Summary Assessment of Radiation Dose due to Indoor Radon in Archaeological Sites in Egypt

Summary

Assessment of Radiation Dose due to Indoor Radon in Archaeological Sites in Egypt.

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The ionizing radiation have dangerous which Produced from exposure to any source of it, whether natural or artificial, so it was necessary to be careful, especially in those places where different types of rocks and granite, such as archaeological sites that I study as these rocks the possibility of radioactive material I collected samples of the soil in the ancient Tanis area and used a gamma ray spectroscopy technique to measure the normal radiation activity to determine the concentration of uranium nuclides 238U, thorium 232Th and 40K potassium in the collected soil samples (CR-39) as well as the use of the Digilert 50 dosimeter to confirm the results and to determine the radioactive dose emitted from the soil and to know the extent of the danger that may affect tourists visiting this tourist area as well as workers in the This area, if any, and achieve the necessary security for the renaissance and development of the field of archaeological tourism.

This thesis includes four chapters:
Chapter 1 (Introduction)
* A brief overview of tourism and its importance to the Egyptian economy as well as the geography of Tanis archaeological site and the importance of the historical Sanh stone area and its important artifacts in ancient Pharaonic civilization.
* Presentation on radiation and its types, whether natural or artificial, its sources and its impact on the individuals it may be exposed to.

* An overview of radon 222 Rn, which is one of the most important sources of natural radiation, as well as its presence in water, soil and closed buildings as well as its impact on public health.
* Finally, the objectives of this study were summarized in several points.

Chapter 2 (Literature review):
In this chapter, previous studies were presented in this research point, which was conducted in different countries in the world for measuring the natural radiation of soil samples as well as concentrations of radon, in order to make a research comparison between the results of this research and the results of other researches.
Chapter 3 (Experimental procedures & Analytical methods ):
This chapter explain how to collect samples from the site where twenty soil samples were collected from different places on the site were illustrated with maps attached to the research and then equipped with drying moisture and screening to obtain homogeneous soil so that it can be measured by different techniques.
The various techniques used in the research were also explained the practical methods of measurement as follows in points
* In this chapter full and general description of the instrument and components of high-purity gamma-ray spectroscopy technology as well as its calibration method and how to measure the concentration of radionuclides in soil samples.
* part of this chapter description of the nuclear solid state detector (CR-39) technology and how it is used to measure the concentration of radon gas in soil samples, whether in site or in the lab, as well as a description of the nature of the nuclear solid state detector (CR-39) and its types and how to calibrate it.
* In this chapter description of the AlfaGuard device component and how use in calibrating the nuclear solid state detector (CR-39).
* Demonstrate the technique of using the Digilert 50 dosimeter to determine the radioactive dose emitted from the soil.

Chapter 4 (Results and Discussion)
This chapter contains the actual measured results of the soil samples measured by the above mentioned devices and techniques as well as using the laws in the calculation of radionuclides in the samples
* Measurement of radionuclide concentrations of 226Ra, 232Th and 40K
in 20 soil samples collected from different places in site using high purity germanium detector. These values were ranged from ( 3.90± 0.78 ) to( 9.44±1.59 )Bqkg-1 with an average value of (5.96 ± 1.66) Bqkg-1 for 226Ra, The 232Th activities were ranged from (1.09±0.42) Bqkg-1 to (9.50±2.65) Bqkg-1 with an average value of ( 3.78 ± 1.65) Bqkg-1 and for 40K, the activities were ranged from (43.77±1.59) Bq kg-1 to(106.69±11.90) Bqkg-1 with an average value of (70.34 ± 7.18) Bqkg-1.

* The maximum acceptable values for radium, thorium and potassium are 30, 35 and 420 BqKg-1, respectively according (UNSCEAR, 2000) which indicates that for all soil samples, all activity values of 226Ra, 232Th and 40K are under the accepted limit.

* The radiological indices which calculation are based on the obtained results of activity concentration such as radium equivalent activities (Raeq) which are in soil samples were ranged from (8.98±1.77) Bq kg-1 to (25.68±6.89)Bqkg-1 with an average value of 16.78±4.58 Bq kg-1 All these values are less than the world wide average value (370 BqKg-1) reported by (UNSCEAR, 2000).

