Previous Year Question
To meet its rapidly growing energy demand, some opine that India should pursue research and development on thorium as the future fuel of nuclear energy. In this context, what advantage does thorium hold over uranium?
Thorium is far more abundant in nature than uranium.
On the basis of per unit mass of mined mineral, thorium can generate more energy compared to natural uranium.
Thorium produces less harmful waste compared to uranium.
Which of the statements given above is/are correct?
Only 1
Only 2 and 3
Only 1 and 3
1, 2 and 3
Correct Answer: D
Detailed Solution
Statements 1, 2 and 3 are correct.
Statement 1 is correct. India possesses much larger resources of thorium than uranium. Thorium occurs in India’s monazite-bearing coastal sands. Therefore, thorium is regarded as the long-term fuel resource of India’s three-stage nuclear power programme.
Statement 2 is correct. Natural uranium contains approximately 0.7% of the directly usable fissile isotope Uranium-235, while most of the remainder is Uranium-238. Thorium-232 is not itself fissile but is a fertile material; after absorbing a neutron in a reactor, it can be converted into fissile Uranium-233. A suitable breeder fuel cycle can utilize a large proportion of the available thorium, giving it the potential to produce more energy per unit mass of mined mineral.
Statement 3 is correct. The thorium fuel cycle produces relatively smaller quantities of plutonium and other long-lived transuranic elements than the uranium–plutonium fuel cycle. Therefore, the long-term radiotoxicity of its high-level radioactive waste can be lower. This does not mean that the thorium cycle is entirely waste-free; it produces fission products, and Uranium-232 makes fuel handling complex.
India’s three-stage programme envisages producing plutonium in the first-stage Pressurised Heavy Water Reactors, generating additional fissile material in the second-stage Fast Breeder Reactors and utilizing Uranium-233 derived from Thorium-232 in the third stage. Therefore, all three statements are correct.