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Radioactivity of the gas pipeline network in Poland
Journal of Environmental Radioactivity 213 (2020) 106143
Contents lists available at ScienceDirect
Journal of Environmental Radioactivity journal homepage: http://www.elsevier.com/locate/jenvrad
Radioactivity of the gas pipeline network in Poland Jakub Nowak a, *, Paweł Jodłowski a, Jan Macuda b a b
AGH University of Science and Technology, Faculty of Physics and Applied Computer Science, Al. Mickiewicza 30, 30-059, Krak� ow, Poland AGH University of Science and Technology, Faculty of Drilling, Oil and Gas, Al. Mickiewicza 30, 30-059, Krak� ow, Poland
A R T I C L E I N F O
A B S T R A C T
Keywords: Natural gas Gas pipeline Radon 210 Pb Black powder
The paper presents the study of the radioactivity connected with the transport of natural gas by the gas pipeline network in the selected points in Poland. In the scope of the study the measurements of activity concentration of radon (222Rn) in the gas samples, radiolead (210Pb) in spent filter cartridges and dust samples (black powder) collected from the gas pipeline network were performed. The results show that the 222Rn activity concentration in natural gas varies from the detection limit of the applied method (30 Bq/m3) to around 1400 Bq/m3. The 210Pb activity concentration in black powder samples and spent filter cartridges varies from 500 to 17000 Bq/kg and from 200 to 2900 Bq/kg respectively. The black powder with highest 210Pb concentration should be classified as low-radioactive waste according to nuclear regulations.
1. Introduction Natural radionuclides commonly occur at varying concentrations in the Earth’s crust. At some places the contents of natural radionuclides may be enhanced due to human activities (TENORM -Technologically Enhanced Naturally Occurring Radioactive Material), for example mining industry. In case of oil and gas industry, the exposure to TENORM is mainly due to the migration of the progeny of uranium and thorium together with a mixture of oil, natural gas and water extracted from the deposit. Due to extractive operations, the radionuclides (mainly 226Ra, 228 Ra,224Ra, 210Pb and 210Po) may occur at high concentration in waste materials: produced water, sludge and hard scale. For example, the radium activity concentrations in sludge and hard scale vary from less than 100 Bq/kg up to 15000 kBq/kg and generally the radium concen trations in sludge are lower than that in hard scales. In case of 210Pb the situation is diametrically different, the concentration of the isotope in hard scales is very low, but in sludge can reach even to 1000 kBq/kg [IAEA, 2003]. In the case of the natural gas extraction the enhanced radioactivity is mostly connected with radon (222Rn) and its progeny: 218Po, 214Pb, 214 Bi, 214Po,210Pb and 210Po. The radon progeny are ion metals, which are easily adsorbed on aerosols and deposited on the inner surfaces of gas pipe and other gas processing equipment such as scrubbers, com pressors, reflux pumps, control valves and product lines creating thin radioactive films. Additionally, radon progeny together with aerosols (in
contrast to radon) are retained on filters. In the aftermath of successive radioactive decay of short-lived radon progeny, long-lived 210Pb is accumulated on filters [OGP, 2008]. With regard to the natural gas transport network the issue of TEN ORM is also related with the presence of 222Rn and its progeny. The radon activity concentration in natural gas transported by gas mainline varies in a wide range from dozens of Bq/m3 to several thousand Bq/m3 and mainly depends on the proximity of mines and geological structure of the deposit from which natural gas is extracted and transported. For example, the mean radon activity concentration in natural gas in the United Kingdom is 170 Bq/m3 [Dixon and Wilson, 2005]. Radon con centrations in Syrian natural gas varies from 15 Bq/m3 to 1140 Bq/m3 [Al-Masri and Shwiekani, 2008]. In the States of Pennsylvania and New York (USA) the activity concentration of radon in the gas pipeline varies from near 630 Bq/m3 to over 1600 Bq/m3 [Anspaugh, 2012]. A study carried out by the United States Geological Survey for the Marcellus deposit showed that the activity concentration of radon in natural gas ranged from 37 Bq/m3 to around 2900 Bq/m3 [Rowan and Kraemer, 2012]. The transport of natural gas can lead to generation material known as black powder which is rich with radon progeny especially 210 Pb. The name ‘black powder’ comes from the colour of the material which ranges from brown to black and is a product of corrosion of steel pipes and other steel elements of the pipeline network caused by liquid aerosols, corrosive species (such as CO2, H2S, organic acids or O2) and microorganisms. The material can be wet or dry and consists of numbers of chemical forms of iron sulphides, iron oxides and iron carbonates
* Corresponding author. E-mail address: [email protected] (J. Nowak). https://doi.org/10.1016/j.jenvrad.2019.106143 Received 3 October 2019; Received in revised form 17 December 2019; Accepted 18 December 2019 Available online 23 December 2019 0265-931X/© 2019 Elsevier Ltd. All rights reserved.
