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Development of special radiation shielding concretes using natural local materials and evaluation of their shielding characteristics
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Progress in Nuclear Energy 50 (2008) 33e36 www.elsevier.com/locate/pnucene
Development of special radiation shielding concretes using natural local materials and evaluation of their shielding characteristics M.H. Kharita a,*, M. Takeyeddin a, M. Alnassar a, S. Yousef b a
Protection and Safety Department, Atomic Energy Commission, Damascus, P.O. Box 6091, Syria Technical Services Department, Atomic Energy Commission, Damascus, P.O. Box 6091, Syria
b
Abstract Two types of typical concretes widely used in Syria (in Damascus and Aleppo) and four other types of concretes, using aggregates from different regions, have been prepared. The shielding properties of these six types were studied for gamma ray (from Cs-137 and Co-60 sources) and for neutrons (from AmeBe source). A reduction of about 10% in the HVL was obtained for the concrete from Damascus in comparison with that from Aleppo, for both neutrons and gammas. One of the other four types of concretes (from Rajo site, mostly hematite) was found to further reduce the HVL by about 10% for both neutrons and gamma rays. Ó 2007 Elsevier Ltd. All rights reserved. Keywords: Shielding; Concrete; Gamma; Neutrons
1. Introduction Concrete is one of the most important materials used for radiation shielding in facilities containing radioactive sources and radiation generating equipment (Kallan, 1989). The concrete shielding properties may vary depending on the composite of the concrete. Aggregates are the largest constituent (about 70e80% of the total weight of normal concrete). Different types of natural and artificial aggregates are used to enhance the properties of the concrete. Good experiences have been gained in concretes for shielding purposes, as each country has to gain its own experience depending on the available cheap and effective local materials. The aim of this work is to develop special concrete with good shielding properties for using natural local materials. 2. Material and methods 2.1. Preparation of the samples Aggregates from five different sources were used to prepare the samples: * Corresponding author. E-mail address: [email protected] (M.H. Kharita). 0149-1970/$ - see front matter Ó 2007 Elsevier Ltd. All rights reserved. doi:10.1016/j.pnucene.2007.10.004
1. Riverside aggregates: natural aggregates from the side of Euphrates river, washed and cleaned of clay and silts. This kind of aggregates is widely used in concrete in Aleppo and in the northern region of Syria. 2. Aggregates crushed from the dolomite rocks in Damascus suburb (Adra site). This kind is widely used in concrete in Damascus and its suburbs. 3. Aggregates crushed from the hematite rocks (rich of iron) in the north of Aleppo (Rajo site). The rocks were crushed and sieved to separate fine aggregates from coarse ones. 4. Aggregates crushed from the serpentine rocks (rich of hydrogen) from the coastal area (Ra’es Albaseet region). The rocks were crushed and sieved in the same manner as described previously. 5. Fine aggregates (black coastal sand): the sand was collected from Ra’es Albaseet region and used in its natural form. The concrete compositions prepared from the riverside aggregates and dolomite rocks were considered as a comparison (control) samples. The samples used in the measurements are: Sample 1 This is an ideal composition for the concrete used in Aleppo, prepared from Euphrates riverside
M.H. Kharita et al. / Progress in Nuclear Energy 50 (2008) 33e36
34
Collimator
Collimator
Sample Ionization Chamber
Radioactive Source
50cm
50cm Electro meter
Fig. 1. Schematic draw of the setup of the measurements.
aggregates following the recommendations of the American code (ASTM C638; ASTM C637). Sample 2 The hematite aggregates were used to prepare high Density concrete for gamma and X-ray shielding. Sample 3 This sample is a mixture of hematite aggregates and black coastal sand. Sample 4 This is an ideal composition for the concrete used in Damascus, prepared from the dolomite aggregates following the recommendations of the American code (ASTM C638). Sample 5 The serpentine aggregates were used to prepare high hydrogen content concrete, expected to be suitable for neutron shielding. Sample 6 Black coastal sand was added to the serpentine aggregates, to increase the Density of the concrete to be suitable for shielding of neutrons and gamma and X-rays.
the penetrating radiation through the three axes of each cube. The average values and standard deviations for the readings were calculated for the accuracy of the measurements and for the homogeny of the cubes in each sample. In the second step the cubes were cut into slabs with different thicknesses to define the attenuation curves and consequently to calculate the half value layer for each sample. Two gamma sources were used Co-60 and Cs-137. The setup during all the measurements was as in Fig. 1. For neutrons AmeBe source was used. The source was put inside a sealed empty plastic tube lays between the center and the surface of a 1 1 1 m3 water container, to get a collimated beam of neutrons. The detector used in this measurement was a spherical neutron detector type Berthold LB-6411. The distance between the center of the source and the center of the detector was set to 100 cm.