* Determination of radiation hazard indices (Hex & Hin) and (I? & I?) in all soil samples under study and all samples show indices less than unity, proposed by the European commission (Ec, 1999)

*Estimation of absorbed gamma ray dose (nGyh-1) for all soil samples The values were varied from (4.38±0.81) nGyh-1 to (11.93±3.15) nGy h-1 with an average value of (8.037±2.09) nGy h-1.This values are less than the world wide recommended value (59 nGyh-1)reported by (UNSCEAR, 2000). Then the adsorbed dose, the annual effective dose equivalent (mSvy-1) is calculated for all soil samples obtained values are less than the permissible limit of unity.

* The results of radon concentrations by SSNTD’S from studied Samples which collected from site and measured in Lab by can technique according are ranged from 87.78 ± 11.47 to 225.49 ± 35.59 Bq/ m3 , with a mean value of (137.96 ± 19.13 ) Bq/ m3. The results of radon concentration measurements by SSNTD’S from studied Samples which fixed in site are ranged from 72.18 ± 8.94 to 143.55 ± 16.26 Bq/ m3, with a mean value of (108.11 ± 12.03 ) Bq/ m3.this results in lab or site are less than the permissible limit.
* Calculation of radon exhalationrate (ERn)(Bqm-2s-1) and radon emanation coefficient (f)% with an average value of (3.78±0.527) 10-5 Bqm-2s-1 and (1.89±1.29) %.

* Radiation dose was calculated by mathematical equations and the results ranged from 272.12 ± 33.70 nS/h to 541.16 ± 61.30 nS/h with a average value 407.56±45.35 nS/h, and the dose was measured using the Digilert 50 dosimeter then the results ranged from 252 ± 12.53 nS/h to 524 ± 26.76 nS/h with average value 389.5±16.9 nS/h and the results were compared.

Chapter 1
Introduction

1.1 Overall view :

Tourism is the most important resources of the economy in most countries of the world, especially in Egypt . As the tourism industry is one of the pillars of the Egyptian economy as it contributes 11.3% of gross national income and provide 19.3% of the total hard currency and a huge proportion of jobs in terms of the proportion of workers in the tourism sector, 12.6% of the total labor force in Egypt and all this rates according to the Egyptian General Authority for Tourism Development.

Due to these great importance it was to be of interest to local or foreign tourists coming to the tourist areas to watch and find out the civilizations of ancient Egypt and protect them from all hazards which they may be exposed during their journey, and especially the health aspect and because these regions contain different types of granite or limestone rocks and soil had to be studied to see its radiation activity and study the concentrations of radon gas out to make sure it will not cause side effects to any of the tourists.
This study addressed the archaeological area Tanis ( San El-hagar ), one of the most important archaeological sites in Egypt.
Tanis ( San El-hagar ) A subsidiary of the city of Husseiniya villages. Located 150 km to the northeast of Cairo.
http://www.sharkia.gov.eg/Tourism1/asar/san.aspx .

Figure( 1.1,a) :Tanis ( San El-hagar ) map with Collected samples map .
( https://upload.wikimedia.org/wikipedia/en/4/4b/Nile_Delta_-_Naucratis.png),(https://commons.wikimedia.org/wiki/File:Tanis_plan_e.jpg)

Figure(1.1,b): the map of ten sample which collected from royal necropolis of Tanis Site. http://www.touregypt.net/featurestories/tanistombs.htm
San El-hagar known in Egyptian texts as «Djant», and there were in the Torah «Zoan», and in the Coptic «Gant», and in the Arab «San». Because of the many stones in the region it has become known San El-hagar as showen in figure (1.1,a).
– The capital of the nineteenth of Nome of Lower Egypt, and the capital of Egypt in the Twenty-First Dynasty era .Because of religious, historical and archaeological importance of the area, the attention began since the invasion of the French expedition to Egypt in 1798. The pry it scored some of its effects, many scientists such as: Lepsius , Broujh , Mariette and Petrie then Monte, who revealed in the royal tombs for «the treasures of Tanis». Since many years working in the region French mission in a bid to unveil a lot of mystery that still surrounds the city’s historical and archaeological point of view.