J. Nowak et al.
Journal of Environmental Radioactivity 213 (2020) 106143
powder occurs in the whole pipeline network. On the one hand, black powder is present in the filters; the one compressor station can generate around 80 kg per year of black powder which mainly accumulate on filters. In the other hand, the pigging along 50 km of the pipeline network may bring even 620 kg of the material. Basic chemical analysis confirms that iron is the main component of black powder in the gas pipeline network in Poland. The exact analysis of content of various chemical compounds of iron was not carried out. 2. Methodology In order to assess the level of radioactivity associated with the transport of natural gas by pipeline network, in the period from June to October 2015 measurements of the radon activity concentration in natural gas samples were carried out at 8 sites (Fig. 1). Additionally, the activity concentration of 210Pb in black powder samples and spent filter cartridges were determined. 2.1. Measurements of
222
Rn concentration in natural gas
The samples of natural gas were analysed for 222Rn using a Pylon AB5 radon field-portable scintillation measurement system equipped with Lucas cells (PYLON 300A). Application of this method, in contrast to other methods, allowed to isolate natural gas samples from high voltage, which is necessary for supplying the detector (a photomultiplier tube). Gas samples were taken from gas stations, gas hubs and compressor stations. Gas samples were collected from sampling valves located at gas mainline into stainless steel vessel of 2.4 L volume. Before collecting, the cylinder was filled by the studied gas and released several times to assure removing any air or remains of the previous sample. The cylinder was filled with gas to a pressure of 10–15 bar, then the gas sample was depressurized to the ambient pressure (atmospheric pressure) into the Lucas cell. During the depressurization process, the gas of around 15 L volume freely flowed through the Lucas cell for around 2–3 min. In order to obtain radioactive equilibrium between radon and its progeny,
Fig. 1. Location of measurement sites.
[Baldwin, 1998; OGP, 2008; Saremi and Kazemi, 2011; Khan et al., 2015]. Detailed information on black powder (characterization, for mation mechanisms, removal and prevention methods) can be found in the review paper of Khan and Al-Shehhi [2015]. Godoy et al. (2005) measured 210Pb content in “black-powder” from the gas pipelines in Brazil. The activity concentration varied from 40 to 4900 Bq/kg. In Poland the natural gas pipeline network is around 11000 km long and it consists of 881 gas pipeline stations, 14 compressor stations and 58 hubs. Each year around 14 billion cubic meters of imported (mainly from Russia) and national gas is transported. The problem with black
Table 1 The radon activity concentration in natural gas from selected locations of gas pipeline network in Poland (measurements were performed in September and October 2015). Location
The activity concentration of222Rn [Bq/m3] The daily temporal variability
a
The weekly temporal variability
b, c
WG-J
14/9 08:00 397 (36)
14/9 10:00 341 (31)
14/9 12:00 366 (33)
14/9 14:00 425 (38)
14/9 16:00 343 (31)
14/9 X
15/9 399 (6)
16/9 396 (36)
17/9 278 (25)
SP-C
15/9 08:00 <30 d
15/9 10:00 <30d
15/9 12:00 <30 d
15/9 14:00 <30 d
15/9 16:00 <30 d
14/9 <30d
15/9 X
16/9 <30 d
17/9 <30 d
WG-L
16/9 08:00 66 (13)
16/9 10:00 71 (14)
16/9 12:00 51.2 (9.7)
16/9 14:00 45.5 (8.6)
16/9 16:00 54 (10)
14/9 70 (13)
15/9 37.0 (7.0)
16/9 X
17/9 <30 d
WG-O(a)
17/9 08:00 <30 d
17/9 10:00 <30 d
17/9 12:00 <30 d
17/9 14:00 <30 d
17/9 16:00 <30 d
14/9 37.6 (7.1)
15/9 <30 d
16/9 <30 d
17/9 X
WG-O(b)
1366 (120)
WG-Lw
28/9 08:00 65 (12)
28/9 10:00 55 (11)
28/9 12:00 80 (15)
28/9 14:00 76 (15)
28/9 16:00 59 (11)
28/9 X
29/9 70 (13)
30/9 58 (11)
1/10 65.0 (2.3)
WG-G
29/9 08:00 63 (12)
29/9 10:00 78 (15)
29/9 12:00 93 (18)
29/9 14:00 82 (16)
29/9 16:00 97 (18)
28/9 72 (14)
29/9 X
30/9 76 (15)
1/10 63 (12)
WG-H
30/9 08:00 81 (15)
30/9 10:00 58 (11)
30/9 12:00 87 (17)
30/9 14:00 91.7 (7.4)
30/9 16:00 79 (15)
28/9 104 � 20
29/9 53 (10)
30/9 X
1/10 83 (16)
SP-B
1/10 08:00 54 (10)
1/10 10:00 64 (12)
1/10 12:00 62 (12)
1/10 14:00 50.9 (9.7)
1/10 16:00 65 (12)
28/9 52 (10)
29/9 46.9 � 8.9
30/9 58 (11)
1/10 X
–
WG-O(a) – imported gas, WG-O(b) – gas from a local mine. WG – a gas hub, SP – a gas station. a First line – date and time of sampling (dd/mm time); second line – the222Rn concentration with standard uncertainty in the brackets. b First line – date of sampling (dd/mm); second line – the222Rn concentration with standard uncertainty. c X means the day on which the daily temporal variability was studied. d The detection limit of applied method. 2
J. Nowak et al.
Journal of Environmental Radioactivity 213 (2020) 106143
Fig. 2. The daily and weekly temporal variability of
Nnetto ⋅C 3⋅t⋅V⋅ε⋅1:07⋅A
Rn activity concentration in natural gas.
