Uses and dangers of radioactivity Flashcards
what is irradiation?
Exposing objects to beams of radiation
why is irradiation safe for sterilisation?
it does not cause the irradiated object to become radioactive.
how are gamma beams controlled so that healthy cells are not damaged? (2)
-beams are aimed at the tumour from many different directions to maximise the dose on the tumour
-but to minimise the dose on the surrounding soft tissue.
how are the long term effects of irradiation reduced in medical applications? (3)
-nature of decay (alpha, beta or gamma)
-half life
-toxicity
what does the half life have to be? (2)
-long enough for the isotope to produce useful measurements,
-short enough for the radioactive sources to decay to safe levels soon after use
what would happen if the half-life was too long? (2)
-If the half-life chosen is too long, the damaging effects of the radiation would last for too long
-and the dose received would continue to rise.
what are the advantages of irradiation? (2)
-Sterilisation can be done without high temperatures.
-It can be used to kill bacteria on things that would melt.
what are the disadvantages of irradiation? (2)
-It may not kill all bacteria on an object.
-It can be very harmful - standing in the environment where objects are being treated by irradiation could expose people’s cells to damage and mutation.
what us contamination?
object has a radioactive material introduced into it.
In medical applications that involve injecting radioactive sources, how do we ensure that contamination does not cause any long term effects? (2)
-have very short half-life -so after a couple of days there will hardly be any radioactive material left in a person’s body
-are not poisonous
why is half-life crucial to predicting the reactivity of radioactive substances? (2)
-it cannot be predicted when a particular nucleus
will decay
-but half-life enables the activity of a very large number of nuclei to be predicted during the decay process
how do PET scanners work? (3)
-use a positron emitter as the contamination tracer.
-positrons emitted will react with electrons in the patient’s body
-and produce gamma rays which can be detected outside the body
why are tracers difficult to maintain? (2)
-have very short half-lives,
-need to be manufactured in the hospital and injected into the patient’s blood soon after manufacture.
how do we use Contamination to check for leaks?
Water supplies can be contaminated with a gamma-emitting radioactive isotope to find leaks in pipes.
how do we identify the leak using contamination? (4)
-Where there is a leak, contaminated water seeps into the ground,
-this causes a build-up of gamma emissions in that area.
-The build-up of gamma emissions can be found using a Geiger-Muller tube,
-this makes it easier to decide where to dig to find the leak.
what must the isotopes used for checking leaks be? (3)
-be a gamma emitter
-have a half-life of at least several days to allow the emissions to build up in the soil
-not be poisonous to humans as it will form part of the water supply
advantages of contamination: (3)
-Radioactive isotopes can be used as medical and industrial tracers
-Use of isotopes with a short half-life means exposure can be limited
-Imaging processes can replace some invasive surgical procedures
disadvantages of contamination: (3)
-Radioactive isotopes may not go where they are wanted
-It can be difficult to ensure that the contamination is fully removed so small amounts of radioisotope may still be left behind
-Exposure to radioactive materials can potentially damage healthy cells
does the object become radioactive with irradiation and contamination? (2)
irradiation: Doesn’t cause the object to become radioactive
contamination: A contaminated object will be radioactive for as long as the source is on or in it
can irradiation and contamination be blocked? (2)
-irradiation: Can be blocked with suitable shielding
-contamination: Once an object is contaminated, the radiation cannot be blocked
can an object be cleared of radiation with irradiation and contamination? (2)
-irradiation: Stops as soon as the source is removed
-contamination: It can be very difficult to remove all of the contamination
why are alpha particles used in smoke alarms?
they are easily absorbed
why is radiation used to gauge the thickness of a material? (2)
-it is absorbed as it passes through materials
-thickness is measured by measuring the amount of radiation that passes through
state the effects of radiation on the eyes and thyroid: (2)
Eyes: High doses can cause cataracts
Thyroid: Radioactive iodine can build up and cause cancer
