Radiation Protection and Environment

ARTICLE
Year
: 2010  |  Volume : 33  |  Issue : 4  |  Page : 189--191

Radiological surveillance in a developing uranium mines at Bagjata, Jharkhand, India


JS Meena, Rajesh Kumar, RL Patnaik, VN Jha, AK Shukla, RM Tripathi 
 Environmental Assessment Division, Bhabha Atomic Research Centre, Trombay, Mumbai, India

Correspondence Address:
J S Meena
Environmental Assessment Division, Bhabha Atomic Research Centre, Trombay, Mumbai
India

Abstract

Current paper summaries the results of measurement of radon and gamma level inside the developing mine of Bagjata, The maximum radon level was observed to be 0.93 kBq m -3 EER which is lower as compared to the recommended DAC of 1 kBqm -3 EER. In most of the measurements, the 222 Rn concentration was lower as compared to the Derived Air Concentration of 1 kBq m -3 EER. Maximum gamma level (5.01 μGy h -1 ) was observed near the exposed ore of the mines. The results presented here will form a basis in improving the design to enhance the effectiveness of engineering control measures during operational phases.



How to cite this article:
Meena J S, Kumar R, Patnaik R L, Jha V N, Shukla A K, Tripathi R M. Radiological surveillance in a developing uranium mines at Bagjata, Jharkhand, India.Radiat Prot Environ 2010;33:189-191


How to cite this URL:
Meena J S, Kumar R, Patnaik R L, Jha V N, Shukla A K, Tripathi R M. Radiological surveillance in a developing uranium mines at Bagjata, Jharkhand, India. Radiat Prot Environ [serial online] 2010 [cited 2022 Jun 28 ];33:189-191
Available from: https://www.rpe.org.in/text.asp?2010/33/4/189/90462


Full Text

 1. Introduction



Development of a mines leads to removal of large quantity of rock, overburden and soil from it's existing position. During the course of development such materials are relocated preferably at a place where least threat is anticipated for man and the environment. In uranium mines, the materials excavated during development contains significant amount of both short and long-lived radionuclides of uranium series. In the absence of control measures, relocation of such materials may pose potential threat to the environment. Apart from this, development process can release abrupt amount of gaseous radionuclide ( 222 Rn, suspended radioactive dust, exhaust gases etc.) into the mine and the surrounding atmosphere. Such releases may exceed the routine regulatory guidelines as the control measures adopted are improperly channelized.

Uranium mining was started in central sector of Singhbhum shear zone during early sixties. Initially uranium mining was confined to Jaduguda only. With the increase in demand of uranium the mining activities were diversified and commercial scale production was started at Narwapahar and Bhatin at a distance of 10 and 2 km from the existing Jaduguda mines. The radiological hazard and environmental safety aspects of these mines are available elsewhere (Khan et al., 2000; Rajesh et al. 2005; Khan et al., 2005; Triphati et al., 2007). By the beginning of 21 st century, it has been proposed to exploit more uranium reserve to cater the energy requirement of the country. New mining sites are developed in Singhbhum region at Bagjata, Turamdih, Banduhurang and Mohuldih. Bagjata is underground uranium deposit of 0.047% U 3 O 8 content. The mining methodology and impact assessment was provided by (Sarangi et al. 2007). Results of monitoring of significant radiological parameters in various environmental matrices are available in (Soma et al. 2005) and (BRNS, 2009).

The detailed features of the proposed site are provided in the text which follows. Current paper briefly summarizes the results of radiological surveillance carried out in the developing uranium mines at Bagjata. The paper considers the distribution of 222 Rn and variations in gamma level at the site incorporating the results of underground and the surface areas adjoining the mines.

Study Area

Bagjata uranium deposit is situated at Latitude of 22 0 28'07" N and Longitude: 86 0 29'36 E in Dalbhum sub division of Singhbhum district in Jharkhand state. Ghatsila (17 km) and Tatanagar (50 km) railway stations are connected from Bagjata by metal road. The deposit is in the valley of adjoining hills with rural population residing nearby. Sankh River is the most prominent SW-NE flowing drainage of the area and is about 1 km north of the deposit.

 2. Materials and Methods



222 Radon inside the mine was measured by the scintillation counting technique. A cylindrical scintillation cell of 150 ml volume made of aluminum is used for collection of the mine air. Inside the cell a thin coating of ZnS (Ag) is provided as scintillation material. 222 Rn sample is collected in a previously evacuated scintillation cell using swedgelock connecting device. To ensure equilibrium between 222 Rn and progeny a sufficient delay (~200 minutes) is provided before counting the alpha activity. The cell being initially evacuated, the duration of sample transfer from the mine atmosphere to the cell is virtually zero because of the pre-sampling pressure gradient. The scintillation cell is connected to the photo multiplier assembly and then counted for alpha activity and concentration of 222 Rn is evaluated using equation given below (Raghavayya et al. 1990). The detection level of this technique is 40 Bq m -3 .

[INLINE:1]

C is the net counts in T seconds (counting time)

λ is the Decay constant of 222 Rn (λ-Rn = 2.06Χ10 6 s -1 ),

E is the Efficiency (in%) of the cell

V is the volume (m 3 ) of the scintillation cell,

t is the delay (~200 minutes) between sampling and counting time (s).

Measurement of gamma level was carried out by using Environmental radiation dosimeter of μR to mR range. The instrument is based on side window GM detector. Inter comparison of the measured radiation level was carried out by using IDENTIFINDER (CE Germany). The instruments were calibrated using different sources at BARC.

