7 Applications of radioactivity Flashcards
How are radioactive isotopes used?
As tracers to help doctors identify diseased organs.
Which organs are we referring to?
Kidneys or the liver.
What is a radioactive tracer?
It is a chemical compound that emits gamma radiation.
How is the tracer taken?
The tracer is taken orally by the patient or injected.
How can you tell that the tracer is working?
The tracer’s journey around the body can be traced using a gamma ray camera.
How are compounds chosen for diagnostic tasks?
Different compounds are chosen for different diagnostic tests.
What is an example of how different compounds are chosen for the thyroid gland?
The isotope iodine-123 is absorbed by the thyroid gland in the same way as the stable form of iodine.
How does this isotope work in the thyroid?
The isotope decays and emits gamma radiation.
How can we then actually look at the thyroid gland?
A gamma ray camera can then be used to form a clear image of the thyroid gland.
What is the half life of iodine-123?
It is about 13 hours.
Why is the fact that its half-life is so short?
A short half-life is important as this means that the activity of the tracer decreases to a very low level in a few days.
What are the other isotopes that are used to image specific parts of the body?
Technetium-99 is the most widely used isotope in medical imaging.
What exactly does technetium do?
It is the most widely used isotope in medical imaging. It is used to help identify medical problems that affect many parts of the body.
Why are imaging techniques useful?
They enable doctors to produce three-dimensional computer images of a patient’s body.
What is said about radiation from isotopes and its effects on our bodies?
Radiation from isotopes can have various effects on the cells that make up our bodies.
What effect does a low dose of radiation have on us?
Low doses of radiation may have no lasting effects.
What effect does a high dose of radiation have on us?
May cause the cells to stop working properly as the radiation damages the DNA in these cells.
What can these high doses of radiation lead to?
Abnormal growths and cancer.
What effect do very high doses of radiation have on us?
They will kill living cells,
How can cancer be treated?
By surgery that involves cutting out cancerous cells.
What is another way of treating cancer?
Another way of treating cancer is to kill the cancer cells inside the body.
How is the treatment of cancer by killing the cells inside the body done?
This can be done with chemicals containing radioactive isotopes.
What is a disadvantage of using chemicals containing radioactive isotopes for cancer treatment?
The radiation kills healthy cells as well as diseased ones.
How can this disadvantage be limited?
To reduce the damage to healthy tissue, chemicals are used to target the location of the cancer in the body.
How do these chemicals work when targeting the location of cancer in the body?
They may emit either alpha or beta radiation.
Why does the fact that they emit either alpha or beta radiation advantageous?
Both these types of radiation have a short range in the body, so they will affect only a small volume of tissue close to the target.
Why is the radioisotope iodine-131 used in the treatment of various diseases in the thyroid gland?
It has a half-life of about eight days and decays by beta particle emission.
What can gamma radiation do?
It can kill bacteria and viruses.
What is bacteria?
Single-celled organisms, some types of which cause illness.
Bearing in mind its anti-disenfectant properties, what is gamma radiation used for?
It is therefore used to kill these microorganisms on surgical instruments and other medical equipment.
What is this technique called?
Irradiation.
During this technique, of irradiation, what happens to the items?
The items to be sterilised are placed in secure bags to ensure that they cannot be re-contaminated before use.
How are the items sterilised while in the bag?
The gamma radiation will pass through the packaging and destroy bacteria without damaging the item.
What does sterilised mean?
Made free of dirt and bacteria.
What can irradiation also be used for, apart from items?
Some food products are treated in a similar way to make sure that they are free from any bacteria that will cause the food to rot or will cause food poisoning.
How is the irradiation of food viewed by the public?
The irradiation of food is an issue that causes concern amongst the public and is not a widely used procedure at the present time.
What should irradiation not be confused with?
Irradiation such as the deliberate exposure of food products and surgical instruments to controlled amounts of radiation should not be confused with radioactive air contamination.
What happens if radioactive waste is accidentally released?
If radioactive waste is accidentally released either into the air or the sea it could result in fish, animals or agricultural crops being contaminated with radioactive material.