1.2 The most important effects of the region :-

1- temples: – The area includes a group of temples built in the reign of King «Ramses II», including the great temple and the small temple and the temple of the goddess «curses». The great temple modeled on the temples of the modern state came layout. The inclusion of a large number of obelisks bearing the name of King Ramses II, additions have been made to the temple during the reign of some of the kings of the two families first and twenty-second session .

Figure( 1.2,a):Temple of Ramses II. Figure( 1.2,b):Tempels of Mut and their child Khonsu.
http://www.touregypt.net/featurestories/tanis.htm

2- city wall.
3- the royal tombs :- is the cemetery, which includes graves of some of the kings of the two families first and twenty-second and twenty-some queens, princes and military commanders. Located on the campus of the great temple of the god Amun in the southwestern corner of it. The detection of the cemetery in 1939 during the French archaeological expedition headed by «Monte» drilling in the region, and was located under the Mud brick houses dating from the Ptolemaic era. It is this cemetery came out masterpieces of jewelry and coffins and tools of daily life and religious of silver, gold and symbols, which abound in the Egyptian Museum in Cairo .

4- the sacred lake: – The area includes sacred lake devoid of water, was part of the Great Temple. And almost the only lake known temples in the Delta. It is known that the sacred lakes were few, despite the large number of Egyptian temples, and perhaps the most famous Karnak Temple Lake and Lake Dendera Temple .

5- obelisks: – The area boasts a wide range of obelisks perhaps the most numerous in any archaeological area in Egypt, but unfortunately languished as a result of the fall in different periods of the history of Egypt, perhaps because of subsidence in the soil or to the occurrence of earthquakes. Some obelisks broke into more than one part, and some have taken to public places in Egypt, also came out some obelisks to Europe to decorate the fields of some countries. All the stone obelisks of pink granite and most of them belonging to King Ramses II .

1.3 Movable effects that came out of the region:

1- Painting the four hundred year: -is the panel set up by King Ramses II in honor of his father and grandfather visit to this city at one time. This was in the reign of King Horemheb, while Grandpa was one of the commanders of the army and the father was an officer in it. This visit has about 1330 BC, had already been on the worship of the god «six» in this city 400 years, and going back 400 years, ie to 1730 BC, the year of the Declaration of the coronation of God «six» god of the country, we find this year is the year of entry of the Hyksos, Egypt .
2- The treasures of Tanis: – found in the tombs of the kings of the two families first and twenty-Althanihwalashran .
3- A group of statues of the Sphinx: – bearing the names of Ramses II and Merenptah and which dates back to the era of the Twelfth Dynasty, and then re-used in the reign of these kings, is on display in the Egyptian Museum.

. Figure( 1.3):Great Sphinx transferred from Tanis
https://www.ancient.eu/image/5855/

4- Many of the obelisks, which fell over a long period of time and the more than ten obelisks .

1.4 Economic importance of the Tanis region :

The archaeological area Of Tanis (San El-hagar) approximately 500 acres in length from north to south, about three kilometers and a width of one and a half kilometers, and an estimated height of thirty meters, making it dominated on the territory of the Western Delta.According to statistics Visitor effects East Delta region that the number of tourists who visited the archaeological area Of Tanis (San El-hagar) in 1999 has reached 2180, the number of foreign students 585, and the number of visitors in 1510 Egyptians visitors.
Tourists who visit the area of the effects of Tanis (San El-hagar) groups of different nationalities (Spain,Italy,Belgium, Poland and America, etc. )
Most of these statues, tombs and temples made of limestone Granite and milk stones, which may contain significant quantities of naturally or technologically enhanced levels of radioactivity
Generally, the specific activities of 238U, 232Th and 40K in this stones Also the body radiation is mainly refers to radon gas existed in these materials which can affect the person’s nervous system, make the person depressed, and even lead to lung cancer and other diseases. So, it was necessary to study these emissions and their different effects on humans and the environment to avoid the radiological hazards effects .

