Fuel of future

Published : Dec 14, 2012 00:00 IST

The Tummalapalle mine in Andhra Pradesh, commissioned in April, will help meet Indias demand for natural uranium, used in indigenous Pressurised Heavy Water Reactors.

in Tummalapalle

THE trail has steep slopes and sharp turns everywhere. Wearing helmet headlamps and gumboots, we hopped on to a passenger carrier to begin our trip to the bowels of the earth. It was dark and scary at first. At one of the turns, a bullhorn sounded from nowhere and our vehicle moved aside quickly to let a behemoth pass bya low-profile dump truck (LPDT). A few minutes later, the carrier glided to a stop. We are 90 metres below the ground, announced an engineer accompanying us as we got out of the vehicle. At a distance was a massive machine called the drill jumbo. A tunnel-boring machine, it was drilling into a wall of rocks. A mine-truck hauled away the rock pieces excavated by it. Elsewhere, a rock bolter was reinforcing the roof, which was 3.2 metres from the floor level. The machine was nailing grid-like structures on to the roof to prevent it from caving in and then stitching every corner of the grid with six-foot- or eight-foot-long iron rods.

Indias newest underground uranium mine at Tummalapalle in YSR district in Andhra Pradesh is a hive of activity. (Kadapa district was renamed YSR district in 2010 in memory of Chief Minister Y.S. Rajasekhara Reddy, who died in a helicopter crash.) The mine is situated 12 kilometres by road from Pulivendula, YSRs hometown, and 500 km from the State capital, Hyderabad. Adjacent to the mine is a mill, or a processing plant, where the uranium ore is converted into sodium diuranate, or yellow cake.

The plant uses an innovative alkali leaching technique developed by the Bhabha Atomic Research Centre, Trombay, to convert the ore into yellow cake. Conventionally, acid leaching is employed in processing plants such as those in Jaduguda and Turamdih in Jharkhand. The uranium ore at Tummalapalle is not amenable to acid leaching. The yellow cake is transported to the Nuclear Fuel Complex (NFC) in Hyderabad, where it is fabricated into fuel bundles for use in Indias indigenous Pressurised Heavy Water Reactors (PHWRs).

Natural uranium is at the heart of Indias nuclear power programme. The countrys 17 operating PHWRs, with an installed capacity of 4,360 MWe, use natural uranium as fuel and light water as both moderator and coolant.

Huge Demand

There is a huge requirement of natural uranium for Indias ambitious project of constructing more PHWRs. Two reactors of 700 MWe each, at Rawatbhatta in Rajasthan and Kakrapar in Gujarat, now under construction, are expected to be commissioned in 2017. Ten more PHWRs of 700 MWe are in the offing: two each at Gorakhpur (Haryana), Chutka and Bhimpur (Madhya Pradesh), Mahi Banswara (Rajasthan) and Kaiga (Karnataka). These are expected to go on stream between 2020 and 2022.

The Uranium Corporation of India Limited (UCIL), a public-sector undertaking of the Department of Atomic Energy (DAE), was established in 1967 to mine and process uranium. The Atomic Minerals Directorate for Exploration and Research (AMD) prospects for uranium all over India. UCIL is already engaged in the mining of uranium ore at Jaduguda, Bhatin, Narwaphar, Turamdih, Banduhurang and Bagjata in East Singhbhum district of Jharkhand. Processing plants situated at Jaduguda and Turamdih convert the ore from these mines into magnesium diuranate (yellow cake), which is despatched to the NFC.

The AMD also found uranium deposits in Meghalaya and Lambapur-Peddagattu in Andhra Pradesh, Mohuldih in Jharkhand and Gogi in Karnataka. Following opposition to mining natural uranium in Meghalaya and Lambapur-Peddagattu, UCIL turned its attention to the Tummalapalle uranium reserve.

The Tummalapalle project owes it in great measure to Rajasekhara Reddy, who, as the legislator from Pulivendula, backed it fully. His son, Jagan Mohan Reddy, is now a Lok Sabha member from Kadapa constituency. The ground-breaking ceremony for the mine and the mill took place on November 20, 2007. On April 20 this year, Srikumar Banerjee, then Chairman, Atomic Energy Commission (AEC), and Secretary, DAE, commissioned the installations at Tummalapalle. The project cost Rs.1,106 crore.

The Tummalapalle deposit holds the promise of being the biggest deposit of uranium in the country, said Ratan Kumar Sinha, Chairman, AEC, in his address to DAE employees on October 30. As of now, about 72,000 tonnes of uranium reserves have been identified at the site. The AMD has adopted the new technology of time-domain electromagnetic system to find newer, deep-seated uranium reserves. Sinha, who is also DAE Secretary now, lauded the AMDs efforts to identify new sources of uranium, which had gone up by 70 per cent in the past five years.

According to N.M. Bahl, Executive Director (Projects, South), UCIL, the Tummalapalle mine is one of the safest and the best in the world. The beauty of the deposit and the method of mining adopted is that the mine development work started yielding uranium ore from day one, he said. The mine now yields 2,000 tonnes of ore a day, and by April 2013, it is expected to reach a capacity of 3,000 tonnes.

The mill has the capacity to process 3,000 tonnes of ore a day. The current shortfall of 1,000 tonnes will be met from the surface stockpile accumulated during mine-development operations. Once the mine achieves its rated capacity, the stockpile will be kept as reserve so that we can use it if there is any bottleneck in production. The mill will not be starved of ore, said Bahl. At the production rate of 3,000 tonnes a day, the life of the mine is estimated to be 30 years.