What is the correlation between irradiation and poisons?
Irradiation will not destroy any poisons that bacteria may have already produced in the food before it is treated.
How is radioactivity used in industry?
- Gamma radiography.
- Gauging.
- Tracing and measuring the flow of liquids and gases.
- Radiocarbon dating.
What is gamma radiography?
A gamma ray camera is like the x-ray cameras used to examine the contents of your luggage at airports.
How is gamma radiography carried out?
A source of gamma radiation is placed on one side of the object to be scanned and a gamma camera is placed on the other.
What is a characteristic of gamma rays in relation to those of x-rays?
Gamma rays pass through more objects than x-rays.
Therefore, how can gamma rays be used?
They can be used to check for faults in casting (making things out of metal) or welding (joining metal objects together).
What is an advantage of gamma radiography?
Without the technique, neither problem could be detected unless the welding or casting were cut through.
What is another advantage of gamma radiography?
An additional advantage of gamma radiography over the use of x-rays for this purpose is that gamma sources can be small and do not require a power source or large equipment.
Where are raw materials and fuels stored in in industrial processes?
Hoppers.
What is an image that shows how radioactive isotopes are used to gauge, or measure, how much material there is in a storage container?
What is an explanation of the readings in this image?
The coal absorbs a large amount of the radiation so the reading on the lower detector will be small. As the upper part of the hopper is empty the upper detector will have a high reading.
Why is gauging used?
This method of gauging has several advantages over other methods.
What are the advantages of gauging?
- There is no contact with the material being gauged.
- Coal dust may cause false readings with an optical gauging system.
- Coal dust is much less dense than coal so the gamma ray system still works properly.
What is another example of gauging?
Another example of gauging uses a similar process to monitor the thickness of plastic sheeting and film.
What does this method of gauging involving the thickness of plastic sheetings tell us?
The thicker the sheet, the greater the amount of radiation it absorbs and the amount passing through gets smaller.
Why is this method of gauging involving the thickness of plastic sheetings useful?
By measuring the amount of radiation that passes through the sheeting, its thickness can be closely controlled during manufacture.
How else are radioisotopes used?
They are used to check the flow of liquids in industrial processes.
What amounts of radiation can be detected by these radioisotopes?
Very tiny amounts of radiation can easily be detected.
What are some more advantages of using radioisotopes in the tracing and measuring the flow of liquids and gases?
- Complex piping systems, like those used in power stations, can be monitored for leaks.
- Radioactive tracers are even used to measure the rate of spread of sewage.
What is a diagram of radioactive tracers released with the sewage allow its spread to be monitored to make sure the concentration does not reach harmful levels in any area?
How is radioactive dating done?
A variety of different methods involving radioisotopes are used to date minerals and organic matter.
What are the methods of radioactive dating?
Radiocarbon dating.
What is radiocarbon dating?
It is used to find the age of organic matter - for example, from trees and animals - that were once living.
What does radiocarbon dating measure?
It measures the level of an isotope called carbon-14.
Where is carbon-14 found?
It is made in the atmosphere.
How is carbon-14 made in the atmosphere?
Cosmic rays from space are continually raining down upon the earth.
How do these cosmic rays cause different isotopes to be made?
These have a lot of energy. When they hit atoms of gas in the upper layers of the atmosphere, the nuclei of the atoms break apart. The parts fly off at high speed. If they hit other atoms they can cause nuclear transformations (changes) to take place.
What do these transformations do?
These transformations turn the elements in the air into different isotopes.
What is an example of this collision?
One such collision involves a fast-moving neutron striking an atom of nitrogen.
What is the nuclear equation for this collision with nitrogen?
14 1 14 1
7 N + 0 n —> 6 C + 1 p
What shows that the mass numbers are conserved?
Notice that, as in the other nuclear equations we have seen, the top numbers (which show the number of nucleons) add up to the same total on each side of the equation. This is because the mass number is conserved.
What else is conserved?