1.5 Naturally Occurring Radioactive Materials (NORM):

NORM is an acronym for Naturally Occurring Radiactive Material, which is likely to include all radioactive elements in the environment. However, the term is used more specifically for all naturally occurring radioactive materials , where human activities have increased exposure compared to unchanging conditions (Ademola, 2009). Actual radionuclide concentrations may or may not have been increased; if they do, the Technically-Enhanced term (TENORM) may be used. Long-lived radioactive elements such as uranium-238 (238U), thorium-232 (232Th) and potassium-40 (40K) and any decay products, such as radium and radon, are examples of NORM. These elements have always existed in the earth’s crust and atmosphere, and are concentrated in some places, such as uranium ore bodies that can be extracted. The term NORM also exists to distinguish “natural radioactive materials” from anthropogenic sources of radioactive materials, such as those produced by nuclear power and used in nuclear medicine, where the radioactive properties of a material can be useful. But from the perspective of radiation doses to people, this distinction is completely arbitrary.

NORM spreads in soil, clay, sand, rocks, and many ores and minerals, goods, products, by-products, recycled waste, and devices used by humans. Because it is widely distributed, it leads to a normal radiation background that varies by approximately two degrees on the ground. This means that all types of organisms are exposed to this radiation, and in most cases this exposure is not controllable.

1.5.1 The Sources of NORM:

NORM is widely diffused and in general very diluted. However, it can be concentrated either through the deliberate nuclear cycle (or unintentionally). For example, radon in the atmosphere is a very minor concern, but when energy-efficient homes are built, the radon levels indoors may be increased by factors of several hundred. Similarly, radium in production water from an oil well may not be a serious concern, but it may lead to a build-up of radioactive scale inside pipes that require special handling in the future.

In many resource-based industries, normal industrial practices may increase the concentration of these elements to levels where special precautions are needed for handling, storing, transporting, and disposing of the elements. Examples of such industries include:
1- working or tunnelling in areas where small amounts of indigenous radioactive minerals or gases may be present, such as in underground caverns, electrical vaults,tunnels, or sewer systems.
• 2- oil and gas production, where trace quantities of NORM may be found in the hydrocarbon bearing geological formations.
• of NORM naturally found in plant materials and in coal.
3- the mining of non-radioactive minerals.
4- water treatment facilities, where fresh or waste water is treated through sorptive media or ion-exchange resins to remove minerals and other impurities from the water being treated.
5- mineral extraction industries, where trace amounts of NORM may be released from the mineral bearing rock, such as in the
phosphate fertiliser industry.
6- forest products and thermal-electric production industries where mineral ashes left from combustion may concentrate small amounts

1.5.2 Natural Background Sources:

1- Cosmic Radiation

The earth, and all living things on it, are constantly bombarded by radiation from space, similar to a steady drizzle of rain. Charged particles from the sun and stars interact with the earth’s atmosphere and magnetic field to produce a shower of radiation, typically beta and gamma radiation. The dose from cosmic radiation varies in different parts of the world due to differences in elevation and to the effects of the earth’s magnetic field. (USNRC Technical Training Center)

2- Terrestrial Radiation :

Terrestrial radionuclides are common in the rocks, soil, in water and oceans and also in building materials used for homes. Also all air contains radon which is responsible for the most doses received by humans. In addition, water contains small amounts of dissolved uranium 238U, thorium 232Th, and radium 226Ra. Some of these materials are ingested with food and water, while others (such as radon) are inhaled. The radiation dose from terrestrial sources varies in different parts of the world, but locations with higher soil concentrations of uranium and thorium generally have higher doses

The three main radioactive series are called Uranium, Thorium and Actinium series headed respectively by 238U, 232Th and 235U. Most naturally occurring radioactive materials undergo radioactive decay in these three chains through a sequence of transformations. The final product in each chain is a stable isotope of lead. The actinium series is less important, since 235U makes up only 0.71% by weight of natural uranium compared to 99.28%for 238U, and the activity ratio 235U/238U is less than 0.05. In addition, most of daughter products of this series are relatively shortlived and do not appear in the environment in significant concentrations (Todsadol, 2012).
The figures( 1.4,a,b) illustrates the decay scheme of radioactive series.

