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Potential of pottery materials in manufacturing radioactive waste containers
ARTICLE IN PRESS
Applied Radiation and Isotopes 59 (2003) 11–16
Potential of pottery materials in manufacturing radioactive waste containers A.A. Helala, A.M. Aliana, H.M. Alyb,*, S.M. Khalifaa b
a Hot Laboratories Center, Atomic Energy Authority, Cairo 13759, Egypt Faculty of Science, Chemistry Department, Benha University, Benha 13518, Egypt
Received 23 September 2002; received in revised form 13 January 2003; accepted 8 February 2003
Abstract Various pottery materials were evaluated for possible use in manufacturing containers for radioactive waste. Their potential was examined from the viewpoints of the effectiveness of disposal and the changes induced in them by gamma rays. Samples of these materials were irradiated with high-energy neutrons and gamma rays in a reactor near its core. the physical and mechanical properties of the materials before and after gamma irradiation (in a 60Co gamma cell) were compared. The study showed that pottery materials are resistant to radiation. Therefore, they were proposed for manufacturing drums for disposal of radioactive waste of high gamma activity. r 2003 Elsevier Science Ltd. All rights reserved. Keywords: Radioactive waste; Disposal; Pottery
1. Introduction In our previous paper, we described how new pottery materials can be used in manufacturing of small vessels for wastes containing radioactive cobalt and iron isotopes. The small vessels can serve as models for larger ones, even as big as normal drum (Alian et al., 2001). The gamma spectra of the reactor-irradiated pottery pieces did feature radioactivity, mainly the gamma rays from 60 Co, 59Fe, 134Cs, and 65Zn. However, storing the irradiated pieces in water or dilute acid solutions for 1 week did not reveal any radioactivity release, which suggested that the material is stable and filled vessels made of it can be safely stored in the ground. It has been also found that the effectiveness of 60Co decontamination by different types of pottery decreases in the following order: brownDwhite>black, and, for the first two types, it reaches about 100% within 1 day. Accordingly, some of our studies were limited only to brown pottery, because the black pottery was prepared
from it by adding tar. A similar result was noticed for the radioactive iron decontamination. The adsorbed radioactive isotopes of cobalt and iron desorbed only negligibly (o1%) from the pots even after several weeks of their storage in water, which confirmed that storing radioactive wastes in pottery vessels can be reliable and safe. The purpose of this work was to study the effect of time on decontamination of Co, Fe, Cd, Cr, Zn, Pb, Mg, and Cu by unirradiated pottery materials using radiotracers and atomic absorption spectrometry. Specimens of these materials were irradiated with high-energy neutrons and gamma rays in a reactor near its core. This work involved studies of the effects of some complexing and oxidizing reagents on the decontamination of radioactive cobalt and iron. The physical and mechanical properties of the pottery materials before and after the gamma irradiation were compared. 2. Experimental 2.1. Sorbents
*Corresponding author. Tel.: +202-302-7487; fax: +202013-222578. E-mail address: [email protected] (H.M. Aly).
Three types of pottery materials were used for preparing 30-ml pots, namely, white, brown, and black.
0969-8043/03/$ - see front matter r 2003 Elsevier Science Ltd. All rights reserved. doi:10.1016/S0969-8043(03)00119-2
ARTICLE IN PRESS A.A. Helal et al. / Applied Radiation and Isotopes 59 (2003) 11–16
12
All of them were basically mixtures of Al2O3 2SiO2 2H2O (kaolinite) and Al2O3 4SiO2 H2O, with smaller amounts of feldspar and quartz (Rado, 1969). The brown color was due to the higher iron oxide content of the materials, while the black color, as mentioned above, resulted from the addition of a small amount of tar to the brown pottery material before its firing. The vessels were made by the common methods used in manufacturing pottery (Alian et al., 2001).
the given range, and the efficiencies at these energies were determined as described elsewhere (Hamid, 1999). Radioactivity measurements for evaluating the sorption of the isotopes within the vessels were carried out using a 3 300 well-type NaI(Tl) detector with a photomultiplier tube and a single-channel analyzer. Atomic absorption measurements were performed on a Hitachi-610Z flame spectrophotometer (Japan) with an acetylene–air mixture as a fuel.
