Radiation Flashcards
State one detector of gamma radiation
- Photographic film
- GM tube
- Bubble chamber
State one source of gamma radiation
- Stars
- Some radioactive substances (e.g. Cobalt 60)
State one use for gamma radiation
- Used as a tracer in medicine
- Used to treat cancer
- Sterilisation of surgical operating instruments
- Gamma rays kill microbes and are used to keep food fresher for longer. This is known as “irradiated” food
- Checking for cracks in aeroplane wings and joints
What are the 3 types of ionising radiation?
- Alpha
- Beta
- Gamma
What is alpha radiation?
It is a helium nucleus
(2 protons and 2 neutrons)
What is beta radiation?
A fast moving electron
What is gamma radiation?
It is a high frequency, high energy wave and part of the electromagnetic spectrum
What is meant by ionisation?
It is the gain or loss of an electron from an atom
Which is the most ionising radiation?
alpha
Which is the least ionising radiation?
Gamma
State 3 detectors if ionising radiation
- Photographic film
- GM tube
- Scintillation counter
What will absorb alpha radiation?
A few centimetres of air or a sheet of paper
What will absorb beta radiation?
A few millimetres of aluminium
What will absorb gamma radiation?
Several centimetres of lead
What is meant by shielding?
Shielding means having something that will absorb radiation between you and the source of the radiation
What will the amount of shielding required depend on?
The amount of energy the radiation has
How can you reduce your exposure to radiation when you are working with it?
- Limit the time you have the source out (only get it when you need it)
- Only handle using tongs
- Keep the source at arms length
- Wash hands before & after use
- Do not eat while handling it
- Wear lead lined gloves/ apron and safety goggles
What is meant by background radiation?
It is the radiation that is all around us
State a source of man-made background radiation
- Nuclear weapons testing
- Waste from the nuclear power industry
- Medical uses: having an x-ray, CT scan, etc
State a source of natural background radiation
- Cosmic rays: radiation from the sun and outer space
- Radon gas: from rocks underground
- Food: can be slightly radioactive because of the soil it has been grown in
What is meant by absorbed dose?
The energy absorbed per unit mass (of tissue)
What is equivalent dose?
It is a way of taking into account the absorbed dose and the type of radiation you are exposed to
What is the radiation weighting factor?
A number which takes into account the type of radiation you are exposed to
What is the link between the radiation weighting factor and the ionisation caused by a source?
The more ionising the radiation, the higher the radiation weighting factor
What is meant by equivalent dose rate?
Equivalent dose absorbed per unit time
Give 2 uses for ionising radiation
- Gamma rays are used for radiotherapy which can treat cancer
- Thickness control of paper or metal sheeting
- Gamma can be used to sterilise medical instruments
- Radio-carbon dating
- Tracers - used in industry in pipes to detect cracks or in the human body to check for blockages
What is meant by the activity of a source?
It is the number of radioactive decays per second
What is meant by the half-life of a source?
It is the time it takes for the activity of a source to decrease by half
Describe how to calculate the half life of a source from a graph
- Choose a ‘nice’ starting value e.g. 20,000 Bq
- Find the time that this happens at e.g. 0 hours
- Once a half life has passed, the activity will be 20,000/2 = 10,000 Bq
- Find the time that this happens at from the graph - 12 hours
- Calculate the time for the change as 12 - 0 = 12 hours
What is meant by fission?
A nucleus of a large mass number splits into 2 nuclei of smaller mass numbers with the release of energy and neutrons
What is meant by fusion?
2 nuclei of smaller mass numbers combine to form a nucleus of larger mass number with the release of energy
What is the fuel in a nuclear fission reactor?
Uranium
How does a nuclear fission power station produce electrical energy?
- The reactor uses fission of uranium to produce large amounts of heat energy
- The heat energy is used to heat water
- The heated water turns into steam and is piped to a turbine
- The steam makes the turbine turn (heat energy transferred to kinetic energy)
- The turbine turns a generator to create electrical energy (kinetic energy transferred to electrical energy)
Give an advantage of producing electricity using a nuclear fission reactor
- Do not produce greenhouse gases
- Do not rely on fossil fuels which a in short supply
- Huge amounts of energy are produced from a small amount of fuel
- Small amount of waste produced
- Reliable source of energy (unlike solar or wind)
Give a disadvantage of producing electricity using a nuclear fission reactor
- The waste produced is radioactive
- It has to be stored safely for a long time
- Uranium in a non renewable fuel
- Risk of radioactive materials being released into the environment if there is an accident
- Expensive to decommission nuclear power stations at the end of their useful life
What are the products in a fission reaction in a nuclear reactor?
- Fission fragments (smaller mass nuclei/daughter nuclei)
- Heat energy
- More neutrons
What particles are found in the nucleus?
Protons and neutrons
What is the charge on a proton?
Positive
What is the charge on a neutron?
No charge
What is the charge on an electron?
Negative
In an atom, which particle orbits the nucleus?
Electron
What are the main parts of an atom?
See diagram
What is the charge on an alpha particle?
Positive
What is the charge on a beta particle?
Negative
What is the charge on a gamma ray?
No charge
What precautions should be taken when storing a radioactive source?
- Source should be clearly labelled as to type
- Stored in lead lined boxes
What is meant by corrected count rate?
It is when background radiation is subtracted from the radiation measured so that the reading is caused by the source only and not the background radiation
Which line on the graph represents the corrected count rate? Give a reason for your answer
The dotted red line
The corrected reading is lower than the other reading as background has been subtracted
The graph shows a 0 reading count rate. This is not possible as there is always background radiation present so must be the corrected graph
What is the annual effective dose of the average annual background radiation in the U.K.?
2.2 mSv
What is the annual effective dose limit for a member of the public?
1 mSv
What is the annual effective dose limit for a radiation worker?
20 mSv
What is the impact of ionising radiation on living cells?
It can kill them
State one method of monitoring exposure to radiation
Radiation film badge
Explain how a radiation film badge is used to monitor the exposure to radiation
The darker the photographic film turns on the badge, the more radiation it has been exposed to
State the equipment you would need to measure the half life of a source
- Timer
- GM tube and counter
- Source of radiation
Explain an experiment to measure the half life of a source
- With no source present, record the number of counts in 1 minute using the GM tube and counter.
- This is the background radiation.
- Put source in position.
- The stop clock and the counter are started at the same time
- Take a reading of the counts per minute every minute.
- Do this for 10 minutes
- The background radiation is subtracted from each of the readings so that the counts per minute for the source only are recorded
- A graph is plotted of counts per minute against time.
- The half-life is calculated from the graph
Where does the energy come from in a fission and a fusion reaction?
Some of the mass is converted into energy
What is meant by a chain reaction?
A neutron causes fission and releases more neutrons. The neutrons produced in the fission reaction go on to cause their own fission reactions
State 2 issues that must be overcome in fusion reactors
- The high temperatures required
- The high pressures required
Why is containment an issue for fusion reactors?
The high temperatures of the plasma would vaporise any materials that we currently know
State an advantage of a fission reactor
- Releases massive amounts of energy
- It is sustainable (unlikely to run out of fuel)
- No greenhouse gases
- No risk of meltdown
Explain how a fusion reactor could generate electrical energy
- At high temperature and pressure small nuclei join together
- This releases huge amounts of heat (nuclear energy transferred to heat energy)
- The heat energy is used to heat water and turn it into steam
- The steam is used to turn a turbine (heat energy transferred to kinetic energy)
- The turbine is used to turn a generator (kinetic energy transferred to electrical energy)
