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Determining optical and radiation characteristics of cathode ray tubes' glass to be reused as radiation shielding glass
Author’s Accepted Manuscript Determining Optical and Radiation Characteristics of Cathode Ray Tubes' Glass to be reused as Radiation Shielding Glass A. Zughbi, M.H. Kharita, A. Shehada www.elsevier.com/locate/radphyschem
PII: DOI: Reference:
S0969-806X(16)30648-X http://dx.doi.org/10.1016/j.radphyschem.2017.02.035 RPC7437
To appear in: Radiation Physics and Chemistry Received date: 8 November 2016 Accepted date: 16 February 2017 Cite this article as: A. Zughbi, M.H. Kharita and A. Shehada, Determining Optical and Radiation Characteristics of Cathode Ray Tubes' Glass to be reused as Radiation Shielding Glass, Radiation Physics and Chemistry, http://dx.doi.org/10.1016/j.radphyschem.2017.02.035 This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting galley proof before it is published in its final citable form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.
Determining Optical and Radiation Characteristics of Cathode Ray Tubes’ Glass to be reused as Radiation Shielding Glass A.Zughbi 1 , M.H.Kharita 2 , A.Shehada 3 1,3
Department of Physics,Faculty of Sciences,Damascus University,Damascus, Syria 2 Department of Protection and Safety,AECS,P.O.Box 6091,Damascus, Syria
Abstract A new method of recycling glass of Cathode Ray Tubes (CRTs) has been presented in this paper. The glass from CRTs suggested being used as raw materials for the production of radiation shielding glass. Cathode ray tubes glass contains considerable amounts of environmentally hazardous toxic wastes, namely heavy metal oxides such as lead oxide (PbO). This method makes CRTs glass a favorable choice to be used as raw material for Radiation Shielding Glass and concrete. The heavy metal oxides increase its density, which make this type of glass nearly equivalent to commercially available shielding glass. CRTs glass have been characterized to determine heavy oxides content, density, refractive index, and radiation shielding properties for different GammaRay energies. Empirical methods have been used by using the Gamma-Ray source cobalt-60 and computational method by using the code XCOM. Measured and calculated values were in a good compatibility. The effects of irradiation by gamma rays of cobalt-60 on the optical transparency for each part of the CRTs glass have been studied. The Results had shown that some parts of CRTs glass have more resistant to Gamma radiation than others. The study had shown that the glass of cathode ray tubes could be recycled to be used as radiation shielding glass. This proposed use of CRT glass is only limited to the available quantity of CRT world-wide..
1
Introduction
The generated amount of waste electrical and electronic equipment (WEEE) or e-waste in the world is growing rapidly as shown in Fig.1. The content of hazardous components in electrical and electronic equipment (EEE) is a major concern during the waste management phase. Ideally, the materials in electronic products should be re-used when the products reach the end of their service life. In the European Union (EU), WEEE represents about 7.5 million tons each year, where computer monitors and TV sets containing cathode-ray tubes (CRTs) represent about 80 % of the total electronic waste [1],[2]. Huge amounts of toxic wastes (for example lead compounds) affect the environment. The total amount of lead in 315 million of personal computers exhausted between 1997 and 2004 in the united states is about 600 000 tons [3]. Additionally, these amounts of personal computers contain about 151.2 tons of gold and 1786.1 tons of silver [4],[5]. The aforementioned statistics indicate to the need to the development of new methods to recycle these costly (both economically and environmentally) products. The glass of cathode ray tubes (CRT) can be classified according to its chemical composition 1 [email protected] 2 [email protected] 3 [email protected]
1
into three parts; Panel glass, Funnel glass and Neck glass. The glass constitute between 50 % and 85 % of the total weight of a computer monitor or a television set [1].
Figure 1. The glass and non glass parts of typical cathode ray tube (CRT) [1].
