 0,03295 0,03262 0,03288 0,03368 0,03608
Energy (MeV)
15Ga (m/r)
0,02 0,02 0,03 0,04 0,05 0,06 0,08 0,10 0,15 0,20 0,30 0,40 0,50 0,60 0,80 1,00 1,50 2,00 3,00 4,00 5,00 6,00 8,00 10,00 15,00
20Ga (m/r)
MCNPX (2.6.0)
WinXcom
MCNPX (2.6.0)
WinXcom
MCNPX (2.6.0)
WinXcom
50,21700 23,82476 23,94710 10,25774 5,85221 3,48700 1,57024 0,89621 0,37112 0,22623 0,13310 0,10314 0,08754 0,07751 0,06714 0,05766 0,04501 0,04124 0,03614 0,03457 0,03399 0,03353 0,03350 0,03404 0,03457
49,22789 22,42028 21,84459 10,08218 5,51036 3,36557 1,56490 0,88770 0,35700 0,21482 0,12948 0,10114 0,08672 0,07757 0,06592 0,05837 0,04723 0,04154 0,03617 0,03394 0,03300 0,03269 0,03298 0,03379 0,03624
51,24017 23,99854 24,24770 10,59854 5,87142 3,51225 1,61250 0,90998 0,37951 0,22891 0,13541 0,10390 0,08761 0,07784 0,06701 0,05750 0,04487 0,04100 0,03607 0,03461 0,03404 0,03374 0,03371 0,03424 0,03471
50,90389 23,22504 22,29298 10,28779 5,62126 3,43201 1,59418 0,90310 0,36171 0,21682 0,13006 0,10135 0,08680 0,07759 0,06590 0,05833 0,04719 0,04152 0,03619 0,03399 0,03308 0,03280 0,03313 0,03398 0,03648
53,58701 25,01175 24,65221 10,71005 5,87541 3,51498 1,61571 0,91014 0,37850 0,22862 0,01339 0,10381 0,08734 0,07781 0,06681 0,05734 0,04463 0,04095 0,03601 0,03495 0,03412 0,03385 0,03386 0,03459 0,03486
52,65838 24,05631 22,33929 10,30421 5,62819 3,43529 1,59511 0,90338 0,36167 0,21675 0,12999 0,10129 0,08675 0,07754 0,06585 0,05829 0,04716 0,04149 0,03618 0,03400 0,03310 0,03282 0,03317 0,03403 0,03655
refers the average atomic number derived from the weighted atomic numbers of the constituent atoms and the formula below is used to calculate the Zeff values [22,23]:
Zeff ¼
sa se
(6)
The macroscopic effective removal cross section (SR) (cm1) is important for the attenuation of fast neutrons in materials. The following formula gives SR values, which are calculated from the value of their constituent elements:
X
R¼
25Ga (m/r)
X X . R r Wi
i
(7)
P where R=r (cm2/g) denotes mass removal cross section of the ith constituent while Wi is the partial density (g/.cm3), which is derived from the following formula:
Wi ¼ r:wi
(8)
WinXcom a web-based database to compute photon cross sections for scattering, total attenuation coefficients, pair production and photoelectric absorption for any mixture, compound or element (Z 100), at energies from 1 keV to 100 GeV.
2.2. MCNPX Monte Carlo code The quantity of researches on the shielding performance of
4
H.O. Tekin, O. Kilicoglu / Journal of Alloys and Compounds 815 (2020) 152484
different types of new-generation shielding materials such as alloys, glassy systems, concretes and compounds to be used in nuclear radiation fileds is increasing day-by-day. This condition also increases the frequency of the type of study methods. A Monte Carlo simulation code substantially models the possible interaction scenario based on simulation principles. In this study, we used MCNPX (Monte Carlo N-Particle Transport Code System-extended) code for investigation of broad range nuclear shielding performance of different types of Pd-Mn binary alloys. The definition of binary alloy samples has been done by considering the chemical compositions of each alloy sample. Previously, different studies have been focused on MCNPX code application on evaluation of nuclear shielding abilities of different types of alloys for various aims [9,11]. In the present investigation, MCNPX (Monte Carlo NParticle Transport Code System-extended) code was used to calculate mass attenuation coefficients of alloy samples by applying the basis of Lambert-Beer rule. Fig. 1 presents the 2-D view of gamma-ray attenuation setup of MCNPX with main simulation equipment. To detect the attenuated photons thru the alloy attenuator sample, a 3 3 inch NaI(Tl) scintillation detector has been modeled considering the basic parameters and dimensions [24]. The 3-D view of modeled detector can be seen in Fig. 2. At last, gamm-ray transmission factors of investigated binary alloy samples have been calculated using MCNPX code. In order to measure the quantity of primary gamma-ray from the source and secondary and attenuated gamma-ray after passing through the sample, two detection areas (F4 Tally Mesh) have been defined, separately. It is to be noted that examined alloy samples was designed as circular geometry with a thickness of 1 cm and a diameter of 5 cm. The 3-D cross-sectional structure of transmission factors calculations obtained from MCNPX Visual Editor (VE X_22S) is also presented in Fig. 3. Finally, it is to be noted that some variance reduction techniques such as energy cut-off and optimum size of simulation mother volume has been defined in input file. To avoid from the unnecessary particle tracking, we have defined the value of energy cut-off as 1 keV. It means that no photon tracking has been done above 1 keV.
