1. Uses of radioactive sources
Radioactivity 5
Uses of radioactive sources

2. Using Gamma Rays
A patient is injected with a radioactive tracer that emits gamma rays.
The gamma ray is electromagnetic radiation of very high penetration power.

3. Using Gamma Rays
Therefore more rays exit the body and are available for detection than interact with the patient's tissue.
These can be detected by a gamma camera and the concentration of radioactive tracer in various parts of the body can be ascertained.

5. Radiotherapy
Smoking kills – in a terrible way sometimes - the image on the next slide shows a smoking related oral cancer emerging from the throat of the patient in its late stage

6. Radiotherapy High doses of ionizing radiation can kill cells;
They are used to kill cancer cells and harmful microorganisms.

7. Radiotherapy
Tumours can be treated using gamma rays (nuclear radiation) or high energy X-rays (which can have the same wavelength as gamma rays – but are not from the nucleus).
Definition: tumour n. (US tumor) a swelling, especially from an abnormal growth of tissue, whether benign or malignant.
It comes from the Latin tumor from tumere ‘ to swell’

8. Radiotherapy
Cells that divide rapidly are more prone to damage by high-energy electromagnetic radiation.
This means that tumour cells are more radiosensitive than their normal counterparts.
Definition: tumour n. (US tumor) a swelling, especially from an abnormal growth of tissue, whether benign or malignant.
It comes from the Latin tumor from tumere ‘ to swell’

9. Radiotherapy
By carefully aiming the rays at the tumour (gamma-ray beams directed from a multitude of angles that result in the maximum gamma ray intensity within the tumour) the harmful effect of the ionising radiation is kept to a minimum in the surrounding tissue.

10. Radiotherapy
This kind of treatment is most hazardous when a brain tumour is being irradiated and the surrounding tissue is vital for normal brain function.

11. Radiotherapy
Several treatments are usually given over a time period of several weeks to minimise the unpleasant side effects (most commonly nausea, sickness, and tiredness).

12. Radiotherapy
New methods of delivering radiation treatment have been developed
Interstitial radiation involves implanting radioactive chemicals (termed seeds) directly into a tumour.
Stereotactic radiosurgery delivers a high, single dose of radiation to a small, well-defined area.

13. Sterilisation of Food and Surgical Instruments
Food and surgical instruments can be irradiated with gamma rays to sterilize them
Gamma rays kill bacteria. Therefore irradiating food or surgical instruments is a good way of ensuring they are sterile.

14. Sterilisation of Food and Surgical Instruments
The gamma rays penetrate packaging, so the food or instrument can be sealed and then sterilized 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.

15. As radiation passes through a material it can be absorbed.
The greater the thickness of a material the greater the absorption.
The absorption of radiation can be used to monitor/control the thickness of materials.

16. The absorption of radiation can be used to monitor/control the thickness of materials
The more radiation that gets through, the thicker the barrier must be.
Circuitry can automatically adjust the roller settings so that a constant count is attained.

17. Alpha Uses Long half life:
Dating of rocks using Uranium-238/lead ratios 
Smoke detectors 
Gas lamp mantles 
Nuclear batteries  

18. Beta Uses Short half life
Tracers in industry - detecting leaks in pipes 
Long half life
Thickness control of very thin metal sheets, paper or cardboard in manufacturing and industry 
C-14 dating 
Emergency sign lighting 

19. Gamma Uses Short half life Medical tracer - used with gamma camera
Tracers in industry - detecting routes of underground rivers and streams 

20. Gamma Uses Long half life High activity - radiotherapy
High activity - sterilization 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 

21. Other Uses
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.

22. Other Uses
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.
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.

23. Nuclear Batteries
The Apollo Moon missions used a radioisotope thermal generator (RTG).
A rod of plutonium-238 weighing approximately 2.5 kilograms provides 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.

24. Smoke Detectors
Some smoke detectors contain a small amount of Americium-241, an alpha emitter (an low energy gamma emitter) with a half life of 460 years.
They consist of an ionization chamber linked to a simple electronic alarm circuit.

25. Smoke Detectors
The Americium ionizes the air between the plates, causing a current to flow.
Smoke entering the detector absorbs some extra alpha particles than the air would , lowering the current, and triggering the alarm.