# KS5 Radioactivity

**Radioactivity & Nuclear Physics ****Learning Objectives**

**Learning Objectives**

**Content**

- Qualitative study of Rutherford scattering.
- Appreciation of how knowledge and understanding of the structure of the nucleus has changed over time.
- Graph of N against Z for stable nuclei.
- Possible decay modes of unstable nuclei including α, β+, β− and electron capture.
- Changes in N and Z caused by radioactive decay and representation in simple decay equations.
- Questions may use nuclear energy level diagrams.
- Existence of nuclear excited states; γ ray emission; application e.g. use of technetium-99m as a γ source in medical diagnosis.
- Estimate of radius from closest approach of alpha particles and determination of radius from electron diffraction.
- Knowledge of typical values for nuclear radius.
- Students will need to be familiar with the Coulomb equation for the closest approach estimate.
- Dependence of radius on nucleon number: R = R
_{0}A^{1/3}derived from experimental data. - Interpretation of equation as evidence for constant density of nuclear material.
- Calculation of nuclear density.
- Students should be familiar with the graph of intensity against angle for electron diffraction by a nucleus.
- Appreciation that E = mc
^{2}applies to all energy changes - Simple calculations involving mass difference and binding energy.
- Atomic mass unit, u.
- Conversion of units; 1 u = 931.5 MeV.
- Fission and fusion processes.
- Simple calculations from nuclear masses of energy released in fission and fusion reactions.
- Graph of average binding energy per nucleon against nucleon number.
- Students may be expected to identify, on the plot, the regions where nuclei will release energy when undergoing fission/fusion.
- Appreciation that knowledge of the physics of nuclear energy allows society to use science to inform decision making.
- Fission induced by thermal neutrons; possibility of a chain reaction; critical mass.
- The functions of the moderator, control rods, and coolant in a thermal nuclear reactor.
- Details of particular reactors are not required.
- Students should have studied a simple mechanical model of moderation by elastic collisions.
- Factors affecting the choice of materials for the moderator, control rods and coolant. Examples of materials used for these functions.
- Fuel used, remote handling of fuel, shielding, emergency shut-down.
- Production, remote handling, and storage of radioactive waste materials.
- Appreciation of balance between risk and benefits in the development of nuclear power.
- Their properties and experimental identification using simple absorption experiments; applications e.g. to relative hazards of exposure to humans.
- Applications also include thickness measurements of aluminium foil paper and steel.
- Inverse-square law for γ radiation: I = k/x
^{2} - Experimental verification of inverse-square law.
- Applications e.g. to safe handling of radioactive sources.
- Background radiation; examples of its origins and experimental elimination from calculations.
- Appreciation of balance between risk and benefits in the uses of radiation in medicine.
- Random nature of radioactive decay; constant decay probability of a given nucleus;
- ∆ N/∆ t = − λN
- N = N
_{0}e^{−λt} - Use of activity, A = λN
- Modelling with constant decay probability.
- Questions may be set which require students to use A = A
_{0}e^{−}^{λ}^{t} - Questions may also involve use of molar mass or the Avogadro constant.
- Half-life equation: T ½ = ln2/λ
- Determination of half-life from graphical decay data including decay curves and log graphs.
- Applications e.g. relevance to storage of radioactive waste, radioactive dating etc.