URANIUM AND THORIUM
- Uranium, Thorium and plutonium are the main atomic minerals. Other atomic minerals are beryllium, lithium and zirconium.
- Plutoniumoccurred naturally, but except for trace quantities it is now not found in the Earth’s crust.
- Plutonium is formed in nuclear power reactors from uranium-238 by neutron capture.
- Uranium deposits occur in Jadugudamines in Singhbhum and Hazaribagh districts of Jharkhand, Gaya district of Bihar, Cuddapha basin (AP) and Mahadek basin (Meghalaya) and in the sedimentary rocks in Saharanpur district of Uttar Pradesh.
- But the largest source of uranium comprises the monazite sands.Monazite sands occur on east and west coasts and in some places in Bihar but the largest concentration of monazitesand is on the Kerala coast.
- Over 15,200 tonnes of uranium is estimated to be contained in monazite.
- Some uranium is found in the copper mines of Udaipur in Rajasthan.
- India produces about 2 per cent of world’s uranium. The total reserves of uranium are estimated at 30,480 tonnes.
- Thorium is also derived from monazite. The other mineral carrying thorium is thorianite.
- The known reserves of thorium in India are estimated to be between 457,000 and 508,000 tonnes. Kerala, Jharkhand, Bihar, Tamil Nadu and Rajasthan are the main producers.
- Beryllium oxideis used as a ‘moderator’ in nuclear reactors. India has sufficient reserves of beryllium to meet her requirement of atomic power generation.
- Lithium is a light metal which is found in lepidolite and spodumene. Lepidolite is widely distributed in the mica belts of Jharkhand, Madhya Pradesh and Rajasthan.
- Zirconium is found along the Kerala coast and in alluvial rocks of Ranchi and Hazaribagh districts of Jharkhand.
- Uranium is a silvery-gray metallic radioactive chemical element. It is only naturally formed in supernova explosions.
- Uranium, thorium, and potassiumare the main elements contributing to natural terrestrial radioactivity.
- Uranium has the chemical symbol U and atomic number 92.
- Uranium isotopes in natural uranium are 238U (99.27%)and 235U (0.72%).
- All uranium isotopes are radioactive and fissionable. But only 235Uis fissile (will support a neutron-mediated chain reaction).
- Traces of Uranium are found everywhere. Commercial extraction is possible only in locations where the proportion of Uranium is adequate.
- Top 10 Uranium producing countries is as below ( Remembering Top 4 is important )
- India has signed bilateral agreements with many of these for import of Uranium. [Discussion on Uranium/NSG is comprehensively covered in International relations.]
A) Distribution of Uranium Across the World
- Largest viable deposits are found in Australia, Kazakhstan, and Canada.
- Olympic Dam and the Ranger mine in Southern Australia are important mines in Australia.
- High-grade deposits are only found in the Athabasca Basinregion of Canada.
- Cigar Lake, McArthur River basin in Canada are other important uranium mining sites.
- The Chu-Sarysu basin in central Kazakhstan alone accounts for over half of the country’s known uranium resources.
B) Uranium in India
- India has no significant reserves of Uranium. All needs are met through imports.
- India imports thousands of tonnes of uranium from Russia, Kazakhstan, France.
- India is trying hard to import uranium from Australia and Canada. There are some concerns regarding nuclear proliferation and other related issues which India is trying to sort out.
- Some quality reserves were recently discovered in parts of Andhra Pradesh and Telangana between Seshachalam forest andSresailam [Southern edge of Andhra to Southern edge of Telangana].
- Thorium is a chemical element with symbol Th and atomic number 90.
- It is one of only two significantly radioactive elements that still occur naturallyin large quantities.
- Thorium metal is silvery and tarnishes black when exposed to air.
- Thorium is weakly radioactive: all its known isotopes are unstable.
- Thorium-232is the most stable isotope of thorium and accounts for nearly all-natural thorium.
- Thorium is estimated to be about three to four times more abundant than uraniumin the Earth’s crust, and is chiefly refined from monazite sands [Monazite contains 2.5% thorium].
- Thorium is predicted to be able to replace uranium as nuclear fuel in nuclear reactors, but only a few thorium reactors have yet been completed.
A) Monazite – Rare Earth Metals (important )
- Monazite is a reddish-brown phosphate mineral containing rare earth metals.
- Rare earths are a series of chemical elements found in the Earth’s crust that are vital to many modern technologies, including consumer electronics, computers and networks, communications, clean energy, advanced transportation, health care, environmental mitigation, national defence, and many others.
- Because of their unique magnetic, luminescent, and electrochemical properties, these elements help make many technologies perform with reduced weight, reduced emissions, and energy consumption; or give them greater efficiency, performance, miniaturization, speed, durability, and thermal stability.
- There are 17 elements that are considered to be rare earth elements. Like Scandium, Yttrium
B) Advantages of Thorium
- Proliferation is not easy: Weapons-grade fissionable material (U-233) is harder to retrieve safely from a thorium reactor [U-233 produced by transmuting thorium also contains U-232, a strong source of gamma radiation that makes it difficult to work with. Its daughter product, thallium-208, is equally difficult to handle and easy to detect].
- Thorium reactors produce far less waste than present-day reactors.
- Thorium produces 10 to 10,000 times less long-lived radioactive waste
- They have the ability to burn up most of the highly radioactive and long-lasting minor actinidesthat makes nuclear waste from Light Water Reactors.
- Thorium reactors are cheaper because they have higher burn up.
- Thorium mining produces a single pure isotope, whereas the mixture of natural uranium isotopes must be enriched[enriching is costly] to function in most common reactor designs.
- Thorium cannot sustain a nuclear chain reaction without priming, so fission stops by default in an accelerator driven reactor.
C) Thorium Distribution
- Thorium is several times more abundant in Earth’s crust than all isotopes of uranium combined and thorium-232 is several hundred times more abundant than uranium-235.
- United States, Australia, and India have particularly large reserves of thorium.
- India and Australia are believed to possess more than half of world’s thorium reserves