All of the three parts of CRT glass contain hazardous heavy elements (i.e. lead, strontium, antimony, barium, europium, selenium etc. . .). Collected monitors are dismantled and treated, and the CRT glass generally ends up in a special landfill licensed for hazardous waste. Hence, in Europe almost 90 % of the end of life (EOL) electronic goods is disposed of in landfills [1]. As the lead content in these waste products represents as much as 80 % of the toxic metals in discard electronics, CRTs represent a clear potential pollution danger to the environment [1]. Therefore, many researches have been carried out to explore new methods for recycling CRTs [5]. The most conventional material used for the purpose of radiation shielding for nuclear reactors and nuclear waste storage is concrete with various aggregates. It is a mixture of light nuclei (primarily hydrogen) and heavy nuclei, giving it the ability to be an effective shield against neutron and gamma radiation. Concrete is relatively inexpensive and easy to cast in many shapes and sizes, in addition to being strong and structurally sturdy. However, prolonged exposure to nuclear radiation results in heating of the concrete, which causes a decrease in density and a possible loss of cooling water and/or gas. Another drawback of concrete is that it is not transparent to visible light, and one cannot see through the concrete to monitor what goes on inside. Glass can also act as effective shielding materials as an alternative to concrete, or as an additive into concrete mixes. They are typically transparent to visible light, if used without concrete mixes, and their properties can be modified significantly by changing composition and adopting variations in preparation techniques. During recent years, there has been increasing interest in the synthesis, structure, and physical properties of heavy metal oxide glass due to their high refractive index, high infrared transparency, high density, and good shielding of gamma rays [6],[7].
2
Materials and Methods
Cathode ray tubes made by Hitachi Co. (after year 2000) have been used in this research. The CRTs were dismantled, the glass parts were separated and cleaned very well, first by water and then by ethanol. The phosphorus deposited layer, and other foreign layers were etched out. The three types of glass in each CRT were separated. The average ratio for each part of glass in the studied samples are: Panel = 65 %, Funnel = 34 %, Neck = 1 % (by wt.). Samples have been analyzed using scanning electron microscopy SEM-EDX technique (the electron beam acceleration tension was fixed to 10 kV), to estimate their main components and their content of 2
heavy metals. The densities of the samples have been measured using Archimedes principle. Refraction indexes were measured using laser source (wavelength between 655 nm ± 25 nm) and by using Snell relation: n0 · sin θ0 = n · sin θ Attenuation coefficients of Gamma rays for the tested samples have been measured experimentally using Cobalt-60 as Gamma-Ray source (the photon energy peaks for Co-60 as the used source 1173.24 and 1332.5 keV), and have been calculated theoretically using the code XCOM [8]. Optical Transmission of the samples have been investigated in the visible range of the spectrum (between 400–800 nm) using UV- visible photo-spectrometer (Cecil instrument limited, model No. 2021). The samples have been prepared for optical transmission test by polishing on lapping machine and SiC polishing papers up to 1200 grits. The samples have been crashed and grinded, and the mixtures have been made from all different parts of CRT glass as the same ratios as existed in the original CRTs (Panel (65 %) + Funnel (34 %) + Neck (1 %); (by wt%)). The grinded glass have been melted in electric box type furnace using Pt crucible, and have been casted in simple stainless steel moulds. The resulted samples have been characterized in the same way as above mentioned. The radiation resistance properties of the prepared samples have been studied against different Gamma-Ray irradiation doses using Co60 as Gamma-Ray source. The glass have been exposed to three doses: 1 kGy, 3 kGy and 5 kGy at dose rate equal to 1 kGy/h. The samples have been stored for 16 hours before doing the measurments of the optical transmission spectra, to get rid of the effect of that fast fading in the recently irradiated samples.