2.2. Radioactive tracers
2.6. Sorption experiments
60
Co and 59Fe with half-life periods of 5.2 yr and 45 days, respectively, were used as tracers for the two elements. The isotopes were prepared by neutron activation of CoCl2 6H2O and FeCl3 with subsequent dissolution of the targets in 0.1 M HCl. Their purity was checked as described earlier (Alian et al., 2001). The acid was evaporated, and the residue was dissolved in distilled water. The final concentrations of the metal ions in the solutions used in the adsorption studies were 5 107 M for Co and 5 105 M for Fe. 2.3. Other chemicals The highest purity materials were used in the preparation of standard solutions to calibrate the atomic absorption spectrophotometer in the usual way (Vogel, 1975). The standard solutions were prepared from Analar CdCl2, CrCl3 6H2O, ZnSO4 7H2O, Pb(CH3COO)2 3H2O, MgSO4 7H2O and CuSO4 5H2O by dissolving portions of these reagents in bidistilled water so that the concentration of each metal in the adsorption test solution would be 10 ppm. 2.4. Additives The list of investigated additives includes humic and fulvic acids, which were isolated from the bottom sediments of Ismailia Canal, Cairo, Egypt, by treating them alternately with 1 M HCl and 0.5 M NaOH. The separation and purification of humic and fulvic acids were performed as described in the literature (Nash and Choppin, 1980). The concentration of each acid was 0.028 g/l. The compounds KMnO4 (0.03 g/l), Ca(OCl)2 (0.01 g/l) and alum (0.1 g/l) were also investigated as additives. The acids occur as impurities in water; the salts are used in water treatment processes. 2.5. Instruments A pure Ge detector and a multichannel analyzer were used to measure the gamma spectra of the pottery materials irradiated in the reactor. The gamma spectrometer was calibrated at various gamma energies within
Sorption experiments were performed with unirradiated pottery vessels. 20-ml portions of the aqueous solutions of each isotope or of an inactive element (in the case of atomic absorption measurements) were placed into a pottery vessel after being spiked with a chosen additive. The pH of the solutions was 5 in the cases of the radioactive isotopes and 7 in the cases of the experiments with atomic absorption measurements. Single-distilled water was used. The experiments were conducted at room temperature (2273 C). The vessels were covered with watch glasses in the open air. Additional water was appended to the solutions to bring their volumes to some standard initial value in order to compensate for losses due to evaporation or filtration through the vessel walls. The radioactivities (At ) of 1-ml portions of a solution were measured at various intervals of time, and the portions were returned to the vessel after each measurement. In the case of the experiments with atomic absorption measurements, 10 ml portions were taken at various intervals of time from each vessel and introduced into the spectrophotometer to measure the concentration of the metal (Ct ). Decontamination degrees were calculated using the following equations: Decontamination; ð%Þ ¼ ðAi At Þ 100=Ai ;
ð1Þ
Decontamination; ð%Þ ¼ ðCi Ct Þ 100=Ci ;
ð2Þ
where Ai is the initial specific radioactivity of the solution, and Ci is the initial concentration of the metal ion in the solution. 2.7. Mechanical properties Unirradiated and gamma-irradiated samples of fired pottery materials (2 2 1 cm3) were tested for resistance to compression with the Instron 1195 system (Instron Corporation, Series IX, Canada). It provided the following characteristics at the maximum load (ML): the load value, the displacement, the stress, and the strain. Samples for these tests were irradiated to 66.5 Mrad (60Co), which is higher than the doses that
ARTICLE IN PRESS A.A. Helal et al. / Applied Radiation and Isotopes 59 (2003) 11–16
the material would receive in the case of a waste of low or intermediate radioactivity.
