Teacher's notes and answers to questions in the book - Hodder Plus ...

WJEC GCSE Additional Science Teacher’s Notes
Discussion point
You can find out about how nuclear reactors work by searching online using key-words such as ‘nuclear
power plant’, ‘animation’ and ‘applet’. Your teacher may show you one of these. How is the heat energy
generated by the reactor transformed into electricity
The heat from the reactor is used to heat water to make steam, which turns a turbine-generator –
the same as in a conventional power station.
Questions
4. What is the main fuel used in a nuclear reactor
Uranium-235
5. What is a ‘chain reaction’
The neutrons released from the fission of one U-235 atom can initiate the fission of other
U-235 atoms, and so on.
6. Why does a nuclear reactor need a moderator
The fission of U-235 by neutrons requires the neutrons to be slow-moving – the moderator,
usually water, is used to slow the neutrons down increasing the likelihood of fission events.
7. How can a nuclear power station reactor be controlled
Control rods, usually made of graphite or boron, absorb neutrons. Raising or lowering the
control rods controls the rate of fission and hence the power output of the reactor.
8. Why is the reactor encased inside a steel vessel surrounded by a thick concrete containment structure
To minimise the escape of highly energetic and penetrating gamma rays (produced inside the
reactor) escaping into the local environment.
9. Why do spent fuel rods need to be stored under water in ponds within the containment structure
The spent fuel rods are still highly radioactive and produce large amounts of heat. The water in
the ponds is used to cool the fuel rods.
10. Draw a flow chart showing how electricity is generated by nuclear fission in a nuclear power station.
Fission of
U-235
Heats water
producing steam
Steam turns turbine
which turns generator
Electricity produced and
delivered to the National
Grid
_ Is there another way (pages 227–30)____________
Questions
11. What is nuclear fusion
Nuclear fusion is the joining together of lighter nuclei to make heavier ones and during the
process emitting large amounts of energy.
12. Inside the core of the Sun, what are the particles involved with nuclear fusion
Inside the Sun, hydrogen nuclei (protons) fuse together during the process of nuclear fusion.
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