Why in News:

• Rosatom State Corporation of Russia has supplied the first batches of more reliable and cost-efficient nuclear fuel over the existing one, the TVS-2M nuclear fuel, to India for the Units 1 & 2 of Kudankulam Nuclear Power Plant (KNPP)

How is the Nuclear fuel made

• Uranium is the most widely used fuel by nuclear power plants for nuclear fission. Nuclear power plants use a certain type of uranium—U-235—as fuel because its atoms are easily split apart. 
• Although uranium is about 100 times more common than silver, U-235 is relatively rare at just over 0.7% of natural uranium. Uranium concentrate is separated from uranium ore at uranium mills or from a slurry at in-situ leaching facilities. 
• It is then processed in conversion and enrichment facilities, which increases the level of U-235 to 3%–5% for commercial nuclear reactors, and made into reactor fuel pellets and fuel rods in reactor fuel fabrication plants.
• After the uranium ore is extracted from an open pit or underground mine, it is refined into uranium concentrate at a uranium mill.
• The concentrated uranium product is typically a black or brown substance called yellowcake (U3O8).
• The next step in the nuclear fuel cycle is to convert yellowcake into uranium hexafluoride (UF6) gas at a converter facility. Three forms (isotopes) of uranium occur in nature: U-234, U-235, and U-238.
• After conversion, the UF6 gas is sent to an enrichment plant where the individual uranium isotopes are separated to produce enriched UF6, which has a 3% to 5% concentration of U-235.
• Once the uranium is enriched, it is ready to be converted into nuclear fuel. At a nuclear fuel fabrication facility, the UF6, in solid form, is heated to gaseous form, and then the UF6 gas is chemically processed to form uranium dioxide (UO2) powder. 
• The powder is then compressed and formed into small ceramic fuel pellets. The pellets are stacked and sealed into long metal tubes to form fuel rods. The fuel rods are then bundled together to make up a fuel assembly.

What is spent Nuclear Fuel

• Spent nuclear fuel, also known as used nuclear fuel, is nuclear fuel that has been through a reactor campaign and is no longer suitable for maintaining the nuclear fission chain reaction in a thermal reactor.
• Residual 235U and converted plutonium, as well as fission-product and transuranic wastes, are found in spent fuel discharged from a power reactor.
• Spent nuclear fuel is extremely radioactive and may be quite dangerous. Spent fuel is hazardous because it contains a variety of fission products, some of which may be long-lived radioactive waste, as well as very poisonous plutonium. 

India’s Nuclear Fuel Reserves 

• India has massive uranium deposits that, with the right technology, can power India’s nuclear power plants. 
• Thorium resources in India are projected to be 360,000 tonnes, and natural uranium deposits are expected to be 70,000 tonnes. 
• The country’s thorium reserves account for 25% of the world’s total.

 References

https://www.eia.gov/energyexplained/nuclear/the-nuclear-fuel-cycle.php

https://www.thehindu.com/news/national/russia-delivers-more-efficient-nuclear-fuel-for-kudankulam-reactors/article65514664.ece