Paper 1 - Nuclear Power Stations

Question 1

Generating electrical energy from nuclear fission.

Answer 1

It is the thermal energy from nuclear fission that is the most useful for the generation of electricity in a power station.

1) fuel rods containing uranium undergo nuclear fission in reactor. Thermal energy released.
2) thermal energy from nuclear fission is taken by the coolant to heat water to produce steam.
3) the steam causes turbines to rotate which turn the generator to generate electricity.
4) the steam is cooled back into water in a condenser so it can be used again. Extra thermal energy is released from cooling towers or into the sea.

Question 2

Controlling a chain reaction in the reactor

Answer 2

• concrete shielding prevents radiation and stray neutrons escaping from the core .
• neutrons that escape from one duel rod can be absorbed by another
• control rods absorb neutrons. Lowering a control rod lowers fission reactions
• a moderator is a material (often graphite or water) that is used to slow down the neutrons so that fission of the uranium- 235 nuclei can occur. The moderator does not absorb neutrons.

Question 3

(WORKED EXAMPLE) Explain how the control rods work in a nuclear power station. (3 marks)

Answer 3

The control rods absorb neutrons. If the control rods are pushed down into the core, more neutrons are absorbed and the chain reaction slows down. If they are pulled out, fewer neutrons are absorbed and the chain reaction speeds up.

Question 4

(WORKED EXAMPLE) describe how nuclear fuel is used in a power station ?

Answer 4

Nuclear fuel undergoes fission to release huge quantities of thermal energy. This is used to heat water and produce steam.

Question 5

(WORKED EXAMPLE) describe what happens to the products of nuclear fission.

Answer 5

The radioactive daughter products need to be disposed of safely. They are usually stored until activity had decreased to a safe level