Uses of Nuclear Radiation

Academic Applications

Industrial applications

Medical Applications

Other Applications



Alpha
Beta
Gamma
Positron
Short half life
  • Tracers in industry - detecting leaks in pipes 
  • Tracers in botony experiments - e.g. phosphorus 32 is a beta emitter - taken up by the plant - can be detected outside the plant as beta penetrates thin plant structures easily - half life of 14 days makes it ideal for this.
Short half life
  • Medical tracer - used with gamma camera  
  • Tracers in industry - detecting routes of underground rivers and streams 
Short half life
  • Medical tracer - PET Scanning 
Long half life
  • Dating of rocks using Uranium-238/lead ratios 
  • Smoke detectors 
  • Gas lamp mantles 
  • Nuclear batteries  
Long half life
  • Thickness control of very thin metal sheets, paper or cardboard in manufacturing and industry 
  • C-14 dating 
  • Emergency sign lighting 
Long half life
  • High activity - radiotherapy  
  • High activity - sterilisation of medical surgical instruments 
  • High activity - irradiation of food to kill bacteria and prolong shelf life 
  • Thickness control of metal sheets (when too thick for beta) in manufacturing and industry 
  • Checking welds 

 
Academic Applications


The most common and accepted method of 'absolute geologic dating' (establishment of actual age) is based on the natural radioactivity of certain minerals found in rocks. As the rate of radioactive decay of any particular isotope is known, the age of a specimen can be worked out from the ratio of the remaining isotope and its decay product.

Dating of Igneous Rocks (Using Uranium Content)

Geologists use this method to date igneous rock samples. If you look carefully at the half-lives of isotopes in the Uranium series you appreciate that the Uranium has a much longer half-life than any of the others. See the Uranium decay series(4N+2).

So, by comparing the proportion of Uranium in the rock to the proportion of Lead produced by its decay you can work out how many half-lives it has been decaying.

Then by using the half-life of Uranium you can work out the time involved.
 

Percentage of Uranium
Percentage of Lead
Ratio of Uranium to Lead
Age (millions of years)
Initial Value
100.00%
0.00%
1:0
0
After one half-life
50.00%
50.00%
1:1
4,500
After two half-lives
25.00%
75.00%
1:3
9,000
After three half-lives
12.50%
87.50%
1:7
13,500
After four half-lives
6.25%
93.75%
1:15
18,000

 

Dating of Ancient Artefacts (Carbon Dating)

Carbon dating measures the remaining amount of the radioactive isotope carbon-14 in organic matter. It can be used to date specimens as old as 35,000 years.

During its lifetime a biological entity (plant or animal) takes an active part in the carbon cycle and it contains the same proportion of the isotope as the atmosphere does (about one ten millionth of the carbon is carbon-14).

The death of an organism terminates the incorporation of this isotope into the fabric of the entity. From the time of death onwards the proportion of carbon-14 decreases as it decays into nitrogen.

By calculating the ratio of C-14 to total carbon in a sample of the artefact it is possible to work out its age. The half-life of carbon-14 is 5,600 years.

E.g.

C-14 in total carbon
Age (years)
Initial Value 1 part in 10 million
0
After one half-life 0.5 parts in 10 million 
5,600
After two half-lives 0.25 parts in 10 million 
11,200
After three half-lives 0.125 parts in 10 million
16,800
After four half-lives 0.0625 parts in 10 million
22,400

 
Industrial Applications
Tracers in Industry
  • Leaks from a pipeline can be traced by adding a radioactive isotope into what ever it is carrying. The source must have a short half-life (a few hours) so that it can be detected as it passes through but not stay radioactive long enough to pose a health hazard.
  • Wear of moving parts can be tested by making the part radioactive and monitoring the proportion of worn parts in the lubricating oil by looking for the level of radioactivity in it. See this page.
  • A gamma source can be used to check welds in metal parts. It is used in a similar way to X-rays on a human body. A photographic plate is placed behind the weld. It is exposed more where the weld is weak.

Sterilisation of Food and Surgical Instruments
 
Gamma rays kill bacteria. Therefore irradiating food or surgical instruments is a good way of ensuring they are sterile. The gamma rays penetrate packaging, so the food or instrument can be sealed and then sterilised so that re-contamination cannot occur.

No radioactive source particles are allowed to get in touch with the irradiated substance. The source is sealed so that only gamma rays get out. Therefore the irradiated substance is sterile but NOT radioactive.

 

Thickness Control in Manufacturing

Automatic control over the thickness of paper in paper mills can be obtained by passing beta radiation through the paper and monitoring the count rate. An isotope with a long half-life is used so that the count-rate hardly changes with time. Electrical circuitry is then set up to ensure that a constant rate is maintained. If the rate is too low the rollers automatically move closer to each other (making the paper thinner) and vice versa.

