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 Table of Contents 
ARTICLE
Year : 2010  |  Volume : 33  |  Issue : 3  |  Page : 106-108  

Assessment of potential inhalation exposure due to radon in uranium mine surface facilities


1 Health Physics Unit, Narwapahar, Jharkhand, India
2 Environmental Assessment Division, Bhabha Atomic Research Centre, Mumbai, India

Date of Web Publication22-Oct-2011

Correspondence Address:
R Topno
Health Physics Unit, Narwapahar, Jharkhand
India
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Source of Support: None, Conflict of Interest: None


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  Abstract 

Uranium mining is only one of it's kinds in the mining industry owing to associated inherent radiological hazards. Ore excavation processes may lead to release of radiologically significant materials into the surrounding environment. Such releases may lead to exposure of individuals during the course of operations near the source. The main features of radiological hazard associated in these are 222 Rn and it's progeny, external gamma levels, long lived alpha activity in the natural uranium ore dust. The most significant internal hazards in an underground uranium mines surface facilities arises due to inhalation of short-lived decay products of radon ( 222 Rn), which are daughter products of uranium ( 238 U). The present paper provides an estimate of inhalation dose to radiation workers engaged at the surface facilities in the vicinity of underground mines of Narwapahar. A radon gas monitor AlphaGuard PQ 2000 PRO (Genitron Instruments, Germany) was used for the measurement of outdoor atmospheric 222 Rn concentrations in the vicinity of underground uranium mines surface facilities. Outdoor atmospheric 222 Rn concentrations were found in the range of 10 to 87 Bq.m -3 with arithmetic mean of 34 Bq.m -3 . Average annual internal dose due to radon and it's progeny to the workers in these areas have been worked out to 0.17 mSv.y -1 .

Keywords: 222 Rn, Ore grade, Underground uranium mines surface facility, internal dose


How to cite this article:
Topno R, Srivastava V S, Patnaik R L, Dandapat B L, Shukla A K, Tripathi R M, Puranik V D. Assessment of potential inhalation exposure due to radon in uranium mine surface facilities. Radiat Prot Environ 2010;33:106-8

How to cite this URL:
Topno R, Srivastava V S, Patnaik R L, Dandapat B L, Shukla A K, Tripathi R M, Puranik V D. Assessment of potential inhalation exposure due to radon in uranium mine surface facilities. Radiat Prot Environ [serial online] 2010 [cited 2022 May 20];33:106-8. Available from: https://www.rpe.org.in/text.asp?2010/33/3/106/86272


  1. Introduction Top


Inhalation of radon gas and it's short lived decay products may leads to internal exposure to population. The radioactive radon ( 222 Rn) gas (half life =3.824 d) is produced by the alpha decay of the radium ( 226 Ra) present in the rocks, soil etc., decays to a number of short lived decay products (progeny). Inhalation of 222 Rn gas cause radiation dose to the lung tissues from alpha radiation emitted during radioactive decays. The chronic exposure to radon progeny is known to be associated with the induction of lung cancer (NAS, 1998, BEIR IV Report) in various mining populations.

In Singhbhum Thrust Belt (STB) of Jharkhand, several mines are found economically viable for the exploration of uranium namely; Jaduguda mines, Narwapahar mines, Bhatin mines, Turamdih Mines and Mohuldih mines. Narwapahar underground mines (22 ° 41' and 86° 16') surface facilities has been selected for the field of present work. This mine is about 12 km NW of Jaduguda mines and 15 km SE of Tatanagar railways station. The ore body is principally mono-mineralic with uranium occurring as Urannite (U 3 O 8 ). The average ore grade of the Narwapahar mines is ~0.042% U 3 O 8 . The underground mine is highly mechanized to minimize workers radiation exposure. The surface facilities of the mines include Ore yard, Waste yard, Sand stowing plant, Vertical shaft, Ore bin, Effluent pond area, East ventilation fan. At these locations elevated 222 Rn concentrations may be anticipated, consequently workers in the vicinity of these locations are likely to get internal exposure due to inhalation. Hence these locations have been included in our study area and measurements of outdoor 222 Rn concentrations have been measured in these areas to assess the inhalation hazards to workers. However, locations such as; mines offices, computer rooms, personnel office etc. are not included in our study area because employees working at these locations are not likely to exposed directly from the exposure due to source.

Studies pertaining to the radiological status of underground uranium mines are reported by several researchers elsewhere. However, studies on radon inhalation to workers in the vicinity of surface facilities within the premises are barely addressed. The present study is intended to estimate the outdoor atmospheric 222 Rn concentrations in the uranium mine surface facilities and to assess the internal dose to the workers working in the vicinity of these facilities.


  2. Materials and Methods Top


A radon gas monitor AlphaGuard PQ 2000 PRO (Genitron Instruments, Germany) was used for measurement of outdoor atmospheric 222 Rn concentrations. It is a portable measuring system for the continuous determination of radon concentration with selected climatic parameters. The instrument is based on the principle of pulse ionization chamber (Alpha Spectroscopy) in which the measuring gas gets in diffusion mode via a large surface glass fibre filter into the ionization chamber. The cylindrical ionization chamber of the AlphaGuard has an active volume of 0.56 L. The Instrument is kept in each selected location at the surface for 1 hour. Each measured radon concentration is the time integrated value of 10 minutes sampling through diffusion.