Nine cubes of each sample have been prepared (total of 54 cubes) 15 15 15 cm3. Six mixtures were selected from a large set of prepared mixtures to be accepted physically and mechanically.
3. Results
2.2. Experimental setup The experimental work consists of two steps. In the first step, the attenuation was studied by measuring the ratio of
The shielding properties of the samples have been studied in the field of gamma emitted by Cs-137 (energy 661 keV) and Co-60 (energy about 1250 keV), and neutrons from AmeBe source. The attenuation coefficients can be summarized in Figs. 2e4, and Table 1e3. Half Value Layer (HVL) 4.0
4.5
3.5
3.5
3.0
3.0
2.5
2.5
(1) (2) (3) (4) (5) (6)
2.0 1.5 1.0 0.5 0.0
Ln(Io/I)
Ln(Io/I)
4.0
(1) (2) (3) (4) (5) (6)
2.0 1.5 1.0 0.5 0.0
0
50
100
150
200
250
Thickness (mm) Fig. 2. Linear attenuation coefficients for the concrete samples for Cs-137 gamma rays.
0
20
40
60
80 100 120 140 160 180 200 220 240 260
Thickness (mm) Fig. 3. Linear attenuation coefficients for the concrete samples for Co-60 gamma rays.
M.H. Kharita et al. / Progress in Nuclear Energy 50 (2008) 33e36 2.5
Ln(Io/I)
2.0
1.5
(1) (2) (3) (4) (5) (6)
1.0
0.5
0
20
40
60
80
100
120
140
160
180
200
220
Thickness (mm) Fig. 4. Linear attenuation coefficients for the concrete samples in the field of neutrons from AmeBe source.
Table 1 Linear attenuation coefficients for the concrete samples for Cs-137 gamma rays Sample
Linear attenuation coefficient (cm 1)
HVL (cm)
TVL (cm)
HVL/HVL (sample 4)
1 2 3 4 5 6
0.155 0.001 0.189 0.002 0.184 0.001 0.174 0.001 0.146 0.001 0.158 0.001
4.47 3.67 3.77 3.98 4.75 4.39
14.86 12.18 12.51 13.23 15.77 14.57
1.12 0.01 0.92 0.01 0.95 0.01 1.00 0.01 1.19 0.01 1.10 0.01
Notes
Comparative
35
is the thickness of the attenuating shield, which gives radiation flux rate of the half intensity (Sauermann, 1985). The Tenth Value Layer (TVL) could be defined in the same way; it is the thickness of the attenuating shield, which gives radiation flux rate of the tenth intensity. By comparison with the published results, it can be noticed that the linear attenuation coefficient for the sample 4 for Co-60 gamma rays, shown in Table 2, is approximately equal to the American and Russian values at the energy of 1 MeV (Walker and Grotenhuis, 1961). Considering that the average energy of gamma radiation from Co-60 is about 1.25 MeV, it can be concluded that the attenuation coefficient for the ordinary Syrian concrete is greater than that in these references. By comparison with the British code BS: 4094 (British Standard, 1966), where the Tenth Value Layer (TVL) (Jaeger et al., 1975) for the energy of Co-60 is about 27.5 cm, it can be noticed from Table 2 that the tenth value layer for Syrian concrete is much better. This might be the result of the higher density of the Syrian concrete. It can be concluded that samples (2&3) (hematite) are the best for shielding of gamma radiation whereas samples (5&6) (serpentine) are the worst. For shielding of neutron radiation, it is clear that samples (2&3) are the best for shielding of neutrons. This behavior may be the result of the high content of iron is there samples and the presence of iron hydroxides (as limonite). The concrete composition that contains serpentine (which contains considerable amount of hydrogen) comes as second best. This composition was expected to show good results for the attenuation of neutrons. It can be noticed that sample 4 gives good results too, which could be attributed to the high content of carbon (Rammah et al., 2003). 4. Conclusion
Table 2 Linear attenuation coefficients for the concrete samples for Co-60 gamma rays Sample
Linear attenuation coefficient (cm 1)
HVL (cm)
TVL (cm)
HVL/HVL (sample 4)
1 2 3 4 5 6
0.133 0.005 0.160 0.009 0.155 0.007 0.144 0.003 0.124 0.005 0.131 0.005
5.21 4.33 4.47 4.81 5.59 5.29
17.31 14.39 14.86 15.99 18.57 17.58
1.08 0.04 0.90 0.05 0.93 0.04 1.00 0.02 1.16 0.05 1.10 0.04
Notes
Comparative
This work shows that sample 2 (the Hematite) was the best composition for shielding purposes of both neutrons and gamma rays. It is possible, using special aggregates, to decrease the thickness of shielding by about 10% in comparison with the concrete in Damascus and 20% in comparison with the concrete in Aleppo both for neutrons and gamma rays. Acknowledgement The authors wish to thank Prof I. Othman without his support this work would not have been possible.