[s], 3 stands for alpha emitters in the 222Rn group (222Rn, 218Po, 214Po), V is Lucas cell volume. In order to remove trace of the sample, the Lucas cells were flushed with nitrogen (99,8% gas purity) after each completed measurement series. The limit of detection for this method is about 30 Bq/m3.
measurements were performed after at least 2 h from filled the Lucas cell. The measurement series lasted 2 h. The activity concentration of 222 Rn in natural gas sample (ARn) was calculated by the following formula: ARn ¼
222
(1)
2.2. Measurements of filter cartridges
where Nnetto is net count of light impulses generated by the photo multiplier tube of PYLON AB5, A stands for correction factor for radon decay from sampling to start measurement, C is correction factor for radon decay during measurement, ε is the detection efficiency of Luas cell, 1.07 stands for correction for radon concentration measurement in methane according with Kitto et al. (2014), t is a measurement time in
210
Pb concentration in black powder and spent
The black powder samples were collected from filters and after pigging process into plastic bags. Spent filter cartridges were cut and packed into plastic bags. After the transport to the laboratory, samples (blach powder and spent filter cartridges) were sealed into beakers. The 3
J. Nowak et al.
Journal of Environmental Radioactivity 213 (2020) 106143
Relatively low radon concentration in natural gas samples is con nected with the fact that the gas in most studied locations was imported one. Therefore, the time elapsed from the gas extraction to the collection of samples was relatively long. In consequence, the concentration of 222 Rn in the gas significantly decreased due to radon decay. Fig. 2a–f presents daily and weekly temporal variability of the 222Rn activity concentration in natural gas from studied locations, for which the radon concentration exceeds the level of the detection limit of the applied method (i.e. no charts for SP-C and WG-O(a)). The horizontal axis presents the elapsed time from the beginning of the week in which measurements were performed. The results show radon concentrations lie within the interval of the mean plus/minus two standard deviations of the mean. This means that the radon activity concentration does not statistically change in daily or weekly time scale. Generally, the elevated radon activity concentrations of several hundreds of Bq/m3 and more in natural gas are observed at locations where the gas directly comes from local gas mines or where there is a blend of the national gas with imported one.
Table 2 The activity concentration of210Pb in black powder samples and spent filter cartridges. Location Black powder WG-J
Description of sample
210
Black Black Black Black Black Black Black Black Black
16 700 (1700) 12 800 (1300) 5690 (600) 2040 (200) 630 (60) 480 (50) 3360 (350) 2670 (250) 11 200 (1100)
powder from powder from powder from powder from powder from powder from powder from powder from powder from
spent filter spent filter spent filter spent filter spent filter spent filter a cleaning pig a MFL pig a MFL pig
SP-C WG-L WG-O(a) SP-B LS-K LS-K LS-DN Spent filter cartridge WG-J Spent filter cartridge WG-PW Spent filter cartridge SP-C Spent filter cartridge
Pb [Bq/kg]
2920 (300) 210 (20) 700 (70)
WG – a gas hub, SP – a gas station, LS – launching station, MFL - Magnetic Flux Leakage testing.
3.2. The 210Pb activity concentration in black powder samples and spent filter cartridges
aluminium cylindrical beakers of the volume of 121 mL were used. In order to obtain radioactive equilibrium in the samples between 226Ra and its progeny: 222Rn, 214Pb and 214Bi, measurements were carried out after at least 21 days from sample sealing. Samples were measured by gamma-spectrometry with an HPGe de tector with relative efficiency of 42% (Canberra GX4020). Spectra were collected for 10–50 h and the measurement time depends on the activity of analysed samples. As standard samples, reference materials RG manufactured by the International Atomic Energy Agency (IAEA) were used. A detailed description of the methodology was described by Jod łowski and Kalita (2010). The 210Pb content was quantified using its 46,5 keV gamma-line, 40K via its 1461 keV gamma-line and U-238 via its 1001 keV gamma-line. The 226Ra content was determined via its progeny 214Pb (352 keV) and 214Bi (609 keV, 1120 keV and 1764 keV) gamma-lines. 228Ra was quantified via the gamma-lines of its progeny 228Ac (911 keV, 967 keV) and 208Tl (583 keV, 2614 keV). The self-attenuation correction in 210Pb measurements accounting the difference of density of the samples and standard ones was introduced follow the transmission method proposed by Cutshall (Cutshall et al., 1983; Jodłowski, 2016).
