UPSC Prelims 2012 Q61: Science & Technology – Energy & Environment
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?
1. Thorium is far more abundant in nature than uranium.
2. On the basis of per unit mass of mined mineral, thorium can generate more energy compared
to natural uranium.
3. Thorium produces less harmful waste compared to uranium.
Which of the statements given above is/are correct?
- (a) 1 only
- (b) 2 and 3 only
- (c) 1 and 3 only
- (d) 1, 2 and 3
Answer: (d) 1, 2 and 3
Explanation
Thorium versus uranium
| Statement | Verdict | Reason |
|---|---|---|
| 1. Thorium is far more abundant in nature than uranium | Correct | Thorium is about three to four times as abundant in the Earth's crust |
| 2. On the basis of per unit mass of mined mineral, thorium can generate more energy compared to natural uranium | Correct | Nearly all mined thorium can be used; only about 0.7 per cent of natural uranium is fissile uranium-235 |
| 3. Thorium produces less harmful waste compared to uranium | Correct | It gives far less plutonium and other long-lived waste |
Thorium and India:
| Point | Detail |
|---|---|
| Reserves | Among the world's largest, in monazite sands of Kerala, Tamil Nadu and Odisha |
| Nature | Fertile, not fissile: thorium-232 changes into fissile uranium-233 |
| Programme | Third stage of Homi Bhabha's three-stage nuclear programme |
| Reactor | Advanced Heavy Water Reactor design; KAMINI at Kalpakkam runs on uranium-233 |
Answer: (d) 1, 2 and 3.
Why each option is right or wrong
- (a) Incorrect. Statements 2 and 3 are also advantages of thorium.
- (b) Incorrect. Statement 1 is also true; thorium is far more abundant.
- (c) Incorrect. Statement 2 is also true; thorium gives more energy per unit mass mined.
- (d) CORRECT. Thorium is more abundant, gives more energy and leaves less harmful waste.
Key point
Thorium: 3 to 4 times as abundant as uranium; fertile thorium-232 becomes uranium-233; less long-lived waste; India's monazite sands; third stage of the nuclear programme.
Remember
Thorium-232 to uranium-233: India's third nuclear stage.
Common mistakes
- Calling thorium fissile; it is fertile and must first be converted.
- Forgetting that only a tiny part of natural uranium is usable as fuel.
- Thinking India already runs its power plants on thorium; that stage is still ahead.
Exam tip
The question asks for advantages, and thorium has all three. Its only drawback is that it needs a starter fuel.
Sources
- Department of Atomic Energy — India's Three-Stage Nuclear Power Programme
- World Nuclear Association — Thorium