13
black pots, respectively. The effects of the additive are considerable. Alum is widely used as an additive in water purification processes. In our case, the reason for
3. Results and discussion 3.1. Reactor irradiation of pottery materials Figs. 1–3 show the gamma spectra of the white, brown, and black pottery materials irradiated in the reactor. They all feature the lines of 46Sc, 59Fe, and 60Co along with the lines from smaller amounts of 134Cs and 65 Zn. It has been shown, however (Alian et al., 2001), that these materials are chemically stable and do not release any radioactivity of the reactor-produced radioisotopes when they are stored in water or diluted acids even for long periods of time. Table 1 lists the results of the compression tests of the materials before and after gamma irradiation. They show that brown pottery (specimens 1–6) are mechanically stronger than white pottery (specimens 7–12) and that gamma irradiation does not change the mechanical properties of either type of pottery. This demonstrates the suitability of these materials for manufacturing vessels for radioactive waste. 3.2. Sorption of metal ions in unirradiated pottery vessels Figs. 4 and 5 show the effect of alum (0.1 g/l) on the decontamination of cobalt from water in white and
Fig. 2. Gamma spectra of irradiated brown pottery: (a) 32 days after irradiation; and (b) 205 days after irradiation. Irradiation time is 5 h and measurement time is 10 min.
Fig. 1. Gamma spectra of irradiated white pottery: (a) 32 days after irradiation; and (b) 205 days after irradiation. Irradiation time is 5 h and measurement time is 10 min.
Fig. 3. Gamma spectra of irradiated black pottery: (a) 32 days after irradiation; and (b) 205 days after irradiation. Irradiation time is 5 h and measurement time is 10 min.
ARTICLE IN PRESS A.A. Helal et al. / Applied Radiation and Isotopes 59 (2003) 11–16
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Table 1 Mechanical characteristics of pottery materials at maximum compression load Sample
Pottery type
Displacement (mm)
Load (kg)
Stress (kg cm2)
Strain (%)
1 2 3 4 5 6 7 8 9 10 11 12
Brown Brown Brown Brown Brown Brown White White White White White White
1.337 1.172 1.208 1.318 1.565 1.218 1.373 1.547 1.044 1.263 1.465 1.327
417.0 424.8 346.5 397.4 385.0 350.6 234.3 224.7 205.4 215.5 245.3 255.8
144.80 147.5 120.3 138.0 133.7 121.7 81.35 78.01 71.33 74.83 85.17 88.83
55.69 48.82 50.35 54.93 65.22 50.73 57.21 64.46 43.48 52.64 61.03 55.31
Decontamination, (%)
100 80 60 40
Blank Alum
20 0 0
2
4 Time (hours)
Decontamination, (%)
Fig. 4. Effect of alum on decontamination of pots.
6
8
100 80 60 40
Blank Alum
20 0 0
60
5
10 15 Time (hours )
Co with white
20
25
Fig. 6. Effect of alum on decontamination of 60Co with brown pots.
100 80
100
60 40
Blank Alum
20 0 0
2
4 Time (hours)
Fig. 5. Effect of alum on decontamination of pots.
6
8
Decontamination, (%)
Decontamination, (%)
The data given in bold correspond to the samples irradiated to 66.6 Mrad; the other data are for control (unirradiated) samples.
80 60 40
Blank HA
20 0
60
Co with black
the increase in decontamination effectiveness appears to be formation of a coagulant. On the other hand, the effect of alum at the same concentration on the decontamination of 59Fe in a brown pot is negligible (Fig. 6). The effects of humic acids, fulvic acids, and chlorine on the uptakes of iron in a brown pot are also negligible (Figs. 7–9). On the other hand, KMnO4 greatly decreases cobalt and iron decontamination in the black and brown pots (Figs. 10 and 11). This can be
0
5
10
15
20
25
30
Time (hours)
Fig. 7. Effect of humic acids on decontamination of brown pots.
59
Fe with
attributed to the competition of the radionuclide ions with the ions of potassium and/or manganese for the free ion-exchanging sites of the pottery materials. To study the effect of the material porosity on the decontamination, two parallel experiments with cobalt solutions in brown pots were conducted; the pores of
ARTICLE IN PRESS A.A. Helal et al. / Applied Radiation and Isotopes 59 (2003) 11–16 100 Decontamination, (%)
Decontamination, (%)
100 80 60 40
blank FA
20 0 0
5
10
15 20 Time (hours )
25
Fig. 8. Effect of fulvic acids on decontamination of brown pots.
