Topic 6 - Radioactivity Flashcards
Background Radiation
- Constant emission of ionising radiation from space and environment
Origins of background radiation in Earth and Space
- Earth : Radon, Foods, X-rays, Gamma-rays, Cancer treatment
- Space : Cosmic Rays
How to detect radioactivity through Geiger-Muller Tube
- Radiation enter through tube and ionises gases inside, which forms a current to flow, which makes a clicking noise
How to detect radioactivity through Photographic Film
- The ionising radiation causes changes in the crystals in the film that can be seen
How is ionising radiation released?
- Unstable nuclei in a random process
Beta +/- is an electron emitted from the…
nucleus
The most ionising decay is…
alpha
The most penetrative decay is…
gamma
1st atomic model
Indivisible mass
2nd atomic model
JJ Thompson - Plum Pudding
3rd atomic model
Nuclear model
Modern atomic model
Bohr model
Beta +/- decay release what electric charges
minus = neutrons -> protons + electrons
plus = protons -> neutrons + positron
All nuclear transmission charge and mass numbers
Alpha P=-2 M=-4
Beta - P=1 M=0
Beta + P=-1 M=0
Gamma P=0 M=0
Neutron P=0 M=-1
Uses of radiation:
- Smoke alarm
- Irradiating food
- Sterilisation of equipment
- Tracing and gauging thicknesses
- Diagnosis and treatment of cancer
How do smoke alarms work?
- Smoke enters alarm
- Breaks circuit formed from radiation
- Bell rings
Precautions taken to ensure safety of people exposed to radiation
- Keep distance
- Reduce time
- PPE (e.g. radiation suit)
- Store underground
Contamination
- Unwanted radioactive materials in or on a body
Irradiation
- Body exposed to but not physically touching
Properties of External Radiation
- Radioactive isotope from machine out of body
- Very precise
- Takes many sessions
- Causes skin irritation, fatigue and damage to nearby tissue
Properties of Internal Radiation
- Placed inside or near tumour
- Better for irregular shaped tumours or tumours in a vital location
- Short treatment (few sessions)
- Causes infections and damage to internal organs
Uses of radioactive substances in the diagnosis of medical conditions:
- Tracers : Emits radiation, which can be tracked to check if organs are working correctly
- PET Scanners: Provide detailed three-dimensional images of metabolic activity in tissues
Isotopes used in PET scanners have to be produced nearby because:
- Short half-life, so they decay quickly
What are the advantages of using nuclear power for electricity generation
Nuclear power stations:
- Produce no polluting gases
- Far less fuel required
- Highly reliable
What are the disadvantages of using nuclear power for electricity generation
Nuclear power stations:
- Produce radioactive waste which is dangerous and expensive to deal with
- Can have catastrophic consequences on the environment and people in the event of a nuclear meltdown
- Expensive start-up and shut down cost
Nuclear reactions can be used as:
- a source of energy
The products of nuclear fission are all:
- radioactive
How fission works:
- Neutron collides with large nucleus
- Nucleus splits
- 2 smaller daughter nuclei are released with 2 or more neutrons
- Gamma rays are emitted (energy released)
Principle of a controlled nuclear chain reaction:
- Using nuclear reactions to produce ongoing energy.
How is a nuclear chain reaction controlled?
- Neutron Moderator (slows down neutrons)
- Control Rods (absorbs excess neutrons)
Electricity is made from thermal energy from the chain reaction. How?
- Nuclear reactor generates thermal
- Boiler makes steam with thermal
- Turbine uses steam to turn thermal to kinetic
- Generator turns kinetic into electricity
What is a star’s energy source?
- Nuclear fusion
How fusion works:
- 2 smaller nuclei fuse to create a larger nuclei
- Results in a loss of mass
- Process releases energy
Nuclear fusion does not happen at low temperatures and pressures because:
- Protons repel and their kinetic energy won’t be high enough
The conditions of fusion is difficult to maintain for practical and economic use because:
- Such high temperatures and pressure required for fusion are hard to contain, meaning only a small amount of fusion occurs
