1. 1
   Scientists at an experimental fusion research facility are attempting to fuse light hydrogen nuclei together inside a specially designed reactor vessel, aiming to release energy in a controlled way.

   (a)

   Scientists at an experimental fusion research facility are trying to make hydrogen nuclei combine to release energy. What is nuclear fusion?

   [1 mark]

   • AThe splitting of a large unstable nucleus into two smaller nuclei
   • BThe joining of two light nuclei to form a heavier nucleus
   • CThe emission of an alpha particle from a heavy nucleus
   • DThe absorption of a neutron by a nucleus without any further change

   (b)

   When two light nuclei fuse together in the reactor, what happens to their combined mass?

   [1 mark]

   • AThe combined mass stays exactly the same as the sum of the two original nuclei
   • BThe combined mass increases because extra particles are created
   • CA small amount of the mass is converted into energy
   • DThe mass is converted entirely into light with no particles remaining

   (c)

   Explain, in terms of mass and energy, why energy is released when the two light nuclei fuse together in the reactor.

   [2 marks]

   Total for question 1: 4 marks

2. 2
   Engineers designing a controlled fusion reactor must heat the hydrogen fuel to extremely high temperatures and compress it to very high pressures inside a strong magnetic field before any fusion reactions can occur.

   (a)

   Engineers designing the fusion reactor must heat the hydrogen fuel to extremely high temperatures before fusion can take place. Why is such a high temperature needed?

   [1 mark]

   • ATo give the nuclei enough energy to overcome the electrostatic repulsion between them
   • BTo make the nuclei lose their electric charge completely
   • CTo reduce the mass of the nuclei so they fuse more easily
   • DTo slow the nuclei down so they collide gently

   (b)

   If the nuclei in the reactor do not have enough energy to overcome their mutual electrostatic repulsion, what happens?

   [1 mark]

   • AThe nuclei get close enough to fuse but release less energy
   • BThe nuclei undergo fission instead of fusion
   • CThe nuclei fuse instantly regardless of their energy
   • DThe nuclei repel each other before getting close enough to fuse

   (c)

   Explain why both very high temperature and very high pressure are needed for fusion to take place in the reactor.

   [2 marks]

   Total for question 2: 4 marks

3. 3
   A physics magazine article compares how the Sun generates energy through nuclear fusion in its core with how a nuclear power station on Earth generates energy through nuclear fission.

   (a)

   A physics magazine article compares energy generation by nuclear fusion with energy generation by nuclear fission. Explain how the fusion process differs from the fission process in terms of what happens to the nuclei involved.

   [3 marks]

   (b)

   Explain why the core of the Sun is able to sustain continuous fusion reactions, while achieving controlled fusion on Earth is so difficult.

   [4 marks]

   Total for question 3: 7 marks

4. 4
   An energy research organisation is investing heavily in developing controlled nuclear fusion power, hoping it could one day supply large amounts of electricity, and is assessing both the scientific challenges and the potential benefits compared with existing fission power stations.

   (a)

   An energy research organisation is investing heavily in fusion power research. Explain, using physics principles, why achieving controlled nuclear fusion on Earth is so difficult despite its potential to generate large amounts of energy.

   [6 marks]

   (b)

   Evaluate the potential advantages that commercially viable nuclear fusion power could offer compared with existing nuclear fission power stations.

   [6 marks]

   Total for question 4: 12 marks

End of questions