59
Fe with
60 40 Blank KMnO4
20
0
10
20 Time (hours)
30
40
Fig. 11. Effect of KMnO4 on decontamination of brown pots.
59
Fe with
100 Decontamination, (%)
Decontamination, (%)
80
0
30
100 80 60 40 Blank Cl
20 0 0
5
10 15 Time (hours)
20
Fig. 9. Effect of chlorine on decontamination of brown pots.
80 60 40
closed system open system
20 0
25
0
5
10
15 20 Time (hours)
25
30
59
Fe with
Fig. 12. The difference between brown pots with open and closed pores in 60Co decontamination rates.
100 Decontamination, (%)
100 Decontamination, (%)
15
80 60 40 Blank KMnO4
20
80
Cd Cr Zn Pb Mg Cu
60 40 20 0 0
0 0
10
20
30 40 Time (hours)
50
Fig. 10. Effect of KMnO4 on decontamination of black pots.
2
4
6
8
10 12 14 16 18 20 22 24 26 Time ( hours)
60
60
Co with
one of the vessels were sealed with wax from outside. As Fig. 12 demonstrates, the open-pore system provides a much higher decontamination, probably due to the higher degree of water penetration into the pores (the experiments were conducted without stirring the solutions). Some water leakage was observed from the openpore system 1–2 h after the start of the experiment; however, the solution collected outside of the vessel was
Fig. 13. Effect of time on decontamination of Cd, Cr, Zn, Pb, Mg, and Cu from solutions using brown pots.
free of radioactivity. This can be explained by effective sorption of the metal ions by the pottery material. Water penetration through the pores of pottery materials is a known phenomenon. The effect of water evaporation from the outer surface is used for cooling drinking water in Egyptian villages. Fig. 13 shows the decrease in the concentrations of cadmium, chromium, zinc, lead, magnesium and copper
ARTICLE IN PRESS A.A. Helal et al. / Applied Radiation and Isotopes 59 (2003) 11–16
16
ions in time measured by atomic absorption spectrometry. The decontamination effectiveness of the material decreases in the order CrDCu>Pb>Zn>Cd>Mg. The decontamination degree exceeds 90% in 10 h for all of the ions. Although the sorption was studied with non-radioactive ions, some of these metals have relatively long-lived radioactive isotopes, such as 51Cr, 65 Zn and 115Cd, which may occur in radioactive waste solutions.
4. Conclusions * *
*
*
Pottery materials are resistant to irradiation. Pottery materials have high adsorption ability with respect to ions of Co, Fe, Cd, Cr, Zn, Pb, Mg, and Cu. Humic acids, fulvic acids, chlorine, and alum have little effect on iron adsorption. Potassium permanganate greatly decreases adsorption of cobalt and iron ions.
Acknowledgements The authors are grateful to Mr. Aly A. Helal for performing some experiments.
References Alian, A., Helal, A.A., Helal, A.A., 2001. In: Proceedings of the Annual Meeting on Nuclear Technology, Bonn, Germany, 2001, Forum Verlag, Inforum-unV Verwaltungsgesellschaft mbH, Bonn, pp. 263–266 (ISSN 0720-9207). Hamid, A., 1999. Analysis of heavy elements in air dust of the Greater Cairo by neutron activation analysis and g-spectrometry, M.Sc. Thesis, Ain Shams University, Cairo, Egypt (in Arabic). Nash, K.L., Choppin, G.R., 1980. Interactions of humic and fulvic acids with Th(IV). J. Inorg. Nucl. Chem. 42, 1045. Rado, P., 1969. An Introduction to the Technology of Pottery. Pergamon Press, London. Vogel, A.I., 1975. Textbook of Quantitative Inorganic Analysis, Including Elementary Instrumental Analysis, Longman Group Limited, 3rd Edition. Longman, London.