3
Results and Discussion
It can be noticed from table 1. that the Funnel and neck parts of CRT contain relatively high contents of lead oxide, while the part Panel contains relatively high content of barium and strontium oxides. This result is in agreement with data existed in literatures. The three tested parts of glass are heavier than ordinary alkali lime silicate glass (density about 2.4 g/cm3 )as shown in table 2. Radiation attenuation efficiency of materials is related to its density. This result support the suggestion of using this type of glass as radiation shielding glass. Tables 3,4 show the linear attenuation coefficients, the half-value layers and the tenth value layers for the tested samples. The calculated and measured values are in a good compatibility. Table 1. Ratios of the oxides in each part of the CRT glass and the Mix (wt%). Oxide B2 O3 Na2 O MgO Al2 O3 SiO2 K2 O CaO SrO ZrO2 Sb2 O3 BaO CeO2 PbO SnO TiO2
Funnel 6.90 5.86 1.71 4.89 45.92 6.08 3.47 1.47 0.82 0.06 0.00 0.42 20.03 0.06 0.47
Panel 7.53 6.78 0.07 1.98 54.72 5.65 0.94 9.48 2.44 0.25 7.88 0.41 0.00 0.00 0.33
3
Nick 5.37 1.58 0.18 2.45 43.21 7.11 1.30 2.27 0.37 0.69 0.42 0.44 33.15 0.11 0.21
Mix 6.21 6.15 0.76 2.74 52.20 6.59 1.55 6.89 2.04 0.14 5.70 0.37 6.50 0.62 0.43
Table 2. The Density and The Refraction Index of the tested samples: Funnel, Panel and Mix. Glass Part Funnel Panel Mix(Mixture)
Density(g/cm3 )(±0.01) 3.01 2.77 2.88
Refractive Index Nd at (655±25)(±3.5%)nm 1.561 1.541 1.505
Table 3. The Linear Attenuation Coefficients of the samples (some type of glass have been added to compare with (has mark * [9])). Glass Type
Funnel Panel Mix Neck RS253G* RS323G* Lead
Density (g.cm−3 )
3.01 2.77 2.88 3.25 2.53 3.23 11.4
Measured Attenuation Coefficients (cm−1 ) At Energy Co-60 (keV)
0.19 0.16 0.17 0.14 0.18 0.66
Attenuation Coefficients Calculated by XCOM (cm−1 )
X-Ray 100 3.60 1.09 1.92 6.07
Cs-137 661.6 0.25 0.21 0.23 0.28
At Energies (keV) Co-60 1173.24 1332.5 0.18 0.17 0.16 0.15 0.17 0.16 0.19 0.18
Table 4. The Half Value and Tenth Value Layers of the samples. The Glass
Funnel Panel Mix Neck RS253G * RS323G * Lead
Half Value Layers At Isotope’s Energies (cm) Cs-137 Co-60 2.77 3.85 3.30 4.33 3.01 4.08 2.48 3.65 3.6 4.9 2.6 3.8 0.6 1.05
Tenth Value Layers At Isotope’s Energies (cm) Cs-137 Co-60 9.21 12.79 10.96 14.39 10.01 13.54 8.22 12.12 11.9 16.3 8.5 12.5 2.0 3.5
The Fig.2 shows optical transmission spectra of the samples; Funnel, Panel, and Mix glass (These spectra are for samples with 1 cm thick). The optical transparent loss is less for Funnel and the Mix glass which is between 30 to 40 % for most of the visible wavelength range. While it is varying between 50% to 15% for panel glass, which suggests the use of longer wavelength light sources to decrease the losses. Fig.2
Fig.3
4
Fig.4
Fig.5
Fig 2: The optical transmission for the Funnel, Panel and Mix glass. Fig 3: The effect of Gamma irradiation on the optical transmission spectrum of the funnel glass. Fig 4: The effect of irradiation on the transmission spectrum of panel glass. Fig 5: The effect of Gamma-Ray irradiation on the transmission spectrum of the Mix glass. Figures 3,4,5 show changes in optical transparency for the three investigated glass, against different Gamma-Ray irradiation doses (1,3 and 5 kGy). The optical transmission of the Funnel glass decreases when irradiation doses increases. The loss of its transparency is obvious at shorter wavelength range. Fig.4 shows that CRTs panel glass did not affected so much by Gamma-Ray irradiation; and the maximum loss of optical transmission in the spectra is about 20%. This radiation resistance of panel glass can be explained by the high content of Strontium oxide where some oxides have been used to stabilize glass [10]. The behavior of the Mix glass is in average of the behavior of the two parts of CRT glass. It has been affected moderately, and the effect getting more obvious in the range of the shorter wavelengths of the optical spectrum. To estimate the radiation resistance of the studied glass, their behavior after irradiation can be compared to the behavior of a well known type of glass with a good resistance for Gamma and X-Rays radiation effects (BK7 Glass) produced by Schott Co. The Glass Bk7 has the following composition: 68.9% SiO2 + 10.1% B2 O3 + 8.8% Na2 O + 8.4% K2 O + 2.8% BaO + 1.0% As2 O3 , with refractive index Nd = 1.517 and density = 2.52 (g.cm−3 ) [11],[12]. The Fig.6 shows the optical transmission spectra before and after Gamma-Ray irradiation, for BK7 glass samples. The samples were irradiated using the Co60 source at dose rate of 24 Gy/h.
