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10.3 Use of Radioactive

Radioisotopes

Radioisotopes are unstable isotopes which decay and give out radioactive emissions.

Radioisotopes are naturally occurring or artificially produced.

Uses of radioisotopes

There are many uses for radioisotopes in a wide range of fields including medicine, agriculture, industry and archaeology.

(1) Medicine

In medicine field radioisotopes are used in the diagnosis of certain diseases , provides information of the specific organs of a patient or treat disease.

(a) Sodium-24

Sodium-24 has a half-life 15 hours is used

to detect the positions of blood clots (thrombosis) in veins.

Sodium-24 is injected into the blood stream and gamma rays and beta rays emitted is detected by a ray camera outside the body.

(b) Technetium -99

Technetium -99 has a half-life of just 6 days is used to study the blood in heart.

It is a gamma- only emitter and produces no harmful alphas or betas inside the body. The Technetium is combined into samples of the protein albumin, and this is injected into the patient. Its movement round the body can be followed by a gamma ray camera, picking up the gammas emitted from the Technetium -99.

(c) Xenon-133

Xenon-133 has a half-life 5 days in used in studying lung function.

A patient can be asked to breathe air containing the gas xenon-133 . The gamma rays emitted are studied using a gamma camera which produces a picture of patient’s lungs from the gamma radiation each one receives. The patient soon breathes out all the xenon and receives only a tiny dose of radiation.

No alpha or beta radiation is produced to cause local internal ionisation damage.

(d) Iodine-131

Iodine-131 has a half-life 8 days.

It emits gamma rays and used for detecting changes in the thyroid glands.

Patients are given an intravenous injection of iodine-131 . A detector is placed near the thyroid to read its activity or function.

(e) Iodine-123

Iodine-131 has a half-life 13 hours.

It is used to detect blockage in the kidneys of patients.

Iodine-123 is injected into a patient. The G-M tube s placed on the patient’s body to trace the radioactive rays.

(f) Iodine-125

Iodine-125 has a half-life 60 days.

It is used to estimate the volume of blood by injecting a measured volume of human serum albumin (HSA) labelled with a sample of iodine-125.

(g) Cobalt-60

Cobalt-60 has a half-life 5 years.

It is widely used to give patient s a large dose of gamma radiation for the treatment of internal cancers. A restricted beam of gamma radiation is carefully directed at cancer site from an external cobalt source. This dangerous source is heavily shielded and its operated by remote control from behind thick lead and concrete walls.

Cobalt-60 also is used to sterilise medical equipments.

(2) Industry

(a) Strontium-90

Strontium-90 has a half-life 28 years.

It is used to measure the thickness of paper in a paper industry . It emits beta

radiation.

A radioactive source containing strontium-90 is placed at one side of the paper and a detector on the other side. The detector registers a higher count if the paper is too thin and a lower count if it is too thick.

(b) Sodium-24

Sodium-24 has a half-life 15 hours is used

to test for leakage of underground pipes. Sodium-24 is added into the water in the storage tank. A G-M tube is moved above the underground pipe , a leakage can be detected. The leakage can be detected when the tube registers a higher reading.

(c) Polonium -210

Polonium -210 has a half-life 140 days. It

emits alpha radiation It is used to neutralise static charge in photographic plates or charges on clothes. The alpha particles ionise the air particles into positive and negative ions which neutralise the photographic plates or the clothes.

(d) Cobalt-60

Cobalt-60 has a half-life 5 years. It is used to check welds in steel structures and pipelines Gamma radiation from a large cobalt-60 source placed on one side of a steel structure exposes a photographic plate at the other side. A flaw such as a bubble or crack inside a weld on a pipeline would be visible on the exposed film.

(e) Americium-241

Americium-241 has a half-life 460 years.

It is used in a smoke alarm.

Americium-241 emits beta particles which

ionise air The air ions will then conduct electricity allowing a small current to flow through. When smoke enters the alarm , the smoke particles get in the way of the beta radiation , reducing the ionisation and the current across the alarm. This drop in current sets off the alarms.

(3) Agriculture

(a) Phosphorus-32

Phosphorus-32 has a half-life 15 days.

Phosphorus-32 is used as a tracer in the study of the effectiveness of fertilizers. The plants are watered with a solution containing phosphorus-32. A leaf is plucked and tested for radioactivity everyday for a week. If the activity recorded increases then the plant has absorbed phosphorus.

(b) Cobalt-60

Cobalt-60 has a half-life 5 years. The gamma radiation emits from cobalt-60 can be used for food preservation. Some foodstuffs, like grain and dried beans, are often attacked by pests while in store. Radiation treatment kill these pests and reduces the losses.

