Uses of Radioactivity

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USES OF RADIOACTIVITY/RADIATION

After reading this section you will be able to do the following:

List and describe uses of radioactivity/radiation.

There are many practical applications to the use of

radioactivity/radiation. Radioactive sources are used to study living

organisms, to diagnose and treat diseases, to sterilize medical

instruments and food, to produce energy for heat and electric

power, and to monitor various steps in all types of industrial

processes.

Tracers

Tracers are a common application of radioisotopes. A tracer is a

radioactive element whose pathway through which a chemical

reaction can be followed. Tracers are commonly used in the medical

field and in the study of plants and animals. Radioactive Iodine-131

can be used to study the function of the thyroid gland assisting in

detecting disease.

Nuclear reactors

Nuclear reactors are devices that control fission reactions

producing new substances from the fission product and energy.

Recall our discussion earlier about the fission process in the making

of a radioisotope. Nuclear power stations use uranium in fission

reactions as a fuel to produce energy. Steam is generated by the

heat released during the fission process. It is this steam that turns

a turbine to produce electric energy.


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Other uses of radioactivity

Sterilization of medical instruments and food is another common

application of radiation. By subjecting the instruments and food to

concentrated beams of radiation, we can kill microorganisms that

cause contamination and disease. Because this is done with high

energy radiation sources using electromagnetic energy, there is nofear of residual radiation. Also, the instruments and food may be

handled without fear of radiation poisoning.

Radiation sources are extremely important to the manufacturing

industries throughout the world. They are commonly employed by

nondestructive testing personnel to monitor materials and processes

in the making of the products we see and use every day. Trained

technicians use radiography to image materials and products muchlike a dentist uses radiation to x-ray your teeth for cavities. There

are many industrial applications that rely on radioactivity to assist

in determining if the material or product is internally sound and fit

for its application.

Charles-Augustin de Coulomb


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Charles-Augustin de Coulomb (14 September 1736 23 August

1806) was a Frenchphysicist. He is best known for

developing Coulomb's law, the definition of the electrostatic force of

attraction and repulsion. The SI unit of charge, the coulomb, wasnamed after him.

Life

Coulomb was born in Angoulme, France, to a well-to-do family. His

father, Henri Coulomb, was inspector of the Royal

Fields in Montpellier. His mother, Catherine Bajet, came from a

wealthy family in the wool trade. When Coulomb was a boy, the

family moved to Paris and there Coulomb studied at the

prestigious Collge des Quatre-Nations. The courses he studied inmathematics there, underPierre Charles Monnier, left him

determined to pursue mathematics and similar subjects as a career.

From 1757 to 1759 he joined his father's family in Montpellier and

took part in the work of the academy of the city, directed by the

mathematician Augustin Danyzy. With his father's approval, Coulomb

returned to Paris in 1759 where he was successful in the entrance

examination for the military school at Mzires.

After he left the school in 1761, Coulomb initially took part in thesurvey for the British coastal charts and was then sent on a mission

to Martinique in 1764 to take part in the construction of the Fort

Bourbon under the orders of the lieutenant-colonel of Rochemore, as

the French colony was insulated in the middle of the English and

Spanish possessions following the Seven Years' War. Coulomb spent
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eight years directing the work, contracting tropical fever. He carried

out several experiments on the resistance of masonries and the

behaviour of the walls of escarpe (supportings), which were inspired

by the ideas ofPieter van Musschenbroek on friction.

Upon his return to France, with the rank of Captain, he was employed

at La Rochelle, the Isle of Aix and Cherbourg. He discovered an

inverse relationship of the force between electric charges and the

square of its distance, later named after him as Coulomb's law.

In 1781, he was stationed permanently at Paris. On the outbreak of

the Revolution in 1789, he resigned his appointment as intendant des

eaux et fontaines and retired to a small estate which he possessed

at Blois. He was recalled to Paris for a time in order to take part in the

new determination ofweights and measures, which had been

decreed by the Revolutionary government. He became one of the first

members of the French National Institute and was appointed

inspector of public instruction in 1802. His health was already very

feeble and four years later he died in Paris.

Coulomb leaves a legacy as a pioneer in the field ofgeotechnical

engineering for his contribution to retaining wall design.

Research

In 1784, his Recherches thoriques et exprimentales sur la force de

torsion et sur l'lasticit des fils de metal[1] (Theoretical research and

experimentation eons of different torsion and the elasticity of metal

wire) appeared. This memoir contained the results of Coulomb's

experiments on the torsional force for metal wires. His general result

is,

"... the moment of the torque is, for wires of the same metal,

proportional to the torsional angle, the fourth power of thediameter and the inverse of the length of the wire..."

It also contained a detailed description of different forms of

his torsion balance. He used the instrument with great success

for the experimental investigation of the distribution ofcharge on

surfaces, of the laws of electrical and magnetic force and of
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the mathematicaltheory of which he may also be regarded as the

founder.

Coulomb's torsion balance

In 1785, Coulomb presented his three reports on Electricity and

Magnetism:

- Premier Mmoire sur lElectricit et le Magntisme[2]. In thispublication, Coulomb describes "How to construct and use an

electric balance (torsion balance) based on the property of the

metal wires of having a reaction torsion force proportional to the

torsion angle." Coulomb also experimentally determined the law

that explains how "two bodies electrified of the same kind of

Electricity exert on each other."

- Deuxieme Mmoire sur lElectricit et le Magntisme[3]. In this

publication, Coulomb carries out the "determination according towhich laws both the Magnetic and the Electric fluids act, either by

repulsion or by attraction."

- Troisime Mmoire sur lElectricit et le Magntisme[4]. "On the

quantity of Electricity that an isolated body loses in a certain time

period, either by contact with less humid air or in the supports

more or less idio-electric."

Four subsequent reports were published in the following years:

- Quatrime Mmoire "Where two principal properties of the

electric fluid are demonstrated: first, that this fluid does not

expand into any object according to a chemical affinity or by an

elective attraction, but that it divides itself between different

objects brought into contact; second, that in conducting objects,

the fluid, having achieved a state of stability, expands on the
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surface of the body and does not penetrate into the interior."

(1786)

- Cinquime Mmoire "On the manner in which the electric fluid

divides itself between conducting objects brought into contact and

the distribution of this fluid on the different parts of the surface of

this object." (1787)

- Sixime Mmoire "Continuation of research into the distribution

of the electric fluid between several conductors. Determination of

electric density at different points on the surface of these bodies."

(1788)

- Septime Mmoire "On magnetism" (1789)

Coulomb explained the laws of attraction and repulsion betweenelectric charges and magnetic poles, although he did not find

anyrelationship between the two phenomena. He thought that the

attraction and repulsion were due to different kinds offluids.
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Uses of Radioactivity