 


 

Other Applications
Nuclear Batteries

The Apollo Moon missions used a radioisotope thermal generator (RTG). The NASA designation for the devices that powered the Apollo Lunar Surface Experiments Package (ALSEP) for missions 12, 14, 15, 16, and 17 was SNAP-27 (Systems for Nuclear Auxiliary Power model number 27). The energy source for this device was a rod of plutonium-238 weighing approximately 2.5 kilograms and providing a thermal power of approximately 1250W. Plutonium-238 is a non-fissile isotope of plutonium that decays by alpha particle emission with essentially zero associated gamma emissions.

Smoke Detectors

Some smoke detectors contain a small amount of Americium-241, an alpha emitter (and low energy gamma emitter) with a half life of 460 years. It consists of an ionisation chamber linked to a simple electronic alarm circuit The Americium ionises the air between the plates, causing a current to flow. Smoke entering the detector blocks some of the alpha particles, lowering the current, and triggering the alarm.
 

Gas Lamp Mantles

Many camping lantern mantles used to contain thorium (alpha emitter with a long half-life see decay series). It apparently improved the flame. This practice has been stopped but old stock may still be around.

 

 

Emergency Exit Sign Lighting

During a fire, it's necessary to make sure that emergency exit signs remain illuminated, even if the power goes out. Some signs have a battery-powered light. Others have used tritium, a beta-emitting isotope of hydrogen, with a half-life of 12.3 years.

'Glow In The Dark' Watches

 

All radium dial watches should be disposed of properly. Above is a demonstration of the radioactivity from a radium-containing 1950's Timex watch dial, using Geiger counter.

They also use tritium, see emergency exit signs above.

Vaseline Glass

Vaseline Glass is a particular color of yellow-green glass that is made by adding 2% Uranium Dioxide to the ingredients when the glass formula is made. The addition of the Uranium Dioxide makes the glass color yellow-green. It glows under ultraviolet rays

 

 

'Glow In The Dark' Clock Hands

Radium was painted on the hands of clocks, so they would glow in the dark. The radium was painted by women, who had the bad habit of licking the brush tips to form them, ingesting the radium. This resulted in illness. See Radium Dial Painting and Its Tragic Consequences

 

http://www.ans.neep.wisc.edu/~ans/point_source/AEI/sep96/Apollo.html

http://www.blackcatsystems.com/science/radiation.html

Medical Applications

Nuclear radiation is used in two ways in medicine:

- as a tracer (also see PET scans) - Radioactive isotopes and radioactively labeled molecules are used as tracers to identify abnormal bodily processes. This is possible because some natural elements tend to concentrate in certain parts of the body: iodine in the thyroid, phosphorus in the bones, potassium in the muscles. When a patient is injected with a radioactive element, a special camera can take pictures of the internal workings of the organ.

- as a medical treatment for cancer (radiotherapy)

 


 
Radioactive Tracer
Radioactive Treatment
Type of treatment Diagnostic Therapy
Aim of treatment To investigate the function of a part of the body by labelling a biologically useful compound with radioactive atoms To destroy malignant tumours with a high dose of radiation that will result in cell death
Type of dose administered Minimal dose to patient Maximum dose to affected part, minimum dose to surrounding tissue
Type of radiation used Gamma Rays Gamma Rays
Example of substances used Pure gamma emitters such as technetium 99m Pure gamma emitters such as cobalt 60 and caesium 137
Half life Short ( about 6 hours) Long (typically 5.3 years)
Treatment Radioactive substance is injected into the patient making him/her mildly radioactive. The nuclear radiation emitted is then 'viewed' using a gamma camera A strong radioactive source is used to deliver nuclear radiation to the affected part. If this is from outside the body the patient doesn't become radioactive BUT if it is from an implanted source (like a radioactive wire inserted into the tumour) the patient does become radioactive and usually has to stay in hospital until the source is removed.
What equipment is used? The 'hardware' in the hospital (a gamma camera) does not deliver radiation but detects it.  The hardware in the hospital (a LINAC - linear accelerator or Cobalt 60 unit) produces ionising radiation which is 'fired' at the patient.
How does the patient feel afterwards? After the investigation the patient does not feel unwell  After the treatment the patient may well feel unwell: sickness, nausea, exhaustion.
Is the patient radioactive afterwards? After the investigation the patient is still mildly radioactive and may need to avoid contact with pregnant women and young children for a couple of days to minimise any risk to them. He/she will be told not to use public transport or to go to public places to avoid inadvertent contact with such individuals. After the treatment the patient is NOT radioactive. He/she may see other people straight away (although feeling unwell may not wish to).

 
LOJ (February 2001) - revised February 2003