Table 2 presents the results of the 210Pb activity concentration in black powder samples and spent filter cartridges collected from selected sites. The activity concentration of 210Pb in black powder samples and spent filter cartridges is significant and varies from 500 to near 17000 Bq/kg and from 200 to 2900 Bq/kg respectively. Among the black powder samples, the highest 210Pb concentration was observed for the sample collected from WG-J filter, where the blend of the national gas (from local mines) with imported one is transported. The high 210Pb concentration (~5700 Bq/kg) was also observed for the sample from the SP-C filter. In case of pigging black powder samples, the 210Pb concen tration varied from 2700 to 11200 Bq/kg. In the remain samples, the content of 210Pb is much lower and varies from 500 to 2000 Bq/kg. Additionally, practically there is no 40K, 226Ra and 232Th in black powder samples and spent filter cartridges. According to Polish and European Union nuclear regulations, ma terials which content more than 10 kBq/kg of 210Pb should be treated as low-radioactivity waste. Therefore, monitoring of radiolead content in black powder from gas pipeline system should be introduced to avoid misclassification to non-radioactive waste during the disposal process.
3. Results and discussion 3.1. The
222
Rn activity concentration in natural gas
4. Conclusions
In order to assess the radon activity concentration and its temporal variability (daily and weekly) in the natural gas from the gas pipeline network, the measurements were performed at 9 locations. The samples for studying daily temporal variability were collected every 2 h from 8 to 17 o’clock during one day. The samples for studying weekly temporal variability were collected on four consecutive days at the same time. A total number of gas samples amounted to 64. The results of radon ac tivity concentration in natural gas samples from gas pipeline network are summarized in Table 1. Generally, the 222Rn activity concentration in natural gas from selected locations of the gas pipeline network varies from 30 Bq/m3 (detection limit of applied method) to around 425 Bq/m3. The highest radon activity concentration (1370 Bq/m3) was observed in gas samples from WG-O(b). For this sample, the gas flowed directly from the nearby gas mine. The average weekly radon concentration in gas samples from WG-J is 368 Bq/m3 and significantly exceeds the average weekly radon con centration for other sampling locations, which varies from 30 Bq/m3 to 80 Bq/m3 (Fig. 2a–f). This phenomenon is related to the fact that the gas from WG-J was a mixture of gas coming from Ukraine and gas from the local Polish mines.
The 222Rn activity concentration in natural gas in Poland depends on the origin of the gas. The imported gas, due to the long time elapsed from the extraction to sampling and the relatively short half-life of radon, is characterized by a low 222Rn concentration (below 100 Bq/m3), while the natural gas from the national mines contains high concentration of radon (up to 1400 Bq/m3). The 210Pb activity concentration in the black powder samples is very high (up to 16700 Bq/kg). The black powder with highest 210Pb con centration should be classified as low-radioactive waste. It should be emphasized that the high 210Pb content in black powder indicates the possibility of radiological risk to employees during direct contact with the black powder. Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.
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Journal of Environmental Radioactivity 213 (2020) 106143
Acknowledgement
IAEA, 2003. Radiation Protection and the Management of Radioactive Waste in the Oil and Gas Industry. In: Safety Reports Series No. 34. International Atomic Energy Agency, Vienna. Jodłowski, P., 2016. A revision factor to the Cutshall self-attenuation correction in 210Pb gamma-spectrometry measurements. Appl. Radiat. Isot. 109, 566–569. Jodłowski, P., Kalita, S., 2010. Gamma-Ray Spectrometry Laboratory for high-precision measurements of radionuclide concentrations in environmental samples. Nukleonika 55 (2), 143–148. Khan, T.S., Al-Shehhi, M.S., 2015. Review of black powder in gas pipelines - an industrial perspective. J. Nat. Gas Sci. Eng. 25, 66–76. Khan, T., AlShehhi, M., Stephen, S., Khezzar, L., 2015. Characterization and preliminary root cause identification of black powder content in a gas transmission network - a case study. J. Nat. Gas Sci. Eng. 27, 769–775. Kitto, M., Torres, M., Haines, D., Semkow, T., 2014. Radon measurement of natural gas using alpha scintillation cells. J. Environ. Radioact. 138, 205–207. OGP, 2008. Managing naturally occurring radioactive material (NORM) in the oil & gas industry, report No. 412, international association of oil & gas producers. htt p://www.iogp.org/pubs/412.pdf accessed 16.10.26. Rowan, E.L., Kraemer, T.F., 2012. Radon-222 Content of Natural Gas Samples from Upper and Middle Devonian Sandstone and Shale Reservoirs in Pennsylvania: Preliminary Data, USGS Open-File Report Series 2012 – 1159. U.S. Geological Survey. Saremi, M., Kazemi, M., 2011. The effect of black powder composition on the erosion of compressor’s impeller in gas transmission line. Adv. Mater. Res. 264–265, 1514–1518.