Figure( 1.4,a) :Decay scheme of 238U series (source of 222Rn and its progenies). http://phenix.vanderbilt.edu/~velkovja/VUteach/P HY225a/UraniumOre.htm.

Fig (1.4,b): Decay scheme of 232Th series (source of 220Rn and its progenies).https://pubs.usgs.gov/of/2004/1050/thorium.htm.

3- Internal Radiation:
In addition to the cosmic and terrestrial sources, all people also have radioactive potassium-40, carbon-14,lead-210, and other isotopes inside their bodies from birth. The variation in dose from one person to another is not as great as the variation in dose from cosmic and terrestrial sources. The average annual dose to a person from internal radioactive material is about 40 millirems/year.

1.5.3 Artificial or (man-made) radioactive sources :

1-Medical radiation sources: x- rays are identical to gamma rays; however, they are produced by a different mechanism. x- Rays are an ionizing radiation hazard.In addition to x- rays, radioactive isotopes are used in medicine for diagnosis and therapy.

2- Consumer products: such as static eliminators (containing polonium-210), smoke detectors (containing americium-241), cardiac pacemakers (containing plutonium-238), fertilizers (containing isotopes from uranium and thorium decay series), and tobacco products (containing polonium-210 and lead-210).

3- Nuclear power plants and radiation accidents:Environmental contamination dose occur through the normal operation of nuclear power plants and releasing radioactive materials. Although these materials are very limited and controlled, there some dose exposure due to mining and milling of uranium ore, Production of power in nuclear reactors and Disposal of radioactive wastes. Otherwise, some severe nuclear and radiation accidents are created radioactive contamination in the environment such as Chernobyl nuclear power plant, the Goiania accident was an incident of radioactive contamination in central Brazil that killed several people and injured many others and recently Fokoshema accident in Japan. (Samar, 2015)

4- Atmospheric testing of nuclear weapons: as a results of fallout radiation from the past atmospheric nuclear bomb tests, during the 1950s and 1960s, many radioactive were produced into the atmosphere. These materials have been transported around the world and eventually fall back to the earth. A wide range of
radioactive materials including: carbon-14, results from irradiation of the atmospheric nitrogen by neutrons resulting from the explosion, together with a number of outputs of nuclear fission, such as: 131I, 137Cs, 90Sr, 95Zr.

5- Industrial uses of radiation: include x-ray machines and radioactive sources radiography) used to test pipe welds, bore-holes, etc. Most people receive little of any dose from these sources (Nadia, 2014)

1.6 Interaction of ?-ray with Matter:

Radiations can be classified roughly into two
categories: non-ionizing radiations such as visible light and ionizing
radiations such as gamma-rays and X-rays. Also, ionizing radiations
can be classified into two categories directly ionizing and indirectly
ionizing radiations. Based on their electrical properties, the ionizing
radiations are classified into charged radiations such as alpha and
beta particles, and uncharged radiations such as gamma-rays and
neutrons. Also, according to their penetration power, radiations are
classified into soft radiations and hard radiations.
Radiations are mainly classified into four groups :
1- Heavy charged particles; including all particles with mass
equal to or heavier than one atomic mass unit (amu) such as
alpha particles, protons and fission products .
2- Light charged particles; including beta particles (negative
electrons), positron (positive electrons), internal conversion
electrons and Auger electrons.
3- Electromagnetic radiations; including gamma-rays (following
radiation decay or nuclear reactions), characteristic X-rays,
Annihilation radiation and Bremsstrahlung.
4-Neutrons; including fast neutrons, intermediate neutrons
epithermal neutrons, thermal neutrons and cold neutrons .

The interaction of radiation with matter define the suitable
detector so the radiation detectors depend basically on the interaction of incident radiation with the detector material, also depending on
both the physical properties of radiation in addition to the physical
and structural properties of detector materials.

