Radiation Protection Dosimetry (2014), Vol. 160, No. 1–3, pp. 117 –119 Advance Access publication 9 April 2014
doi:10.1093/rpd/ncu065
RADON CONTRIBUTION TO THE TOTAL EFFECTIVE DOSE OF URANIUM MINERS P. Otahal1,*, I. Burian1, M. M. Nasir2 and Z. Gregor2 1 National Institute for NBC Protection, Kamenna 71, 26231 Milin, Czech Republic 2 GEAM, Subsidiary of the State Uranium Company DIAMO, Dolni Rozinka, Czech Republic *Corresponding author:[email protected]
INTRODUCTION
MATERIALS AND METHODS 220
Rn In addition to exposure to gamma radiation, (thoron) and 222Rn (radon) decay products, uranium workers are also exposed to airborne long-lived radioactive dust (1). Not surprisingly, radon levels are highest where the highest uranium concentration occurs in rocks, and historically it was in uranium mines that the potential hazard from radon progeny inhalation was first recognised(2). It is therefore no wonder that the US Bureau of Mines introduced the first personal dosemeters for uranium underground workers already in 1979(3). The radiation workers of category A in uranium mine Rozna I have been equipped with ALGADE personal dosemeters (company ALGADE, France) since 1998. It is a portable, compact, battery sampler that allows monitoring of all three components of the total effective dose. For the purpose of the Czech uranium miners it was modified in order to estimate the contribution of the short-lived radon decay products to the total effective dose. The dosemeters are evaluated at monthly intervals by the National Institute for Nuclear, Chemical and Biological Protection (Czech Republic). The integral monthly results of individual contributions to the total effective workers dose are recorded in a database that is sent periodically to the Czech Central Registry of Occupational Exposure. The ALGADE dosemeter is worn on the belt along with the mining lamp. The dosemeter is powered by a small rechargeable battery, which is able to operate .10 h when fully charged. The full charging takes 14 h. The sampler is designed to operate at a sampling flow rate of 4 l.h21 (4).
The following detectors and procedures are used to determine the individual components of the effective dose in the personal dosemeter ALGADE. Determination of the intake of long-lived alphaparticle-emitting radionuclides of uranium– radium series The intake of long-lived alpha-particle-emitting radionuclides of uranium-radium series is determined by measuring the gross activity of the filter used in the personnel dosemeter. The detection efficiencies of the measuring devices must be greater than 0.1 (per disintegration). The distance between the measuring filter and the detector has to be ,2 cm and the mass of any cover sheet of the detector has to be below 1 mg.cm22. The minimal detectable gross activity for receiving of a mixture of the long-lived alphaparticle-emitting radionuclides is 5 Bq, which corresponds to an equivalent dose of 0.055 mSv. TLD measurement of kerma The dosemeter contains two thermoluminescence tablets (TLD—LiF:Mg, Cu, P). Thermoluminiscence peak area is determined by HARSHAW 3500. The range of measurable dose (kerma) is from 0.01 to 20 mSv. The period during which the dosemeters are placed into the charging stand and are exposed in nonworking time is deducted from the total exposure based on the knowledge of the absorbed dose of the TL dosemeters, which are placed in the charging
# The Author 2014. Published by Oxford University Press. All rights reserved. For Permissions, please email: [email protected]
Downloaded from http://rpd.oxfordjournals.org/ at Universite Laval on July 2, 2015
Exposure to radon and its decay products is one of the three parts that create the total effective dose of uranium miners. Photons from gamma radiation and exposition to long-lived alpha emitters which are members of uranium family are the other two parts. The monthly total effective dose of uranium miners in mine Rozna I (Czech republic) is determined by the personal dosemeter ALGADE, which ensures the continual individual monitoring of all three parts. The exposed dosemeters are evaluated in the National Institute for Nuclear, Chemical and Biological Protection in Kamenna near Pribram. This paper describes the individual parts of miners’ total effective dose considering the different types of work activities and workplaces. The main input data are the evaluation results of the uranium miners’ personal dosemeters ALGADE in mine Rozna I in the time period from 2000 till 2012.