Applied Radiation and Isotopes 59 (2003) 11–16
Potential of pottery materials in manufacturing radioactive waste containers A.A. Helala, A.M. Aliana, H.M. Alyb,*, S.M. Khalifaa b
a Hot Laboratories Center, Atomic Energy Authority, Cairo 13759, Egypt Faculty of Science, Chemistry Department, Benha University, Benha 13518, Egypt
Received 23 September 2002; received in revised form 13 January 2003; accepted 8 February 2003
Abstract Various pottery materials were evaluated for possible use in manufacturing containers for radioactive waste. Their potential was examined from the viewpoints of the effectiveness of disposal and the changes induced in them by gamma rays. Samples of these materials were irradiated with high-energy neutrons and gamma rays in a reactor near its core. the physical and mechanical properties of the materials before and after gamma irradiation (in a 60Co gamma cell) were compared. The study showed that pottery materials are resistant to radiation. Therefore, they were proposed for manufacturing drums for disposal of radioactive waste of high gamma activity. r 2003 Elsevier Science Ltd. All rights reserved. Keywords: Radioactive waste; Disposal; Pottery
1. Introduction In our previous paper, we described how new pottery materials can be used in manufacturing of small vessels for wastes containing radioactive cobalt and iron isotopes. The small vessels can serve as models for larger ones, even as big as normal drum (Alian et al., 2001). The gamma spectra of the reactor-irradiated pottery pieces did feature radioactivity, mainly the gamma rays from 60 Co, 59Fe, 134Cs, and 65Zn. However, storing the irradiated pieces in water or dilute acid solutions for 1 week did not reveal any radioactivity release, which suggested that the material is stable and filled vessels made of it can be safely stored in the ground. It has been also found that the effectiveness of 60Co decontamination by different types of pottery decreases in the following order: brownDwhite>black, and, for the first two types, it reaches about 100% within 1 day. Accordingly, some of our studies were limited only to brown pottery, because the black pottery was prepared
from it by adding tar. A similar result was noticed for the radioactive iron decontamination. The adsorbed radioactive isotopes of cobalt and iron desorbed only negligibly (o1%) from the pots even after several weeks of their storage in water, which confirmed that storing radioactive wastes in pottery vessels can be reliable and safe. The purpose of this work was to study the effect of time on decontamination of Co, Fe, Cd, Cr, Zn, Pb, Mg, and Cu by unirradiated pottery materials using radiotracers and atomic absorption spectrometry. Specimens of these materials were irradiated with high-energy neutrons and gamma rays in a reactor near its core. This work involved studies of the effects of some complexing and oxidizing reagents on the decontamination of radioactive cobalt and iron. The physical and mechanical properties of the pottery materials before and after the gamma irradiation were compared. 2. Experimental 2.1. Sorbents
*Corresponding author. Tel.: +202-302-7487; fax: +202013-222578. E-mail address: [email protected] (H.M. Aly).
Three types of pottery materials were used for preparing 30-ml pots, namely, white, brown, and black.
0969-8043/03/$ - see front matter r 2003 Elsevier Science Ltd. All rights reserved. doi:10.1016/S0969-8043(03)00119-2
ARTICLE IN PRESS A.A. Helal et al. / Applied Radiation and Isotopes 59 (2003) 11–16
12
All of them were basically mixtures of Al2O3 2SiO2 2H2O (kaolinite) and Al2O3 4SiO2 H2O, with smaller amounts of feldspar and quartz (Rado, 1969). The brown color was due to the higher iron oxide content of the materials, while the black color, as mentioned above, resulted from the addition of a small amount of tar to the brown pottery material before its firing. The vessels were made by the common methods used in manufacturing pottery (Alian et al., 2001).
the given range, and the efficiencies at these energies were determined as described elsewhere (Hamid, 1999). Radioactivity measurements for evaluating the sorption of the isotopes within the vessels were carried out using a 3 300 well-type NaI(Tl) detector with a photomultiplier tube and a single-channel analyzer. Atomic absorption measurements were performed on a Hitachi-610Z flame spectrophotometer (Japan) with an acetylene–air mixture as a fuel.
