Uses & Dangers of Radiation Flashcards
All 30 cards in this deck
What two kinds of harm can ionising radiation do to living cells?
It can damage/kill cells (tissue damage) and cause mutations in the DNA, which can lead to cancer.
What is a mutation caused by ionising radiation?
A change to the DNA of a cell, which may make the cell divide uncontrollably (cancer) or be passed on to offspring.
Name three precautions a worker can take to reduce their radiation dose from a source.
Shielding (lead box/barrier), limiting the time of exposure, and staying at a greater distance (e.g. using tongs).
Why are radioactive sources kept in lead-lined boxes when not in use?
Lead absorbs the radiation, so the dose to people nearby is reduced.
True or false? A radiation monitoring badge protects the person wearing it from radiation.
False. It only measures and records the dose they have received, so exposure can be checked.
How is the radiation dose to a patient kept as low as possible during a diagnostic scan?
Use the smallest activity that still gives a clear result, and an isotope with a short half-life so it soon decays away.
What is irradiation?
Being exposed to radiation from a source outside the object or person; no radioactive material is transferred.
What is radioactive contamination?
Radioactive material getting onto or inside an object or person, where it keeps decaying.
True or false? An object that has been irradiated becomes radioactive.
False. Irradiation does not transfer any radioactive material, so the object is not radioactive afterwards.
True or false? The hazard from irradiation stops as soon as you move away from the source.
True. Moving away (or shielding the source) stops the exposure, unlike contamination which travels with you.
Why is contamination by an alpha emitter especially hazardous?
Inside the body there is no skin or air to absorb the alpha particles, and alpha is highly ionising, so it damages nearby cells.
Which type of radiation is the greatest hazard from a source outside the body, and why?
Gamma (and beta), because it is penetrating enough to pass through skin and reach organs; alpha is stopped by the skin.
What type of source is used in a household fire (smoke) alarm, and how does it work?
An alpha emitter: alpha ionises the air so a small current flows; smoke absorbs the alpha, the current drops and the alarm sounds.
True or false? Food that has been irradiated with gamma rays becomes radioactive.
False. Irradiation kills bacteria so the food keeps longer, but leaves no radioactive material in the food.
Why is gamma radiation used to sterilise medical equipment?
It kills bacteria and other microorganisms, and is penetrating enough to work through sealed packaging without heating the equipment.
Which type of source is used to gauge the thickness of paper or metal foil, and why?
A beta emitter: some beta passes through, so the count rate reaching the detector changes if the thickness changes.
Which type of source is used as a tracer to find a leak in an underground pipe, and why?
A gamma emitter, because gamma can penetrate the pipe and soil to be detected at the surface above the leak.
Why is a source with a very short half-life hazardous?
Its activity is very high, so it emits a lot of ionising radiation in a short time.
Why is a source with a very long half-life hazardous?
It stays radioactive for a very long time, so it remains a hazard and must be stored or disposed of safely for years.
What half-life is suitable for an isotope injected into a patient as a tracer?
A few hours: long enough for the scan to be taken, but short enough that it soon decays away inside the patient.
True or false? A medical tracer should have a half-life of several days.
False. It would stay in the body too long, giving the patient an unnecessarily high dose.
Why is an isotope with a half-life of a few minutes unsuitable for a scan lasting 30 minutes?
It decays too quickly to give a reading for the whole scan.
Why does a thickness gauge in a factory use a source with a very long half-life?
So the count rate stays steady over time and the source does not need replacing or recalibrating often.
Why is an alpha source used inside the body to treat a tumour?
Alpha has a short range and low penetration (it is highly ionising), so it must be placed close to the tumour and damages little healthy tissue.
Why can a gamma source be used outside the body to treat a tumour?
Gamma is highly penetrating (weakly ionising), so it passes through the skin and reaches the tumour from outside.
What is a radioactive tracer used in medical diagnosis?
A radioactive substance injected or swallowed, whose radiation is detected outside the body to show how an organ is working.
What does a PET scanner detect?
Gamma rays produced when positrons emitted by the tracer annihilate with electrons in the body.
Why must an isotope used in a PET scanner, such as fluorine-18, be produced close to the hospital?
It has a short half-life, so it must be used as soon as possible after making or it decays too much during transport.
When using a Geiger–Müller tube to compare the count rates from two radioactive sources, what extra count must be measured and allowed for?
The background count rate, measured with no source near the tube, then subtracted from each reading.
True or false? When placing a radioactive source in front of a Geiger–Müller tube, it should be picked up with tongs and held at arm's length rather than with bare fingers.
True. Tongs increase the distance from the source and stop it touching the skin, reducing dose and avoiding contamination.