Table 3 Linear attenuation coefficients for the concrete samples in the field of neutrons from AmeBe source Sample
Linear attenuation coefficient (cm 1)
HVL (cm)
1 2 3 4 5 6
0.104 0.002 0.124 0.003 0.123 0.003 0.114 0.003 0.112 0.002 0.117 0.003
6.27 0.12 4.69 0.14 4.73 0.14 5.00 0.16 5.40 0.11 5.01 0.12
Notes
References ASTM C637. Standard Specification for Aggregates for Radiation Shielding Concrete. ASTM C638. Standard Descriptive Nomenclature of Constituents of Aggregates for Radiation Shielding Concrete. British Standard: 4094 Part 1, 1966. Recommendation for Data on Shielding from Ionizing Radiation. British Standard Institution. Jaeger, R.G., Blizard, E.P., Chilton, A.B., Grotenhuis, M., Hoenig, A., Jaeger, Th.A., 1975. Engineering Compendium on Radiation Shielding. In: Shielding Materials, vol. II. Springer-Verlag.
36
M.H. Kharita et al. / Progress in Nuclear Energy 50 (2008) 33e36
Kallan, M.F., 1989. Concrete Radiation Shielding. Longman Scientific & Technical, England. Rammah, S., Al-Hent, R., Yousef, S., 2003. Availability of Special Local Rock Materials for Using in Radiation Shielding Concrete. Department of Geology, A.E.C.S.
Sauermann, P.F., 1985. Abshirmungspraxis aus 25 Jahren Erfahrung (1960e 1985). Kernforschungsanlage Juelich GmbH, Institute fuer Chemie e Strahlenschutz (in German). Walker, R., Grotenhuis, M., 1961. A Summary of Shielding Constants for Concretes. USAEC report ANL-6443, Argonne National Laboratory.
Progress in Nuclear Energy 50 (2008) 33e36 www.elsevier.com/locate/pnucene
Development of special radiation shielding concretes using natural local materials and evaluation of their shielding characteristics M.H. Kharita a,*, M. Takeyeddin a, M. Alnassar a, S. Yousef b a
Protection and Safety Department, Atomic Energy Commission, Damascus, P.O. Box 6091, Syria Technical Services Department, Atomic Energy Commission, Damascus, P.O. Box 6091, Syria
b
Abstract Two types of typical concretes widely used in Syria (in Damascus and Aleppo) and four other types of concretes, using aggregates from different regions, have been prepared. The shielding properties of these six types were studied for gamma ray (from Cs-137 and Co-60 sources) and for neutrons (from AmeBe source). A reduction of about 10% in the HVL was obtained for the concrete from Damascus in comparison with that from Aleppo, for both neutrons and gammas. One of the other four types of concretes (from Rajo site, mostly hematite) was found to further reduce the HVL by about 10% for both neutrons and gamma rays. Ó 2007 Elsevier Ltd. All rights reserved. Keywords: Shielding; Concrete; Gamma; Neutrons
1. Introduction Concrete is one of the most important materials used for radiation shielding in facilities containing radioactive sources and radiation generating equipment (Kallan, 1989). The concrete shielding properties may vary depending on the composite of the concrete. Aggregates are the largest constituent (about 70e80% of the total weight of normal concrete). Different types of natural and artificial aggregates are used to enhance the properties of the concrete. Good experiences have been gained in concretes for shielding purposes, as each country has to gain its own experience depending on the available cheap and effective local materials. The aim of this work is to develop special concrete with good shielding properties for using natural local materials. 2. Material and methods 2.1. Preparation of the samples Aggregates from five different sources were used to prepare the samples: * Corresponding author. E-mail address: [email protected] (M.H. Kharita). 0149-1970/$ - see front matter Ó 2007 Elsevier Ltd. All rights reserved. doi:10.1016/j.pnucene.2007.10.004
1. Riverside aggregates: natural aggregates from the side of Euphrates river, washed and cleaned of clay and silts. This kind of aggregates is widely used in concrete in Aleppo and in the northern region of Syria. 2. Aggregates crushed from the dolomite rocks in Damascus suburb (Adra site). This kind is widely used in concrete in Damascus and its suburbs. 3. Aggregates crushed from the hematite rocks (rich of iron) in the north of Aleppo (Rajo site). The rocks were crushed and sieved to separate fine aggregates from coarse ones. 4. Aggregates crushed from the serpentine rocks (rich of hydrogen) from the coastal area (Ra’es Albaseet region). The rocks were crushed and sieved in the same manner as described previously. 5. Fine aggregates (black coastal sand): the sand was collected from Ra’es Albaseet region and used in its natural form. The concrete compositions prepared from the riverside aggregates and dolomite rocks were considered as a comparison (control) samples. The samples used in the measurements are: Sample 1 This is an ideal composition for the concrete used in Aleppo, prepared from Euphrates riverside
M.H. Kharita et al. / Progress in Nuclear Energy 50 (2008) 33e36
34
Collimator
Collimator
Sample Ionization Chamber
Radioactive Source
50cm
50cm Electro meter
Fig. 1. Schematic draw of the setup of the measurements.