3. Results and discussion MAC (mm) of the binary alloys are estimated at various photon energies through derived from through MCNPX simulation code. These samples are initially derivative of Pd-Mn based alloys. The Fig. 1 gives the corresponding MAC values between 0.02 MeV and 15 MeV. From this figure, it can be seen that the MAC values sharply decrease while the photon energy increases to 0.511 MeV. The cross
Fig. 2. MCNPX Visual Editor (VE X_22S) Screenshot of modeled 3 3 inch NaI(Tl) detector.
section of the photoelectric absorbing effect is a function of the atomic number as Z45 in low energy region, where most of the interaction between the alloy samples and the photons occurs. MAC values becomes smaller after 0.511 MeV and almost constant for all selected samples, and that result of the linear dependence between cross-section of Compton scattering and the atomic number. The pair production mechanism becomes the dominant process in the higher energy region, and it yields a small increase in the mm values. From Fig. 4, it is seen that the MAC has the maximum values for 25Ga. From that figure, it can be seen that both energy and chemical structure of the alloys samples are vital for the values of mm. The values of mm are higher in the low energy regions, even though their structures consist of Ga. The photoelectric effect becomes dominant in the low energy regions yielding an inverse relations between mm values and energy levels. The photoelectric cross section changes proportionally with Z45 and an inversely proportional incident photon energy is given as E3.5. However, at higher energy regions, the pair production dominates the process while Z2 at higher energies is related to the cross section for this process. Similar behaviors have been observed by Shams et al., in the same photon energy regions for mentioned radiation-matter einteractions [25]. With regard to the of chemical composition of alloys samples, as 25Ga contain more Ga elements than the other samples, photon energy is high for them while low for 0Ga and 5Ga.
Fig. 1. The appearance of simulation setup and position of equipment obtained from MCNPX Visual Editor (VE X_22S).
H.O. Tekin, O. Kilicoglu / Journal of Alloys and Compounds 815 (2020) 152484
5
Fig. 5. Half value layer (HVL) of the binary alloys samples.
Fig. 3. MCNPX Visual Editor (VE X_22S) Screenshot of modeled setup for gamma-ray transmission factors (TF) simulations.
These two are the reference samples and depicted in the Fig. 4. In the medium level energies from 0.511 MeV upward Compton scattering grows into dominant process. Thus, the mm values of the alloys decline gradually and become constant under 1 MeV due to the linear correlation of the atomic number Z and cross-section of Compton scattering. Small TVL, HVL, and MFP are vital parameters determining the ability of radiation attenuation of the given materials. The variation in the TVL and HVL values with respect to changing energy graphically depicted in the Fig. 5 and Fig. 6, respectively. It can be clearly seen from the Figs. 5 and 6 that the TVL and HVL are proportional to the photon energy contrary to the
Fig. 4. Mass attenuation coefficient of the selected binary alloys with photon energy 0.02 MeVe15 MeV.
MAC. Thus, as the energy rises, the TVL and HVL values increase as well. Fig.s 5 and 6 reveal that TVL, HVL, and MFP (Fig. 7) values initially increase as the photon energy increase and then stay stable with 5 MeV and upper level energy levels. As the energy values increase, the photon energy the HVL values rapidly increase and maximum HVL is observed at 5 MeV for all alloy samples. The behavior of HVL with energy can be clarified similarly to the aforementioned discussion of mm. The behaviors of HVL, TVL and MFP are directly depend on linear attenuation coefficients of alloy samples (see the equations (2)e(5)). The linear attenuation coefficient (m) is directly related with material density. Therefore, densities of the investigated alloys have influenced the obtained HVL, TVL and MFP values. For example, with higher density 0Ga and 5Ga alloy samples have bigger TVL and HVL values with regards to other. For these five binary alloys, the MFP (1/m) values are also assessed for the energy region of 0.015 MeVe15 MeV as given Fig. 7. MFP values of 0Ga, 5Ga, 10Ga, 15Ga, 20Ga and 25Ga are in the range of 0.0025e2.9948 cm, 0.0024e2.9974 cm, 0.0023e3.0149 cm, 0.0022e3.0369 cm, 0.0022e3.0587 cm and 0.0021e3.0967, respectively. As in the TVL and HVL, 20 Ga and 25Ga are the samples with the minimum MFP. Zeff values are also proporational to photon energy. As it shown in Fig. 8. we can see that Zeff has decline swiftly in the low energy region below 0.356 MeV, where photoelectric absorption dominates the process and variation in Zeff values are large. This can be due to that samples of binary alloys have no heavy
Fig. 6. Tenth value layer (TVL) of the binary alloys samples.
6
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Fig. 7. Mean free path (MFP) of the binary alloys samples.
