1.Which reactor produces more fissionable material than it consumes ?

Ans: Breeder reactor.

2.Which reactor uses natural uranium as fuel ?

Ans: Gas cooled reacator.

3.Which reactor uses heavy water as moderator ?

Ans: CANDU.

4.Which reactor requires no moderator ?

Ans: Breeder reactor.

5.Which reactor uses primary coolant as fluoride salts of lithium, beryllium, thorium and uranium ?

Ans: Molten salt breeder reactor.

6.Why an increase in area is required to produce an increase of velocity in case of supersonic flow ?

Ans: Increase in area for increase in velocity for supersonic flow is required because the density decreases faster than velocity increases at supersonic speeds and to maintain continuity of mass, area must increase.

7.Under what circumstances would there be an increase in pressure in a diver¬gent nozzle ?

Ans: For subsonic flow at inlet section of a diffuser a lower velocity and higher pressure will exist at the exit section. For supersonic isentropic flow at the inlet section a higher velocity and lower pressure will exist at the exit but if a shock wave occurs in the diffuser then a higher pressure will exist at the exit.

8.Why water can’t be used as refrigerant for small refrigerating equipment ?

Ans: The refrigerant should be such that vapour volume is low so that pumping work will be low. Water vapour volume is around 4000 times compared to R- for a given mass.

9.Which parameter remains constant in a throttling process ?

Ans: Enthalpy.

10.What is the difference between isentropic process and throttling process ?

Ans: In isentropic process, heat transfer takes place and in throttling process, enthalpy before and after the process is same.