RADIOACTIVITY:
- When a nucleus decays it becomes more stable , but the loss of neutrons and Protons makes it a different element . The original nucleus is called Parent Nucleus . The nucleus formed is known as the daughter nucleus.
- Parent and daughter nucleus are called the Decay Products.
- Radioactive decay is a random event where the unstable nuclei in some materials will break up or disintegrate.
- This disintegration of nuclei is called Radioactive decay.
IMPORTANT NOTES:
- Mass Number (Nucleon Number) = Total Number of Nucleons (protons + Neutrons) in the Nucleus .
- Atomic Number (Proton Number) also shows the relative charge on the Nucleus.
RADIOACTIVE DECAY EXAMPLES:
The element radium has been formed from the decay of the Thorium.
HALF-LIFE PERIOD:
INTRODUCTION:
- In this new era of atomic energy for nuclear power generation , Uranium and Thorium constitute the potential atomic fuels.
- Uranium was discovered in 1789 by Klaproth in Pitchblende.
- Thorium was discovered in 1828 by Berzelius in Thorite .
- Thorium and Uranium metals are extremely gas and air sensitive and so their extraction has to be carried out under inactive gases such as Argon and Helium.
PROPERTIES OF URANIUM:
- Uranium is a radioactive element which breaks down at steady rate and after passing through a number of intermediate stages, it is finally changed into a form on lead i.e. Pb 206 that is not radioactive.
- Uranium is not found in Native State.
- Uranium metal is white and hard. Pure uranium is silver in colour and readily oxidizes in air.
- Specific Gravity- 18.68. It is one of the Heaviest among all the naturally occurring elements when arranged based on increasing mass of their nuclei on a scale.
- Uranium exists in various slightly different forms known as " Isotopes".. Natural Uranium was found to be a mixture of two isotopes U-238 accounts for 99.3% and U-235 around 0.7%..
MINERALOGICAL CHARACTERSTICS:
To view the table of characteristics tap on the given link : CHARACTERSTICS TABLE.
GEOLOGICAL SETTING:
2. Unconformities : Uranium deposits can be found at unconformities, which are geological boundaries between different rock units that represents gaps in geological record . These deposits are often characterized by the presence of mineralization along the unconformity.
3. Metamorphic rocks: Uranium deposits can also occur in metamorphic rocks, which are formed the alteration of existing rocks due to heat, pressure or chemical reactions.
4. Igneous rocks: Uranium deposits can occur in igneous rocks, which are formed from the solidification of molten magma or lava.
GENESIS:
The mineralisation of Uranium is formed by 4 processes:
- Magmatic Concentration
- Hydrothermal Processes
- Oxidation and supergene enrichment Process
- Metasomatic Replacement Process.
MAGMATIC CONCENTRATION PROCESS:
- As the magma approaches the earth surfaces its temperature and pressure drop with the result of crystallization and differentiation of different minerals in a definite sequence.
- These differentiated minerals collectively forms the magmatic deposits.
- Uranium deposits are formed when uranium rich magma crystallizes.
HYDROTHERMAL PROCESS:
- Hydrothermal mineral deposits are formed by hot aqueous solutions/fluids called " Hydrothermal Solutions/ fluids" in form of veins , stockworks and replacement deposits.
- This fluid also contain radioactive minerals such as uranium - rich minerals.
- On the basis of mode of formation Hydrothermal deposits are divided into cavity filling and replacement deposits.
- Cavity filling consists in deposition of minerals in rock opening from aqueous solution.
- It is a process of simultaneous solution and deposition whereby one mineral replaces another.
- Uranium are also deposited by this process.
- Replacement occurs when a mineralizing solution encounters minerals unstable in its presence. The original mineral is dissolved and almost simultaneously exchanged for another.
- Massive
- Replacement Lodes
- Disseminated
OXIDATION AND SUPERGENE ENRICHMENT:
- When ore deposits are exposed to the oxidation zone they are weathered and altered with the country rocks.
- An ore body thus becomes oxidized and generally leached of many of its valuable materials down to the groundwater table or to depth where oxidation cannot takes place.
- As the cold, dilute leaching solutions trickle downwards, their metallic content may be precipitated in the form of secondary sulfides to gives rise to a zone of supergene Sulphide enrichment.
- Uranium can also leached and Tapped in zone of oxidation .
URANIUM DEPOSITS:
1. Unconformity-related deposits: Unconformity - type uranium deposits host high grades relative to other uranium deposits and include some of the largest and richest deposits known.
2. Sandstone Deposits: Uranium precipitates under reducing conditions, and thus the presence of a reducing environment is essential for formation of uranium deposits in sandstone.
3.Vein-Deposits: Vein deposits consist of uranium minerals filling in cavities such as cracks, veins, fractures , breccias and stockworks associated with steeply dipping fault systems.
DISTRIBUTION :
IN INDIA-
- Jaduguda in Singhbhum Thrust Belt in state of Jharkhand. It is the first Uranium Deposits in the country.
- Some deposits like Bhatin , Narwapahar and Turamdih are well known uranium mines of the country.
- Deposits like Bagjata , Banduhurang and Mohuldih are take up for commercial mining operations.
- Areas like Garadih , Kanyaluka , Nimdih and Nandup in this belt limited reserves with poor grades are present.
IN WORLD:
- Canada - It is one of the largest world producer of uranium.
- Kazakhstan- It is another major producer of uranium.
- China- It has significant uranium resources , with deposits located in various provinces including Xinjiang , Inner Mongolia and Jiangxi.
