Application of radiation in science, technology and society

The widespread use of isotopes is based on two fundamental properties exhibited by all radioactive substances. The first property is that the disintegration rate of an isotopic sample is directly proportional to the number of radioactive atoms in the sample. Thus, measurement of its disintegration rate serves to analyze a radioactive compound. With nearly all chemical elements (notable exceptions being nitrogen and oxygen, which have no suitable radioactive isotopes), an isotope may be incorporated in a chemical compound, and thereafter, masses of this compound may be measured with a high precision. The second property is that the disintegration rate is completely unaffected by the chemical form of the isotope, and conversely, the property of radioactivity does not affect the chemical properties of the isotope. By substituting or labeling a particular atom within a molecule, isotopes can be used to trace the fate of that atom during a chemical reaction.

Although radiation can be harmful and should be handled with care, it can be used safely and is important in many scientific procedures.

Archaeologists use the half-lives of naturally occurring radioisotopes to establish the ages of fossils and other ancient artifacts. Carbon-14 has been used most extensively. The method was developed in the late 1940s by Willard Libby, who received the Nobel Prize in Chemistry for his work in 1960. It is based on the fact that radiocarbon (carbon-14) is constantly being created in the atmosphere by the interaction of cosmic rays with atmospheric nitrogen. The resulting carbon-14 combines with atmospheric oxygen to form radioactive carbon dioxide, which is incorporated into plants by photosynthesis; animals then acquire carbon-14 by eating the plants. When the animal or plant dies, it stops exchanging carbon with its environment, and from that point onwards the amount of carbon-14 it contains begins to decrease as the carbon-14 undergoes radioactive decay. Measuring the amount of carbon-14 in a sample from a dead plant or animal such as a piece of wood or a fragment of bone provides information that can be used to calculate when the animal or plant died. The older a sample is, the less carbon-14 there is to be detected, and because the half-life of carbon-14 (the period of time after which half of a given sample will have decayed) is about 5,730 years, the oldest dates that can be reliably measured by this process date to around 50,000 years ago, although special preparation methods occasionally permit accurate analysis of older samples. Measurement of radiocarbon was originally done by beta-counting devices, which counted the amount of beta radiation emitted by decaying carbon-14 atoms in a sample. More recently, accelerator mass spectrometry has become the method of choice; it counts all the carbon-14 atoms in the sample and not just the few that happen to decay during the measurements; it can therefore be used with much smaller samples (as small as individual plant seeds), and gives results much more quickly.Carbon-14 dating is a good example of how chemistry helps researchers in other areas.

Neutron activation analysis is used to detect trace amounts of elements in samples. In this technique, a sample is bombarded with neutrons from a radioactive source. This causes the atoms in the sample to become radioactive. The half-life and type of radiation emitted by the radioisotopes is detected and processed by a computer. Since this information is characteristic for each element, scientists can tell what radioisotopes are produced and what elements were originally present in the sample. This is one of the most sensitive techniques for detecting trace amounts of elements. It is capable of measuring g of an element in a sample. Neutron activation analysis is used by museums to detect art forgeries and by crime laboratories to analyze gunpowder residues.

Radioisotopes called tracers are used by chemists and biochemists to study chemical reactions and molecular structures. One of the reactants, labeled with a radioisotope, is added to the reaction mixture. After the reaction is over, the radiation of the product is measured to determine the uptake of the tracer. By comparing this amount with the amount originally added, scientists can learn much about the reaction mechanism. Reactions with many steps can be studied using this method.

Agricultural researchers use radioisotopes to test the effects of herbicides, pesticides, and fertilizers. The tracer is introduced into the substance being tested to make it radioactive. Next, the plants are treated with the radioactive substance. Then, the radioactivity of the plants is measured to determine the location of the substance. Often the tracer is also monitored in animals that consume the plants, in water, and in soil. This information helps scientists determine the effects of using the substance.

Radioisotopes are used to diagnose some diseases. Iodine-131 is used to detect thyroid problems. The thyroid gland extracts iodide ions from the bloodstream and uses them to make thyroxine. To diagnose thyroid disease, the patient is given a small amount of iodine-131 in a liquid. After about two hours, the amount of iodide uptake is measured by scanning the patient's throat with a radiation detector. In a similar way, technetium-99m is used to detect brain tumors, and phosphorus-32 is used to detect skin cancer.

Radiation is used to treat some cancers. This group of diseases is characterized by rapidly dividing abnormal cells. These cells are more sensitive to radiation than are normal cells. The cancerous area can be treated with radiation to kill the cancer cells. Some normal cells are also killed, however, and cancer cells at the center of the tumor may be radiation resistant. Therefore, the benefits of killing the cancer cells and the risks to the patient must be evaluated.

