5 — Nuclear Physics (2026–2028 Revised Additions)
Updated Terminology and Definitions
- Isotopes — atoms of the same element having equal numbers of protons but different numbers of neutrons.
- Nuclide notation — used to represent isotopes clearly, with the mass number (A) at the top left and atomic number (Z) at the bottom left of the chemical symbol.
-
Example:
¹⁴₆C(carbon-14) → mass number 14, atomic number 6. - Nuclear energy is the energy stored in the nucleus of an atom, released in nuclear reactions such as fission or fusion.
Clarifications on Half-Life and Radioactive Decay
- Half-life is constant for each isotope and is unaffected by temperature, pressure, or chemical state.
- The radioactive decay process is random and spontaneous — individual decays cannot be predicted.
- New syllabus stresses understanding of probabilistic decay behaviour and the use of decay graphs to determine half-life.
Radiation Safety — Updated Guidance
- Emphasis on contamination control — avoid allowing radioactive material to come into contact with skin or clothing.
- When handling sources, use tongs and wear protective gloves.
- Store all radioactive sources in lead-lined containers labelled with the hazard symbol.
- Minimise exposure using the TDS principle — Time, Distance, and Shielding.
New Additions to Isotope Applications
| Field | Isotope Example | Type of Radiation | Purpose |
|---|---|---|---|
| Medicine | ⁹⁹ᵐTc (Technetium-99m) |
Gamma (γ) | Used as a tracer for imaging organs such as the liver and kidneys. |
| Medicine | ⁶⁰Co (Cobalt-60) |
Gamma (γ) | Employed in radiotherapy for treating cancers. |
| Industry | ²⁴Na (Sodium-24) |
Gamma (γ) | Used to detect leaks in pipelines. |
| Archaeology | ¹⁴C (Carbon-14) |
Beta (β⁻) | Determines age of ancient organic remains (carbon dating). |
| Engineering | ¹³¹I (Iodine-131) |
Gamma (γ) | Used in the diagnosis and treatment of thyroid disorders. |
Revised Safety and Handling Wording
- Radiation exposure should be kept As Low As Reasonably Achievable (ALARA).
- Distinguish between irradiation and contamination.
- Workers in radiation zones should wear film badges to track exposure levels.
- Lead screens and remote handling tools reduce direct exposure effectively.
Modern Nuclear Energy Notes
The revised section emphasises the importance of nuclear fission and nuclear fusion as energy sources.
- Fission: A heavy nucleus (like uranium-235) splits into two lighter nuclei, releasing energy and neutrons.
- Fusion: Two light nuclei (like hydrogen isotopes) combine to form a heavier nucleus, releasing energy.
- Fusion requires extremely high temperatures and pressures, as found in stars.
Environmental and Safety Considerations
- Used nuclear fuel and waste remain radioactive for long periods and must be safely stored.
- Shielding and controlled disposal prevent environmental contamination.
- Fusion energy offers a cleaner alternative but remains under experimental research (e.g., ITER project).
Summary of Key Updates
| Topic Area | Old Syllabus (2023–2025) | Updated (2026–2028) |
|---|---|---|
| Notation | Simple symbol form (e.g., C-14) | Full nuclide notation (¹⁴₆C) |
| Safety | Basic time, distance, shielding | Added contamination, ALARA principle, and film badges |
| Isotope Applications | Basic medical and industrial examples | Expanded to include tracers, leak detection, archaeology |
| Energy Topics | Brief mention of fission | Detailed contrast of fission vs. fusion with environmental focus |
Explore more at Smart Exam Resources.