This work was (partially) supported by the Ministry of Science and Higher Education, project no. 16.16.220.842 B02. References Al-Masri, M.S., Shwiekani, R., 2008. Radon gas distribution in natural gas processing facilities and workplace air environment. J. Environ. Radioact. 99 (2008), 574–580. Anspaugh, L., 2012. Scientific Issues Concerning Radon in Natural Gas Texas Eastern Transmission, LP and Algonquin Gas Transmission, LLC New Jersey – New York Expansion Project. Docket No. CP11-56. http://www.slideshare.net/MarcellusDN/sc ientific-issues-concerning-radon-in-natural-gas. accessed 16.10.26. Baldwin, R.M., 1998. “Black Powder” in Gas Industry – Sources, Characteristics and Treatment, Report No. TA 97-4. Gas Machinery Research Council. Cutshall, N.H., Larsen, I.L., Olsen, C.R., 1983. Direct analysis of Pb-210 in sediment samples: a self-absorption corrections. Nucl. Instrum. Methods Phys. Res. 206, 309–312. Dixon, D., Wilson, C., 2005. Developments in the management of exposures from radon in natural gas in the UK. Radioact. Environ. 7 (2005), 1064–1070. Godoy, J.M., Carvalho, F., Cordilha, A., Matta, L.E., Godoy, M.L., 2005. 210Pb content in natural gas pipeline residues (‘‘black-powder’’) and its correlation with the chemical composition. J. Environ. Radioact. 83 (2005), 101–111.
5
Contents lists available at ScienceDirect
Journal of Environmental Radioactivity journal homepage: http://www.elsevier.com/locate/jenvrad
Radioactivity of the gas pipeline network in Poland Jakub Nowak a, *, Paweł Jodłowski a, Jan Macuda b a b
AGH University of Science and Technology, Faculty of Physics and Applied Computer Science, Al. Mickiewicza 30, 30-059, Krak� ow, Poland AGH University of Science and Technology, Faculty of Drilling, Oil and Gas, Al. Mickiewicza 30, 30-059, Krak� ow, Poland
A R T I C L E I N F O
A B S T R A C T
Keywords: Natural gas Gas pipeline Radon 210 Pb Black powder
The paper presents the study of the radioactivity connected with the transport of natural gas by the gas pipeline network in the selected points in Poland. In the scope of the study the measurements of activity concentration of radon (222Rn) in the gas samples, radiolead (210Pb) in spent filter cartridges and dust samples (black powder) collected from the gas pipeline network were performed. The results show that the 222Rn activity concentration in natural gas varies from the detection limit of the applied method (30 Bq/m3) to around 1400 Bq/m3. The 210Pb activity concentration in black powder samples and spent filter cartridges varies from 500 to 17000 Bq/kg and from 200 to 2900 Bq/kg respectively. The black powder with highest 210Pb concentration should be classified as low-radioactive waste according to nuclear regulations.
1. Introduction Natural radionuclides commonly occur at varying concentrations in the Earth’s crust. At some places the contents of natural radionuclides may be enhanced due to human activities (TENORM -Technologically Enhanced Naturally Occurring Radioactive Material), for example mining industry. In case of oil and gas industry, the exposure to TENORM is mainly due to the migration of the progeny of uranium and thorium together with a mixture of oil, natural gas and water extracted from the deposit. Due to extractive operations, the radionuclides (mainly 226Ra, 228 Ra,224Ra, 210Pb and 210Po) may occur at high concentration in waste materials: produced water, sludge and hard scale. For example, the radium activity concentrations in sludge and hard scale vary from less than 100 Bq/kg up to 15000 kBq/kg and generally the radium concen trations in sludge are lower than that in hard scales. In case of 210Pb the situation is diametrically different, the concentration of the isotope in hard scales is very low, but in sludge can reach even to 1000 kBq/kg [IAEA, 2003]. In the case of the natural gas extraction the enhanced radioactivity is mostly connected with radon (222Rn) and its progeny: 218Po, 214Pb, 214 Bi, 214Po,210Pb and 210Po. The radon progeny are ion metals, which are easily adsorbed on aerosols and deposited on the inner surfaces of gas pipe and other gas processing equipment such as scrubbers, com pressors, reflux pumps, control valves and product lines creating thin radioactive films. Additionally, radon progeny together with aerosols (in
contrast to radon) are retained on filters. In the aftermath of successive radioactive decay of short-lived radon progeny, long-lived 210Pb is accumulated on filters [OGP, 2008]. With regard to the natural gas transport network the issue of TEN ORM is also related with the presence of 222Rn and its progeny. The radon activity concentration in natural gas transported by gas mainline varies in a wide range from dozens of Bq/m3 to several thousand Bq/m3 and mainly depends on the proximity of mines and geological structure of the deposit from which natural gas is extracted and transported. For example, the mean radon activity concentration in natural gas in the United Kingdom is 170 Bq/m3 [Dixon and Wilson, 2005]. Radon con centrations in Syrian natural gas varies from 15 Bq/m3 to 1140 Bq/m3 [Al-Masri and Shwiekani, 2008]. In the States of Pennsylvania and New York (USA) the activity concentration of radon in the gas pipeline varies from near 630 Bq/m3 to over 1600 Bq/m3 [Anspaugh, 2012]. A study carried out by the United States Geological Survey for the Marcellus deposit showed that the activity concentration of radon in natural gas ranged from 37 Bq/m3 to around 2900 Bq/m3 [Rowan and Kraemer, 2012]. The transport of natural gas can lead to generation material known as black powder which is rich with radon progeny especially 210 Pb. The name ‘black powder’ comes from the colour of the material which ranges from brown to black and is a product of corrosion of steel pipes and other steel elements of the pipeline network caused by liquid aerosols, corrosive species (such as CO2, H2S, organic acids or O2) and microorganisms. The material can be wet or dry and consists of numbers of chemical forms of iron sulphides, iron oxides and iron carbonates
* Corresponding author. E-mail address: [email protected] (J. Nowak). https://doi.org/10.1016/j.jenvrad.2019.106143 Received 3 October 2019; Received in revised form 17 December 2019; Accepted 18 December 2019 Available online 23 December 2019 0265-931X/© 2019 Elsevier Ltd. All rights reserved.
