The Health Hazards of Ionising Radiation
1)
- Ionising radiation can damage the molecules that make up the cells of living tissue. Cells suffer this kind of damage all the time for many different reasons. Fortunately, cells can repair or replace themselves given time so, usually, no permanent damage results.
- However, if cells suffer repeated damage because of ionising radiation, the cell ay be killed or the cell may start to behave in an unexpected way. We can call this effect cell mutation. Some types of cancer can happen because damaged cells start to divide
uncontrollably.
2)
- Different types of ionising radiation present different risks. Alpha particles may have the greatest ionising effect, but they have little penetrating power. This means that alpha source presents little risk, as alpha particles do not penetrate the skin. The problem occurs when alpha particles are taken into the body.
- Radiation will be close to many different cells and this may be damaged if exposure is prolonged.
- Alpha emitters can be breathed in or taken eating food.
- Radon gas is decay of radium and is an alpha emitter, therefore presents risk to smokers as they take smoke into their lungs.
3)
- Beta and gamma radiation to provide a serious health risk when outside the body.
- Both can penetrate the skin and flesh and can cause damage by ionisation.
- Gamma is the most penetrative.
- Damaged caused by gamma rays will depend on how much energy is absorbed by ionising atoms along their path.
- Gamma and beta emitters that are absorbed by the body present little risk than alpha emitters, because of their lower ionising power.
In all cases the longer the period of exposure to radiation, the greater the risk of serious damage.
Safe Handling of Radioactive Materials
Samples of radiation are stored in lead containers to block even the most penetrating form of radiation. The samples are handled using tongs and are kept as far from the body as possible.
Very energetic sources will be handled remotely by operators who are shielded by lead, concrete and thick glass viewing panels.
Nuclear waste must be stored in sealed containers that must be capable of containing the radioactivity for enormously long periods of time.
Structure of the Atom
● The proton and neutron are both found in the nucleus.
● A nucleon is the protons and the neutrons, and is always situated in the nucleus.
● Atomic number = how many protons each atoms contains.
● Nucleon number = how many protons and neutrons in the nucleus of an atom.
Half-life
Radioactive decay is random; you cannot tell when a particular atom will decay. However, because there are such a large number of particles, statistically we can measure the half-life of a sample. This is the amount of time, on average, it takes half of the initial number of radioactive particles to decay.
To measure the half-life of a sample, we:
- Measure background count
- Measure the activity of the sample over time
- Subtract background count from all measurements
- Plot a graph of activity against time
- Use the graph to calculate the half-life as an average
Radioactive Dating
We can use radioactivity as a kind of clock to find the age of a material. All organic materials take in carbon-14 during respiration. Once the material dies, this exchange ceases. We know the initial ratio of carbon-14 to carbon-12 to be 1:100,000. Hence, if we calculate the ratio of the material, now, we can see how much carbon-14 has decayed and if we know its half-life, how long this has taken.
Rocks are inorganic and are dated in a similar way since the isotope u-238 is radioactive and decays to lead over a half-life of 4,500,000,000 years.
Uses of Radioactivity
Using tracers in diagnosis
Radioactive isotopes are used as tracers to help doctors identify diseased organs. A radioactive tracer is a chemical compound that emits gamma radiation. The tracer is taken orally by the patient or injected. Its passage around the body can then be traced using a gamma ray camera.
Imaging techniques enable doctors to produce 3-D computer images of parts of a patient’s body.
Treatment
Radiation from isotopes can have various effects in the cells that make up our bodies. Low doses of radiation may have no lasting effect. Higher doses may cause the normal function of cells to be changed. This can lead to abnormal growth and caner. Very high doses will kill living cells.
One way of treating cancer can be done with chemicals containing radioactive isotopes. Unfortunately, the radiation kills healthy cells as well as diseased ones. To reduce the damage to healthy tissue, chemicals are used to target the location of the cancer. They may emit either alpha or beta radiation. 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.
Organic food
Plants and crops are sprayed with radioactive compounds to help them fight off bacteria and last longer without damaging or rotting.
Fire alarm
Radioactive emissions are used to complete an electric circuit. When smoke particles stop them, the fir alarm goes off.
Coal mines
Coal gives off radioactive emissions.
Detecting leaks
Radioactive emissions can be put in gas of water pipes. If there is a leak, the radioactive substance is given off as well. These emissions can be picked up using a Geiger-Muller counter and the leak can be detected.
Industry
Gamma radiography
A gamma ray camera is like the X-ray cameras used to examine the contents of your luggage at airports. A source of gamma radiation is placed on the sides of the object to be scanned and a gamma camera s placed on the other. Gamma rays are more penetrating than X-rays. They can be used to check for imperfections in welded joins and for the flaws in metal castings. 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 cumbersome equipment.
Gauging
In industrial processes, raw materials and fuel are stored in large tanks or hoppers. Radioactive isotopes are used to gauge, or measure, how much material there is in a storage vessel.
The coal absorbs a large amount of 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.
This method of gauging has several advantages over other methods. There is no contact with the material being gauged. Also, coal dust might cause false readings with an optical gauging system. Coal dust is much less dense than coal so the gamma ray system still works properly.
Tracing and measuring the flow of liquids and gases
Radioisotopes are used to track the flow of liquids in industrial processes. Very tiny amounts of radiation can easily be detected. Complex piping systems, heat exchangers in power stations, can be monitored for leaks. Radioactive tracers are even used to measure the rate or dispersal of sewage.