1.6.1 Interaction of Photons with Matter :

The Photons have zero rest mass and charge and they have an
energy E. The relationship between the energy of a photon, its
wavelength ?, and frequency is ? (Knoll, 2000)

(1.1) E = h ? =
Where c is the light velocity and equals to 3×108 m/sec and h is
the Planck’s constant. Gamma and X-rays have well defined
energies, monoenergetic, and have different origins. Gamma-rays
have originated from the nuclei, while X-rays have originated from
the outer shells atoms. Bremsstrahlung radiation is produced by
accelerating and de-accelerating charged particles and has a
continuous energy spectrum.
There are three main mechanisms of interaction of gamma and
X-rays with matter that play the important role in radiation detection
processes. These mechanisms are known as photoelectric absorption,
Compton scattering and pair production. These interaction
mechanisms lead to the partial or complete transfer of gamma-ray
photon energy in the detector.

1.6.2 Photoelectric Absorption Process:

When gamma-rays interact with a bound atomic, some of the
gamma-ray energy is used to overcome the binding energy of the
orbital electron and most of the remainder is transferred to the free
electron as kinetic energy as illustrated in Figure (1.5). A very small
amount of recoil energy remains with the atom to conserve
momentum. Photoelectric absorption is important for gamma-ray
detection because the gamma-ray gives up all its energy, and the
resulting pulse falls in the full-energy peak.

Figure (1.5): Schematic representation of the photoelectric absorption .Process
Depending on the photon energy, the bounded orbital electrons
in the K or L shells will absorb a part of the incident photon energy
and are removed completely from the atom with a kinetic energy Ee
given by(Knoll, 2000).

Ee = h ? – Eb (1.2)
where; h? is the photon energy and Eb is the binding energy of the
electron. Ejected photo-electrons are energetic electrons and interact
with the matter exactly like beta particles. These electrons leave the
atom and create an electron vacancy in the inner orbits of the
residual excited atom. Either a free electron or an electron from a
higher orbit of the atom filled this vacancy and generate X-ray.
These X-rays can again interact with the absorber atoms and produce
another new photo-electron with less binding energy electron
(known as Auger electron) than the original photo-electron .
The probability of photoelectric absorption depends on the
gamma-ray energy, the electron binding energy, and the atomic
number of the atom(knoll, 2000).

: 1.6.3 Compton Scattering Process

Compton scattering is the process whereby a gamma-ray
interacts with a free or weakly bound electron in the outer shells of
the atom (E? >> Eb) and transfers part of its energy to the electron.
So the Compton scattering is an inelastic collision between the
incident photon and an electron, nearly free, in the absorbing
material. The incident photon dissipates a part of its energy and
deflects with a scattering angle ?. The simplest diagram illustrating
the Compton scattering is shown in Figure (1.6).

Figure(1.6): Compton scattering process .

Because the binding energy of the ejected electron is very
small compared to the incident gamma-ray energy, the kinetic
energy (Ee) of the electron is very nearly equal to the difference
between the incident and deflected photon energies and is given by:

Ee= h? – h?’ (1.3)

The energy of the scattered photon is given by:

h?’ = h? (1.4)

Where( h?) is the incident photon energy, (h?’) is the scattered photon
energy and m0 is the rest mass of the electron. The probability of
Compton scattering ? is given approximately by N.Tsoulfanidis,1995;

? = NZ f(E? ) (1.5)

Where N is the atomic density N = , f (E?) is a function of the
energy of incident photon, NA is the Avogadro’s number, A is themass number of the atom and ? is the mass density.

1.6.4 Pair Production Process :

Pair production is the main interaction mechanism for the
energetic photon. Practically, it becomes significant for the few MeV
energy photons. A gamma-ray with energy of at least 1.022 MeV
can create an electron-positron pair when it is under the influence of
the coulomb field in the vicinity of nuclei of the absorber atoms as
shown in Figure (1.7). In this interaction the nucleus receives a very
small amount of recoil energy to conserve momentum, but the
nucleus is otherwise unchanged and the gamma-ray disappears. This
interaction has a threshold of 1.022 MeV because that is the
minimum energy required to create an electron and a positron. If the
gamma-ray energy exceeds 1.022 MeV, the excess energy is shared
between the electron and positron as kinetic energy.

Ee- + Ee+ = E? – 1.022 MeV (1.6)

Figure(1.7): Schematic representation of pair production .

The electron and positron from pair production are rapidly
slowed down in the absorber. After losing its kinetic energy, the
positron combines with an electron in an annihilation process, which
releases two gamma-rays with energies of 0.511 MeV.