P. OTAHAL ET AL.
room. As a result, kerma is determined. This is done by converting a factor of 1.4 Sv Gy21 into deep-dose equivalent Hp(10).
2000 to 2012. In the Table 2 are not included the cases of work professions containing less than 5 members. RESULTS
Determination of potential alpha-energy intake estimated by ALGADE
Table 1. The main centres and the individual profession in mine Rozna I. Name of the centre The centre of production (ore mining) The centre of extraction (transport of ore to the surface and crushing)
The centre of maintenance (department of machines and energy) The centre of geology and geophysics The ventilation centre The centre of testing laboratories The centre of chemical treatment Mine rescue service
Work profession Stope workers Auxiliary operations Horizontal transport Vertical transport Surface ore crushing Machine part Electrical part Stope sampling Surface ore measuring Ventilation crew Dosimetry service Chemical treatment Professional rescue
Table 2. Description of the main work professions. Work profession
Number Place of work
Stope workers
100– 200 5 –15
Underground
RGL
Underground
R
10–20 20–40
Surface Underground
GL R
5 –15
Underground
GR
70–100
Surface
G
20–30
Underground
—
10–40
Underground
RGL
10–15
Underground
—
20–40
Underground
—
70–100
Underground
GL
5 –10
Underground
RL
10–15
Underground
—
Dosimetric service Ore crushing Mine electricians Geologists and geophysicists Chemical treatment Mining locomotive driver Auxiliary workers Mine elevator operator Maintenance of mine elevator Horizontal transport of ore Ventilation technics Mine rescue service
Predominant component of the total effective dose
R, short-lived radon decay products; G, gamma irradiation; L, intake of long-lived alpha-particle-emitting radionuclides of uranium-radon series.
118
Downloaded from http://rpd.oxfordjournals.org/ at Universite Laval on July 2, 2015
The area density of tracks is determined by tracks in the sensitive layer of the detector foil Kodak LR 115. Knowing the volume and the duration of use for the individual personal dosemeter, it is possible to determine the time integral of the short-lived concentration on the radon decay products. After etching the detector there are registered tracks with a diameter .8 mm. The determined value is the latent energy of shortlived radon decay products. The minimum detectable value intake dose is 0.05 mSv. Uranium mine radiation workers (category A) are defined as employees probably receiving an effective dose higher than 6 mSv (in accordance with Decree 307/2002 Coll about Radiation Protection as amended by Decree 499/2005 Coll by the State Office for Nuclear Safety). Radiation workers of category A in mine Rozna I are divided into several centres (departments) according to the nature of the work activity. The main centres and individual work professions are presented in Table 1. The main work professions and their description are presented in Table 2. The number of workers in individual professions presents a cast of jobs based on the results of dosimetry uranium mine workers Rozna I database from
The results of the dosimetric database from 2003 to 2013 have been processed in more detail. The section that has been processed contains almost 40 000 records of individual employees of category A. They were compared results belonging to underground and surface work places (in the last case were divided into two categories) - see Figures 1 and 2. Monthly averages of the intake of long-lived alpha-particleemitting radionuclides of uranium–radium series (alpha), gamma photon irradiation (gamma), shortlived radon decay products intake (RnDP) and the monthly average of the effective dose (HEM) are presented in Figure 1. The values with zero residence time of workers were not counted in the averages presented in Figure 1.
DOSE FROM RADON RECEIVED BY URANIUM MINERS
of the percentage contributions of individual components in them shows the largest contribution (40 %) due to external gamma radiation photons. The comparison of the average total effective dose to surface and underground workers shows that underground workers receive 50 % greater total effective dose in comparison with surface workers. CONCLUSIONS
ACKNOWLEDGEMENTS Many thanks for the amount of important consultation and information provided by Prof. R. Holub. Figure 2. The percentage contribution of the total effective dose.