Radioactive pharmaceuticals containing radioisotopes of gold, iodine, or phosphorus are sometimes given in radiation therapy. A larger dose of iodine-131 than that given to detect thyroid disease can be given to treat the disease. The radioactive iodine collects in the thyroid and emits beta and gamma rays to provide therapy.

 

COMPREHENSION ASPECT

Ex.1. Say whether the following statements are true or false. Correct the false ones.

1. Radiation chemistry is used to study nuclear reactions and chemical changes resulting from the absorption of high-energy ionizing radiation.

2. With all chemical elements, an isotope may be incorporated in a chemical compound, and thereafter, masses of this compound may be measured with a high precision.

3. The disintegration rate is completely unaffected by the chemical form of the isotope, and conversely, the property of radioactivity does not affect the chemical properties of the isotope.

4. Carbon-14 is constantly being created in the atmosphere by the interaction of cosmic rays with atmospheric nitrogen.

5. Accelerator mass spectrometry counts the amount of beta radiation emitted by decaying carbon-14 atoms in a sample, therefore it can be used with very small samples.

6. A larger dose of iodine-131 than that given to detect thyroid disease can’t be given to treat the disease, since the radioactive iodine accumulates in the thyroid and emits beta and gamma rays, which are considered to be very harmful for organism.

7. Radioisotopes called tracers are used by chemists and biochemists to determine the effects of using herbicides, pesticides, and fertilizers.

 

Ex.2. Match the words and expressions in the left-hand column with their definitions in the right hand column. They appear in the text you have just read.

1. indiscriminate	a. introducing a statement or idea that reverses one that has just been made or referred to
2. fission	b. to use or add in place of
3. precision	c. a large ductless gland in the neck that secretes hormones regulating growth and development through the rate of metabolism
4. conversely	d. splitting, cleavage, disintegration
5. to substitute	e. a flowering plant's unit of reproduction, capable of developing into another such plant
6. extensively	f. done at random or without careful judgment
7. seed	g. over a large area or range
8. thyroid	h. the quality, condition, or fact of being exact and accurate

Ex.3. Complete the following passage using the words from the box.

Number, cause, unlike, occur, artificially, changes, undergo, nuclear, protons

 

Traditional chemical reactions (1) … as a result of the interaction between valence electrons around an atom's nucleus. Nuclear reactions involve (2)... in particles in an atom's nucleus and thus (3)... a change in the atom itself. (4)... normal chemical reactions that form molecules, (5)... reactions result in the transmutation of one element into a different isotope or a different element altogether (remember that the (6) … of protons in an atom defines the element, so a change in (7) … results in a change in the atom). While many elements (8) … radioactive decay naturally, nuclear reactions can also be stimulated (9) ….

 

Ex.4. Divide the text into logical parts. Find and write out the main idea of each part. Highlight the key words that help you to generate your ideas. Write a three-sentence summary of the text using your key words, without referring back to the text. Then compare your summary with the rest of the class.

 

Ex.5. Split into groups or pairs and discuss the following questions. Make your own research, find out the necessary information.

1. What is the subject of study of radiation chemistry? What original erroneous conclusion was made concerning a short-lived radioisotope of barium which was isolated from neutron irradiated uranium and how was it corrected later?

2. What fundamental properties exhibited by all radioactive substances is the widespread use of isotopes based on?

3. Fill in the table dwelling on radioisotope applications.

 

Area of application	Purpose	Brief description of the technique used

 

GRAMMAR ASPECT

THE PARTICIPLE

	Active	Passive
Participle I	closing – закрывающий, закрывая	being closed – закрываемый, закрывающийся, будучи закрыт(-ым) (= когда закрыли)
Perfect Participle	having closed – закрыв	having been closed – так как (после того как) был закрыт
Participle II		closed – закрытый, закрываемый, когда (так как) закрыт

Note:

Participle I expresses simultaneous action with the main verb.

· Studying the properties of any substance, the chemist has to perform a number of experiments.

· There are a number of different procedures being used in qualitative analysis.

 

Perfect participleexpresses the action preceding the action expressed by the main verb:

· Having finished the experiment we must process the data.

· Having been shown this chart we paid attention to the figures.

 

Participle II has the meaning of the passive voice.

· The two substances investigated were homogeneous.

· When cooled to the original temperature the substance becomes solid.

NB! Pay attention to the translation of some special cases of Participle II.

· The acid involved acted as a catalyst.

Используемая кислота действовала в качестве катализатора.

· The substance affected by a magnetic field must be a metal.

Вещество, на которое воздействует магнитное поле, должно быть является металлом.

· When (if) carried out carefully, this experiment can give reliable data.

При аккуратном проведении этот эксперимент может дать достоверные данные.

 

Ex.1. Choose the correct form of the Participle.