aggregates following the recommendations of the American code (ASTM C638; ASTM C637). Sample 2 The hematite aggregates were used to prepare high Density concrete for gamma and X-ray shielding. Sample 3 This sample is a mixture of hematite aggregates and black coastal sand. Sample 4 This is an ideal composition for the concrete used in Damascus, prepared from the dolomite aggregates following the recommendations of the American code (ASTM C638). Sample 5 The serpentine aggregates were used to prepare high hydrogen content concrete, expected to be suitable for neutron shielding. Sample 6 Black coastal sand was added to the serpentine aggregates, to increase the Density of the concrete to be suitable for shielding of neutrons and gamma and X-rays.
the penetrating radiation through the three axes of each cube. The average values and standard deviations for the readings were calculated for the accuracy of the measurements and for the homogeny of the cubes in each sample. In the second step the cubes were cut into slabs with different thicknesses to define the attenuation curves and consequently to calculate the half value layer for each sample. Two gamma sources were used Co-60 and Cs-137. The setup during all the measurements was as in Fig. 1. For neutrons AmeBe source was used. The source was put inside a sealed empty plastic tube lays between the center and the surface of a 1 1 1 m3 water container, to get a collimated beam of neutrons. The detector used in this measurement was a spherical neutron detector type Berthold LB-6411. The distance between the center of the source and the center of the detector was set to 100 cm.
Nine cubes of each sample have been prepared (total of 54 cubes) 15 15 15 cm3. Six mixtures were selected from a large set of prepared mixtures to be accepted physically and mechanically.
3. Results
2.2. Experimental setup The experimental work consists of two steps. In the first step, the attenuation was studied by measuring the ratio of
The shielding properties of the samples have been studied in the field of gamma emitted by Cs-137 (energy 661 keV) and Co-60 (energy about 1250 keV), and neutrons from AmeBe source. The attenuation coefficients can be summarized in Figs. 2e4, and Table 1e3. Half Value Layer (HVL) 4.0
4.5
3.5
3.5
3.0
3.0
2.5
2.5
(1) (2) (3) (4) (5) (6)
2.0 1.5 1.0 0.5 0.0
Ln(Io/I)
Ln(Io/I)
4.0
(1) (2) (3) (4) (5) (6)
2.0 1.5 1.0 0.5 0.0
0
50
100
150
200
250
Thickness (mm) Fig. 2. Linear attenuation coefficients for the concrete samples for Cs-137 gamma rays.
0
20
40
60
80 100 120 140 160 180 200 220 240 260
Thickness (mm) Fig. 3. Linear attenuation coefficients for the concrete samples for Co-60 gamma rays.
M.H. Kharita et al. / Progress in Nuclear Energy 50 (2008) 33e36 2.5
Ln(Io/I)
2.0
1.5
(1) (2) (3) (4) (5) (6)
1.0
0.5
0
20
40
60
80
100
120
140
160
180
200
220
Thickness (mm) Fig. 4. Linear attenuation coefficients for the concrete samples in the field of neutrons from AmeBe source.