J. Nowak et al.
Journal of Environmental Radioactivity 213 (2020) 106143
powder occurs in the whole pipeline network. On the one hand, black powder is present in the filters; the one compressor station can generate around 80 kg per year of black powder which mainly accumulate on filters. In the other hand, the pigging along 50 km of the pipeline network may bring even 620 kg of the material. Basic chemical analysis confirms that iron is the main component of black powder in the gas pipeline network in Poland. The exact analysis of content of various chemical compounds of iron was not carried out. 2. Methodology In order to assess the level of radioactivity associated with the transport of natural gas by pipeline network, in the period from June to October 2015 measurements of the radon activity concentration in natural gas samples were carried out at 8 sites (Fig. 1). Additionally, the activity concentration of 210Pb in black powder samples and spent filter cartridges were determined. 2.1. Measurements of
222
Rn concentration in natural gas
The samples of natural gas were analysed for 222Rn using a Pylon AB5 radon field-portable scintillation measurement system equipped with Lucas cells (PYLON 300A). Application of this method, in contrast to other methods, allowed to isolate natural gas samples from high voltage, which is necessary for supplying the detector (a photomultiplier tube). Gas samples were taken from gas stations, gas hubs and compressor stations. Gas samples were collected from sampling valves located at gas mainline into stainless steel vessel of 2.4 L volume. Before collecting, the cylinder was filled by the studied gas and released several times to assure removing any air or remains of the previous sample. The cylinder was filled with gas to a pressure of 10–15 bar, then the gas sample was depressurized to the ambient pressure (atmospheric pressure) into the Lucas cell. During the depressurization process, the gas of around 15 L volume freely flowed through the Lucas cell for around 2–3 min. In order to obtain radioactive equilibrium between radon and its progeny,
Fig. 1. Location of measurement sites.
[Baldwin, 1998; OGP, 2008; Saremi and Kazemi, 2011; Khan et al., 2015]. Detailed information on black powder (characterization, for mation mechanisms, removal and prevention methods) can be found in the review paper of Khan and Al-Shehhi [2015]. Godoy et al. (2005) measured 210Pb content in “black-powder” from the gas pipelines in Brazil. The activity concentration varied from 40 to 4900 Bq/kg. In Poland the natural gas pipeline network is around 11000 km long and it consists of 881 gas pipeline stations, 14 compressor stations and 58 hubs. Each year around 14 billion cubic meters of imported (mainly from Russia) and national gas is transported. The problem with black
Table 1 The radon activity concentration in natural gas from selected locations of gas pipeline network in Poland (measurements were performed in September and October 2015). Location
The activity concentration of222Rn [Bq/m3] The daily temporal variability
a
The weekly temporal variability
b, c
WG-J
14/9 08:00 397 (36)
14/9 10:00 341 (31)
14/9 12:00 366 (33)
14/9 14:00 425 (38)
14/9 16:00 343 (31)
14/9 X
15/9 399 (6)
16/9 396 (36)
17/9 278 (25)
SP-C
15/9 08:00 <30 d
15/9 10:00 <30d
15/9 12:00 <30 d
15/9 14:00 <30 d
15/9 16:00 <30 d
14/9 <30d
15/9 X
16/9 <30 d
17/9 <30 d
WG-L
16/9 08:00 66 (13)
16/9 10:00 71 (14)
16/9 12:00 51.2 (9.7)
16/9 14:00 45.5 (8.6)
16/9 16:00 54 (10)
14/9 70 (13)
15/9 37.0 (7.0)
16/9 X
17/9 <30 d
WG-O(a)
17/9 08:00 <30 d
17/9 10:00 <30 d
17/9 12:00 <30 d
17/9 14:00 <30 d
17/9 16:00 <30 d
14/9 37.6 (7.1)
15/9 <30 d
16/9 <30 d
17/9 X
WG-O(b)
1366 (120)
WG-Lw
28/9 08:00 65 (12)
28/9 10:00 55 (11)
28/9 12:00 80 (15)
28/9 14:00 76 (15)
28/9 16:00 59 (11)
28/9 X
29/9 70 (13)
30/9 58 (11)
1/10 65.0 (2.3)
WG-G
29/9 08:00 63 (12)
29/9 10:00 78 (15)
29/9 12:00 93 (18)
29/9 14:00 82 (16)
29/9 16:00 97 (18)
28/9 72 (14)
29/9 X
30/9 76 (15)
1/10 63 (12)
WG-H
30/9 08:00 81 (15)
30/9 10:00 58 (11)
30/9 12:00 87 (17)
30/9 14:00 91.7 (7.4)
30/9 16:00 79 (15)
28/9 104 � 20
29/9 53 (10)
30/9 X
1/10 83 (16)
SP-B
1/10 08:00 54 (10)
1/10 10:00 64 (12)
1/10 12:00 62 (12)
1/10 14:00 50.9 (9.7)
1/10 16:00 65 (12)
28/9 52 (10)
29/9 46.9 � 8.9
30/9 58 (11)
1/10 X
–
WG-O(a) – imported gas, WG-O(b) – gas from a local mine. WG – a gas hub, SP – a gas station. a First line – date and time of sampling (dd/mm time); second line – the222Rn concentration with standard uncertainty in the brackets. b First line – date of sampling (dd/mm); second line – the222Rn concentration with standard uncertainty. c X means the day on which the daily temporal variability was studied. d The detection limit of applied method. 2
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Journal of Environmental Radioactivity 213 (2020) 106143
Fig. 2. The daily and weekly temporal variability of
Nnetto ⋅C 3⋅t⋅V⋅ε⋅1:07⋅A
Rn activity concentration in natural gas.