In areas where 222 Rn concentration was in the lower range, measurements of radon were carried out using Alpha guard. The measurements were taken at least for one hour in diffusion mode at specified locations and the hourly average was taken. The instrument directly gives the 222 Rn concentration in Bq m -3 .

 3. Results and Discussion



Only two levels have been developed so far i.e. 60 mL and 100 mL. Results of 222 Rn concentration monitoring are presented in [Figure 1]. The results reflect that out of 127 measurements 60% of the data is within 10% of the DAC (1 kBq m -3 EER). The data distribution is neither normal nor lognormal. The same is attributed to change in radiological conditions during development. The maximum concentration of 0.93 kBq m -3 EER was found during the month of March 2008. During this period the development work at 60 mL was completed and the activities were extended to 100 mL. The ventilation circuit was disrupted leading to increase in 222 Rn level. Conditions were restored in the subsequent months, an increase in the 222 Rn level was again observed during July 08 to Aug 08. Mine development is dynamic process and change in ventilation status may lead to large variation in 222 Rn level (Patnaik et al. 2009). Apart from the ventilation, the variation in 222 Rn concentration is also attributed to parameters like temperature, pressure, humidity, nature of the geological formations etc. (S Jha et al. 1999). Mine water is also a potential source of 222 Rn in the mine atmosphere. The dissolved 222 Rn is coming out from the water as a result of agitation (Jha et al. 2005). {Figure 1}

In 100 mL 222 Rn concentration was less as compared to 60 mL, which is evident from the box plot [Figure 2]. First quartile, median, third quartile, rest of the data and outliers are presented in [Figure 2]. The 95% confidence interval is 0.04-0.26 kBq m -3 EER. The median concentration in 60 mL was 0.09 kBq m -3 EER, which is, higher as compared to 100 mL (median 0.05 kBq m -3 EER). Out of 191 data there were 13 outliers [Figure 2] reflecting the dynamic nature of the mine development and frequent change in ventilation status. Like 60 mL, data distribution is neither normal nor log normal. {Figure 2}

The elevated levels were observed during Feb and July 2008. During the development of mine for approaching the ore body dose rate inside the levels varied from 0.38-1.35 μGy h -1. Dose rate in contact near the exposed ore varied from 3.35 to 5.01 μGy h -1 . The gamma level in ore yard surveyed after development of the above two levels varied from 3.20 to 4.80 μGy h -1 . The gamma level at the decline mouth was comparable to the background of the surface facilities of mining areas, ranging from 0.10 to 0.12. The earlier entry in the mines was through incline and the dose rate near the incline mouth varied from 0.19 to 0.26 μGy h -1 . Variation in the dose rate depends on the type of associated rock (Ore, waste rock, mixed overburden etc). Overall area background near the site was 0.10 to 0.15 μGy h -1 . Dose rate inside the mines has not been exceeded the derived limit of 8 μGy h -1 (Raghavayya et al. 1999). (in the level areas the maximum value found was 5.01 μGy h -1 in contact with the exposed ore body).

Occupancy of workers in the working areas was limited for few hours depending on development requirements. The dosimetric aspects are not included in the findings as the job allocation is improperly addressed. A slight variation in overall area background of mines surface facilities (0.15 to 0.30μGy.h -1 ) can be attributed to partial uses of waste rock and overburden in areas of limited access.

 4. Conclusion



Present study is confined to the evaluation of radiological status of Bagjata uranium mines and allied facilities during development. The study is based on monitoring results of routine surveillance carried out for the last three years at the mines during development. The same may serve the purpose of comparison for formulating a detailed radiological safety protocol during operations. So far the radon concentrations in the developing areas are well within the derived limit of 1 kBq m -3 EER.

 5. Acknowledgements



The authors express their thanks to Shri V.D. Puranik, Head, EAD, BARC for his support and encouragement during this study. Suggestions received from colleagues of Health Physics Unit, Jaduguda are also acknowledged. Thanks are due to the Uranium Corporation of India Limited, for facilities and assistance provided during this investigation.

 6. References





BRNS (2009), Baseline studies of Bagjata and Banduhurang sites of UCIL. Board of Research in Nuclear Sciences, A collaborative study of BARC and Indian School of mines. Giri, Soma., kumar, Mukesh., Sethy, N.K., Jha, V.N., Singh, Gurdeep and Tripathi R.M.(2008), Estimation of radionuclides in chicken and egg samples around the Bagjata and Banduhurang mining areas (East Singhbhum, Jharkhand), Proc. of 28 th IARP National Conference on management of nuclear and radiological emergencies, 19-21 Nov, 2008, Vol. 31, No.1-4, 355-357.ICRP (1993), International Commission on Radiological Protection (ICRP), Protection against Radon at home and at work, ICRP publication-65, Annals of the ICRP, 23(2).Jha, S., Khan, A.H., Mishra, U.C. (2000), Environmental Rn levels around an Indian Uranium Complex, Journal of Environmental Radioactivity, Vol. 48, 223-234.Kumar, Rajesh., Jha V.N, Sahoo, S.K., Shukla, A.K.(2005), Pre-operational Radiological Monitoring Around proposed Uranium mining and Ore processing Site at Tummalapalle, Andhra Pradesh, Journal of the Association of Environmental Geochemists, Vol. 8, 137-142.Patnaik, R.L., Srivastav, V.S., Jha, V.N., Shukla, A.K., Tripathi, R.M., Puranik, V.D. (2009), Radiological safety aspect of low grade Uranium mine in India" Mine ventilation congress Vol. 2, 1013-1022.Raghavayya, M., Iyengar, M.A.R., and Markose, P.M. (1990), Estimation of Radium-226 by Emanometry, Bull. Radiat. Protec., Vol. 3, (4), 11-15.