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Nuclear Fission

Q7.

(a)

(i) State the function of the moderator in a thermal nuclear reactor.

(ii) By considering the free neutrons in a thermal nuclear reactor to behave like the atoms of an ideal gas, estimate the speed of free neutrons in the core of a thermal nuclear reactor when the core temperature is 700 K.

(4 marks)

(b) In the core of a nuclear reactor, a fission neutron moving at a speed of 3.9 × 106 m s-1 collides with a carbon-12 nucleus which is initially at rest. Immediately after the collision, the carbon nucleus has a velocity of 6.0 × 105 m s-1 in the same direction as the initial direction of the neutron.

molar mass of carbon 12 = 0.012 kg

(i) Show that the neutron rebounds with a speed of 3.3 × 106 m s-1.

 

(ii) Show that the collision is an elastic collision.

 

(iii) Calculate the percentage of the initial kinetic energy of the neutron that is transferred to the carbon nucleus.

7 marks

(Total 11 marks)