0647126_DA545_nadeina_l_v_radioekologiya

contributor to the absorption coefficient. The scattering occurs without the loss of energy. Scattering is mainly in the forward direction.

Photodisintegration (PD) is the process by which the x-ray photon is captured by the nucleus of the atom with the ejection of a particle from the nucleus when all the energy of the x-ray is given to the nucleus. Because of the enormously high energies involved, this process may be neglected for the energies of x-rays used in radiography.

13.1 Find the answers to the following questions.

1)What types of interactions do you know?

2)What do the interactions include?

3)Does the subsequent emission of lower energy photons contribute to the image making process?

4)Why does the x-ray photon lose energy?

5)What does the x-ray photon continue to do after losing energy?

6)What does the energy shift depend on?

7)Does scattering occur without the loss of energy?

8)Why may photodisintegration be neglected for the energies of X-rays used in radiography?

13.2 Join the parts of sentences.

Pair production
Photoelectric absorp-		when the x-ray photon interacts with
tion of x-rays
		the whole atom so that the photon is
		scattered with no change in internal en-
Thomson scattering	occur(s)	ergy to the scattering atom, nor to the x-
	is	ray photon.
Compton scattering		when the x-ray photon is absorbed,
		resulting in the ejection of electrons
Photodisintegration		from the outer shell of the atom, and
		hence the ionization of the atom.
		51

the process by which the x-ray pho-

ton is captured by the nucleus of the atom with the ejection of a particle from the nucleus when all the energy of the x- ray is given to the nucleus.

when an electron and positron are

created with the annihilation of the x-ray photon.

when the incident x-ray photon is de-

flected from its original path by an interaction with an electron.

14. Choose the correct answer.

1.Who is given credit for the discovery of X-ray?

a)Henri Becquerel

b)Wilhelm Roentgen

c)Marie Curie

d)Pierre Curie

2.After traveling through two half-value layers, the incident radiation has been reduced to

a)50%

b)35%

c)20 %

d)None of the above

3.Who is given credit for the discovery of radioactive materials?

a)Henri Becquerel

52

b)Wilhelm Roentgen

c)Marie Curie

d)Pierre Curie

4.Stationary lab or shop X-ray systems usually rely on what to limit exposure to the radiation?

a)Distance controls

b)Time limits

c)Shielding

c)All of the above

5.X-rays and Gamma rays are a form of

a)Light

b)Particle radiation

c)Electromagnetic radiation

d)Both B and C

6.X-rays and Gamma rays have significant penetrating power due to their

a)Short wavelength

b)Medium wavelength

c)Long wavelength

d)Wide range of wavelengths

7.A specific radioactive source will always produce gamma rays at the same

a)Intensity

b)Activity

c)Energy levels

d)None of the above

8.Ionizing radiation can be used in industrial radiography because the health hazards

a)Have been eliminated with controls and procedures

b)Are minimized through controls and procedures

c)Are worth the risk

d)Are being ignored

9.Higher energy radiation will have more

a)Speed

b)Incident intensity

c)Penetrating power

d)Both B and C

53

10.Radiographic contrast describe

a)The sharpness of lines in a radiograph

b)The differences in photographic density in a radiograph

c)The average photographic density in a radiograph

d)The difference in density between two different radiographs

11.There are four types of radiation-matter interactions that can contribute to the total attenuation. These are

a)Compton scattering, pair production, photoelectric absorption, rayleigh scattering

b)Compton scattering, electron exchange, photoelectric absorption, rayleigh scattering

c)Electron exchange, pair production, photoelectric absorption,

e)rayleigh scattering

f)None of the above

12.X-rays and Gamma rays are often referred to as photons because

a)They possess a charge

b)They have mass

c)They occur as small packets of energy

d)None of the above

13.Which of the following does not affect radiographic contrast?

a)Attenuation differences in the component being inspected

b)The wavelength of the radiation used

c)The amount of scattered radiation

d)The level of current used for the exposure

14.In comparison with lower-voltage radiographs, high voltage radiographic images have

a)Less contrast sensitivity

b)Greater contrast sensitivity

c)Greater amounts of scatter radiation relative to primary beam intensity

d)Less latitude

15.Film contrast is determined by

a)The type of film used

b)The process by which the film was developed

54

c)The radiation energy used

d)Both A and B

16.Which two types of radiation-matter interactions account for the majority of attenuation in typical industrial radiography?

a)Compton scattering and photoelectric absorption

b)Compton scattering and pair production

c)Pair production and photoelectric absorption

d)None of the above

17.A radiograph made with an exposure of 8mAm produces a density of 1.8. The sensitometric curve shows a difference in relative exposure between a density of 1.8 and the target density of 2.5 is 4. What must the new exposure time be to produce a radiograph with a density of 2.5?

a)4 mAminutes

b)2 mAminutes

c)32 mAminutes

d)None of the above

18.When using geometric magnification to produce a radiograph, the penumbra will be reduced by

a)A longer exposure

b)A faster film speed

c)A smaller source spot size

d)More X-ray energy

19.When flaws are in unknown locations, radiography is best suited for the detection of

a)Volumetric defects such as porosity

b)Tight linear defects such as cracks

c)Material delaminations

d)The flaw type does not matter

20.X-rays and Gamma rays present a health risk because they are a form of ionizing radiation, which means that the radiation has enough energy to

a)Vibrate water molecules and generate heat

b)Break chemical bonds

c)Break physical bonds

d)None of the above

55

15. Here some key phrases and words to do the presentation. Choose one of four subjects below and give a presentation.

Let me start by saying just a few words about my own background. I am

………….

I’m going to inform you about ……..

