XA0103131 URANIUM MINING AND HEAP LEACHING IN INDIA AND RELATED SAFETY MEASURES — A CASE STUDY OF JAJAWAL MINES V.P. SAXENA Atomic Minerals Division, Department of Atomic Energy, Uniara Garden, Jaipur S.C. VERMA Atomic Minerals Division, Department of Atomic Energy Civil Lines, Nagpur India Abstract Exploration and exploitation of uranium involves drilling, mining, milling and extraction processes including heap leaching in some cases. At the exploration stage, the country's laws related to statutory environmental clearance covering forest and sanctuaries or Coastal Regulatory Zones (CRZ) are: equally applicable for atomic minerals. At the developmental mining or commercial exploitation stage in addition to the environmental impact assessment, the provisions of Atomic Energy (working of Mines, Minerals and handling of Prescribed Substances) Rules 1984 are also to be followed which covers radiation monitoring, pollution control and other safety measures which are enforced by licensing authorities and the Atomic Energy Regulatory Board (AERB) of India. In India, Jaduguda, Bhatin, Narwapahar in Singhbhum Thrust Belt (STB), Asthota and Khiya in Siwaliks, Domiasiat in Cretaceous sandstones, Bodal and Jajawal in Precambrian crystallines, are some of the centres, where mining has been carried out up to various underground levels. Substantial amount of dust and radon gas are generated during mining and milling operations. Though uranium mining is considered as hazardous for contamination by radionuclides, it is observed that many non-uranium mines have registered up to 100 mWL radon concentration, e.g. copper mines in STB area show up to 900 mewl in a few cases. Compared to this the Uranium mines in India have not shown any increase over the limits prescribed by AERB. Specific problems associated with mining include release of radon and other radioactive pollutants like Th-230, Ra-226, Pb-210 and Po-210, substantial dust generation, ground water contamination, proximity of population to working mines and environmental surveillance. These problems are adequately handled by periodical monitoring of various radiological parameters such as radon daughter working level, long lived alpha activity and concentration of radionuclides in gaseous, liquid and solid medium. Pre-project and post-operational data collections both in the project areas and in the surrounding drainage systems are mandatory and overviewed by AERB before clearance. In Jajawal underground mines in Central India, the radiation level is registered at 0.12-0.25 mR/hr and radon daughter working level is measures at 0.005 to 0.015 WL for air. These levels have shown an increase of 15 to 20% during the operations. About 1000 tonnes of low grade ore was heap leached on the surface as technology demonstration project. Measurements of water in pre-heap leaching stage, have indicated concentrations of different nuclides at 0.90 mg/cu.m. (U Nat.), 35 bq/cu.m. (Ra-226), 33 bq/cu.m. (Th-230) and <2 bq/cu.m. (Po- 210). Long lived alpha activity in and around heap leaching site has been measured at 0.13 to 0.38 bq/cu.m during the process of operation. Post operational biological uptake of radionuclides, viz. U (natural) : 0.057 mg/kg; Ra-226 : 1.69 Bq/kg; Th-230 : 5.13 Bq/kg and Po-210 : 2.98 Bq/kg, show an increase of 20 to 30% above the pre-operational measurements. The radionuclide related pollution could be contained to manageable limits by current strategy of ventilation of underground mines, disposal by isolation and burial of waste, use of wet scrubbers, adding neutralizing agents to tailing liquids, besides following the principle of ALARA. 1. INTRODUCTION Uranium deposits in India are known in several geological settings and amongst them, vein type, sandstone type and unconformity-related, are the most important. The deposits of low to medium grade (0.03-0.1%) and moderate to low tonnage are known to occur in different 201 geological periods commencing from Lower Proterozoic to Middle Miocene as at Jaduguda, Bhatin, Narwapahar in the Proterozoic Singhbhum Thrust Belt (STB), Bodal and Jajawal in Precambrian crystallines, Asthota and Khiya in the Miocene Siwalik sandstones, Domiasiat in Cretaceous sandstones. Uranium mining has been carried out up to different stages such as exploratory and production at different places. Production mining of uranium ore at present is essentially confined to some deposits of Singhbhum Trust Belt (STB), namely Jaduguda, Bhatin and Narwapahar. Besides, the uranium mining, heap leaching operations and milling have also been carried at certain places. The successive stages of exploration leading up to the final exploitation of uranium ores, require stringent implementation of different statutory clearances and adherence to such regulations has been an endeavour of utmost importance both by Government Agencies as well as by Non-Governmental Organizations. Atomic minerals industry is also governed by the country's laws related to statutory environmental clearance covering forests and sanctuaries or Coastal Regulatory Zones. Developmental/exploratory mining and commercial mining are governed by the provisions of Atomic Energy Rules, 1984 (AER), besides the stipulation of environmental impact assessment as applied under Environmental Protection Act, 1986 (EPA). EPA mandates for the preparation of the Environmental Management Plan (EMP) to satisfy the statutory provisions of the Ministry of Environment and Forest. AER stipulates radiation monitoring, pollution control and other safety measures which are enforced by licensing authorities and Atomic Energy Regulatory Board (AERB) of India. 