Uses of radioactive isotopes including safety precautions Flashcards
Radioactive substances decay at a rate we can determine, we can use them to discover how
old objects and animals are. The best-known example of this is ____________.
radiocarbon dating
All living things contain carbon. Plant gets this from atmospheric carbon-dioxide, which
they use in photosynthesis. Plant-eating animals get it from the plants they eat to build
their bodies. Meat eating animals get it from their prey. Most carbon is carbon – 12 ,
which is not radioactive. A __________ fraction is radioactive carbon – 14 , with a half-life of
5370 years. (It emits beta radiation)
tiny and fixed
When a living organism dies, the carbon – 14 in its
body _________. As time passes, the amount of radioactive carbon atom ________. If we can measure the
amount remaining, we can work out when the organism was alive.
decays, decreases
There are two ways to measure the amount of carbon – 14 present in an object.
• By measuring the activity of the sample using a detector such as a _______
• By counting the number of carbon – 14 atoms using a mass spectrometer
Geiger counter.
As a material moves above a ______ source, the particles that are able to penetrate it can be monitored using a detector
If the material gets thicker more particles will be __________, meaning that less will get through
If the material gets thinner the opposite happens
This allows the machine to make adjustments to keep the thickness of the material constant
Note: Devices like this use beta radiation because it will be ________ absorbed by the material
If __________ particles were used all of them would be absorbed and none would get through
If gamma were used almost all of it would get through and the detector would not be able to sense any difference if the thickness were to change
beta, absorbed,partially. alpha
__________ are radioactive isotopes that can be added to some fluid so that the flow of that fluid can be monitored.
Tracers
In medicine tracers can be added to the blood to check blood flow around the body and search for ___________________
In industry tracers may be added into an oil pipeline in order to check for any ________
blockages (blood clots), leaks
In all cases:
The amount used is kept to a to __________ reduce people’s exposure to radiation
Isotopes are chosen that have ________ half-lives of around a few hours: long enough to carry out the procedure, but not so long that they cause long-term harm
____________ is used as it is highly penetrating (you can detect it) and low ionising (minimising harm)
minimum,short, Gamma radiation
Medical instruments are sterilised by exposing them to __________
The _________ kill bacteria on the instruments and destroy viruses
____________ are far more effective at killing bacteria than either boiling water or chemical treatment and are able to penetrate the instruments reaching areas that may otherwise not be properly sterilised
gamma rays (all blanks)
Alpha, beta and gamma radiation can all damage living cells.
recall how?
Alpha particles, due to their
strong ability to ionise other particles, are particularly dangerous to human tissue. Gamma
radiation is dangerous because of its high penetrating power. However cells have repair
mechanisms that make ordinary levels of radiation relatively harmless.
What are the safety precautions when handling radioactive sources?
Store the sources in lead-lined boxes and keep at a distance from people
Minimise the amount of time you handle sources for and return them to their boxes as soon as you have finished using them
During use, keep yourself (and other people) as far from the sources as feasible. When handling the sources do so at arm’s length, using a pair of tongs
Why should be be precautionary in handling radioactive materials?
When radiation passes close to atoms the radiation can knock out electrons, ionising the atom
Ionisation can cause chemical changes in materials
If these chemical changes occur in living cells it can damage the cell and:
- Cause mutations
- Cause a cell to become cancerous
- Kill the cell
