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15 Cards in this Set

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What are short half life beta sources used for?
Tracers in industry - detecting leaks in pipes.

The half life needs to be short because you do not want to leave the radioactive material in the environment at a high intensity for very long. But it cannot be too short, otherwise you will not have time to find the leak!
What are short half life gamma sources used for in medicine?
As a medical tracer - used with gamma camera.
You need a short half life so that the patient does not have an excessive exposure to radiation. The half life of Tc99m is ideal - 6 hours is long enough for medical tests to be carried out but doesn't put the patient in too much risk.
What are short half life gamma sources used for in industry?
Tracers in industry - detecting routes of underground rivers and streams. Their penetrating power means you can detect their route even when they are quite deep underground.
The half life needs to be short because you do not want to leave the radioactive material in the environment at a high intensity for very long. But it cannot be too short, otherwise you will not have time to find the route the stream takes!
What are long half life beta sources used for?
Thickness control of very thin metal sheets, paper or cardboard in manufacturing and industry.

Emergency sign lighting
What are long half life alpha sources used for?
Smoke detectors
Gas lamp mantles
Nuclear batteries
Name an application of a long half life alpha source?
Dating of rocks using Uranium-238/lead ratios
Name an application of a long half life beta source?
C-14 dating
What are long half life gamma sources used for?
High activity - radiotherapy (killing of cancer cells by burning them with high doses)
High activity - sterilisation of medical surgical nstruments
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 in aircraft manufacture
Explain how nuclear radiation is used in the sterilization of 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.
Explain how nuclear radiation is used in 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.
Explain how nuclear radiation is used in 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. 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.
Explain how nuclear radiation is used in emergency 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.
Explain how nuclear radiation is used to check welds.
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.
Explain how nuclear radiation is used to check wear on moving parts
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.
Explain how nuclear radiation is used to detect leaks in a pipeline.
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.