  3. Results and Discussion Top


The activity concentrations of 222 Rn were measured in air at Narwapahar underground mines surface facilities as per requirement through out the year.

The results of 119 data on atmospheric 222 Rn concentrations show that the values were varied in the range of 10-87 Bq.m -3 with arithmetic mean of 34 Bq.m -3 during day time. The average value of 222 Rn concentration in the underground uranium mines surface facilities is marginally elevated compared to the worldwide typical radon concentration of 10 Bq.m -3 (Iida et al, 1996). These values are comparable with the value quoted by the previous investigators (Binnset et al., 1998; Jha et al, 2000; Srivastava et al., 2005 & Kumar et al., 2005) as summarized in [Table 1].
Table 1: Comparison of 222Rn concentrations in narwapahar uranium mines surface facilities with other regions

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The measured radon concentrations, even though covering a wide range, are well below the derived limit of 1000 Bq.m -3 , EER (Raghavayya, 1999) as applicable in uranium mining field of India.


  4. Assessment of Internal Dose Top


In order to assess the internal dose, the measured 222 Rn concentration is converted into working level month (WLM) by using the following relation:



Where; C Rn = Absolute Radon concentration (Bq.m -3 )

Feq = Equilibrium factor

T= Exposure time (Hours) and 170 is working hours in a month

The assessment of internal dose is based on actual occupancy hours at work site (Average attendance: 220 days, average 7 hours working per day) and value of equilibrium factor 0.4 (ICRP-65, 1993) at these locations. In the above equation (1), the ICRP-65 dose conversion factor (1WLM=5mSv for occupational workers) have been used for the computation of annual internal dose. The assessed internal dose is comparable with the earlier studies done by several investigators in India as summarized in [Table 2].
Table 2: Inhalation dose due to Rn and It's progeny at narwapahar mines surface Facilities Vs other regions

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The assessed annual internal dose to workers engaged in the vicinity of mines surface facilities have been found significantly low compared to the prescribed limit of 20 mSv.y -1 (given by Atomic Energy Regulatory Board on the basis of recommendations of International Commission for Radiation Protection; ICRP-60, 1990).


  5. Conclusions Top


The measurements of radon concentration in the vicinity of mines surface facilities have been carried out during day time as workers are engaged in these areas in day time only. The values of 222 Rn concentration in these areas have been found in the range of 10-87 Bq.m -3 with arithmetic mean of 34 Bq.m -3 . Based on the above measurements, internal dose of the occupational workers worked out to 0.17mSvy -1 . The estimated internal dose to workers engaged in uranium mines surface facilities is well below the prescribed limit.


  6. Acknowledgements Top


The authors are thankful to Shri H.S. Kushwaha, Director, Health, Safety & Environment Group, BARC, for his keen interest and constant encouragement. The authors express their sincere thanks to Shri R. Gupta, C&MD, UCIL, for his interest and inspiration in the work and extending infrastructural facilities and support to carry out the work. The wholehearted support and encouragement by Shri D. Acharya, Director Technical, UCIL, and Shri Ajay Ghade, DGM, UCIL, is gratefully acknowledged.


  7. References Top


  1. Binns D.A.C, Fingered N., Mole V.P. and Gouvea V.A. (1998), Radon-222 Measurements in Uranium-Prospecting area in Brazil; J. Environ. Radioactivity, Vol. 38 (2), 249-254.
  2. IAEA (2003), International Atomic Energy Agency, Radiation protection against radon in workplaces other than mines. Safety Report series No. 33, Viena.
  3. ICRP-60 (1990), International Commission for Radiation Protection: Recommendations of ICRP, Annals of ICRP-21 (13), Pergamon Press, Oxford.
  4. ICRP-65 (1993), International Commission on Radiological Protection, Protection against radon-222 at home and work. Pergamon Press, Oxford.
  5. Iida, T.Y., Lkebe, K., Suzuki et al., (1996), Continuous measurements of outdoor radon concentration at various locations in East Asia, Environ. Int., 22 (Suppl. 1), S139-S147.
  6. Jha S., Khan A.H. and Mishra U.C. (2000), Environmental Rn levels around an Indian Uranium Complex, J. Environ. Radioactivity, Vol. 48, 223-234.
  7. NAS (1998), Health risk of radon and other internally deposited alpha emitters, BEIR IV Report, National Academy of Science, National Academic press, Washington D.C.
  8. Raghavayya, M. (1999), Secondary limits of exposure in facilities handling uranium, BARC Report No. BARC/1999/E/020.
  9. Rajesh Kumar, V.N. Jha, S.K. Sahoo and A.K. Shukla (2005), Pre-operational radiological Monitoring Around proposed Uranium mining and processing Site at Tummalapalle, Andhra Pradesh, Journal of the Association of Environmental Geochemists, Vol-8, 137-142.
  10. Srivastava V.S., Patnaik R.L., Shukla A.K. and Khan A.H. (2005), Background Outdoor radiation Dose to Inhabitants around Proposed Bagjata Mine; Journal of Association of Environmental Geochemists, Vol-8, 407-409.
  11. UNSCEAR (1993),United Nations Scientific Committee on Effects of Atomic Radiations; Sources and effects of Ionizing radiations, New York, United Nations.




 
 
    Tables

  [Table 1], [Table 2]



 

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Abstract
1. Introduction
2. Materials and...
3. Results and D...
4. Assessment of...
5. Conclusions
6. Acknowledgements
7. References
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