21) The detonating tendency in petrol engines increases with increase of compression ratio.

22) Each fission of U₂₃₅ produces on the average __________ fast neutrons as a product of reaction.

23) Reactors for propulsion applications are designed for

24) The primary fuel used in nuclear power plants is

25) In petrol engine, using a fixed octane rating fuel and fixed compression ratio, supercharging will __________ the knocking tendency.