The probability of pair production varies approximately as the
square of the atomic number Z and is significant in high-Z elements
such as lead or uranium. It may be written in the form (Tsoulfanidis, 1995;Ali, 2011).

k = NZ2 f (E? ,Z) (1.7)

1.7 Radon gas:

In the early 1900s was the first discovery of radon During the early studies of radioactive elements at the turn of the century. Radon is a naturally occurring gas produced by the radioactive decay of radium and it was found that gaseous emanations themselves are radioactive elements. The gas associated with uranium and radium was called radon. The original “radon “is now known to be radon –222. Chemically, radon is a noble gas. In this way it is similar for example , to helium and neon(Borham,1998 ) . The radon hazards do not come primarily whatever they contact. The radon daughters are produced in the decay of radon (222Rn ). These products, called the “radon daughters” are also radioactive but , unlike radon .
The main problem on health is the stem from inhaling of radon daughters ,or dust particles carrying them, and the subsequent lodging of radon daughters in the lungs which may lead to many serious diseases such as cancer.

1.7.1 Isotopes and Properties of Radon:

Radon is a colorless and odorless mono-atomic gas. Atomic number of radon is 86, boiling temperature is – 61.8 °C and its density is 9.73 kg. m-3. It dissolves with water at a temperature of 20 °C. It is chemically inert and is the heaviest of the six noble gases constituting group O of the periodic table of elements. Unlike other gases in this group, it has no stable isotopes, and all of its isotopes are radioactive. There are three naturally occurring isotopes of radon, each associated with the radionuclides 238U, 232Th and 235U, respectively. 222Rn, which has a 3.82 day half – life, is part of the uranium (238U) decay chain. This nuclide is the most important of the three radon isotopes because of its concentrations in indoor air and due to the health effects associated with exposures to its radioactive decay products. 220Rn, alternatively referred to as thoron, is part of the thorium (232Th) decay series and has a half-life of 56.6 s. The third isotope is 219 Rn (named actinon), is a part of the (235U)decay series, does not contribute significantly to human radiation exposures due to both to the low natural abundance of the 235U precursor (approximately 20 times smaller activity concentration than 238U) and the very short (3.96 s)half-life (Abd Ali, 2002;Nagda, 1994).

1.7.2 Source of Indoor Radon:

The most of the radon found in homes comes from the soil air, which moves to the atmosphere by diffusion. A complicating factor is that this radon in soil air often dissolves in ground water, which then transports the radon to sites distant from where it was formed. The radon will emanate from the ground water when the water reaches the surface near foundations or near sumps. Drinking water from wells (or potable ground water) can also be the source of radon to the air.
1-Soil:
One formed in or on the rocks and soil particles the radon atoms must reach the air in the soil capillaries before they can be transported to the atmosphere through diffusion or pressure – induced flow. The amounts of radon, thoron and actinon in the atmosphere depend primarily upon the concentration of uranium and thorium in the soil and rocks.

The origin of radon and thoron in the earth’s crust stems is directly from the uranium and thorium and their decay products which distributed during minute in the ground soil within a few meters of earth’s surface.

The effectiveness of radium in supplying radon to the soil pores for transport to the atmosphere depends not only upon the total concentration of radium atoms present per unit mass but also upon the fraction of those atoms in the soil particle surface so that the newly f ormed radon atoms can escape into the pores and capillaries. The ratio of the radium atoms so situated to the total number of radium atoms present is called the emanating coefficient”. This fraction is also referred to as “emanating power” (Wilkening, 1990).
The radium concentration in soil usually lies in the range of 10
Bq.kg-1 to 50 Bq.kg-1, but it can reach values of hundreds Bq.kg-1, but an estimated average is 40 Bq / kg (ECA,1995). The ingress of radon from the soil is predominantly one of pressure – driven flow, with diffusion playing a minor role. The magnitude of the inflow varies with several parameters,the most important being the air pressure difference between soil air and indoor air, the tightness of the surfaces in contact with the soil on the site,and the radon exhalation rate of the underlying soil (ECA,1995).