The ore deposits at Tummalapalle extend to over a distance of 5.6 km. Indications are that the ore body is continuous and goes to a depth of 500 metres. This means that the reserves will be available for many more years even after stepping up the rate of production to 4,500 tonnes a day as per UCILs plans.

The mine has three declines to access the underground working areas. One of these is for the personnel to enter and exit the mine; the second is for machines and material; and the third is for trucks carrying the ore to the adjoining processing plant. Plans are on to install a conveyor belt to ferry the ore to the mill through the third decline.

Mining activities

When Frontline visited the mine, UCIL had driven more than 21 km of tunnel length as part of mine development. The mine was busy with the movement of loading, hauling and dumping trucks (LHDT); scissors trucks; tunnel borers; and rock bolters. An LPDT can carry 30 tonnes of ore and climb a gradient of nine degrees. A big electricity substation inside the mine supplies and distributes power for illumination, ventilation, and so on. Ventilation fans, specific to the requirements in uranium mines, ensure that radon and other gases do not accumulate and that the dust concentration is kept low. The Indian School of Mines, Dhanbad, was involved in the design of the ventilation system. For backup power supply, diesel generators are available. And there are garages inside the mine to repair the vehicles.

The working environment in the mine adheres to specific conditions laid down by the Directorate General of Mines Safety and the Atomic Energy Regulatory Board. The Central Mining Research Institute, Dhanbad, conducted hydro-geological studies of the area for scientific assessment of the groundwater regime and underground working conditions in the mine.

Ten working levels have been opened on the mines eastern side and nine on the western side, said Koppula Kamalakar Rao, Mines Manager at Tummalapalle. As you deepen the mines, you expose additional working levels.

The mill is highly automated. Leaching of the ore is done in two huge pressure vessels, or autoclaves. Several control rooms with an array of computers monitor the machinery in the spacious plant. All machines, including those which crush and grind the rocks to micron-level dust and those used in the production of yellow cake, are operated from the local control rooms. A central control room situated in the chemical house monitors the entire operations in the mill.

At Tummalapalle, the host rock that contains natural uranium is dolomite, whose calcium-magnesium-carbonate content is high. Although the Tummalapalle deposit was discovered in 1986, UCIL could not mine and process the ore because of its low grade and complex nature. Its composition is different from that of the ore found in the Singhbhum belt in Jharkhand.

S.K. Malhotra, DAE spokesperson, said that since the host rock had a lot of lime, it was not amenable to acid leaching. This is the first time we are using the alkali leaching process. Pilot plant studies were carried out at Jaduguda, he said.

S.K. Shrivastava (Director, Technical), UCIL, said the mined ore in sizes of 150 mm and above was crushed and ground in the mill before the alkaline leaching process. Grinding is a wet process, done by adding water.

The uranium content in the ore is extracted by subjecting the ground slurry to leaching reaction. Reagents such as sodium carbonate and sodium bicarbonate are added to the slurry along with oxygen and steam into the autoclave to enable the leaching reaction, said Shrivastava.

Processing plant

It is hard to believe that the mine and the processing plant were built in just five years in as remote a place as Tummalapalle, which did not have any infrastructure to back these greenfield projects. For instance, at the peak of the construction activity, UCIL required about 3,000 workers. Since only agricultural labourers were available in and around Tummalapalle, industrial workers had to be brought from Bihar, Jharkhand and Orissa. Besides, the dearth of industries or workshops around Tummalapalle forced UCIL to bring all the equipment it needed from Bangalore, which is 200 km away, or from Hyderabad.

What was more challenging was laying the pipeline from the Chitravati reservoir, 52 km away, to the processing plant.

A. Madhusudana Rao, Deputy General Manager (Mechanical), UCIL, who was in charge of the project, said, Sinking of intake wells up to a depth of 32 metres inside the reservoir was a big challenge. A lot of precaution had to be taken so that the wells did not cave in.

Besides, convincing the villagers to allow the pipeline to go through their villages was a big task, he said. The pipeline had to take detours at the foot of the hills or by the side of roads.

The entire project of laying the pipeline, and setting up the water treatment plant, the effluent treatment plant and the dimineralisation plant cost UCIL Rs.66.40 crore. (Dimineralised water is used in the boiler in the mill.)

Although the State government had permitted UCIL to draw 6,000 cubic feet of water a day from the Chitravati reservoir, UCIL was using only 4,000 cubic feet of water a day, said Madhusudana Rao. The Chitravati reservoir has a capacity of 3 tmcft (thousand million cubic feet). Gravity pulls water from the reservoir to Kommanula village, 10.2 km away, and from there it is pumped over the next 40 km.

Tailing ponds

Another engineering feat is the setting up of the tailing ponds. This involved the design and construction of fail-proof earthen dams, where the slurry discharged from the mill is transported by a pipeline for containment. The tailing pond at Tummalapalle is in a valley surrounded by hills on three sides.

Right now the height of the tailing pond/dam is 15 metres. We will increase the height as it gets filled up, Bahl said. As the level of the slurry goes up, water from the slurry will flow into a decantation plant from where it will be taken for treatment.

Meanwhile, UCIL is attending to basic issues such as education, health care and hygiene at Tummalapalle and surrounding villages. It has provided furniture to primary schools and instituted scholarships for high school students. A qualified doctor visits the villages once a week.

The ease with which land acquisition was accomplished for building the mine and the reprocessing plant is one thing that Bahl is proud of. There is not a single grievance with regard to compensation, he said. More and more people are willing to give their land to UCIL in recognition of its corporate social responsibility activities and the benefits extended by UCIL to genuine, native landowners.

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