0647126_DA545_nadeina_l_v_radioekologiya

ous elements, they turned for a time to the «materialization» of positive electrons through the action of gamma-rays of high energy.

An interesting feature of this discovery is that it was not so long in coming; the phenomenon of artificial activity had been expected, and sought for, since the earliest days of radioactivity. For this discovery the Joliot-Curies were awarded the Nobel Prize for Chemistry in 1935.

During her studies Marie had heard about Henri Becquerel’s discovery of some sort of radiation emitting from uranium salts and decided to investigate these mysterious «uranium rays» for her doctoral thesis. She soon discovered that the intensity of the rays was in direct proportion to the amount of uranium in her sample. Nothing she did to the uranium affected the rays.

Marie Curie in her chemistry laboratory at the Radium Institute in France, April 1921.

This, she said «shows that radioactivity is an atomic property». She also found that two minerals, pitchblende and chalcite, were much more radioactive than uranium itself, and realized that they must contain a new radioactive element. Her husband Pierre abandoned his research on crystals to join Marie in her work. In July 1898, using basic chemical refining methods, they iso-

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lated a product from pitchblende about 400 times more active than uranium. This they named polonium in honour of Marie’s native Poland.

«It was exthausting work to move the containers about, to transfer the liquids and to stir for hours at a time, with an iron bar, the boiling material in the cast iron basin». They continued with the painstaking refining and by December 1898 the couple announced the discovery of an even more radioactive substance in pitchblende which they called radium. This discovery had far-reaching effects; opening up the fields of radiotherapy and nuclear medicine.

William Crookes designed the spinthariscope (from the Greek «spintharis», a spark) in 1903 which counted alpha-particles emitted by radium. The instrument consists of a phosphorescent screen of zinc sulphide placed over a minute trace of a radium salt (supplied to Crookes by Marie Curie). The al- pha-particles cause visible flashes of light (scintillations) and these are observed through a microscope.

The examples pictured are four of the original instruments made by Crookes and show progressive stages in their development. Even after the invention of more sophisticated electric counting devices, Ernest Rutherford used these scintillation counting methods for the estimation of an activity.

Sir William Crookes is also known for his 1861 discovery of thallium, and his invention of the radiometer.

(www: Marie Curie and the history of radioactivity Marie Curie’s blog.htm)

8.2 Tell the text «The Curies: Lives Devoted to Research» using these phrases:

to be born – родиться

to be responsible for smth – быть ответственным за что-л. to be famous for – быть известным

to be introduced to – быть представленным кому-л. to be awarded smth for – быть награжденным за что-л. to be tragically killed in – трагически погибнуть в

to be enshrined in – бережно сохраняться to be honoured in – заслужить

to be received by – приниматься (восприниматься) to be developed by – создаваться, разрабатываться to be measured on – измеряться

to be devoted to – посвящаться

to be published in – публиковаться

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to be followed by – следовать

to be observed through – наблюдать to be known for – быть известным

9.Translate these sentences into English.

1.В имеющихся обзорах по истории развития учения о радиоактивности, как правило, обсуждаются достижения ученых Европы и Европейской части России, тогда как имеющиеся в Томске архивные материалы позволяют утверждать (Рихванов, Лозовский и др., 1991; Хахалкин, 1991), что и в Азиатской части России, особенно в центре сосредоточения научной мысли – Томске, исследования этого явления проводились не менее активно, чем в столичных городах России. 2. Этому способствовало то, что первые сибирские вузы (Томский государственный университет с его медицинским факультетом и Томский технологческий институт) укомплектовывались научными кадрами Московского и Санкт-Петербургского университетов, имеющих прочные связи с научными кругами Европы. 3. Так, один из ректоров ТГУ, профессор Н.А. Гезехус, был выходцем из Санкт-Петербургского технологического института и занимался изучением теплового действия лучей радия. 4. Его работы по этому направлению обсуждались в научных кругах уже в 1903 г., т.е. непосредственно в тот год, когда это явление было обнаружено. 5. Выпускниками европейских вузов России были и другие первые исследователи радиоактивности и радиоактивных элементов в Сибири (П.П. Орлов, В.С. Титов, Д.В. Алексеев, П.П. Пилипенко, П.П. Гудков, М.Н. Соболев, В.А. Обручев). 6. Хаос Гражданской войны разметал и уничтожил многие архивные материалы тех лет, а то, что осталось нетронутым, частично или полностью было изъято из открытого пользования и помещено в спецхранилища (материалы П.П. Орлова), либо уничтожено в годы репрессий. 7. Сегодня эти материалы собираются по крупицам из различных разрозненных, не систематизированных источников, средств массовой информации.