1. ( Being, having been) very brittle antimony can be easily pulverized. 2. When (preparing, prepared) a substance on a commercial scale the method chosen must utilize inexpensive and readily available materials. 3. When (heating, heated) concentrated sulphuric acid reacts with metals. 4. Many ethers take up oxygen from the atmosphere, (forming, formed) peroxyethers. 5. Organometallic compounds are exceedingly reactive, (being hydrolyzed, having been hydrolyzed, hydrolyzed) vigorously by water. 6. Neutral water when (saturating, saturated) with O₂ is a fairly good (oxidizing, oxidized) agent. 7. There are only few elements not (attacking, attacked) by oxygen. 8. Magnesium is not (attacking, attacked) by water despite favorable potential unless (amalgamating, amalgamated). 9.Carbon reduction (followed, following) roasting to oxides is used to prepare tin and lead fromtheir ores. 10. Once (starting, started) some reactions liberate heat and light. 11. Oxygen as ordinarily (obtained, obtaining) is widely used in laboratory practice. 12. The steam (liberating, liberated) condensed as the temperature fell. 13. The (discussed, discussing) compounds are characteristic of the transition metals. 14. The electron volt (e.v.) is the kinetic energy (being acquired, acquiring) by an electron when it passes through potential difference of 1 volt. 15. (Indicating, indicated) the proportion of hydrogen and oxygen present in sulphuric acid the formula H₂SO₄ is used. 16. Tinand lead are prepared from their ores by (roasted, roasting) to oxides (followed, following) by carbon reduction.

 

Ex.2. Open the brackets translating the Russian words into English.

1. Oxygen can be converted to a liquid (путем кипения) at − 183°C. 2. Oxides of bismuth are basic, (образующие) salts such as bismuth chloride. 3. The iodine ions are easily oxidized, (изменяясь) to free iodine by chlorine, oxygen and many other oxidizing agents. 4. (Охладив) the concentrated solution of naphthalene in hexane we obtained white precipitate of pure naphthalene. 5. (После пропускания) through a hot tube hydrogen arsenide deposited arsenic in form of metallic film. 6. The salts (образованные) by hydrochloric acid are called chlorides. 7. Copper tarnishes when (выставлена) to air. 8. Solutions (содержащие) much of the solute and little of the solvent are called strong or concentrated solutions. 9. Any element (при соединении) with oxygen forms oxide. 10. (Получив) the necessary data on the density of the liquid we could begin the determination of the index of refraction. 11. (После охлаждения) to a very low temperature many substances acquire quite new properties. 12. (При нагревании) concentrated sulphuric acid reacts with metals. 13. Hydrogen burns readily in air or in oxygen, and product (образованный) is water. 14. Radioactivity is the property (не поддающееся влиянию) by any known catalyst. 15. Inert gases are the substances (не поддающиеся воздействию) by oxygen.

Ex.3. Translate the following sentences, pay attention to the forms and functions of the Participles.

1. Bond formation involving elements toward the middle of the periodic table occurs by the process of electron sharing. 2. The calculation of hydrogen ion concentration in a solution containing a weak electrolyte is a difficult one for the average student first facing this problem. 3. Elements composed of atoms containing only one or two valence electrons usually form positive ions. 4. We are surrounded by naturally-occurring radioactive elements in the soil and stones. 5. The amount of energy deposited in a particular mass of human tissue is called the absorbed dose. 6. The equivalent dose is expressed in a unit called the Sievert. 7. Radiation doses normally encountered are expressed in millisievert or microsievert. 8. The total of weighted equivalent doses is a quantity called the effective dose. 9. Radioisotopes decay at specific rates called half-lives.

Ex.4. Translate the following sentences into English.

1. Вода, используемая в паровых котлах, должна быть свободна от веществ, вызывающих коррозию. 2. Работа, проведенная учеными, имела большое значение. 3. Машины, производящие эти товары, должны быть обновлены. 4. Этот вид излучения состоит из тока положительно заряженных частиц. 5. Производя новые виды материалов, следует особо внимательно относиться к их качеству. 6. Завод по производству этих товаров был построен в прошлом году. 7. Открыв радиоактивность, учёные подняли ряд новых вопросов. 8. Вещество, исследуемое нами, может быть использовано и в этом эксперименте. 9. Очистив воду от веществ, вызывающих коррозию, мы можем использовать её в паровых котлах. 10. Волокна, исследованные ими, были достаточно прочны. 11. Метод, о котором идет речь, зависит от ряда факторов, описанных выше. 12. Энергия, образующаяся путем расщепления ядра атома, называется ядерной или атомной энергией. 13. В основном атомы содержат незаряженные частицы, называемые нейтронами. 14. При нагревании молекулы жидкости движутся быстрее. 15. Изучив все свойства новой воды, они смогли понять тайну серебристых облаков. 16. Растворенные материалы могут быть растворимыми твердыми веществами, жидкостями или газами.