1. Which reactor has no moderator ?

Ans: Fast breeder reactor.

2. What are thermal neutrons ?

Ans: Thermal neutrons are slow neutrons (having energy below 1 eV) which are in thermal equilibrium with their surroundings.

3. What is big advantage of fast breeder reactor ?

Ans: It has rapid self breeding of fissile fuel during the operation of the reactor, and thus, it offers about sixty times the output with same natural uranium resources through ordinary non-breeder nuclear reactor.

4. What is the purpose of biological shield in nuclear plants ?

Ans: Biological shield of heavy concrete prevents exposure to neutrons, beta rays and gamma rays which kill living things.

5. Which two elements have same percentage in proximate and ultimate analysis of coal?

Ans: Moisture and ash.

6. On which analysis is based the Dulong's formula for the heating value of fuel ?

Ans: On ultimate analysis.

7. Which element causes difference in higher and lower heating values of fuel ?

Ans: Hydrogen.

8. Which heating value is indicated by a calorimeter and why ?

Ans: Gross heating value because steam is condensed and heat of vapour formed is recovered.

9. State the difference between ultimate and proximate analysis of coal ?

Ans: In ultimate analysis, chemical determination of following elements is made by weight: Fixed and combined carbon, H, O, N, S, water and ash. Heating value is due to C, H and S.

In proximate analysis following constituents are mechanically determined by weight. Moisture, volatile matter, fixed carbon and ash. Heating value is due to fixed carbon and volatile matter.

10. What is fuel ratio ?

Ans: Fuel ratio is the ratio of its % age of fixed carbon to volatile matter.