Definitions in Nuclear Energy
Fission- When a nucleus splits into two or more pieces usually after
bombardment by neutrons.
Fusion- A process taking place inside stars in which small nuclei are
forced together to make larger nuclei. Energy is released in the
process.
Chain reaction - A series of nuclear fissions that may or may not be
controlled. The neutrons that are released cause the reaction.
Critical Mass: Minimum mass of fissile material for a self-sustaining chain reaction |
Key Points in Nuclear Energy
Fission:
Used in nuclear reactors & bombs.
Releases 2-3 neutrons per event → can cause chain reaction.
Controlled with control rods (graphite/cadmium).
Fusion:
Powers the sun & stars.
More energy per nucleon than fission.
Hard to achieve on Earth due to electrostatic repulsion; needs high temp/pressure.
Binding Energy Graph:
Most stable nuclei: mass numbers 40–80 (e.g., iron-56).
Fusion: energy released for nuclei < iron.
Fission: energy released for nuclei > iron.
Australia:
1/3 of world’s uranium, no nuclear power plants.
Relies on coal & gas.
Risks of Nuclear Power:
Radioactive waste—long half-lives.
Security of uranium (weapons risk).
Accidents (Chernobyl, Fukushima).
Fusion Power:
Not yet practical; research ongoing (e.g., ITER, JET).
Goal: produce more energy than consumed. |
Activity Formula
Activity is measured in becquerel's (Bq)
1 Bq = 1 disintegration per second
Dose Formulas
Used to calculate radiation energy absorbed per kg of tissue.
Absorbed dose is measured in J/Kg or Greys (Gy).
Dose Formulas
Takes into account Absorbed Dose so that must be calculated first
Equivalent dose is measured in Sieverts (Sv).
Dose Formulas
Effective dose (in Sieverts) is found by calculating the sum of equivalent doses multiplied by the weighting factor, W, for each organ affected
e.g: .. = (0.04 x 1) + (0.01 x 1) +.... -> Each multiplication is a separate organ
Mass Defect
Used for E = mc2
E = binding energy (J)
m = mass defect
c = 3.0 x 108 ms-1
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Electron Volt
1 eV = 1.602 176 x 10-19 J |
KeV = 103, MeV =106, GeV = 109, TeV = 1012 |
Isotopes
Isotope: An atom with the same number of protons but different numbers of neutrons. |
Radioisotope: A radioactive isotope that are sometimes unstable. |
Atomic Notation
Mass Number (A) = Total number of protons & neutrons in the nucleus = Nucleons
Atomic Number (Z) = Number of protons in the nucleus
Radioactivity or Decay
Properties:
Alpha -> Heavy, slow-moving, double positive charge, low penetration, travels less than 10% of c
Beta -> Lighter than Alpha, fast-moving, travels up to 90% of c
Gamma -> High frequency, no charge, high penetration, travels 100% of c
Ionising Radiation
Alpha, beta, and gamma are all ionising radiation |
Alpha has the greatest ionising power, followed by beta, then gamma |
They are harmful to living things and have enough energy to remove outer-shell electrons to create ions |
There are two types of effects of radiation on living organisms: Somatic and Genetic
Effects of Radiation
Somatic (physical) effects arise when ordinary body cells are damaged and depends on the size of the dose. |
Genetic effects arise when the cells in the reproductive organs are damaged, genetic changes that happen in the developed ova or sperm could be passed on to a developing embryo. |
Radiation in Therapy
Radioisotopes are used in the diagnosis and treatment of cancer. |
Medical imaging is used in the diagnosis of different diseases. |
X-rays, CT, Gamma radiation scans, MRI, PET scans, SPECT are all examples. |
Cancer Treatment through Radiotherapy
Cobalt-60 external beam therapy: Gamma rays from C-60 source is directed through a patient into the tumour site. |
Tomotherapy |
The Gamma Knife: high dose of gamma radiation, treats brain tumours. |
Chemotherapy: radioisotope must have a short half-life, emit alpha or beta, and not too much gamma |
Brachytherapy: Kills abnormal cells using small wires/seeds |
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