IGCSE Physics 0625 – Energy Resources: Nuclear Fusion
1.7.3 Energy Resources – Nuclear Fusion
Learning Objective
Understand that research is being carried out to investigate how the energy released by nuclear fusion can be used to produce electrical energy on a large scale.
What is Nuclear Fusion?
Nuclear fusion is the process in which two light atomic nuclei combine to form a heavier nucleus, releasing a large amount of energy. The most studied reaction for energy production is the deuterium‑tritium (D‑T) reaction:
\$^21\text{H} + ^31\text{H} \rightarrow ^4_2\text{He} + n + 17.6\ \text{MeV}\$
Energy released can be related to mass loss by Einstein’s equation \$E=mc^2\$.
Why Fusion Is Attractive for Power Generation
Fuel is abundant – deuterium from seawater and tritium can be bred from lithium.
Produces no long‑lived radioactive waste compared with fission.
Inherent safety – the reaction stops if confinement fails.
Very high energy density – far greater than chemical fuels.
Current International Research Projects
ITER (International Thermonuclear Experimental Reactor) – a tokamak being built in France, aiming to produce 500 MW of fusion power from 50 MW of input.
National Ignition Facility (NIF) – a laser‑driven inertial confinement facility in the USA, working toward achieving “ignition”.
Joint European Torus (JET) – the largest operational tokamak, providing valuable data for ITER.
China’s EAST and Korea’s KSTAR – superconducting tokamaks exploring long‑duration plasma confinement.
Key Technical Challenges
Achieving extremely high temperatures (≈100 million °C) so that nuclei have enough kinetic energy to overcome electrostatic repulsion.
Plasma confinement – keeping the hot plasma away from reactor walls using magnetic fields (tokamaks, stellarators) or inertial compression (laser beams).
Materials durability – walls must withstand intense neutron bombardment and heat flux.
Net energy gain – the reactor must produce more energy than is required to heat and confine the plasma.
How Fusion Energy Can Be Converted to Electricity
The basic scheme is similar to conventional thermal power stations:
Fusion reactions heat a blanket of lithium‑containing coolant.
The hot coolant produces high‑pressure steam.
Steam drives a turbine connected to an electrical generator.
Thus the fusion core provides the “heat source”, and the rest of the plant converts that heat to electricity.
Comparison of Major Energy Sources
Aspect
Fission
Fusion
Renewables (e.g., wind, solar)
Fuel Availability
Uranium, limited reserves
Deuterium (seawater) & lithium – abundant
Depends on location & weather
Radioactive Waste
Long‑lived, requires disposal
Short‑lived activation products
None (except manufacturing)
Safety
Risk of meltdowns, runaway chain reactions
Self‑limiting; reaction stops if confinement fails
Generally safe
Energy Density (J kg⁻¹)
≈\$8\times10^{13}\$
≈\$3\times10^{14}\$
≈\$10^{6}\$–\$10^{7}\$ (chemical)
Current Commercial Use
Yes (≈400 GW worldwide)
Research stage – no commercial plants yet
Growing rapidly
Future Outlook
If the technical challenges are overcome, fusion could provide a large‑scale, low‑carbon source of electricity for many decades. The next milestones include:
ITER achieving its first plasma (planned 2025) and later full‑power operation.
Demonstration of net‑positive energy gain (Q > 1) in a sustained experiment.
Development of commercial‑scale “Demo” reactors in the 2040s.
Suggested diagram: Schematic of a tokamak fusion reactor showing magnetic coils, plasma chamber, and blanket for heat extraction.
Key Points to Remember
Fusion combines light nuclei, releasing energy according to \$E=mc^2\$.
Research projects such as ITER aim to prove that fusion can generate more power than it consumes.
The main obstacles are achieving and maintaining the required temperature and confinement.
When successful, fusion could supply large amounts of clean electricity with minimal waste.