[Maximum number: 3]

This question is about nuclear power production.

(a)

Outline the reason why fuel enrichment is necessary for the fuel used in a commercial nuclear reactor.

[ 3 ]

[Maximum number: 2]

This question is about the use of energy resources.

(a)

Nuclear reactors are also used to generate energy in France. In a particular nuclear reactor, neutrons collide elastically with carbon-12 nuclei $\left({ }_{6}^{12} \mathrm{C}\right)$ that act as the moderator of the reactor. A neutron with an initial speed of $9.8 \times 10^{6} \mathrm{~m} \mathrm{~s}^{-1}$ collides head-on with a stationary carbon-12 nucleus. Immediately after the collision the carbon-12 nucleus has a speed of $1.5 \times 10^{6} \mathrm{~m} \mathrm{~s}^{-1}$ .

[ 2 ]

(i)

Outline why the reduction in energy is necessary for this type of reactor to function.

[ 2 ]

[Maximum number: 3]

This question is about energy sources.

A small island is situated in the Arctic. The islanders require an electricity supply but have no fossil fuels on the island. It is suggested that wind generators should be used in combination with power stations using either oil or nuclear fuel.

(a)

A nuclear reactor requires both control rods and a moderator to operate. Outline, with reference to neutrons, one similarity and two differences in the function of each of these components.

[ 3 ]

[Maximum number: 1]

A suitable material for use as a moderator in a nuclear reactor is...

A

cadmium.

B

concrete.

C

uranium-238.

D

water.

[Maximum number: 1]

Which two components of a nuclear power station are primarily responsible for ensuring that a controlled chain reaction is maintained?

A

Control rods and heat exchangers

B

Moderators and shielding

C

Shielding and heat exchangers

D

Moderators and control rods

[Maximum number: 1]

A nucleus of uranium- $235\left({ }_{92}^{235} \mathrm{U}\right)$ absorbs a neutron and decays into two nuclides, xenon-140 ( ${ }_{54}^{140} \mathrm{Xe}$ ) and strontium-94 ( ${ }_{38}^{94} \mathrm{Sr}$ ).

How many neutrons are released in this reaction?

A

1

B

2

C

3

D

4

[Maximum number: 1]

In a simple model of a nuclear reactor, four neutrons are emitted per fission on average.

The average number of neutrons absorbed by the control rods is $N_{\mathrm{c}}$ per fission.
The average number of neutrons that are lost through the walls of the reactor is $N_{1}$ per fission.
Any remaining neutrons induce further fissions.
What are possible values for $N_{\mathrm{c}}$ and $N_{1}$ for the reactor to maintain a steady reaction?

$\boldsymbol{N}_{\mathbf{c}}$

$\boldsymbol{N}_{\mathbf{1}}$

1

3

2

1

2

[Maximum number: 1]

Which of the following is the primary function of the moderator in a nuclear power station?

A

To control the rate of fission reactions

B

To absorb neutrons

C

To prevent the power station from becoming unsafe

D

To slow down neutrons

[Maximum number: 1]

The moderator in a nuclear power station...

A

increases the proportion of U-235 in the fuel source.

B

transfers internal energy from the reactor to the turbines.

C

allows operators to regulate the rate of power production.

D

decreases the kinetic energy of neutrons in the reactor.

[Maximum number: 1]

Which component is responsible for slowing down neutrons in a nuclear reactor to increase the likelihood of nuclear fission?

A

Moderator

B

Control rods

C

Fuel rods

D

Heat exchanger

Question 3

Question 3(b)

Question 4

Question 4(d)

Question 4(d)(v)

Question 4

Question 4(g)

Question 23

Question 23

Question 24

Question 24

Question 24

Question 24

Question 24