UPSC Prelims 2012 · GS Paper I
Question 61: Science and Technology
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?
AnswerUPSC’s answer is (d).
Thorium is about three to four times more abundant than uranium, and India has large reserves in its monazite sands. Natural thorium is almost entirely thorium-232, which a reactor can convert into fissile uranium-233, whereas natural uranium is only about 0.7 per cent fissile uranium-235; so in a breeder cycle, thorium can yield more energy per unit mass mined. The thorium cycle also produces less long-lived radioactive waste.
- 1. Thorium is far more abundant in nature than uranium.
- 2. Nearly all natural thorium can be used as fuel in a breeder cycle, unlike natural uranium.
- 3. The thorium cycle produces less long-lived waste.
How you could have got this
- If you were sure statement 1 is correct, (b) goes: it leaves 1 out.
What you needed to know: Thorium is far more abundant in nature than uranium.
- Then, if you were sure statement 2 is correct, (a) and (c) go: each of them leaves 2 out.
What you needed to know: Nearly all natural thorium can be used as fuel in a breeder cycle, unlike natural uranium.
Only (d) is left. You didn’t need statement 3.
Which options go is worked out from UPSC’s key and the options, not by a model.
Why each option is right or wrong
- (a) Incomplete: thorium also yields more energy per unit mass mined and less harmful waste.
- (b) Incomplete: thorium's greater abundance is also an advantage.
- (c) Incomplete: more energy per unit mass of mined mineral is also an advantage.
- (d) Correct: abundance, energy per unit mass mined, and less harmful waste.
Answer: UPSC’s key. Explanation: written by UPSC Grade, not by UPSC.
Source: UPSC, Civil Services (Preliminary) Examination 2012, General Studies Paper I, Series A. The paper on upsc.gov.in.