[s], 3 stands for alpha emitters in the 222Rn group (222Rn, 218Po, 214Po), V is Lucas cell volume. In order to remove trace of the sample, the Lucas cells were flushed with nitrogen (99,8% gas purity) after each completed measurement series. The limit of detection for this method is about 30 Bq/m3.
measurements were performed after at least 2 h from filled the Lucas cell. The measurement series lasted 2 h. The activity concentration of 222 Rn in natural gas sample (ARn) was calculated by the following formula: ARn ¼
222
(1)
2.2. Measurements of filter cartridges
where Nnetto is net count of light impulses generated by the photo multiplier tube of PYLON AB5, A stands for correction factor for radon decay from sampling to start measurement, C is correction factor for radon decay during measurement, ε is the detection efficiency of Luas cell, 1.07 stands for correction for radon concentration measurement in methane according with Kitto et al. (2014), t is a measurement time in
210
Pb concentration in black powder and spent
The black powder samples were collected from filters and after pigging process into plastic bags. Spent filter cartridges were cut and packed into plastic bags. After the transport to the laboratory, samples (blach powder and spent filter cartridges) were sealed into beakers. The 3
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Journal of Environmental Radioactivity 213 (2020) 106143
Relatively low radon concentration in natural gas samples is con nected with the fact that the gas in most studied locations was imported one. Therefore, the time elapsed from the gas extraction to the collection of samples was relatively long. In consequence, the concentration of 222 Rn in the gas significantly decreased due to radon decay. Fig. 2a–f presents daily and weekly temporal variability of the 222Rn activity concentration in natural gas from studied locations, for which the radon concentration exceeds the level of the detection limit of the applied method (i.e. no charts for SP-C and WG-O(a)). The horizontal axis presents the elapsed time from the beginning of the week in which measurements were performed. The results show radon concentrations lie within the interval of the mean plus/minus two standard deviations of the mean. This means that the radon activity concentration does not statistically change in daily or weekly time scale. Generally, the elevated radon activity concentrations of several hundreds of Bq/m3 and more in natural gas are observed at locations where the gas directly comes from local gas mines or where there is a blend of the national gas with imported one.
Table 2 The activity concentration of210Pb in black powder samples and spent filter cartridges. Location Black powder WG-J
Description of sample
210
Black Black Black Black Black Black Black Black Black
16 700 (1700) 12 800 (1300) 5690 (600) 2040 (200) 630 (60) 480 (50) 3360 (350) 2670 (250) 11 200 (1100)
powder from powder from powder from powder from powder from powder from powder from powder from powder from
spent filter spent filter spent filter spent filter spent filter spent filter a cleaning pig a MFL pig a MFL pig
SP-C WG-L WG-O(a) SP-B LS-K LS-K LS-DN Spent filter cartridge WG-J Spent filter cartridge WG-PW Spent filter cartridge SP-C Spent filter cartridge
Pb [Bq/kg]
2920 (300) 210 (20) 700 (70)
WG – a gas hub, SP – a gas station, LS – launching station, MFL - Magnetic Flux Leakage testing.
3.2. The 210Pb activity concentration in black powder samples and spent filter cartridges
aluminium cylindrical beakers of the volume of 121 mL were used. In order to obtain radioactive equilibrium in the samples between 226Ra and its progeny: 222Rn, 214Pb and 214Bi, measurements were carried out after at least 21 days from sample sealing. Samples were measured by gamma-spectrometry with an HPGe de tector with relative efficiency of 42% (Canberra GX4020). Spectra were collected for 10–50 h and the measurement time depends on the activity of analysed samples. As standard samples, reference materials RG manufactured by the International Atomic Energy Agency (IAEA) were used. A detailed description of the methodology was described by Jod łowski and Kalita (2010). The 210Pb content was quantified using its 46,5 keV gamma-line, 40K via its 1461 keV gamma-line and U-238 via its 1001 keV gamma-line. The 226Ra content was determined via its progeny 214Pb (352 keV) and 214Bi (609 keV, 1120 keV and 1764 keV) gamma-lines. 228Ra was quantified via the gamma-lines of its progeny 228Ac (911 keV, 967 keV) and 208Tl (583 keV, 2614 keV). The self-attenuation correction in 210Pb measurements accounting the difference of density of the samples and standard ones was introduced follow the transmission method proposed by Cutshall (Cutshall et al., 1983; Jodłowski, 2016).