(Л.П. Рихванов «Радиоактивные элементы в окружающей среде и проблемы радиоэкологии, Томск, 2009).

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10. This ten question multiple choice quiz tests your understanding of nucleonics. It covers alpha, beta and gamma radiation, radioactive dating, fission and fusion.

1.	Uranium isotopes have different
	a) atomic numbers	b) atomic masses
	c) numbers of protons	d) numbers of electrons
2.	Marie and Pierre Curie discovered
	a) chlorine	b) hydrogen
	c) radium	d) uranium

3. The combination of two atomic nuclei into one, accompanied by a release

of energy, is called
a) fission	b) fusion
c) radioactive decay	d) chain reaction

4. Nuclear changes differ from normal chemical changes in that all nuclear

changes
a) absorb energy	b) release energy	c) produce explosions

d)involve the protons and/or neutrons (nucleus) of an atom

5.An alpha particle is a

a) helium nucleus	b) fast electron
c) high energy photon	d) neutron

6. Carbon-14 dating could be used to estimate the age of all of the following

except
a) fossils	b) petrified wood
c) ancient scrolls	d) medieval tapestries

7. Whether or not a nuclear fission reaction becomes self-sustaining depends

on the release of
a) alpha particles		b) protons
c) neutrons		d) electrons
8. Atoms of Uranium-235 and Uranium-238 differ by three
a) protons	b) neutrons	c) electrons
d) photons	e) isotopes
9. The hydrogen in a hydrogen bomb is converted into
a) helium		b) tritium
c) plutonium		d) uranium
10. A beta particle is
a) a proton	b) a neutron	c) an electron
d) a photon		e) a helium nucleus

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11. Match the terms with the definition:

1. radioactivity	a) A «speculative» chemical system originating in China.
	It includes the conversion (transmutation) of reactive
	metals to gold and the discovery of the philosopher's
	stone. It also provides single cures to diseases and a way
	to prolong life indefinitely.
2. proton	b) Charged particles emitted from a radioactive atom.
	Each charged particle consists of two protons and two
	neutrons.
3. polonium	c) This is the smallest unit of an element. It contains a
	nucleus with neutrons and protons, surrounded by orbit-
	ing electrons.
4. phosphores-	d) The mass of an atom usually expressed as atomic
cence	mass unit (amu).
5. piezoelectricity	e) Charged particles emitted from a radioactive atom.
	These particles are identical except for their charge. The
	charge is classified as positive (positron) or negative
	(electrons or negatron).
6. pernicious	f) Electrons originating at the cathodes of gaseous dis-
anemia	charge devices. These electrons are often focused in a
	small area such as a tube and intensified on a surface.
	The most familiar form of a cathode-ray tube is the tele-
	vision picture tube.
7. patents	g) It is the constant C in the equation (I=I0e-ct) to deter-
	mine the half life of radioactive material.
8. nuclear physics	h) The science dealing with the chemical changes ac-
	companying the passage of an electric current or the
	source of energy to produce an electrical current. One
	example is the battery.
9. neutron	i) A negative charged particle that orbits the nucleus of
	an atom. It is lighter in weight than a proton or neutron.
10. naval shell	j) An element is a substance made up of atoms with the
	same atomic number. 75% of the elements are metals and
	the others are nonmetals. A few examples are oxygen,
	iron, gold, chlorine, and uranium.
11. magnetic field	k) Electrons absorb energetic radiation (for example ul-
	traviolet light) raising an electron to a higher «Bohr» or-
	bit. The energized electron soon drops down in a series
	of steps through lower energy states and in the process
	45