Figure 6. Optical transmission spectra for the glass BK7 before and after Gamma-Ray irradiation by Co60 source at dose rate of 24 Gy/h (thickness = 0.5 cm)[12].
5
Figure 7. Optical transmission Comparison between two glass: panel and BK7 (Schott) at dose of 8.63 kGy. From Figure 7,the glass Pannel have better optical transparency than glass BK7 when almost the entire range of the visible wavelength where the difference is about 25% at the beginning of the spectrum (500 nm), and this despite the fact that the refractive index of the glass Pannel is slightly larger than the glass BK7 (an increase of refractive index means less optical transparency), and also despite the fact that the glass Pannel have been irradiated at dose rate greater about 40 times (1000 Gy / h) than has been done for glass BK 7 (24 Gy / h).
4
Conclusion
As a result of this work, the glass of cathode ray tubes can be recycled and reused to obtain radiation protection glass for many purposes, in medical physics or hot cells in radioactive laboratories. This way of using this kind of glass can remarkably reduce heavy oxide glass wastes and reused agian in appropriate way. Also it can reduce the costs and energy of production, because of its contain of oxides which have low melting point temperatures. This glass can be improved for its shielding and optical properties by adding some heavy oxides. The glass of Panel, Funnel and the Mixture of them are all recyciable. The resulted glass have good radiation attenuation and optical properties and suitable stability against irradiation effects.
References [1] F.Me´ar, P.Yot, M.Cambon, M.Ribes; The characterization of waste cathode-ray tube glass, Waste Management 26 (2006) 1468–1476. [2] Source: Data from eT Forecasts, compiled by Jeremy Reimer, Personal Computer Market Share: 19752004 ; accessed Dec 15, 2004,,http://www.pegasus3d.com/total share.html. [3] Source:”Computers”, Efficient Products.org, accessed Mar 15,2006,http://www.efficientproducts.org/computers. [4] Fifth Annual Computer Report Card, Silicon Valley Toxics Coalition and Computer Take Back Campaign, May 19, 2004,http://www.svtc.org/cleancc/pubs/2003report.html. [5] Background Document on Recycling Waste from Computers; Prepared by Randall Conrad & Assoc. Ltd. for State place Alberta Environment August 10, 2000, ISBN No. 0-7785-1729-2, Pub No. I/888. [6] Gamma-ray Mass Attenuation Coefficient and Half Value Layer Factor of Some Oxide Glass Shielding Materials, Waly et al., Annals of Nuclear Energy, Vol. 96, pp. 26-30, June 2016.
6
[7] Gamma-ray and neutron shielding efficiency of Pb-free gadolinium-based glasses; Singh, V.P., Badiger, N.M., Kothan, S. et al. NUCL SCI TECH (2016) 27: 103. doi:10.1007/s41365-016-0099-1. [8] M.J.Berger and J.H.Hubbell; The (NIST),http://physics.nist.gov/XCOM
National
Institute
of
Standards
and
Technology
[9] R.G.Jaeger, Engineering Compendium on Radiation Shielding, International Atomic Energy Agency, Viena, Springer- Verlag, 1975. [10] R.G.Jaeger, E.P.Blizard, A.B.Chilton, M.Grotenhuis, A.Hoenig, Th.A.Jaeger, H.H.Eisenlohr, Engineering Compendium on Radiation Shielding Vol II: Shielding Materials, Springer-Verlag, 1975. [11] American Institute of Physics Translation Series: Optical Glass; T.S.Izumitani, Hoya Corporation, Tokyo, Japan; New York 1986. [12] Andrei Gusarov, Dominic Doyle, Leonid Glebov, Francis Berghmans: Radiation-induced transmission degradation of borosilicate crown optical glass from four different manufacturers, Optical Engineering 46, 043004 (April 2007).
