Background radiation Flashcards
where does background radiation come from
- natural sources such as rocks and cosmic rays from space
- man-made sources such as the fallout from nuclear weapons
testing and nuclear accidents.
dose of radiation is measured in
Radiation dose is measured in sieverts (Sv)
1000 millisieverts (mSv) in Sv
1000 millisieverts (mSv) = 1 sievert (Sv)
How might the level of background radiation you are exposed to be affected by
The level of background radiation and radiation dose (you are exposed to) may be
affected by occupation and/or location
people living in certain parts of the uk experience a greater level of background radiation e.g. people living in regions with large amounts of granite e.g. Cornwall, Northern Scotland
people working in certain occupations can experience greater levels of background radiation
cabin crew and airline pilots may be exposed to higher levels of cosmic radiation
HOW TO DETECT THE RADIATION RELEASED
USING A GEIGER-MULLER TUBE
Explain why the geiger muller tube still gives a reading, if there is no radioactive isotope near
This is because there is radiation all around us, all the time
What is background radiation
The radiation which surrounds us at all times, arising from both natural and man-made sources
State some natural sources of background radiation
(radioactive) rocks - including granite - we find it in the ground - (in some parts of uk such as cornwall this can be a major source of background radiation)
cosmic rays from space - cosmic rays (very high energy particles which travel through space and crash into the Earth’s atmosphere)
– radiation from space
state some man-made sources of background radiation
fallout from nuclear weapons - nuclear weapons testing has released radioactive isotopes into the environment for decades.
nuclear accidents - radioactive isotopes are released by accidents at nuclear power stations
explain why the hazards associated with
radioactive material differ according to the half-life involved.
A short half life means the activity falls quickly - because the nuclei are very unstable and rapidly decay
Sources with a short half-life can be dangerous because of the high amount of radiation they emit at the start, but they quickly become safe
A long half life means the activity falls more slowly because most of the nuclei don’t decay for a long time - the source just sits there, releasing small amounts of radiation for a long time.
This can be dangerous because nearby areas are exposed to radiation for (millions of) years
what are nuclear radiations used for
Nuclear radiations are used in medicine for the:
- exploration of internal organs
- control or destruction of unwanted tissue
describe how nuclear radiations are used in medicine for the exploration of internal organs
Radioactive tracers are used to in the exploration of internal organs
This can be very useful .E.g. to check whether an organ is functioning properly or to see if a cancer has developed
Certain radioactive isotopes can be injected into people (or swallowed) and their progress around the body can be followed using an external detector. A computer converts the reading to display where the strongest reading is coming from.
A tracer is a radioactive isotope that can be used to track the movement of substances, like blood, around the body
Iodine-123 is a radioactive isotope, commonly used as a tracer in medicine
Describe how iodine-123 can be used to detect whether the thyroid gland is absorbing as it normally should do
Iodine-123 is absorbed by the thyroid gland just like normal iodine-127 but it is radioactive and gives out gamma radiation
This radiation can be detected outside the patient
The radiation produced can be monitored to see if the thyroid gland is working correctly
(if the scan shows that the thyroid has absorbed too much or too little iodine then the doctor can use this diagnose the patient’s condition)
Issues to consider when using radioactive tracers
The tracer must emit radiation that can pass out of the body and be detected (usually tracers emit gamma or beta radiation - alpha emitters are not used as tracers, as alpha particles will not pass out of the body)
The tracer must not be strongly ionising to minimise damage to body tissue ( this makes gamma emitters good tracers
The tracer must not decay into another radioactive isotope
The tracer must have a short half-life so it not present in the body for a long period. (so radioactivity inside the patient quickly disappears)
How can a tracer be used to detect a leak in a pipe
A leak in an underground industrial pipe can be found by adding a radioactive tracer to the liquid in the pipe.
This radiation travels through the pipe
A detector is moved along the ground above where the pipe
is buried.
The count rate will be found to increase where
the pipe is leaking as a larger amount of liquid containing the
radioactive tracer will collect there.
the radiation from the radioactive source will be picked up above the ground, enabling the leak in the pipe to be detected.
What type of Radioactive Tracer is used to Detect Leaks?
The radioactive tracer would need to be a gamma emitter.
Gamma rays can penetrate through the ground (and metal pipe)
and be detected at the surface. Alpha and beta radiation would
not penetrate through to the surface and could not be detected.