The average results show the maximal radiation exposure of the ventilation and production centre workers. The total monthly average of these two centres exceeds 1 mSv significantly. In comparison with the average of all workers, these workers receive by .30 % greater total effective dose. The percentage contribution to the total effective dose is presented in Figure 2. The largest contribution to the total effective dose is obtained from long-lived alpha-particle-emitting radionuclides of uranium –radium series (55+9 %). The smallest contribution from this component has chemical treatment workers. Contribution from gamma photon radiation and radon short-lived decay products represents an average of 22 + 6 %. Chemical treatment workers receive on average one of the smallest total effective doses of all monitored professions of category A. However, the comparison
FUNDING The work was created within the project ‘Study of selected routes of natural radioactivity’ (200402SONS). REFERENCES 1. Duport, P. and Horvath, F. Practical aspects of monitoring and dosimetry of long-lived dust in uranium mines and mills. Radiat. Prot. Dosim. 26(1/4), 43– 48 (1989). 2. Cothern, C. B. and Smith, J. E. Environmental radon, environmental science research. Vol. 35. Plenum Press, pp. 136– 140 (1987). 3. Harley, H. N. and Fisenne, I. N. Alpha dose from long lived emitters in underground uranium miners. In: Proceeding of the International Conference on Occupational Radiation Safety in Mining, Toronto, 14–18 October 1984, Stocker, H. Eds. Canadian Nuclear Association, pp. 518 – 522 (1985). 4. Bjorndal, B., Cubbon, G., Moridi, R. and Betrand, C. CAIRS-ALGADE personal alpha dosimeter. IRPAInternational Congress, IRPA, pp. 50–52 (1996).
119
Downloaded from http://rpd.oxfordjournals.org/ at Universite Laval on July 2, 2015
Figure 1. Monthly averages marked with a standard deviation of individual contributions and the total effective dose in years 2003– 2012.
The paper summarises dosimetry results of the radiation workers of category A in uranium mine Rozna I. Work activities are grouped as applicable to individual work centres (departmens). The average effective dose for all workers does not exceed 1 mSv month21. The workers of the production and ventilation centre receive the maximal effective dose, in average 30 % greater than the total average. The main contribution to the total effective dose is the intake of long-lived alpha-particle-emitting radionuclides of uranium – radium series. Radon decay products intake accounts for 20 % of the total effective dose. As expected, surface workers receive far less total effective dose than underground workers.
doi:10.1093/rpd/ncu065
RADON CONTRIBUTION TO THE TOTAL EFFECTIVE DOSE OF URANIUM MINERS P. Otahal1,*, I. Burian1, M. M. Nasir2 and Z. Gregor2 1 National Institute for NBC Protection, Kamenna 71, 26231 Milin, Czech Republic 2 GEAM, Subsidiary of the State Uranium Company DIAMO, Dolni Rozinka, Czech Republic *Corresponding author:[email protected]
INTRODUCTION
MATERIALS AND METHODS 220
Rn In addition to exposure to gamma radiation, (thoron) and 222Rn (radon) decay products, uranium workers are also exposed to airborne long-lived radioactive dust (1). Not surprisingly, radon levels are highest where the highest uranium concentration occurs in rocks, and historically it was in uranium mines that the potential hazard from radon progeny inhalation was first recognised(2). It is therefore no wonder that the US Bureau of Mines introduced the first personal dosemeters for uranium underground workers already in 1979(3). The radiation workers of category A in uranium mine Rozna I have been equipped with ALGADE personal dosemeters (company ALGADE, France) since 1998. It is a portable, compact, battery sampler that allows monitoring of all three components of the total effective dose. For the purpose of the Czech uranium miners it was modified in order to estimate the contribution of the short-lived radon decay products to the total effective dose. The dosemeters are evaluated at monthly intervals by the National Institute for Nuclear, Chemical and Biological Protection (Czech Republic). The integral monthly results of individual contributions to the total effective workers dose are recorded in a database that is sent periodically to the Czech Central Registry of Occupational Exposure. The ALGADE dosemeter is worn on the belt along with the mining lamp. The dosemeter is powered by a small rechargeable battery, which is able to operate .10 h when fully charged. The full charging takes 14 h. The sampler is designed to operate at a sampling flow rate of 4 l.h21 (4).
