CHAPTER 6: NUCLEAR ENERGY

6.3.USES OF RADIOACTIVE SUBSTANCES

5 main categories of the uses radioactive substances

In industry

In food technology

In archaeology

In medicine

In agriculture

6.3.1 Controlling the thickness of substances

To control the thickness of paper, aluminium foil and other sheets during the manufacturing process.The amount of radioactivity which passes through a materialcan be detected and used to control the thickness of the material.

In paper mills, the thickness of the paper can be controlled by measuring how much beta radiation passes through the paper to a Geiger counter.

The radioactive source is a b emitter (beta emitter).This has the right amount of penetration to be usefulfor thickness control of aluminium foil.

The counter controls the pressure of the rollers to give the correct thickness. With paper, or plastic, or aluminium foil, beta rays are used, because it will not go through the paper.

6.3.2 Food preservation

Ready made food must be preserved

from deterioration due to bacteria and so on before being shipped

to consumers.

Irradiate the food with

gamma radiation

Even after it has been packaged, gamma rays can be used to kill bacteria, mould and insects in food. This process prolongs the shelf-life of the food, but sometimes changes the taste.

As tracers in medical diagnosis

6.3.3 Radioactive tracer

Tracers: bone scans, kidney scans,and others. Radioactive isotopes andradioactively labeled molecules areused as tracers to identify abnormalbodily processes. This is possiblebecause some natural elements tendto concentrate in certain parts of thebody: iodine in the thyroid,phosphorus in the bones, potassiumin the muscles. When a patient isinjected with a radioactive element,a special camera can take pictures ofthe internal workings of the organ.

To detect leakage of liquids, such as water and oil, from underground pipes

A little radioactive

substance is added to the liquid at the

source

Using a radiation detector , the

level of radiation at the surface is

monitored

The radiation rate will be high

at the point where there is

leakage

6.3.4 Radioactive dating

Animals and plants have a known proportion of Carbon-14 (a radioisotope of Carbon) in their tissues.When they die they stop taking Carbon in, then the amount of Carbon-14 goes down at a known rate (Carbon-14 has a half-life of 5700 years). The age of the ancient organic

materials can be found by

measuring the amount of Carbon-

14 that is left.

The radioactive source would be a g emitter (gamma emitter).

g radiation can penetrate through the ground (and metal pipe)and be detected at the surface.

Alpha and beta radiation would not penetrate through to the surface.The g emitter would have a short half-life to minimize the possible danger to living organisms near to the pipe.

A short half-life means that the amount of radioactivitybeing emitted from the pipe would decrease quickly.

Radiations can also be used to kill cancerous cells in patient’s body

Called as (Radiotheraphy)

Usually beta ray are used

Gamma rays are also used to irradiate the affected region of a patient from the outside

6.3.5 Destroying cancer cells (Medicine)

As sterilisers:

Gamma rays are also used to sterilise hospital equipment, especially plastic syringes, surgical gloves and so on that would be damaged if heated.

6.3.6 Agriculture

AS TRACERS:

phosphorus-32 is a radioisotope that emits beta particles

This is used partially in the production of fertilisers

The fertiliser will be absorbed by the plants and then transported to various parts of the plants

By detecting the radiation from this radioactive phophorus from outside the plant, agriculturists can determine how much phosphorus is needed by various parts of the plant

For genetic modification:

Gamma radiation can cause modifications to the gene of cells.

This is known as mutation

To produce better quality seeds which are more resistant to pests, changes in weather and so on