The bottom numbers - which show the amount of charge on the particles - are also conserved.
What is the result of the collision of a neutron with a nitrogen atom?
A nuclear transformation.
What is an explanation of how this is a nuclear transformation?
The nitrogen atom is transformed into an atom of the radioactive isotope of carbon, carbon-14.
What is important to mention about isotopes?
Isotopes of an element have the same chemical behaviour.
What do the isotope characteristics link about carbon-14 and carbon-12?
This means that the carbon-14 atoms react with oxygen in our atmosphere to form carbon dioxide, just like the much more common and stable isotope, carbon-12.
Where does this carbon dioxide go?
This carbon dioxide is then absorbed by plants in the process of photosynthesis.
What is photosynthesis?
The process in green plants that uses light from the sun to produce energy for the plant to grow.
What does this uptake of carbon dioxide through photosynthesis result in?
As a result, a proportion of the carbon that makes up any plant will be in the radioactive form, carbon-14.
How does carbon-14 enter the food chain?
Included in plant material, the radioactive carbon-14 enters the food chain.
What does the entrance of carbon-14 into the food chain mean for organisms?
Which means that animals and humans will also have a proportion of carbon-14 in their bodies.
What happens in terms of decay for carbon-14?
These carbon-14 atoms will decay but, in living plants and animals, they are continuously replaced by new ones.
When does the replacement of carbon-14 stop?
When an organism dies, the replacement process stops.
What is an example of the replacement process stopping?
As time passes, the radioactive carbon decays and the proportion of radioactive carbon in the remains of the plant or animal, compared with the stable carbon isotope, decreases.
What is an approximation for the half-life of the decay of carbon-14?
5600 years.
What does this half life of the decay of 5600 years mean?
This means that every 5600 years the proportion of carbon-14 in dead plant and animal material will halve.
How do you find out the amount of carbon-14 present in a sample of an animal?
It is found by measuring the activity of the sample.
After measuring the activity of the sample, how do we actually find out the amount of carbon-14 present?
You compare the measure of the activity of the sample with the amount of carbon-14 that would’ve been present when the sample was part of a living organism. From this, it is possible to estimate when the source of the sample died.
What is a disadvantage of the method of radiocarbon dating?
It assumes the level of cosmic radiation reaching the earth is constant, which is not necessarily accurate.
How do we deal with the limitation of carbon dating where it assumes that the level of cosmic radiation reaching the earth is not accurate?
The technique has been adjusted to take the variations of cosmic ray activity into account. This is done by testing samples of a known age, like materials from mummies of Egyptian pharaohs and from very ancient living trees.
What is the radiocarbon method used on?
It is not used to date samples older than 50 000 - 60 000 years.
Why is the radiocarbon method only used to date recent things?
This is because after 10 half-lives, the amount of carbon-14 remaining in samples is too small to measure accurately.
What are some of the dangers to health of ionising radiation?
Cell mutation.
Why does cell mutation happen?
Ionising radiation can damage the molecules that make up the cells of living tissues.
Is cell damage normal?
Cells suffer this kind of damage all the time for many different reasons.
Why is cell damage deemed to be normal?
Fortunately, cells can repair or replace themselves given time so, usually, no permanent damage results.
So, why is ionising radiation then so bad?
If cells suffer repeated damage because of ionising radiation, the cell may be killed. Alternatively, the cell may start to behave in a certain way because it has been damaged.
What do we call this effect on the cells?
Cell mutation.
What’s important to note about ionising radiation though?
Different types of ionising radiation pose different risks.
What are the characteristics of alpha particles?
Alpha particles have the greatest ionising effect, but they cannot pass through any materials.
What does an alpha particle’s inability to pass through any materials mean about their risk?
This means that an alpha source presents little risk, as they do not penetrate the skin.
When does alpha radiation become problematic?
The problem of alpha radiation is much greater if the source of alpha particles is taken into the body. Here, the radiation will be very close to many different types of cells and they may be damaged if the exposure is prolonged.
How can alpha emitters be taken in?