7
PII: DOI: Reference:
S0969-806X(16)30648-X http://dx.doi.org/10.1016/j.radphyschem.2017.02.035 RPC7437
To appear in: Radiation Physics and Chemistry Received date: 8 November 2016 Accepted date: 16 February 2017 Cite this article as: A. Zughbi, M.H. Kharita and A. Shehada, Determining Optical and Radiation Characteristics of Cathode Ray Tubes' Glass to be reused as Radiation Shielding Glass, Radiation Physics and Chemistry, http://dx.doi.org/10.1016/j.radphyschem.2017.02.035 This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting galley proof before it is published in its final citable form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.
Determining Optical and Radiation Characteristics of Cathode Ray Tubes’ Glass to be reused as Radiation Shielding Glass A.Zughbi 1 , M.H.Kharita 2 , A.Shehada 3 1,3
Department of Physics,Faculty of Sciences,Damascus University,Damascus, Syria 2 Department of Protection and Safety,AECS,P.O.Box 6091,Damascus, Syria
Abstract A new method of recycling glass of Cathode Ray Tubes (CRTs) has been presented in this paper. The glass from CRTs suggested being used as raw materials for the production of radiation shielding glass. Cathode ray tubes glass contains considerable amounts of environmentally hazardous toxic wastes, namely heavy metal oxides such as lead oxide (PbO). This method makes CRTs glass a favorable choice to be used as raw material for Radiation Shielding Glass and concrete. The heavy metal oxides increase its density, which make this type of glass nearly equivalent to commercially available shielding glass. CRTs glass have been characterized to determine heavy oxides content, density, refractive index, and radiation shielding properties for different GammaRay energies. Empirical methods have been used by using the Gamma-Ray source cobalt-60 and computational method by using the code XCOM. Measured and calculated values were in a good compatibility. The effects of irradiation by gamma rays of cobalt-60 on the optical transparency for each part of the CRTs glass have been studied. The Results had shown that some parts of CRTs glass have more resistant to Gamma radiation than others. The study had shown that the glass of cathode ray tubes could be recycled to be used as radiation shielding glass. This proposed use of CRT glass is only limited to the available quantity of CRT world-wide..
1
Introduction
The generated amount of waste electrical and electronic equipment (WEEE) or e-waste in the world is growing rapidly as shown in Fig.1. The content of hazardous components in electrical and electronic equipment (EEE) is a major concern during the waste management phase. Ideally, the materials in electronic products should be re-used when the products reach the end of their service life. In the European Union (EU), WEEE represents about 7.5 million tons each year, where computer monitors and TV sets containing cathode-ray tubes (CRTs) represent about 80 % of the total electronic waste [1],[2]. Huge amounts of toxic wastes (for example lead compounds) affect the environment. The total amount of lead in 315 million of personal computers exhausted between 1997 and 2004 in the united states is about 600 000 tons [3]. Additionally, these amounts of personal computers contain about 151.2 tons of gold and 1786.1 tons of silver [4],[5]. The aforementioned statistics indicate to the need to the development of new methods to recycle these costly (both economically and environmentally) products. The glass of cathode ray tubes (CRT) can be classified according to its chemical composition 1 [email protected] 2 [email protected] 3 [email protected]
1
into three parts; Panel glass, Funnel glass and Neck glass. The glass constitute between 50 % and 85 % of the total weight of a computer monitor or a television set [1].
Figure 1. The glass and non glass parts of typical cathode ray tube (CRT) [1].