2.2. Radioactive tracers
2.6. Sorption experiments
60
Co and 59Fe with half-life periods of 5.2 yr and 45 days, respectively, were used as tracers for the two elements. The isotopes were prepared by neutron activation of CoCl2 6H2O and FeCl3 with subsequent dissolution of the targets in 0.1 M HCl. Their purity was checked as described earlier (Alian et al., 2001). The acid was evaporated, and the residue was dissolved in distilled water. The final concentrations of the metal ions in the solutions used in the adsorption studies were 5 107 M for Co and 5 105 M for Fe. 2.3. Other chemicals The highest purity materials were used in the preparation of standard solutions to calibrate the atomic absorption spectrophotometer in the usual way (Vogel, 1975). The standard solutions were prepared from Analar CdCl2, CrCl3 6H2O, ZnSO4 7H2O, Pb(CH3COO)2 3H2O, MgSO4 7H2O and CuSO4 5H2O by dissolving portions of these reagents in bidistilled water so that the concentration of each metal in the adsorption test solution would be 10 ppm. 2.4. Additives The list of investigated additives includes humic and fulvic acids, which were isolated from the bottom sediments of Ismailia Canal, Cairo, Egypt, by treating them alternately with 1 M HCl and 0.5 M NaOH. The separation and purification of humic and fulvic acids were performed as described in the literature (Nash and Choppin, 1980). The concentration of each acid was 0.028 g/l. The compounds KMnO4 (0.03 g/l), Ca(OCl)2 (0.01 g/l) and alum (0.1 g/l) were also investigated as additives. The acids occur as impurities in water; the salts are used in water treatment processes. 2.5. Instruments A pure Ge detector and a multichannel analyzer were used to measure the gamma spectra of the pottery materials irradiated in the reactor. The gamma spectrometer was calibrated at various gamma energies within
Sorption experiments were performed with unirradiated pottery vessels. 20-ml portions of the aqueous solutions of each isotope or of an inactive element (in the case of atomic absorption measurements) were placed into a pottery vessel after being spiked with a chosen additive. The pH of the solutions was 5 in the cases of the radioactive isotopes and 7 in the cases of the experiments with atomic absorption measurements. Single-distilled water was used. The experiments were conducted at room temperature (2273 C). The vessels were covered with watch glasses in the open air. Additional water was appended to the solutions to bring their volumes to some standard initial value in order to compensate for losses due to evaporation or filtration through the vessel walls. The radioactivities (At ) of 1-ml portions of a solution were measured at various intervals of time, and the portions were returned to the vessel after each measurement. In the case of the experiments with atomic absorption measurements, 10 ml portions were taken at various intervals of time from each vessel and introduced into the spectrophotometer to measure the concentration of the metal (Ct ). Decontamination degrees were calculated using the following equations: Decontamination; ð%Þ ¼ ðAi At Þ 100=Ai ;
ð1Þ
Decontamination; ð%Þ ¼ ðCi Ct Þ 100=Ci ;
ð2Þ
where Ai is the initial specific radioactivity of the solution, and Ci is the initial concentration of the metal ion in the solution. 2.7. Mechanical properties Unirradiated and gamma-irradiated samples of fired pottery materials (2 2 1 cm3) were tested for resistance to compression with the Instron 1195 system (Instron Corporation, Series IX, Canada). It provided the following characteristics at the maximum load (ML): the load value, the displacement, the stress, and the strain. Samples for these tests were irradiated to 66.5 Mrad (60Co), which is higher than the doses that
ARTICLE IN PRESS A.A. Helal et al. / Applied Radiation and Isotopes 59 (2003) 11–16
the material would receive in the case of a waste of low or intermediate radioactivity.