The gamma radiation is also used to control insect pests which damage crops. Male insects are bred in laboratory and then irradiated. This does not kill them but damages their sex cells, making them sterile- unable to produce offspring. These males are then released in great numbers in affected areas. They breed as usual with normal females ,but no new generation of the insects is hatched. So the pest is controlled.

(c) Radioactive radiation also used to induce genetic mutation in a plant ( change the genes of plants) in order to produce a better strain which has a higher resistance against diseases.

(4) Archeology

(a) Carbon-14

Carbon-14 has a half-life 5 700 years

It is used to measure the age of a

archaeological specimen by carbon dating method.

Ordinary carbon contains a very small proportion of carbon-14 , produced when cosmic rays from space collide with nitrogen-14 in atmosphere. Living plants take up the carbon-14 in the carbon dioxide they use for photosynthesis, as do animals when they eat the plants for food. While the plant or animal is alive, the proportion of cabon-14 to ordinary carbon-12 in their tissues stays constant, but once they die, the carobn-14 begins to decay – with a half-life of 5 700 years. To date an archeological specimen , a small sample of carbon is extracted from it.

(b) Uranium-238

Uranium-238 has a half-life of 5000 million years. It is used to measure the geological time.

During the formation of rocks, some radioisotopes such as uranium-238 are trapped. As the decays continues, the proportion of uranium-238 decreases slowly resulting in the equally slow growth of its product lead-206 and the age of the rock can b estimated.

The negative effects of radioactive substances.

People are exposed to a variety of radioactive radiations which are dangerous because the radiations have penetration power and ionisation power.

As the radiations penetrate through living cells ,the ionizations process occur. Ionisations cause the ions react with other atoms in the cell to cause damage, changed permanently or die.

Factors affecting the severity of radiation are:

(1) Types of radiation

(2) Dosage and exposure time

(3) Methods of insertion into the body

(4) Exposure of different parts of the body.

The harmful effects of radiation on humans can be divided into two categories:

(1) Somatic effect

Somatic effects appear in the person exposed to radiation. The seriousness of the effect depends on the dose of radiation received.

Somatic effect cause all parts of the body damage except the reproductive organs.

Examples of somatic effects are;

(a) Radiation burns (skin burn)

(b) Fatigue

(c) Nausea

(d) Hair loss

(e) Leukemia

(f) Cataracts

(g) Vomiting

(h) Infertility in male

(i) Organ failure

(j) Death

(2) Genetic effect

Genetic effect appear in future generations of the exposed person as a result of radiation damage to reproductive cells

Examples of somatic effects are;

(a) Chromosome abnormalities

(b) Birth defects

(c) Congenital defects

( Down Syndrome, Klinefelter

Syndrome and Turner

Syndrome)

(d) Premature death

(e) Cancer in later life

Safety precautions in the handling of Radioactive Substances

(1) No eating, drinking , smoking or applying cosmetics are not allowed where any radioactive materials are handled.

(2) Disposable gloves and protective clothing are worn.

(3) Eye glasses made of lead are used at all times when handling radioactive substances.

(4) Masks are worn in mines where radioactive dust particles are air-borne

(5) Using shielding such as laboratory coats, long pants, close-toe footwear and especially to shield the sex organs using lead aprons.

(6) Keeping a large distance between the person and the source

(7) Keeping exposure times as short as possible

(8) Radioactive substances are kept in thick lead containers

(9) Room, buildings, containers and radioactive storage places must be labelled with the sign for radioactive substance.

(10) Radioactive wastes must be disposed using suitable and safe methods

(11) Nuclear reactors should be built on islands or areas far from residents

(12) Use remote-controlled tools through a lead-glass screen.

(13) Use tongs or forceps to move radioactive material

(14) Sit behind a shielding wall made of lead and concrete

(15) Wear a film badge which gives a permanent record of radiation dose received

(16) Workers are checked for radiation contamination by using sensitive radiation monitors before they leave their place of work.

(17) When radioactive material are used in medicine , the material with a short half-life is chosen.

Radioactive Waste Management

Radioactive waste consists of a variety of materials requiring different methods of management to protect people and the environment.

They are classified as low-level, medium level and high-level.

(1) Low level wastes

Generated : From hospitals, nuclear power stations, research laboratories and industries.

Examples: Comprises paper, rags tool, clothing, filters, gloves, wrappers, biohazard suit and shoes.

Half-life : Short

Management: Solid wastes are stored in a

closed container and buried in shallow landfill sites (underground).

(2) Medium level wastes

Generated: Nuclear power stations, research laboratories and industries.

Examples: Comprises resins, chemical sludge, reactor components.

Half-life: Long

Management: Solidified in concrete or bitumen and then buried underground

(3) High level wastes

Generated: Nuclear power stations.

Examples: Used fuel rods or liquid waste

from fuel reprocessing

Half-life: Long

Management: Submerged in a pool of water to

cool them down and then stored in steel container which are buried deep underground.

5 Responses

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