All of the three parts of CRT glass contain hazardous heavy elements (i.e. lead, strontium, antimony, barium, europium, selenium etc. . .). Collected monitors are dismantled and treated, and the CRT glass generally ends up in a special landfill licensed for hazardous waste. Hence, in Europe almost 90 % of the end of life (EOL) electronic goods is disposed of in landfills [1]. As the lead content in these waste products represents as much as 80 % of the toxic metals in discard electronics, CRTs represent a clear potential pollution danger to the environment [1]. Therefore, many researches have been carried out to explore new methods for recycling CRTs [5]. The most conventional material used for the purpose of radiation shielding for nuclear reactors and nuclear waste storage is concrete with various aggregates. It is a mixture of light nuclei (primarily hydrogen) and heavy nuclei, giving it the ability to be an effective shield against neutron and gamma radiation. Concrete is relatively inexpensive and easy to cast in many shapes and sizes, in addition to being strong and structurally sturdy. However, prolonged exposure to nuclear radiation results in heating of the concrete, which causes a decrease in density and a possible loss of cooling water and/or gas. Another drawback of concrete is that it is not transparent to visible light, and one cannot see through the concrete to monitor what goes on inside. Glass can also act as effective shielding materials as an alternative to concrete, or as an additive into concrete mixes. They are typically transparent to visible light, if used without concrete mixes, and their properties can be modified significantly by changing composition and adopting variations in preparation techniques. During recent years, there has been increasing interest in the synthesis, structure, and physical properties of heavy metal oxide glass due to their high refractive index, high infrared transparency, high density, and good shielding of gamma rays [6],[7].
2
Materials and Methods
Cathode ray tubes made by Hitachi Co. (after year 2000) have been used in this research. The CRTs were dismantled, the glass parts were separated and cleaned very well, first by water and then by ethanol. The phosphorus deposited layer, and other foreign layers were etched out. The three types of glass in each CRT were separated. The average ratio for each part of glass in the studied samples are: Panel = 65 %, Funnel = 34 %, Neck = 1 % (by wt.). Samples have been analyzed using scanning electron microscopy SEM-EDX technique (the electron beam acceleration tension was fixed to 10 kV), to estimate their main components and their content of 2
heavy metals. The densities of the samples have been measured using Archimedes principle. Refraction indexes were measured using laser source (wavelength between 655 nm ± 25 nm) and by using Snell relation: n0 · sin θ0 = n · sin θ Attenuation coefficients of Gamma rays for the tested samples have been measured experimentally using Cobalt-60 as Gamma-Ray source (the photon energy peaks for Co-60 as the used source 1173.24 and 1332.5 keV), and have been calculated theoretically using the code XCOM [8]. Optical Transmission of the samples have been investigated in the visible range of the spectrum (between 400–800 nm) using UV- visible photo-spectrometer (Cecil instrument limited, model No. 2021). The samples have been prepared for optical transmission test by polishing on lapping machine and SiC polishing papers up to 1200 grits. The samples have been crashed and grinded, and the mixtures have been made from all different parts of CRT glass as the same ratios as existed in the original CRTs (Panel (65 %) + Funnel (34 %) + Neck (1 %); (by wt%)). The grinded glass have been melted in electric box type furnace using Pt crucible, and have been casted in simple stainless steel moulds. The resulted samples have been characterized in the same way as above mentioned. The radiation resistance properties of the prepared samples have been studied against different Gamma-Ray irradiation doses using Co60 as Gamma-Ray source. The glass have been exposed to three doses: 1 kGy, 3 kGy and 5 kGy at dose rate equal to 1 kGy/h. The samples have been stored for 16 hours before doing the measurments of the optical transmission spectra, to get rid of the effect of that fast fading in the recently irradiated samples.