13
black pots, respectively. The effects of the additive are considerable. Alum is widely used as an additive in water purification processes. In our case, the reason for
3. Results and discussion 3.1. Reactor irradiation of pottery materials Figs. 1–3 show the gamma spectra of the white, brown, and black pottery materials irradiated in the reactor. They all feature the lines of 46Sc, 59Fe, and 60Co along with the lines from smaller amounts of 134Cs and 65 Zn. It has been shown, however (Alian et al., 2001), that these materials are chemically stable and do not release any radioactivity of the reactor-produced radioisotopes when they are stored in water or diluted acids even for long periods of time. Table 1 lists the results of the compression tests of the materials before and after gamma irradiation. They show that brown pottery (specimens 1–6) are mechanically stronger than white pottery (specimens 7–12) and that gamma irradiation does not change the mechanical properties of either type of pottery. This demonstrates the suitability of these materials for manufacturing vessels for radioactive waste. 3.2. Sorption of metal ions in unirradiated pottery vessels Figs. 4 and 5 show the effect of alum (0.1 g/l) on the decontamination of cobalt from water in white and
Fig. 2. Gamma spectra of irradiated brown pottery: (a) 32 days after irradiation; and (b) 205 days after irradiation. Irradiation time is 5 h and measurement time is 10 min.
Fig. 1. Gamma spectra of irradiated white pottery: (a) 32 days after irradiation; and (b) 205 days after irradiation. Irradiation time is 5 h and measurement time is 10 min.
Fig. 3. Gamma spectra of irradiated black pottery: (a) 32 days after irradiation; and (b) 205 days after irradiation. Irradiation time is 5 h and measurement time is 10 min.
ARTICLE IN PRESS A.A. Helal et al. / Applied Radiation and Isotopes 59 (2003) 11–16
14
Table 1 Mechanical characteristics of pottery materials at maximum compression load Sample
Pottery type
Displacement (mm)
Load (kg)
Stress (kg cm2)
Strain (%)
1 2 3 4 5 6 7 8 9 10 11 12
Brown Brown Brown Brown Brown Brown White White White White White White
1.337 1.172 1.208 1.318 1.565 1.218 1.373 1.547 1.044 1.263 1.465 1.327
417.0 424.8 346.5 397.4 385.0 350.6 234.3 224.7 205.4 215.5 245.3 255.8
144.80 147.5 120.3 138.0 133.7 121.7 81.35 78.01 71.33 74.83 85.17 88.83
55.69 48.82 50.35 54.93 65.22 50.73 57.21 64.46 43.48 52.64 61.03 55.31
Decontamination, (%)
100 80 60 40
Blank Alum
20 0 0
2
4 Time (hours)
Decontamination, (%)
Fig. 4. Effect of alum on decontamination of pots.
6
8
100 80 60 40
Blank Alum
20 0 0
60
5
10 15 Time (hours )
Co with white
20
25
Fig. 6. Effect of alum on decontamination of 60Co with brown pots.
100 80
100
60 40
Blank Alum
20 0 0
2
4 Time (hours)
Fig. 5. Effect of alum on decontamination of pots.
6
8
Decontamination, (%)
Decontamination, (%)
The data given in bold correspond to the samples irradiated to 66.6 Mrad; the other data are for control (unirradiated) samples.
80 60 40
Blank HA
20 0
60
Co with black
the increase in decontamination effectiveness appears to be formation of a coagulant. On the other hand, the effect of alum at the same concentration on the decontamination of 59Fe in a brown pot is negligible (Fig. 6). The effects of humic acids, fulvic acids, and chlorine on the uptakes of iron in a brown pot are also negligible (Figs. 7–9). On the other hand, KMnO4 greatly decreases cobalt and iron decontamination in the black and brown pots (Figs. 10 and 11). This can be
0
5
10
15
20
25
30
Time (hours)
Fig. 7. Effect of humic acids on decontamination of brown pots.
59
Fe with
attributed to the competition of the radionuclide ions with the ions of potassium and/or manganese for the free ion-exchanging sites of the pottery materials. To study the effect of the material porosity on the decontamination, two parallel experiments with cobalt solutions in brown pots were conducted; the pores of
ARTICLE IN PRESS A.A. Helal et al. / Applied Radiation and Isotopes 59 (2003) 11–16 100 Decontamination, (%)
Decontamination, (%)
100 80 60 40
blank FA
20 0 0
5
10
15 20 Time (hours )
25
Fig. 8. Effect of fulvic acids on decontamination of brown pots.
