1. 1
   A nuclear power station generates electricity by controlling nuclear fission reactions inside its reactor core, where fuel rods contain a fissionable isotope.

   (a)

   A nuclear power station uses fuel rods to generate electricity. Which isotope is most commonly used as the fuel in these reactors?

   [1 mark]

   • AUranium-235
   • BCarbon-14
   • CCobalt-60
   • DHydrogen-1

   (b)

   What happens when a nucleus of the fuel isotope absorbs a neutron inside the reactor core?

   [1 mark]

   • AThe nucleus becomes more stable and stops decaying
   • BThe nucleus joins with another nucleus to form a heavier one
   • CThe nucleus emits an alpha particle and remains unchanged
   • DThe nucleus becomes unstable and splits into two smaller nuclei

   (c)

   Describe what is produced when a fuel nucleus undergoes fission after absorbing a neutron.

   [2 marks]

   Total for question 1: 4 marks

2. 2
   Engineers in a nuclear power station control room monitor the reactor core and adjust the position of control rods to manage how many of the neutrons released by fission go on to cause further fission events.

   (a)

   Engineers in the reactor control room can raise or lower control rods into the reactor core. What is the main purpose of the control rods?

   [1 mark]

   • ATo cool the reactor core using flowing water
   • BTo absorb neutrons produced by fission and control the rate of the chain reaction
   • CTo provide the fuel for the fission reactions
   • DTo generate the electricity directly from the reactor

   (b)

   If the control rods are withdrawn too far and more than one neutron from each fission event goes on to cause further fission, what is likely to happen to the reaction rate?

   [1 mark]

   • AThe reaction rate stays exactly the same
   • BThe reaction stops completely
   • CThe reaction rate rapidly increases, releasing energy uncontrollably
   • DThe fuel nuclei stop absorbing neutrons

   (c)

   Explain how the engineers use the control rods to keep the chain reaction in the reactor core at a steady, manageable rate.

   [2 marks]

   Total for question 2: 4 marks

3. 3
   An energy company is comparing two possible ways of generating a fixed amount of electricity: burning coal in a conventional power station, or using nuclear fission of uranium-235 in a nuclear power station.

   (a)

   An energy company is comparing the energy released by burning a kilogram of coal with the energy released by nuclear fission of a similar mass of uranium-235. Explain why nuclear fission releases a far greater amount of energy per reaction than a chemical reaction such as combustion.

   [3 marks]

   (b)

   Describe, in the correct order, the sequence of events that occurs during a single nuclear fission reaction in the uranium-235 fuel.

   [4 marks]

   Total for question 3: 7 marks

4. 4
   A national government is deciding whether to build a new nuclear fission power station to help meet the country's growing electricity demand, and is weighing the benefits of nuclear power against its risks and long-term costs.

   (a)

   Explain why the radioactive waste produced by nuclear fission remains hazardous for a very long time, and what this means for how it must be managed.

   [6 marks]

   (b)

   Evaluate the advantages and disadvantages of generating electricity using nuclear fission, considering both the chain reaction process inside the reactor and the issue of radioactive waste.

   [6 marks]

   Total for question 4: 12 marks

End of questions