We are here today to decide \ agree \ learn about……

I shall only take ( ) minutes of your time.

I have divided my presentation into X sections......

In the first section I will \ am going to describe.............

Then I will \ am going to go on to .........

After that I will am going to look at.........

Finally I will \ am going to..........

If we can now look at……….

If you have a look at this figure here.......

As you can see from the table.......

This particular slide shows.......

The main explanation for this is……

This is \ can be explained by two factors. First…. Second………..

Some of you may be wondering how can this be done?

This means that...........

As a result............

Are there any questions so far?

I welcome questions if at any point you don’t understand something.

So, we have looked at…. and we’ve seen that……

To summarize, I’d like to……..

I would like to thank you for your interest and attention

If you have any questions please I’m ready to answer them.

1)First therapeutic applications of X-rays.

2)Greek philosopher Anaxagoras states that matter cannot be created nor destroyed.

3)Discovery of radioactivity of thorium by G. Schmidt.

4)Thomas Edison reports eye injuries from X-rays.

16. To get the additional information read Appendix.

56

Unit III

Radioactive materials in the environment: HOT PARTICLES

Warming-up

Fallout is the residual radiation hazard from a nuclear explosion, so named because it "falls out" of the atmosphere into which it is spread during the explosion. It commonly refers to the radioactive dust created when a nuclear weapon explodes. This radioactive dust, consisting of hot particles, is a kind of radioactive contamination.

Picture 1

Picture 2

«Hot» or radioactive particle in lung tissue» photo by Del Tredici, Burdens of Proof by Tim Connor,

Energy Research Foundation (1997)

57

This is a photo of a «hot particle» (in this case it is a 1 micron particle of plutonium, and it shows the alpha tracks emitted from that particle in one year).

Look at the picture2 and answer the questions:

1.What does the dark, star-like image in this photograph show?

2.Can alpha radiation from plutonium and other alpha-emitting radionuclides be blocked by skin or even a piece of paper?

3.Is it the most biologically destructive form of ionizing radiation when the alpha-emitting substance is deposited in the soft tissue of internal organs like the lung?

4.How do you think what period of time the alpha tracks shown in picture 2 were captured?

1. Mind the meaning of the following words and use them to read the text «Investigating fallout from nuclear testing».

English	Russian
explosion	взрыв, вспышка
disperse	рассеивать
yield	выход, отдача
precipitation	выпадение, осаждение
fallout	радиоактивные осадки
tiny	крошечный, очень маленький
contamination	загрязнение, заражение
trial	испытание
fissile	делящийся, расщепляющийся
encompass	охватывать
tropopause	тропопауза
irradiation	иррадиация, излучение
ingestion	всасывание
detonation	детонация, взрыв
fireball	ядерный гриб, ядерное облако
mixture	смесь, смешение
coagulation	свертывание, коагуляция
decay	затухать
leakage	утечка
eject	извергать, выбрасывать
	58

altitude	высота
binary	бинарный, двойной
discrete	дискретный
homogeneity	однородность, гомогенность
debris	осколки, обломки, руины
measure	измерять
hazard	риск, опасность
caution	предостережение, предупреждение
fission	деление атома ядра при цепной реакции
detectable	обнаруживаемый

2. Pay attention to the pronunciation these chemical elements.

plutonium [plu:´təuniəm]		nickel	[´nikl]
aluminum [ə´lu:minəm]		chromium [´krəumiəm]
potassium [pə´tæsiəm]		cobalt	[´kəubɔ:lt]
calcium	[´kælsiəm]	carbonate	[´ka:b(ə)neit]
iron	[´aiən]	chlorine	[´klɔ:ri:n]
uranium [juə´reiniəm]		lead	[led]
neptunium [nep´tj:niəm]		americium [ˏæmə´risiəm]
manganese [´mæŋgəni: z]		titanium [tai´teiniəm]

3. Match the numbers with the letters and find out the meaning of word combinations.

1)concentrations of certain	a) роль, которую играют горячие
radionuclides	частицы при оценивании радиаци-
	онных	рисков
2) tiny bits of materials contain-	b) те же современные аналитиче-
ing radioactive chemical ele-	ские технологии, используемые для
ments	исследования «горячих частиц»
3) further separation of the con-	c) явления, ведущие к образованию
densate	«горячих частиц»
4) because of the influence of	d) крошечные частицы вещества,
wind, gravity and the turbulence	содержащие радиоактивные хими-
	59

of the atomic cloud	ческие элементы
5) analysis of radioactive mate-	e) из-за воздействия ветра, плотно-
rial deposited on the ground	сти и турбулентности атомного об-
	лака
6) ingestion of contaminated	f) дальнейшее отделение
food	конденсата
7) the nature and concentrations	g) морфологические свойства «го-
of radionuclides	рячих частиц» и их поведение в ес-
	тественной среде
8) the major elements identified	h) информация о «горячих
	частицах», полученная посредст-
	вом радиохимического, химическо-
	го и физического анализов облом-
	ков
9) the detonation point	i) анализ осажденного в почве ра-
	диоактивного материала
10) the contamination of consid-	j) прием зараженной пищи
erable portions of land
11) the behaviour of the core of	k) характер и концентрация радио-
nuclear devices under simulated	нуклидов
faulty detonation conditions
12) the information on hot parti-	l) поведение активной зоны ядер-
cles obtained through radio-	ного устройства в условиях искус-
chemical, chemical and	ственного взрыва
physical analyses of debris
13) morphological properties of	m) загрязнение значительной части
hot particles and their behaviour	территории
in the natural environment
14) the phenomena leading to	n) начало детонации
the formation of hot particles
15) the same modern analytical	o) большинство установленных
techniques used to investigate	элементов
	60