59
Fe with
60 40 Blank KMnO4
20
0
10
20 Time (hours)
30
40
Fig. 11. Effect of KMnO4 on decontamination of brown pots.
59
Fe with
100 Decontamination, (%)
Decontamination, (%)
80
0
30
100 80 60 40 Blank Cl
20 0 0
5
10 15 Time (hours)
20
Fig. 9. Effect of chlorine on decontamination of brown pots.
80 60 40
closed system open system
20 0
25
0
5
10
15 20 Time (hours)
25
30
59
Fe with
Fig. 12. The difference between brown pots with open and closed pores in 60Co decontamination rates.
100 Decontamination, (%)
100 Decontamination, (%)
15
80 60 40 Blank KMnO4
20
80
Cd Cr Zn Pb Mg Cu
60 40 20 0 0
0 0
10
20
30 40 Time (hours)
50
Fig. 10. Effect of KMnO4 on decontamination of black pots.
2
4
6
8
10 12 14 16 18 20 22 24 26 Time ( hours)
60
60
Co with
one of the vessels were sealed with wax from outside. As Fig. 12 demonstrates, the open-pore system provides a much higher decontamination, probably due to the higher degree of water penetration into the pores (the experiments were conducted without stirring the solutions). Some water leakage was observed from the openpore system 1–2 h after the start of the experiment; however, the solution collected outside of the vessel was
Fig. 13. Effect of time on decontamination of Cd, Cr, Zn, Pb, Mg, and Cu from solutions using brown pots.
free of radioactivity. This can be explained by effective sorption of the metal ions by the pottery material. Water penetration through the pores of pottery materials is a known phenomenon. The effect of water evaporation from the outer surface is used for cooling drinking water in Egyptian villages. Fig. 13 shows the decrease in the concentrations of cadmium, chromium, zinc, lead, magnesium and copper
ARTICLE IN PRESS A.A. Helal et al. / Applied Radiation and Isotopes 59 (2003) 11–16
16
ions in time measured by atomic absorption spectrometry. The decontamination effectiveness of the material decreases in the order CrDCu>Pb>Zn>Cd>Mg. The decontamination degree exceeds 90% in 10 h for all of the ions. Although the sorption was studied with non-radioactive ions, some of these metals have relatively long-lived radioactive isotopes, such as 51Cr, 65 Zn and 115Cd, which may occur in radioactive waste solutions.
4. Conclusions * *
*
*
Pottery materials are resistant to irradiation. Pottery materials have high adsorption ability with respect to ions of Co, Fe, Cd, Cr, Zn, Pb, Mg, and Cu. Humic acids, fulvic acids, chlorine, and alum have little effect on iron adsorption. Potassium permanganate greatly decreases adsorption of cobalt and iron ions.
Acknowledgements The authors are grateful to Mr. Aly A. Helal for performing some experiments.
References Alian, A., Helal, A.A., Helal, A.A., 2001. In: Proceedings of the Annual Meeting on Nuclear Technology, Bonn, Germany, 2001, Forum Verlag, Inforum-unV Verwaltungsgesellschaft mbH, Bonn, pp. 263–266 (ISSN 0720-9207). Hamid, A., 1999. Analysis of heavy elements in air dust of the Greater Cairo by neutron activation analysis and g-spectrometry, M.Sc. Thesis, Ain Shams University, Cairo, Egypt (in Arabic). Nash, K.L., Choppin, G.R., 1980. Interactions of humic and fulvic acids with Th(IV). J. Inorg. Nucl. Chem. 42, 1045. Rado, P., 1969. An Introduction to the Technology of Pottery. Pergamon Press, London. Vogel, A.I., 1975. Textbook of Quantitative Inorganic Analysis, Including Elementary Instrumental Analysis, Longman Group Limited, 3rd Edition. Longman, London.