Table 2 presents the results of the 210Pb activity concentration in black powder samples and spent filter cartridges collected from selected sites. The activity concentration of 210Pb in black powder samples and spent filter cartridges is significant and varies from 500 to near 17000 Bq/kg and from 200 to 2900 Bq/kg respectively. Among the black powder samples, the highest 210Pb concentration was observed for the sample collected from WG-J filter, where the blend of the national gas (from local mines) with imported one is transported. The high 210Pb concentration (~5700 Bq/kg) was also observed for the sample from the SP-C filter. In case of pigging black powder samples, the 210Pb concen tration varied from 2700 to 11200 Bq/kg. In the remain samples, the content of 210Pb is much lower and varies from 500 to 2000 Bq/kg. Additionally, practically there is no 40K, 226Ra and 232Th in black powder samples and spent filter cartridges. According to Polish and European Union nuclear regulations, ma terials which content more than 10 kBq/kg of 210Pb should be treated as low-radioactivity waste. Therefore, monitoring of radiolead content in black powder from gas pipeline system should be introduced to avoid misclassification to non-radioactive waste during the disposal process.
3. Results and discussion 3.1. The
222
Rn activity concentration in natural gas
4. Conclusions
In order to assess the radon activity concentration and its temporal variability (daily and weekly) in the natural gas from the gas pipeline network, the measurements were performed at 9 locations. The samples for studying daily temporal variability were collected every 2 h from 8 to 17 o’clock during one day. The samples for studying weekly temporal variability were collected on four consecutive days at the same time. A total number of gas samples amounted to 64. The results of radon ac tivity concentration in natural gas samples from gas pipeline network are summarized in Table 1. Generally, the 222Rn activity concentration in natural gas from selected locations of the gas pipeline network varies from 30 Bq/m3 (detection limit of applied method) to around 425 Bq/m3. The highest radon activity concentration (1370 Bq/m3) was observed in gas samples from WG-O(b). For this sample, the gas flowed directly from the nearby gas mine. The average weekly radon concentration in gas samples from WG-J is 368 Bq/m3 and significantly exceeds the average weekly radon con centration for other sampling locations, which varies from 30 Bq/m3 to 80 Bq/m3 (Fig. 2a–f). This phenomenon is related to the fact that the gas from WG-J was a mixture of gas coming from Ukraine and gas from the local Polish mines.
The 222Rn activity concentration in natural gas in Poland depends on the origin of the gas. The imported gas, due to the long time elapsed from the extraction to sampling and the relatively short half-life of radon, is characterized by a low 222Rn concentration (below 100 Bq/m3), while the natural gas from the national mines contains high concentration of radon (up to 1400 Bq/m3). The 210Pb activity concentration in the black powder samples is very high (up to 16700 Bq/kg). The black powder with highest 210Pb con centration should be classified as low-radioactive waste. It should be emphasized that the high 210Pb content in black powder indicates the possibility of radiological risk to employees during direct contact with the black powder. Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.
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Journal of Environmental Radioactivity 213 (2020) 106143
Acknowledgement
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This work was (partially) supported by the Ministry of Science and Higher Education, project no. 16.16.220.842 B02. References Al-Masri, M.S., Shwiekani, R., 2008. Radon gas distribution in natural gas processing facilities and workplace air environment. J. Environ. Radioact. 99 (2008), 574–580. Anspaugh, L., 2012. Scientific Issues Concerning Radon in Natural Gas Texas Eastern Transmission, LP and Algonquin Gas Transmission, LLC New Jersey – New York Expansion Project. Docket No. CP11-56. http://www.slideshare.net/MarcellusDN/sc ientific-issues-concerning-radon-in-natural-gas. accessed 16.10.26. Baldwin, R.M., 1998. “Black Powder” in Gas Industry – Sources, Characteristics and Treatment, Report No. TA 97-4. Gas Machinery Research Council. Cutshall, N.H., Larsen, I.L., Olsen, C.R., 1983. Direct analysis of Pb-210 in sediment samples: a self-absorption corrections. Nucl. Instrum. Methods Phys. Res. 206, 309–312. Dixon, D., Wilson, C., 2005. Developments in the management of exposures from radon in natural gas in the UK. Radioact. Environ. 7 (2005), 1064–1070. Godoy, J.M., Carvalho, F., Cordilha, A., Matta, L.E., Godoy, M.L., 2005. 210Pb content in natural gas pipeline residues (‘‘black-powder’’) and its correlation with the chemical composition. J. Environ. Radioact. 83 (2005), 101–111.
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