Telephone services India

Telephone services developments in India

Prior to-1902 – Cable telegraph.

1902 – First wireless telegraph station established between Sagar Island and Sandhead.
1907 – First Central Battery of telephones introduced in Kanpur.
1913–1914 – First Automatic Exchange installed in Shimla.
1927 – Radio-telegraph system between the UK and India, with Imperial Wireless Chain beam stations at Khadki and Daund. Inaugurated by Lord Irwin on 23 July by exchanging greetings with King George.
1933 – Radiotelephone system inaugurated between the UK and India.
1947 - First Electronics & Telecommunications Engineering department started in India at the Government Engineering College, Jabalpur.
1953 – 12 channel carrier system introduced.
1960 – First subscriber trunk dialling route commissioned between Lucknow and Kanpur.[citation needed]
1975 – First PCM system commissioned between Mumbai City and Andheri telephone exchanges.
1976 – First digital microwave junction.
1979 – First optical fibre system for local junction commissioned at Pune.
1980 – First satellite earth station for domestic communications established at Sikandarabad, U.P..
1983 – First analogue Stored Programme Control exchange for trunk lines commissioned at Mumbai.
1984 – C-DOT established for indigenous development and production of digital exchanges.
1995 – First mobile telephone service started on non-commercial basis on 15 August 1995 in Delhi.
1995 – Internet Introduced in India starting with Laxmi Nagar, Delhi 15 August 1995

Uranium Ore processing

Uranium ore processing

Uranium ores are normally processed by grinding the ore materials to a uniform particle size and then treating the ore to extract the uranium by chemical leaching. The milling process commonly yields dry powder-form material consisting of natural uranium, "yellowcake," which is sold on the uranium market as U3O8

Heap leaching is an extraction process by which chemicals (usually sulfuric acid) are used to extract the economic element from ore which has been mined and placed in piles on the surface. Heap leaching is generally economically feasible only for oxide ore deposits. Oxidation of sulfide deposits occur during the geological process called weathering. Therefore, oxide ore deposits are typically found close to the surface. If there are no other economic elements within the ore a mine might choose to extract the uranium using a leaching agent, usually a low molar sulfuric acid.

Acid Leaching

Acid leaching has the advantage of being more effective with difficult ores, requiring lower temperatures and leaching times compared to alkaline solutions. It also requires less pretreatment than alkaline leaching, most notably because the particle size from the grinding process does not need to be as small. Acid leaching is sometimes also referred to as heap leaching because the leaching process can be performed on large "heaps" of uranium ore that have been collected from mines. The chemistry of the leaching process revolves around oxidation of the uranium compounds, which is typically achieved using manganese dioxide (MnO2), sodium chlorate (NaClO3), and Fe(II) salts. Fig. below shows a typical reaction pathway for the acid leaching process using sulfuric acid. Sulfuric acid is typically used due to the solubility of uranyl sulfate complexes. The reaction is typically performed at slightly elevated temperatures (~60C) and can often release H2, H2S, and CO2 gases during the process. The uranium, which typically begins in the tetravalent state, goes through a series of reactions, eventually leading to the formation of the desired complex, [UO2(SO4)3]4-. While the solubility of this complex makes sulfuric acid a desirable leaching agent, nitric and hydrochloric acid can also be used, but are typically not due to their higher cost and corrosiveness.

Alkaline Leaching

While both acidic and alkaline leaching agents are used, alkaline leaching has some significant advantages. Alkaline solutions tend to be more selective to uranium minerals, which means the solution will contain fewer impurities. Consequently, the uranium oxide (commonly called "yellowcake") can be directly precipitated without purification. Furthermore, the solutions are less corrosive and can be recycled without the annoyance of increasing impurity concentrations. Fig. 2 shows a list of reactions involved in the alkaline uranium leaching process. The alkaline leaching process relies on the formation of highly soluble uranyl tricarbonate, UO2(CO3)34-. As in the case of acid leaching, oxidizers are used to maintain the presence of the hexavalent U6+ cation. This can be achieved by simply introducing oxygen into the solution by bubbling air into the solution. The leaching agents used are sodium bicarbonate and sodium carbonate. This prevents the formation of uranyl hydroxide compounds. Due to the slower reactivity of the alkaline solutions, increased pressures and temperatures are sometimes used to accelerate the process.

Mineralogical Composition of

Tummalapalle Uranium Ore:

Mineral                      % Weight

Carbonates                           83.2

Quartz + Feldspar                11.3

Collophane                            4.3

Pyrite                                     0.47

Chalcopyrite                          0.05

Galena Traces Magnetite      0.15

Ilmenite + Leucoxene           0.25

Iron Hydroxide (Goethite)    0.27

Pitchblende in intimate         0.1

association with Pyrite

Total                                  100.0