The gamma emitter tracer would have a short half-life
to minimize the danger to living organisms near to the pipe.
A short half-life means that the amount of radioactivity
being emitted from the tracer in the pipe would decrease quickly.
Explain why radioactive isotopes that have very long half-lives do not make good tracers
This is because they continue to decay in the body for a long time, and it can cause significant damage to body tissue
The tracer must have a short half-life so it not present in the body for a long period. (so radioactivity inside the patient quickly disappears)
describe how nuclear radiations are used in medicine for controlling or destroying of unwanted tissue
Certain cancers can be destroyed using ionising radiation (since high doses of ionising radiation will kill all living cells - it can be used to treat cancers)
This is called radiotherapy
Gamma rays pass into the body and destroy the tumour (usually beta-emitters) can be put next to or inside tumours
Gamma rays are directed careful at just the right dosage to kill the cancer cells without damaging too many normal cells.
Radiation emitting implants
Problems with radiotherapy
Problems with this type of treatment is that healthy tissue may also be damaged as the radiation passes through the body.
Where can the radiation source be when undergoing radiotherapy
The source of radiation can be outside the body
The radiation source can be placed inside the body
What is the benefit of having the radiation source placed inside the patients body (for radiotherapy)
Benefit is that this radiation is targeted very precisely to the tumour.
There is less damage to healthy tissue
Disadvantage of radiotherapy
A bit of damage is done to the normal cells, which makes the patient feel very ill
But if the cancer is successfully killed off in the end, then its worth it
Risks to using radiation
Radiation can enter living cells and ionise atoms and molecules within them. This can lead to tissue damage
Lower doses tend to cause minor damage without killing the cells. This can give rise to mutated (mutant) cells which divide uncontrollably. This is cancer
Higher doses tend to kill cells completely, causing radiation sickness (leading to vomiting, tiredness and hair loss) if a lot of cells all get blasted at once)
What is nuclear fission
Nuclear fission is the splitting of a large and unstable nucleus (eg
uranium or plutonium).
What type of nuclear fission is rare
Spontaneous fission is rare.
For fission to occur, what must the unstable nuclear do first
Spontaneous fission is rare.
Usually, for fission to occur the unstable nucleus must first absorb a neutron
Describe how a chain reaction is set up
When a uranium nucleus absorbs a neutron, this triggers the nucleus to undergo fission (split).
When the nucleus splits, it forms two smaller nuclei roughly equal in size (these nuclei are called the daughter nuclei)
It also emits two or three neutrons plus gamma radiation
Energy is also released during the fission reaction. All of the fission products have kinetic energy.
The neutrons (emitted during fission) can now be absorbed by more uranium nuclei and trigger fission again.
In a very short time a huge number of uranium nuclei have undergone fission and an enormous amount of energy has been released
This is called a chain reaction.
What is the result of a chain reaction
In a very short time a huge number of uranium nuclei have undergone fission and an enormous amount of energy has been released
Two types of chain reactions
Controlled chain reaction
Uncontrolled chain reaction
What is a controlled chain reaction used for
The chain reaction is controlled in a nuclear reactor to control the
energy released (in a nuclear reactor).
What is an explosion in a nuclear weapon caused by
The explosion in a nuclear weapon is caused by an uncontrolled fission chain reaction.
What is nuclear fusion
Nuclear fusion is the joining of two light nuclei (e.g. hydrogen) to form a heavier nucleus.
What could happen during nuclear fusion
In this process some of the mass (of the nuclei) may be converted into the energy, which is released as radiation.
Explain the difference between nuclear fusion and nuclear fission
Nuclear fission is the splitting of a large and unstable nucleus (eg
uranium or plutonium).
Nuclear fission is the opposite of nuclear fission
Nuclear fusion is the joining of two light nuclei (e.g. hydrogen) to form a heavier nucleus.
Describe how fusion works
In nuclear fission, two light nuclei collide at high speed and join (fuse) to create a form a larger, heavier nucleus
Example of a nuclear fusion reactor
Hydrogen nuclei can fuse to produce a helium nucleus
Explain why , in nuclear fusion, the heavier nucleus does not have as much mass as the two separate light nucleus did
In this process some of the mass (of the nuclei) was converted into the energy, which is released as radiation.
Which releases more energy, nuclear fission or nuclear fusion
Nuclear fusion releases more energy than nuclear fission (for a given mass of fuel)
