Nuclear Fuel - Uranium 235!

Ever wondered how the most talked/feared fuel of the world, Uranium-235, is extracted from the earth crust and made ready to use in power plant? Probably you know three simple steps of Uranium mineral extraction: Digging - Cleaning - Spinning. But we are talking about one of the most advanced fuels that humankind has discovered to power the world. It fuels 11 % of the world power generation capacity. Let’s dig it up little further and see how exactly Uranium reach to the stage of Pellets (HEU - Highly Enriched Uranium), the form where it is 8000 times efficient than Coal!

Stage I

Ores are obtained by mining Uranium 238, which is naturally abundant. It contains 99.3 % U-238 and only 0.7 % of U-235. We want U-235 for fuelling the Nuclear Power Plants. Ore is crushed and heated to remove carbon dirt items like gangue particles and clay. This is basically an extraction and cleaning stage.

In India, Uranium is mined at Jaduguda and Narwapahar (Singhbhum Belt - Jharkhand) largely. Other sites where Uranium is found in India are, Aravallis in Rajasthan, Mahadek Basin in Meghalaya, Cuddapah Basin in Andhra Pradesh, Bhima Basin in Karnataka.

Australia, Canada and Kazakstan contribute 2/3rd of the world’s uranium production.

Stage II

The slurry of ore and water is leached with Sulphuric Acid (H2SO4). Here, Uranium bonds with Sulphur and Oxygen to form Uranium Oxide liquid. This process further cleans the ore. 

Stage III

Ammonia solution is used to prepare Yellow Cakes of Uranium Oxide, which we have seen in Sunny Deol’s “Maa Tujhe Salaam” (Bollywood Movie-2002) and also in some of Sci-Fi Hollywood Movie. The Yellow Cake is still not that radioactive. You can stand at 2 meters distance from Yellow Cake and not get affected by it. The concentration of radioactive U-235 is very less. The Yellow Cake is the reason why the symbol of Nuclear Danger is Yellow.

Stage IV

Yellow Cake Uranium is first turned into a gas by chemical reaction with Florine. The reaction produces Uranium Hexa-Fluoride gas. The gas form is purer than Cake. Gas is also easier to handle in the next stage of Uranium concentration.

Stage V

Nuclear Centrifuge Process - The principle of the centrifuge device is simple. When the wheel starts spinning at very high speed, the heavy particles are thrown outside towards the circumference, while the lighter particles remain closer to centre. Same physics principle is used to manufacture sugar candy (Buddhi Ke Baal). Heavier U-238 is thrown to circumference while relatively lighter U-235 remains near the centre.

Stage VI

Nuclear Centrifuge Process Returns - Since there is only 1 % mass difference between U-238 and U-235, the process has to be repeated thousands of time. Eventually, the gas at the centre gets more and more enriched with U-235. 

Stage VII

When we reach the enrichment level of 4-5 % U-235, it becomes usable in most of the Nuclear Power Plants. For Weapon Grade, the enrichment should be 80 to 90 % of U-235.

This also tells us that, those countries which can purify Uranium for Nuclear Power Plant, can also enrich Uranium for the Weaponry purpose. And to avoid misuse of Nuclear Cooperation in weapons manufacturing, IAEA (International Atomic Energy Agency) keeps eye on reactors of NPT signatory countries. India is non-signatory to discriminatory NPT but has followed the principle of non-proliferation of Nuclear Weapon beyond Minimum Credible Deterrence stock. We have opened our 14 reactors for IAEA out of 22 operating reactors in India.

Stage VIII

Enriched Uranium Hexa Fluoride is then turned into solid by adding Calcium. It forms salt-containing only Uranium Oxide, the pellet material. Pellets are manufactured by the extrusion process. These pellets are mounted on rods, depending upon the needs of the particular power plant where they will be used as fuel.

In India, we have the Nuclear Fuel Fabrication Complex in Hyderabad. This facility supplies fuel to Seven Nuclear Power Plants which houses 22 reactors. The manufacturing capacity will expand with the completion of Jaitapur Project, Kovvada Project, and expansion of Kudankulam’s capacity, other coming up nuclear power plants in India.

We should also look into the processes to obtain Plutonium 239 and Thorium 232, but some other time. 

P. S.: Stay home to avoid COVID-19 infection. 

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