The following detectors and procedures are used to determine the individual components of the effective dose in the personal dosemeter ALGADE. Determination of the intake of long-lived alphaparticle-emitting radionuclides of uranium– radium series The intake of long-lived alpha-particle-emitting radionuclides of uranium-radium series is determined by measuring the gross activity of the filter used in the personnel dosemeter. The detection efficiencies of the measuring devices must be greater than 0.1 (per disintegration). The distance between the measuring filter and the detector has to be ,2 cm and the mass of any cover sheet of the detector has to be below 1 mg.cm22. The minimal detectable gross activity for receiving of a mixture of the long-lived alphaparticle-emitting radionuclides is 5 Bq, which corresponds to an equivalent dose of 0.055 mSv. TLD measurement of kerma The dosemeter contains two thermoluminescence tablets (TLD—LiF:Mg, Cu, P). Thermoluminiscence peak area is determined by HARSHAW 3500. The range of measurable dose (kerma) is from 0.01 to 20 mSv. The period during which the dosemeters are placed into the charging stand and are exposed in nonworking time is deducted from the total exposure based on the knowledge of the absorbed dose of the TL dosemeters, which are placed in the charging
# The Author 2014. Published by Oxford University Press. All rights reserved. For Permissions, please email: [email protected]
Downloaded from http://rpd.oxfordjournals.org/ at Universite Laval on July 2, 2015
Exposure to radon and its decay products is one of the three parts that create the total effective dose of uranium miners. Photons from gamma radiation and exposition to long-lived alpha emitters which are members of uranium family are the other two parts. The monthly total effective dose of uranium miners in mine Rozna I (Czech republic) is determined by the personal dosemeter ALGADE, which ensures the continual individual monitoring of all three parts. The exposed dosemeters are evaluated in the National Institute for Nuclear, Chemical and Biological Protection in Kamenna near Pribram. This paper describes the individual parts of miners’ total effective dose considering the different types of work activities and workplaces. The main input data are the evaluation results of the uranium miners’ personal dosemeters ALGADE in mine Rozna I in the time period from 2000 till 2012.
P. OTAHAL ET AL.
room. As a result, kerma is determined. This is done by converting a factor of 1.4 Sv Gy21 into deep-dose equivalent Hp(10).
2000 to 2012. In the Table 2 are not included the cases of work professions containing less than 5 members. RESULTS
Determination of potential alpha-energy intake estimated by ALGADE
Table 1. The main centres and the individual profession in mine Rozna I. Name of the centre The centre of production (ore mining) The centre of extraction (transport of ore to the surface and crushing)
The centre of maintenance (department of machines and energy) The centre of geology and geophysics The ventilation centre The centre of testing laboratories The centre of chemical treatment Mine rescue service
Work profession Stope workers Auxiliary operations Horizontal transport Vertical transport Surface ore crushing Machine part Electrical part Stope sampling Surface ore measuring Ventilation crew Dosimetry service Chemical treatment Professional rescue
Table 2. Description of the main work professions. Work profession
Number Place of work
Stope workers
100– 200 5 –15
Underground
RGL
Underground
R
10–20 20–40
Surface Underground
GL R
5 –15
Underground
GR
70–100
Surface
G
20–30
Underground
—
10–40
Underground
RGL
10–15
Underground
—
20–40
Underground
—
70–100
Underground
GL
5 –10
Underground
RL
10–15
Underground
—
Dosimetric service Ore crushing Mine electricians Geologists and geophysicists Chemical treatment Mining locomotive driver Auxiliary workers Mine elevator operator Maintenance of mine elevator Horizontal transport of ore Ventilation technics Mine rescue service
Predominant component of the total effective dose
R, short-lived radon decay products; G, gamma irradiation; L, intake of long-lived alpha-particle-emitting radionuclides of uranium-radon series.