Fig. 8. Effective atomic numbers of the binary alloys samples with photon energy.
elements in their compositions. That is the main factor yielding the sudden declines in the Zeff values. While Compton scattering become the dominant processes in the medium energies between 0.511 MeV < E < 1.33 MeV, Zeff values reach the lowest level. 20 Ga and 25Ga are two alloys with the highest Zeff values of 32.75e35.83and 32.94e36,01respectively. Pair production becomes dominating processes in the high energy region between 5 MeV and 20 MeV and Zeff grows slowly due to a weaker Z2 dependence in this region. The variations of Zeff with regard to changing photon energy can be seen in the Fig. 8. From the figure, we see that the Zeff decreases in low energy region (E < 1 MeV) for all of the selected alloys with the increasing photon energies. That result derives from decreasing mm values as the photon energy rises. Larger atomic number in Ga element cause increasing Zeff values. For example, 20 Ga and 25Ga, alloys, which have larger portion of Ga in their composition, have larger Zeff values than other materials do. The Fig. 4 shows that 20Ga and 25Ga have highest Zeff values respectively. For almost all of the alloy samples, Zeff values stay explicitly constant in medium energy level since the changes in Z and cross section of the Compton process. As shown in Fig. 9 the gamma-ray transmission factors of alloy samples changed with changing Ga concentration from % 0 to % 0,255% (wt). Among the binary alloy samples examined, the highest Ga-containing sample, unlike other alloy samples, provied the lowest gamma-ray transmission, which means having the highest m value. Similar relationship between Sb2O3 and WO3 and effects on transmission factors of various amorphous materials have been reported previously by Sayyed et al., [26]. The effective removal cross-section (SR) has generated for Ga containing alloys by the means of Equations (10) and (11). It is fair to claim that there is a negative correlation between increasing Ga in the binary alloys. Minor variations in the SR values deriving from density of the alloys samples can be observed. The highest SR value belongs to the 0Ga sample (Fig. 10). The term of effective removal cross-section can be obtained with the information of elemental weigth fractions in sample (%) and (SR)i of each element. It can be seen from the Table 1, 0Ga sample is the sample with highest amount of Mn additive. Among the investigated alloy samples, Mn constituent has the higest SR with 0.0203 [27]. Since the effective removal cross-section is directly
Fig. 9. Gamma-ray transmissions of investigated alloy samples.
H.O. Tekin, O. Kilicoglu / Journal of Alloys and Compounds 815 (2020) 152484
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energy region. This can be due to differences between density and elemental mass fractions of 25Ga and Ag92.5/Cu7.5 samples. The differences between obtained mass attenuation coefficients have been decreased up to 500 keV. The differences between the mass attenuation coefficients have been gradually decreased above 500 keV energy. 4. Conclusion
Fig. 10. Effective removal cross-section values of the binary alloys with density.
The term of alloy is a well-known material type in terms of radiation equipment. Due to their advanced material properties, alloys can provide direct solutions for the radiation shielding and collimation of radiation beam. Some of the well-known alloys for radiation facilities are Tungsten alloys and Lead Alloys. Their potenital in the radiation sciences and lack in the literature have encouraged us to investigate the nuclear shieldnig abilities of Pd/ Mn binary alloys and impact og Ga additive. The aim of this study was to present the gamma-ray and neutron shielding properties of different type of Ga additive Pd/Mn binary alloys. The mm values were calculated by using the MCNPX simulation code in the 0.02e15 MeV energy region. By using the obtained mm values, HVL, TVL, MFP and Zeff gamma shielding parameters were calculated for the investigated alloy samples to determine the gamma radiation shielding ability. The results underlined that both mm and Zeff values are increased as the Ga concentration increases. Thus, the study is indicates that 25Ga alloy sample owns distinguished protection ability to attenuate the photon and proton radiations. The outcomes of the recent investigation has underlined the status of 25Ga sample for radiation shielding application. The wide-range of basic shielding parameters of Pd/Mn binary alloys with Ga additive can be useful for advanced investigations on those samples with their own chemical structure. It can be concluded that effect of Ga can be investigated in terms of another materials properties and rest of the nuclear shielding properties for future applications. Declaration of competing interest None. Acknowledgements None.
Fig. 11. A comparison between mass attenuation coefficients of 25Ga (this study) and Ag92.5/Cu7.5 [28] samples.
proportional to SR, decreasing of Mn amount in the alloy samples has caused to reduction of effective removal cross-section of alloy samples. Finally, to compare the shielding performances of investigated alloy samples with previous investigations, mass attenuaation coefficients have been calculated in the photon energy range of 81e1333 keV. Previously, Akman et al., have investigated the shielding performances of four (Ag92.5/Cu7.5, Ag72/Cu28, Pd94/ Cr6 and Pd60/Cu40) different types of alloys [28]. Among the investigated alloy samples, Ag92.5/Cu7.5 sample has been reported as superior shielding material against to gamma-ray. Similar to their study, we have calculated mass attenuation coefficients of 25Ga sample (superior gamma shielding sample of the present investigation) in the photon energy range of 81e1333 keV. Next, we have compared the obtained mass attenuation coefficients (see Fig. 11). It can be seen from the Fig. 11 that slight differences have been occured in the low energy region. The sample encoded Ag92.5/Cu7.5 has showed better shielding performance in the low-
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