	releases photons at lower energy states corresponding to
	visible light. The bright color occurs because the photons
	are concentrated in a narrow range of wavelengths.
12. half-life	l) The period of time it takes for half the nuclei of a ra-
	dioactive element to undergo decay to another nuclear
	form.
13. fluorescence	m) All magnetic fields are created by moving electric
	charge. The single moving electron around a nucleus is a
	tiny electric current. These orbiting electrons create
	magnetic fields and their net effect is to provide the atom
	with a magnetic field.
14. elements	n) Refers to a bullet from a gun
15. electron	o) A particle with no charge that is located in the nucleus
	of an atom.
16. electrochem-	p) A branch of physics that includes the study of the nu-
istry	clei of atoms, their interactions with each other, and with
	constituent particles.
17. decay con-	q) A certificate granted by a government given one(s)
stant	exclusive right to an invention for a limited period of
	time. Often during this time others can not make, use, or
	sell the invention.
18. cathode rays	r) A severe blood disease where there is a decrease in
	number and increase in size of red blood cells. The ill-
	ness is characterized by pallor, weakness and the inabil-
	ity to absorb vitamin B12.
19. beta particle	s) Electricity resulting from the application of mechani-
	cal pressure on a dielectric (a substance with a steady
	electric field) crystal, for example quartz.
20. atomic mass	t) Luminescence that persists after a light source has
	been removed. Materials such as phosphors or phos-
	phorogens are activated from a light source to emit the
	light in the form of photons of light.
21. atom	u) A chemical element, Po, atomic number 84. It is used
	in photographic film to reduce the static charge.
22. alpha particle	v) A positively charged particle that is located in the nu-
	cleus of an atom.
23. alchemy	w) A behavior of an element in which nuclei are under-
	going change and emitting particles. This occurs natu-
	rally in approximately fifty elements. It can be produced
	artificially.
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24. X rays

x) A chemical element, Ra, that has an atomic number

88.It is used as a source of neutrons and makes lightning rods more effective.

25.uranium y) A chemical element, Th, that has an atomic number

90.It is used in the manufacturing of sun lamps.

26.thorium z) A chemical element, U, that has an atomic number 92.

It reactive with nearly all nonmetals and is used as fuel for nuclear reactors.

Grammar in Use

12. Translate the following text paying attention to italicized grammar constructions. (See the table p. 9)

The Electromagnetic Spectrum

X-rays and gamma rays differ only in their source of origin. X-rays are produced by an x-ray generator and gamma radiation is the product of radioactive atoms. They are both part of the electromagnetic spectrum. They are waveforms, as are light rays, microwaves, and radio waves. X-rays and gamma rays cannot be seen, felt, or heard. They possess no charge and no mass and, therefore, are not influenced by electrical and magnetic fields and will generally travel in straight lines. However, they can be diffracted (bent) in a manner similar to light.

Both X-rays and gamma rays can be characterized by frequency, wavelength, and velocity. However, they act somewhat like a particle at times in that they occur as small "packets" of energy and are referred to as «photons». Due to their short wavelength they have more energy to pass through matter than do the other forms of energy in the electromagnetic spectrum. As they pass through matter, they are scattered and absorbed and the degree of penetration depends on the kind of matter and the energy of the rays.

Properties of X-Rays and Gamma Rays

They are not detected by human senses (cannot be seen, heard, felt, etc.).

•They travel in straight lines at the speed of light.

•Their paths cannot be changed by electrical or magnetic fields.

•They can be diffracted to a small degree at interfaces between two different materials.

•They pass through matter until they have a chance encounter with an atomic particle.

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•Their degree of penetration depends on their energy and the matter they are traveling through.

•They have enough energy to ionize matter and can damage or destroy living cells.

