4. Atomic structure (half-life, background radiation, nuclear fission and fusion) Flashcards
What is irradiation?
An object that has been exposed to ioinsing radiation
What are the uses for radiation?
- Producing electricty through nuclear fission
- Medical procedures including diagnosis and treatment
- Testing materials
- Determining the age of ancient artefacts
- Checking the thickness of materials
- Smoke detectors
How are alpha particles used in smoke detectors?
- Alpha particles are used in smoke detectors
- The alpha radiation will normally ionise the air within the detector creating a current
- The alpha emmiter is blocked when smoke enters the detector
- The alarm is triggered by a microchip when the sensor no longer detects the alpha radiation
How is gamma radiation used for in medical tracers?
- Radioactive isotope is either injected, or swallowed into the body
- Used as an external detector
What is the radius of an atom?
What can electrons do if the atom absorbs electromagnetic radiation?
Electrons can move from lower to higher energy levels
What happens when an atom emits electromagnetic radiation?
The electron returns back to the lower energy levels
What is activity?
The rate at which the source of an unstable nucleus decays
What is activity measured in?
Bequerels
How can you measure the activity of a radioactive source?
Using a gieger muller tube
What is count rate?
The number of decays recorded each second by a detector
What is ionising power?
When radiation collides with atoms that can cause atoms to lose electrons and form ions
What is the half-life of a radioactive isotope?
The time it takes for the number of nuclei in the isotope in a sample to half
How can you protect yourself against radiation?
Sheilding methods such as wearing: gloves, aprons and lead walls
Why does the object when being sterilised with radiation not become radioactive?
Because the object is just exposed to radiation, it does not come into contact with the actual radioactive isotope
What is a radiation monitor used to do?
It monitors how much radiation somebody has recieved. If they have recieved close to the maximum amount of radiation they can have, they will stop being exposed to it
What is radioactive contamination?
When unwanted radioactive isotopes end up on other materials
What is background radiation?
The radiation that is everywhere and all around us
What are examples of natural forms of background radiation?
- Radioactive rocks, granite
- Cosmic rays from space
What are examples of man made sources of background radiation?
- Fallout from nuclear weapons testing
- Nuclear accidents at nuclear power stations
What is the dose of radiation measured in?
Sieverts
What must radioactive tracers do/not do in order to be safe to use?
- They must not be strongly ionising
- They must have a short half-life
- They must emit radiation that can pass out of the body
What is nuclear fission?
- In nuclear fission the nucleus of large and unstable elements (eg. uranium and plutonium) splits
How does nuclear fission work?
- When a uranium nucleus absorbs a neutron this triggers the nucleus to undergo fission (split)
- When a nucleus splits it forms 2 smaller nuclei roughly equal in size
- It also emits 2 or 3 neutrons and gamma radiation
- Energy is also released during the reaction
- The neutrons emmited can now be absorbed by more uranium nuclei, triggering fission again
What is a chain reaction?
When the neutrons emmited during nuclear fission is absorbed by more uranium nuclei, triggering fission again
Where is controlled chain reactions used?
In a nuclear reactor
What is nuclear fusion?
- When 2 light nuclei are joined to form a heavier nucleus
- Some of the mass of the nuclei can be converted into energy which is released as radiation