3
Results and Discussion
It can be noticed from table 1. that the Funnel and neck parts of CRT contain relatively high contents of lead oxide, while the part Panel contains relatively high content of barium and strontium oxides. This result is in agreement with data existed in literatures. The three tested parts of glass are heavier than ordinary alkali lime silicate glass (density about 2.4 g/cm3 )as shown in table 2. Radiation attenuation efficiency of materials is related to its density. This result support the suggestion of using this type of glass as radiation shielding glass. Tables 3,4 show the linear attenuation coefficients, the half-value layers and the tenth value layers for the tested samples. The calculated and measured values are in a good compatibility. Table 1. Ratios of the oxides in each part of the CRT glass and the Mix (wt%). Oxide B2 O3 Na2 O MgO Al2 O3 SiO2 K2 O CaO SrO ZrO2 Sb2 O3 BaO CeO2 PbO SnO TiO2
Funnel 6.90 5.86 1.71 4.89 45.92 6.08 3.47 1.47 0.82 0.06 0.00 0.42 20.03 0.06 0.47
Panel 7.53 6.78 0.07 1.98 54.72 5.65 0.94 9.48 2.44 0.25 7.88 0.41 0.00 0.00 0.33
3
Nick 5.37 1.58 0.18 2.45 43.21 7.11 1.30 2.27 0.37 0.69 0.42 0.44 33.15 0.11 0.21
Mix 6.21 6.15 0.76 2.74 52.20 6.59 1.55 6.89 2.04 0.14 5.70 0.37 6.50 0.62 0.43
Table 2. The Density and The Refraction Index of the tested samples: Funnel, Panel and Mix. Glass Part Funnel Panel Mix(Mixture)
Density(g/cm3 )(±0.01) 3.01 2.77 2.88
Refractive Index Nd at (655±25)(±3.5%)nm 1.561 1.541 1.505
Table 3. The Linear Attenuation Coefficients of the samples (some type of glass have been added to compare with (has mark * [9])). Glass Type
Funnel Panel Mix Neck RS253G* RS323G* Lead
Density (g.cm−3 )
3.01 2.77 2.88 3.25 2.53 3.23 11.4
Measured Attenuation Coefficients (cm−1 ) At Energy Co-60 (keV)
0.19 0.16 0.17 0.14 0.18 0.66
Attenuation Coefficients Calculated by XCOM (cm−1 )
X-Ray 100 3.60 1.09 1.92 6.07
Cs-137 661.6 0.25 0.21 0.23 0.28
At Energies (keV) Co-60 1173.24 1332.5 0.18 0.17 0.16 0.15 0.17 0.16 0.19 0.18
Table 4. The Half Value and Tenth Value Layers of the samples. The Glass
Funnel Panel Mix Neck RS253G * RS323G * Lead
Half Value Layers At Isotope’s Energies (cm) Cs-137 Co-60 2.77 3.85 3.30 4.33 3.01 4.08 2.48 3.65 3.6 4.9 2.6 3.8 0.6 1.05
Tenth Value Layers At Isotope’s Energies (cm) Cs-137 Co-60 9.21 12.79 10.96 14.39 10.01 13.54 8.22 12.12 11.9 16.3 8.5 12.5 2.0 3.5
The Fig.2 shows optical transmission spectra of the samples; Funnel, Panel, and Mix glass (These spectra are for samples with 1 cm thick). The optical transparent loss is less for Funnel and the Mix glass which is between 30 to 40 % for most of the visible wavelength range. While it is varying between 50% to 15% for panel glass, which suggests the use of longer wavelength light sources to decrease the losses. Fig.2
Fig.3
4
Fig.4
Fig.5
Fig 2: The optical transmission for the Funnel, Panel and Mix glass. Fig 3: The effect of Gamma irradiation on the optical transmission spectrum of the funnel glass. Fig 4: The effect of irradiation on the transmission spectrum of panel glass. Fig 5: The effect of Gamma-Ray irradiation on the transmission spectrum of the Mix glass. Figures 3,4,5 show changes in optical transparency for the three investigated glass, against different Gamma-Ray irradiation doses (1,3 and 5 kGy). The optical transmission of the Funnel glass decreases when irradiation doses increases. The loss of its transparency is obvious at shorter wavelength range. Fig.4 shows that CRTs panel glass did not affected so much by Gamma-Ray irradiation; and the maximum loss of optical transmission in the spectra is about 20%. This radiation resistance of panel glass can be explained by the high content of Strontium oxide where some oxides have been used to stabilize glass [10]. The behavior of the Mix glass is in average of the behavior of the two parts of CRT glass. It has been affected moderately, and the effect getting more obvious in the range of the shorter wavelengths of the optical spectrum. To estimate the radiation resistance of the studied glass, their behavior after irradiation can be compared to the behavior of a well known type of glass with a good resistance for Gamma and X-Rays radiation effects (BK7 Glass) produced by Schott Co. The Glass Bk7 has the following composition: 68.9% SiO2 + 10.1% B2 O3 + 8.8% Na2 O + 8.4% K2 O + 2.8% BaO + 1.0% As2 O3 , with refractive index Nd = 1.517 and density = 2.52 (g.cm−3 ) [11],[12]. The Fig.6 shows the optical transmission spectra before and after Gamma-Ray irradiation, for BK7 glass samples. The samples were irradiated using the Co60 source at dose rate of 24 Gy/h.
