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Radioisotopes in Industry

Radioisotopes in Industry

This project/demonstration will help students understand how radioisotopes are used in industry for gauging or other uses.


A) Lay a flashlight on a table. Darken the room and turn on the flashlight. Hold a sheet of paper in the beam of light (about one foot from the flashlight). How much light goes through the paper? Now hold two sheets of paper in the position. How much light goes through? Add sheets of paper until no light can be seen through the stack of papers.

Compare the light beam to particles or rays being given off by a radioactive isotope.

Ask students if they can explain how it might be used to gauge the thickness of metal, plastic, or paper coming from a manufacturing plant. [When the capability of a particular radioactive emission to penetrate a substance (metal, plastic, paper, etc.) is known, the amount of that emission that can penetrate a sample of the material can be used to determine the thickness of that particular sample.]

B) Place a transparent glass bottle or jar on the table. Direct the light beam from a flashlight through it. Hold a piece of paper on the side of the jar or bottle that is opposite the light source. Have someone fill the bottle with milk or a colored liquid while you observe the light coming through (onto the paper, or even through the paper).

By watching the light that comes through the bottle, is it possible to determine the height of the liquid in the bottle?

Ask students to describe how radiation might be used to operate an automatic shut-off valve for a tank being filled with liquid. [With no liquid in the tank, the radioactive emissions could easily travel from one side to another. As the tank filled, some of the emissions would (potentially) be blocked by the liquid. It would be possible to set the shut-off valve to operate when the radioactive emissions fail to penetrate or move across the tank.]

Variation: If you have a Geiger counter and a radioactive source, you can try adapting this activity using a radioactive source rather than a beam of light. Some possible radioactive sources include:  beta or gamma discs from a science supplier; a piece of red Fiestaware (which gives off alpha, beta and gamma radiation); a camping lantern mantle (with thorium in it). You will use the Geiger counter to measure the radiation that passes through either the paper or the jar. Before utilizing this variation in class, you will need to experiment to determine what distances to use between the radiation source and the Geiger counter for observable results. You may want to consider using both the light beam and the radiation sources for the demo – the visible light to provide a “model” and the radiation for a more direct demonstration

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