Надеина Л.В. Радиоэкология

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ous elements, they turned for a time to the «materialization» of positive elec-

trons through the action of gamma-rays of high energy.

An interesting feature of this discovery is that it was not so long in com-

ing; 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 investi-

gate these mysterious «uranium rays» for her doctoral thesis. She soon dis-

covered 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 radioac-

tive 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-

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 De-

cember 1898 the couple announced the discovery of an even more radioac-

tive substance in pitchblende which they called radium. This discovery had

far-reaching effects; opening up the fields of radiotherapy and nuclear medi-

cine.

William Crookes designed the spinthariscope (from the Greek «spintha-

ris», 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 ob-

served 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 in-

vention 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

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 радиоак-

тивности, как правило, обсуждаются достижения ученых Европы и Ев-

ропейской части России, тогда как имеющиеся в Томске архивные ма-

териалы позволяют утверждать (Рихванов, Лозовский и др., 1991; Ха-

халкин, 1991), что и в Азиатской части России

, особенно в центре со-

средоточения научной мысли – Томске, исследования этого явления

проводились не менее активно, чем в столичных городах России. 2.

Этому способствовало то, что первые сибирские вузы (Томский госу-

дарственный университет с его медицинским факультетом и Томский

технологческий институт) укомплектовывались научными кадрами Мо-

сковского и Санкт-Петербургского университетов, имеющих прочные

связи с научными кругами Европы. 3. Так, один из ректоров ТГУ, про-

фессор Н.А. Гезехус, был выходцем из Санкт-Петербургского техноло-

гического 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 эле-

ментов в Сибири (П.П. Орлов, В.С. Титов, Д.В. Алексеев, П.П. Пили-

пенко, 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 от-

крытого 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 систематизи-

рованных источников, средств массовой информации.

(Л.П. Рихванов «Радиоактивные элементы в

окружающей среде и

проблемы радиоэкологии, Томск, 2009).

10. This ten question multiple choice quiz tests your understanding of nu-

cleonics. It covers alpha, beta and gamma radiation, radioactive dating, fis-

sion 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

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-

cence

d) The mass of an atom usually expressed as atomic

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

anemia

f) Electrons originating at the cathodes of gaseous dis-

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

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-

istry

p) A branch of physics that includes the study of the nu-

clei of atoms, their interactions with each other, and with

constituent particles.

17. decay con-

stant

q) A certificate granted by a government given one(s)

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.

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 con-

structions. (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 radio-

active 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, wave-

length, 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 «pho-

tons». 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 dif-

ferent materials.

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

atomic particle.

• 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.

12.1 Remember 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

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 be-

tween 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 disap-

pearing. Several interaction events are usually involved and the total attenua-

tion is the sum of the attenuation due to different types of interactions. These

interactions include the photoelectric effect, scattering, and pair production.

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 scat-

tering (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 ab-

sorbed and does not contribute to (or hinder) the image making process. Pho-

toelectron absorption is the dominant process for x-ray absorption up to ener-

gies 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 de-

flected 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 me-

dium.

Pair production (PP) can occur when the x-ray photon energy is great-

er 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 disap-

pear (positron annihilation) with the formation of two photons of 0.51 MeV

energy. Pair production is of particular importance when high-energy pho-

tons 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 classi-

cal 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