Table 1 Linear attenuation coefficients for the concrete samples for Cs-137 gamma rays Sample
Linear attenuation coefficient (cm 1)
HVL (cm)
TVL (cm)
HVL/HVL (sample 4)
1 2 3 4 5 6
0.155 0.001 0.189 0.002 0.184 0.001 0.174 0.001 0.146 0.001 0.158 0.001
4.47 3.67 3.77 3.98 4.75 4.39
14.86 12.18 12.51 13.23 15.77 14.57
1.12 0.01 0.92 0.01 0.95 0.01 1.00 0.01 1.19 0.01 1.10 0.01
Notes
Comparative
35
is the thickness of the attenuating shield, which gives radiation flux rate of the half intensity (Sauermann, 1985). The Tenth Value Layer (TVL) could be defined in the same way; it is the thickness of the attenuating shield, which gives radiation flux rate of the tenth intensity. By comparison with the published results, it can be noticed that the linear attenuation coefficient for the sample 4 for Co-60 gamma rays, shown in Table 2, is approximately equal to the American and Russian values at the energy of 1 MeV (Walker and Grotenhuis, 1961). Considering that the average energy of gamma radiation from Co-60 is about 1.25 MeV, it can be concluded that the attenuation coefficient for the ordinary Syrian concrete is greater than that in these references. By comparison with the British code BS: 4094 (British Standard, 1966), where the Tenth Value Layer (TVL) (Jaeger et al., 1975) for the energy of Co-60 is about 27.5 cm, it can be noticed from Table 2 that the tenth value layer for Syrian concrete is much better. This might be the result of the higher density of the Syrian concrete. It can be concluded that samples (2&3) (hematite) are the best for shielding of gamma radiation whereas samples (5&6) (serpentine) are the worst. For shielding of neutron radiation, it is clear that samples (2&3) are the best for shielding of neutrons. This behavior may be the result of the high content of iron is there samples and the presence of iron hydroxides (as limonite). The concrete composition that contains serpentine (which contains considerable amount of hydrogen) comes as second best. This composition was expected to show good results for the attenuation of neutrons. It can be noticed that sample 4 gives good results too, which could be attributed to the high content of carbon (Rammah et al., 2003). 4. Conclusion
Table 2 Linear attenuation coefficients for the concrete samples for Co-60 gamma rays Sample
Linear attenuation coefficient (cm 1)
HVL (cm)
TVL (cm)
HVL/HVL (sample 4)
1 2 3 4 5 6
0.133 0.005 0.160 0.009 0.155 0.007 0.144 0.003 0.124 0.005 0.131 0.005
5.21 4.33 4.47 4.81 5.59 5.29
17.31 14.39 14.86 15.99 18.57 17.58
1.08 0.04 0.90 0.05 0.93 0.04 1.00 0.02 1.16 0.05 1.10 0.04
Notes
Comparative
This work shows that sample 2 (the Hematite) was the best composition for shielding purposes of both neutrons and gamma rays. It is possible, using special aggregates, to decrease the thickness of shielding by about 10% in comparison with the concrete in Damascus and 20% in comparison with the concrete in Aleppo both for neutrons and gamma rays. Acknowledgement The authors wish to thank Prof I. Othman without his support this work would not have been possible.
Table 3 Linear attenuation coefficients for the concrete samples in the field of neutrons from AmeBe source Sample
Linear attenuation coefficient (cm 1)
HVL (cm)
1 2 3 4 5 6
0.104 0.002 0.124 0.003 0.123 0.003 0.114 0.003 0.112 0.002 0.117 0.003
6.27 0.12 4.69 0.14 4.73 0.14 5.00 0.16 5.40 0.11 5.01 0.12
Notes
References ASTM C637. Standard Specification for Aggregates for Radiation Shielding Concrete. ASTM C638. Standard Descriptive Nomenclature of Constituents of Aggregates for Radiation Shielding Concrete. British Standard: 4094 Part 1, 1966. Recommendation for Data on Shielding from Ionizing Radiation. British Standard Institution. Jaeger, R.G., Blizard, E.P., Chilton, A.B., Grotenhuis, M., Hoenig, A., Jaeger, Th.A., 1975. Engineering Compendium on Radiation Shielding. In: Shielding Materials, vol. II. Springer-Verlag.
36
M.H. Kharita et al. / Progress in Nuclear Energy 50 (2008) 33e36
Kallan, M.F., 1989. Concrete Radiation Shielding. Longman Scientific & Technical, England. Rammah, S., Al-Hent, R., Yousef, S., 2003. Availability of Special Local Rock Materials for Using in Radiation Shielding Concrete. Department of Geology, A.E.C.S.
Sauermann, P.F., 1985. Abshirmungspraxis aus 25 Jahren Erfahrung (1960e 1985). Kernforschungsanlage Juelich GmbH, Institute fuer Chemie e Strahlenschutz (in German). Walker, R., Grotenhuis, M., 1961. A Summary of Shielding Constants for Concretes. USAEC report ANL-6443, Argonne National Laboratory.