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
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 gamma radiation?
Several centimetres of lead
What will absorb beta radiation?
A few millimetres of aluminium
What will absorb alpha radiation?
A few centimetres of air or a sheet of paper
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
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 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 meant by absorbed dose?
The energy absorbed per unit mass (of tissue)
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
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
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
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
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
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
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 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
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 radiation worker?
20 mSv
What is the annual effective dose limit for a member of the public?
1 mSv
State one method of monitoring exposure to radiation
Radiation film badge
What is the impact of ionising radiation on living cells?
It can kill them
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
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
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
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
What is activity
the number of nuclear disintegrations in a period of time.
How can activity be measured
Activity can be measured using a Geiger-Muller tube, also called a Geiger counter.
Activity=
number of disintegrations/time
Absorbed dose=
Energy/Unit mass of material
Equivalent dose=
Absorbed Dose x Radiation Weighting Factor.
When does a fusion reaction occur
Fusion reactions occur when two small nuclei combine and fuse together to form a larger nucleus. This causes a large release of energy.
This is the reaction that creates the energy within the Sun.
What are Fission reactions
Fission reactions are chain reactions, where a neutron collides with a large atom nucleus, releasing a large amount of energy and causing the nucleus to split into smaller atoms. More neutrons are released, causing more collisions with large nuclei.
This is the reaction harnessed in nuclear bombs.