2. SAFETY PROBLEMS IN URANIUM MINES Uranium mining besides affecting radiation levels and dust levels, also influences the environment in several ways such as noise pollution, air pollution, degradation of land and environment by contamination of ground water, surface water and soil. Atomic Minerals Division (AMD) has undertaken the task of generating baseline data on all the projects for better environmental management. Specific problems associated with uranium mining include release of radon and other hazardous radioactive pollutants, besides those mentioned above. These problems are adequately handled by periodic monitoring of various radiological parameters such as radon daughter working level, long-lived alpha activity and concentration of radio-nuclides in gaseous, liquid and solid medium. These safety measures are enforced by AERB through constant monitoring during different stages of mining and milling operations. Radium present in the ore is the major source of radon in mines. Radon produced by the decay of radium located in the ore matrix moves out by recoil into pore spaces. This locked up radon is released during fresh blasting. With relatively long half-life of radon, the decay products seldom reach secular equilibrium with radon. Thus the decaying radionuclides attach to available surfaces and form radioactive aerosols. The radon produced by the decay of radium and radon progeny available as radioactive aerosoles are major pollutants. Thus removal of these aerosols is an important factor to reduce the health hazard for occupational workers. This depends on mine layout, ventilation system, concentrations of condensation-nuclei, aerosol and dust as also on the available exposed mine surfaces. These are best achieved by proper ventilation, sprinkling of water in the mines along exposed mine surfaces and closures of unused mine sections. The above measures undertaken in uranium mining industry have helped in containing the level of radon in mines. Data of some mines is presented in Table I. 202 3. RADIOLOGICAL PARAMETERS FOR NON-URANIUM MINES Compared to uranium mines, measurements undertaken in some non-uranium mines in India have brought out an interesting study. The survey was conducted in major mineral mines from various parts of India [1]. The coal sector has indicated very low radon levels, mostly below 10 mWL. The underground metalliferous mines, in general, have enhanced levels of radon activity ranging from 10 to 100 mWL. In many copper mines, the air activity levels were considerably high, ranging from 100 to 300 mWL. Except for one mine each of lead & zinc, gold and mica, all the mines that exceeded 30 mWL, were copper mines (Table II). hi one mine, the radon level was as high as 900 mWL. TABLE I. GROSS RADIATION, RADON AND ITS DAUGHTERS IN AIR AND WATER AROUND SOME UNDERGROUND URANIUM MINES IN INDIA [MODIFIED AFTER 3]. SI. Area/Deposit External radiation Annual Dose in Water No. in mines (uSv/hr) mines (uSv/yr) 1. Jaduguda mine, Seepage water from uranium Bihar mill U (mg/1) Ra-226 (pCi/1) 0.52 to 3.29 0.82-2.56 2. Jajawal mine, 0.3-1.5 1.6 (External) Radon dissolved in water Madhya Pradesh 6.1 (Internal) (kBq/cu.m) 7.7 (Total) (60) Mine water 3.8 Well water 1.15 Stream 2.00 3. Bodal mines, 1-1.6 13.0 (External) Radon dissolved in water Madhya Pradesh 6.8 (Internal) (kBq/cu.m) 19.8 (30) Mine water 1.7 Well water 0.5 Tube well 1.9-4.7 4. Astotha mine, 0.2-2.5 1.40 (External) Radon dissolved in water Himachal 3.00 (Internal) Pradesh Spring 0.7 4.40 (30) Stream 0.5 TABLE II. RADON LEVEL-WISE CLASSIFICATION OF NON-URANIUM UNDERGROUND MINES IN INDIA [1] S No Average Radon No. of Mines Mineral wise Level (in WL) 1. Coal - 9, Gold - 3, Manganese - 2, Mica - 4 2. 10-30 Lead & Zinc - 2, Barites - 2, Mica - 2, Manganese - 1 3. 30-1000 Lead & Zinc - 1, Copper - 4, Gold - ]., Mica - 1 4. 100 - 300 Copper - 3 5. >300 (900 m WL) Copper - 1 Total = 36 Mines 203 Percaput and collective dose equivalent of 80 mSv/Y and 16 person Sv/Y can be calculated with an occupancy factory of 0.75 and 2000 working hours per year for an activity level of 900 mWL. Compared to this, the Jaduguda Uranium mine has given percaput and collective dose equivalent values of 26 mSv/y and 28 person Sv/y, respectively.