118
Downloaded from http://rpd.oxfordjournals.org/ at Universite Laval on July 2, 2015
The area density of tracks is determined by tracks in the sensitive layer of the detector foil Kodak LR 115. Knowing the volume and the duration of use for the individual personal dosemeter, it is possible to determine the time integral of the short-lived concentration on the radon decay products. After etching the detector there are registered tracks with a diameter .8 mm. The determined value is the latent energy of shortlived radon decay products. The minimum detectable value intake dose is 0.05 mSv. Uranium mine radiation workers (category A) are defined as employees probably receiving an effective dose higher than 6 mSv (in accordance with Decree 307/2002 Coll about Radiation Protection as amended by Decree 499/2005 Coll by the State Office for Nuclear Safety). Radiation workers of category A in mine Rozna I are divided into several centres (departments) according to the nature of the work activity. The main centres and individual work professions are presented in Table 1. The main work professions and their description are presented in Table 2. The number of workers in individual professions presents a cast of jobs based on the results of dosimetry uranium mine workers Rozna I database from
The results of the dosimetric database from 2003 to 2013 have been processed in more detail. The section that has been processed contains almost 40 000 records of individual employees of category A. They were compared results belonging to underground and surface work places (in the last case were divided into two categories) - see Figures 1 and 2. Monthly averages of the intake of long-lived alpha-particleemitting radionuclides of uranium–radium series (alpha), gamma photon irradiation (gamma), shortlived radon decay products intake (RnDP) and the monthly average of the effective dose (HEM) are presented in Figure 1. The values with zero residence time of workers were not counted in the averages presented in Figure 1.
DOSE FROM RADON RECEIVED BY URANIUM MINERS
of the percentage contributions of individual components in them shows the largest contribution (40 %) due to external gamma radiation photons. The comparison of the average total effective dose to surface and underground workers shows that underground workers receive 50 % greater total effective dose in comparison with surface workers. CONCLUSIONS
ACKNOWLEDGEMENTS Many thanks for the amount of important consultation and information provided by Prof. R. Holub. Figure 2. The percentage contribution of the total effective dose.
The average results show the maximal radiation exposure of the ventilation and production centre workers. The total monthly average of these two centres exceeds 1 mSv significantly. In comparison with the average of all workers, these workers receive by .30 % greater total effective dose. The percentage contribution to the total effective dose is presented in Figure 2. The largest contribution to the total effective dose is obtained from long-lived alpha-particle-emitting radionuclides of uranium –radium series (55+9 %). The smallest contribution from this component has chemical treatment workers. Contribution from gamma photon radiation and radon short-lived decay products represents an average of 22 + 6 %. Chemical treatment workers receive on average one of the smallest total effective doses of all monitored professions of category A. However, the comparison
FUNDING The work was created within the project ‘Study of selected routes of natural radioactivity’ (200402SONS). REFERENCES 1. Duport, P. and Horvath, F. Practical aspects of monitoring and dosimetry of long-lived dust in uranium mines and mills. Radiat. Prot. Dosim. 26(1/4), 43– 48 (1989). 2. Cothern, C. B. and Smith, J. E. Environmental radon, environmental science research. Vol. 35. Plenum Press, pp. 136– 140 (1987). 3. Harley, H. N. and Fisenne, I. N. Alpha dose from long lived emitters in underground uranium miners. In: Proceeding of the International Conference on Occupational Radiation Safety in Mining, Toronto, 14–18 October 1984, Stocker, H. Eds. Canadian Nuclear Association, pp. 518 – 522 (1985). 4. Bjorndal, B., Cubbon, G., Moridi, R. and Betrand, C. CAIRS-ALGADE personal alpha dosimeter. IRPAInternational Congress, IRPA, pp. 50–52 (1996).
119
Downloaded from http://rpd.oxfordjournals.org/ at Universite Laval on July 2, 2015
Figure 1. Monthly averages marked with a standard deviation of individual contributions and the total effective dose in years 2003– 2012.
The paper summarises dosimetry results of the radiation workers of category A in uranium mine Rozna I. Work activities are grouped as applicable to individual work centres (departmens). The average effective dose for all workers does not exceed 1 mSv month21. The workers of the production and ventilation centre receive the maximal effective dose, in average 30 % greater than the total average. The main contribution to the total effective dose is the intake of long-lived alpha-particle-emitting radionuclides of uranium – radium series. Radon decay products intake accounts for 20 % of the total effective dose. As expected, surface workers receive far less total effective dose than underground workers.