Figure 6. Optical transmission spectra for the glass BK7 before and after Gamma-Ray irradiation by Co60 source at dose rate of 24 Gy/h (thickness = 0.5 cm)[12].
5
Figure 7. Optical transmission Comparison between two glass: panel and BK7 (Schott) at dose of 8.63 kGy. From Figure 7,the glass Pannel have better optical transparency than glass BK7 when almost the entire range of the visible wavelength where the difference is about 25% at the beginning of the spectrum (500 nm), and this despite the fact that the refractive index of the glass Pannel is slightly larger than the glass BK7 (an increase of refractive index means less optical transparency), and also despite the fact that the glass Pannel have been irradiated at dose rate greater about 40 times (1000 Gy / h) than has been done for glass BK 7 (24 Gy / h).
4
Conclusion
As a result of this work, the glass of cathode ray tubes can be recycled and reused to obtain radiation protection glass for many purposes, in medical physics or hot cells in radioactive laboratories. This way of using this kind of glass can remarkably reduce heavy oxide glass wastes and reused agian in appropriate way. Also it can reduce the costs and energy of production, because of its contain of oxides which have low melting point temperatures. This glass can be improved for its shielding and optical properties by adding some heavy oxides. The glass of Panel, Funnel and the Mixture of them are all recyciable. The resulted glass have good radiation attenuation and optical properties and suitable stability against irradiation effects.
References [1] F.Me´ar, P.Yot, M.Cambon, M.Ribes; The characterization of waste cathode-ray tube glass, Waste Management 26 (2006) 1468–1476. [2] Source: Data from eT Forecasts, compiled by Jeremy Reimer, Personal Computer Market Share: 19752004 ; accessed Dec 15, 2004,,http://www.pegasus3d.com/total share.html. [3] Source:”Computers”, Efficient Products.org, accessed Mar 15,2006,http://www.efficientproducts.org/computers. [4] Fifth Annual Computer Report Card, Silicon Valley Toxics Coalition and Computer Take Back Campaign, May 19, 2004,http://www.svtc.org/cleancc/pubs/2003report.html. [5] Background Document on Recycling Waste from Computers; Prepared by Randall Conrad & Assoc. Ltd. for State place Alberta Environment August 10, 2000, ISBN No. 0-7785-1729-2, Pub No. I/888. [6] Gamma-ray Mass Attenuation Coefficient and Half Value Layer Factor of Some Oxide Glass Shielding Materials, Waly et al., Annals of Nuclear Energy, Vol. 96, pp. 26-30, June 2016.
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[7] Gamma-ray and neutron shielding efficiency of Pb-free gadolinium-based glasses; Singh, V.P., Badiger, N.M., Kothan, S. et al. NUCL SCI TECH (2016) 27: 103. doi:10.1007/s41365-016-0099-1. [8] M.J.Berger and J.H.Hubbell; The (NIST),http://physics.nist.gov/XCOM
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[9] R.G.Jaeger, Engineering Compendium on Radiation Shielding, International Atomic Energy Agency, Viena, Springer- Verlag, 1975. [10] R.G.Jaeger, E.P.Blizard, A.B.Chilton, M.Grotenhuis, A.Hoenig, Th.A.Jaeger, H.H.Eisenlohr, Engineering Compendium on Radiation Shielding Vol II: Shielding Materials, Springer-Verlag, 1975. [11] American Institute of Physics Translation Series: Optical Glass; T.S.Izumitani, Hoya Corporation, Tokyo, Japan; New York 1986. [12] Andrei Gusarov, Dominic Doyle, Leonid Glebov, Francis Berghmans: Radiation-induced transmission degradation of borosilicate crown optical glass from four different manufacturers, Optical Engineering 46, 043004 (April 2007).
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