Alpha emitters can be breathed in or taken in through eating food.
What is an example of an alpha emitter?
Radon gas is a decay product of radium and is an alpha emitter.
What is a property of radon as it’s an alpha emitter?
It therefore presents a real risk to health.
Why are smokers more susceptible to alpha damage?
Smokers greatly increase their exposure to this kind of damagers as they draw the radiation source right into their lungs (cigarette smoke contains radon).
Are beta and gamma radiation like alpha radiation?
No, Beta and gamma radiation do provide a serious health risk when outside the body.
Why are beta and gamma radiation more dangerous outside the body?
Both can penetrate skin and flesh (body) and can cause cell damage by ionisation.
What is a characteristic of gamma radiation?
Gamma radiation, as we have mentioned earlier, is the most penetrating.
What will the damage caused by gamma radiation depend on?
The damage caused by gamma rays will depend on how much of their energy is absorbed by ionising atoms along their path.
In terms of outside the body, do beta and gamma particles present more of a risk or do alpha particles?
Beta and gamma emitters that are absorbed by the body present less risk than alpha emitters, because of their lower ionising power.
What is the general rule of thumb in terms of danger for all cases of radiation?
In all cases, the longer the period of exposure to radiation the greater the risk of serious cell damage.
How do workers in the nuclear industry stay safe?
Workers in the nuclear industry wear badges to indicate their level of exposure.
What are the type of badges that they wear?
- Photographic film.
- Thermoluminesence.
What are these photographic film badges and how do they work?
Some are pieces of photographic film that become increasingly ‘foggy’ (unclear) as the radiation exposure increases.
What are these thermoluminescent badges and how do they work?
Another type of badge uses a property called thermoluminescence.
Thermoluminescence means that the exposed material will give out light when it is warmed. The radiation releases energy to make heat so the thermoluminescent badges give out more light when exposed to higher levels of radiation.
How do these badges help keep the workers safe?
Workers have their badges checked regularly and this gives a measure of their overall exposure to radiation.
Why are the samples of radioactive isotopes so small in schools and colleges?
This is to limit the risk to users, particularly those who use them regularly - the teachers! Although the risk is small, certain precautions must be followed.
What are the precautions that must be followed with radioactive isotopes in schools and colleges?
- Lead lined containers.
- Labelled containers.
- Distance.
Why do we store the isotopes in lead-lined containers?
The samples are stored in lead-lined containers to block even the most penetrating form of radiation, gamma rays.
Why do we store the isotopes in labelled containers?
The containers are clearly labelled as a radiation hazard (danger) and must be stored in a locked metal cabinet.
What is different between the radioactive isotopes in schools and colleges and those in research laboratories?
In the nuclear industry and research laboratories, much larger amounts of radioactive material are used. These have to be handled with great care.
What do we mean by distance?
The samples are handled using tongs and are kept as far from the body as possible.
How are very energetic radiation sources handled?
Very energetic sources will be handled remotely by operators who are protected by lead shields, concrete and thick glass viewing panels.
What is stored underwater and why is it stored there?
As has been mentioned earlier, neutron radiation is absorbed by lighter elements and waste materials, like spent uranium fuel rods from nuclear reactors, are stored under water until the neutron radiation levels drop to a safe level.
What is the major problem with nuclear materials?
It is their long-term storage.
Why are their long-term half lives such an issue?
Some materials have extremely long half-lives so they remain active for thousands and sometimes tens of thousands of years.
Therefore, how do we store nuclear materials with long half-lives?
Nuclear waste must be stored in sealed containers that must be capable of containing the radioactivity for enormously long periods of time.
What are the problems arising from the disposal of radioactive waste and how can the associated risks be reduced?
Used fuel and other materials at nuclear power stations can be highly radioactive. This waste must be stored safely - if it leaks it would contaminate the surrounding air, ground or water. Highly radioactive waste can develop high temperatures as it decays, and needs cooling. Some have very long half -lives, and the waste will remain harmful for millions of years. This material must be encased in glass or metal containers and buried in managed areas deep underground.