12.1Remember the pronunciation

attenuation	[ə͵tenju´eiʃ(ə)n]	angle	[´æŋgl]
penetrating	[´penitreitiŋ]	significant	[sig´nifikənt]
approximation	[ə͵prɔksi´meiʃ(ə)n]	annihilation	[ə͵naiə´leiʃ(ə)n]
coefficient	[͵kəui´fiʃ(ə)nt]	circumstance	[´sə:kəmstæn(t)s]
ejection	[i´ʤekʃ(ə)n]	negligible	[´negliʤəbl]
subsequent	[´sʌbsikwənt]	applet	[´æplit]
neutral	[´nju:tr(ə)l]	vault	[vɔ:lt]
electron	[i´lektrɔn]	nucleus	[´nju:kliəs]
incoherent	[͵inkəu´hiər(ə)nt]	source	[sɔ:s]

13. Read the text bellow using these words and do the tasks.

English	Russian
photon	фотон
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attenuation	затухание, ослабление, истощение
event	случай, факт, явление
penetrating	проникающий
involve	включать, вовлекать, втягивать
sum	сумма, величина, количество
interaction	взаимодействие, взаимосвязь
scattering	рассеивание
approxim tion	приблизительное значение, приближение
abs rption	поглощение, абсорбция
coefficient	коэффициент, показатель
majority	большая часть, большинство
occur	происходить, случаться
ejection	выброс, эжекция
subsequent	последующий, дальнейший
neutral	нейтральный
contribute	способствовать, содействовать
electron	электрон
wavelength	длина волны
incoherent	непоследовательный, некогерентный
angle	угол, ракурс
significant	значительный
annihilation	(полное) уничтожении, аннигиляция
circumstance	условие, обстоятельство, случай
negligible	незначительный, неважный
minor	несущественный, незначительный
neglect	пренебрегать
vault	свод
nucleus	ядро, центр
source	источник, причина

Sources of Attenuation

The attenuation that results due to the interaction between penetrating radiation and matter is not a simple process. A single interaction event between a primary x-ray photon and a particle of matter does not usually result in the photon changing to some other form of energy and effectively disappearing. Several interaction events are usually involved and the total attenuation is the sum of the attenuation due to different types of interactions. These interactions include the photoelectric effect, scattering, and pair production.

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The figure below shows an approximation of the total absorption coefficient, (µ), in red, for iron plotted as a function of radiation energy. The four radia- tion-matter interactions that contribute to the total absorption are shown in black. The four types of interactions are: photoelectric (PE), Compton scattering (C), pair production (PP), and Thomson or Rayleigh scattering (R). Since most industrial radiography is done in the 0.1 to 1.5 MeV range, it can be seen from the plot that photoelectric and Compton scattering account for the majority of attenuation encountered.

Photoelectric (PE) absorption of x-rays occurs when the x-ray photon is absorbed, resulting in the ejection of electrons from the outer shell of the atom, and hence the ionization of the atom. Subsequently, the ionized atom returns to the neutral state with the emission of an x-ray characteristic of the atom. This subsequent emission of lower energy photons is generally absorbed and does not contribute to (or hinder) the image making process. Photoelectron absorption is the dominant process for x-ray absorption up to energies of about 500 KeV. Photoelectron absorption is also dominant for atoms of high atomic numbers.

Compton scattering (C) occurs when the incident x-ray photon is deflected from its original path by an interaction with an electron. The electron gains energy and is ejected from its orbital position. The x-ray photon loses energy due to the interaction but continues to travel through the material along an altered path. Since the scattered x-ray photon has less energy, it, therefore, has a longer wavelength than the incident photon. The event is also known as incoherent scattering because the photon energy change resulting from an interaction is not always orderly and consistent. The energy shift depends on the angle of scattering and not on the nature of the scattering medium.

Pair production (PP) can occur when the x-ray photon energy is greater than 1.02 MeV, but really only becomes significant at energies around 10 MeV. Pair production occurs when an electron and positron are created with the annihilation of the x-ray photon. Positrons are very short lived and disappear (positron annihilation) with the formation of two photons of 0.51 MeV energy. Pair production is of particular importance when high-energy photons pass through materials of a high atomic number.

Below are other interaction phenomenon that can occur. Under special circumstances these may need to be considered, but are generally negligible.

Thomson scattering (R), also known as Rayleigh, coherent, or classical scattering, occurs when the x-ray photon interacts with the whole atom so that the photon is scattered with no change in internal energy to the scattering atom, nor to the x-ray photon. Thomson scattering is never more than a minor

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