2-Building Material :

Natural materials such as sand, soil, rock and cement, etc, which
contain traces of natural radioactivity of 238U,226Ra and40K were used as building materials for construction of houses and buildings, etc. 222Rn from uranium series, may be released from ground, rocks and also from building materials, and accumulate, with its short lived progeny in the atmosphere inside of the dwellings (Amrani etal., 1999).
Since most of the building materials produce some radon, certain materials can act as significant sources of indoor radon. Such materials have a combination of elevated levels of 226Ra (the radioactive parent of radon) and a porosity that allows the radon gas to escape (UNSCEAR, 2006).
Radon exhalation from building materials depends not only on the radium concentration, but also on factors such as the fraction of radon produced which is released from the material, the porosity of the material and the surface preparation and finish of the walls (ECA, 1995).
: 3-Water
Since rocks and soil contain radium, therefore, underground water and surface water should contain the dissolved 222Rn gas. The concentration of 222Rn in ground water depends on the concentration of its parent 226Ra in underlying rock. The short-life of 222Rn (3.82 d) together with the slow rate of migration of ground water allows the 222Rn in solution to be in approximate secular equilibrium with the 226Ra in the local rock. Radon concentration in water has been known to be high in most granite and in high-grade metamorphic rocks, whereas less metamorphosed rocks have somewhat less 226Ra (Sevasekarapandian et al., 2002). The most of investigation were made to correlate 222Rn concentration in water supplies with indoor radon levels lead to semi empirical relation that gave the ratio of indoor level to water level of radon to be of the order of 10-4.

: 4- Natural Gas

Natural gas can accumulate radon gas from radium in the rocks and materials surrounding the gas formation. Almost all natural gas is processed, stored, and shipped by pipeline. Some of the original radon will have decayed simply due to the time elapsed between initial production from the well and final delivery to the point of use. Other major appliances such as gas furnaces and water heaters are vented, and the radon released in these applications will be vented outdoors with the combustion gases (Nagda, 1994). Radon emanates from the porous geological formations and mixes with the natural gas. Then the radon gas moves along with the natural gas to the point of use of the natural gas such as kitchens and room heating. The amount of radon concentration in natural gas at production wells have been measured from undetectable limits up to about 5.4*104 Bq.m-3 (Tufail, 1992; Aamir, 2013).

1.7.3 Health hazards from radon:

The exposure to high level of radon gas through breathing of air increases the risk of lung cancer, where alpha particles can cause damage to tissues as well as to the DNA in the cells nuclei as showen in figure (1.8) (Ramadhan, 2012).Cancer is generally thought to require the occurrence of at least one mutation, and proliferation of intermediate cells that have sustained some degree of DNA damage which can greatly increase the pool of cells available for the development of cancer (World Health Organization, 2009).

Figure (1.8): Inhalation of radon gas and alpha particles cause damage to tissues and DNA .http://radonattahoe.com/problem.htm .

Radon can be found inside of buildings as well as in the outside atmosphere.222Rn decays into many others particles such as218Po and 214Po. The decay of 222Rn,218Po and 214Po causes an emission of alpha particles. When alpha particles enter the lung will causing genetic damage to the epithelial cells lining the air ways and may lead to lung cancer (Weitberg, 2002). Therefore, it is unlikely that there is a threshold concentration below which radon does not have the potential to cause lung cancer. Health effects of radon, most notably lung cancer,have been investigated for several decades. Initially, investigation focused on underground miners exposed to high concentrations of radon in their occupational environment. However, in the early 1980,several surveys of radon concentrations in homes and other building were carried out, and the results of these surveys, together with risk estimates based on
the studies of mine workers, provided indirect evidence that radon may be an important cause of lung cancer in the general population (World Health Organization, 2009).

The excess lung cancer risk is defined as the occurrence of excess deaths per million persons per year (MPY) due to the lung cancer as a result of exposure to radon and its daughter products. The risk coefficient, defined as the number of lung cancer cases per MPY per working level month (WLM), is determined from the occupationally exposed mine workers.

The excess lung cancer risk is calculated using the following
Relation:

Excess Cancer Risk = Equilibrium Factor * Occupancy Factor * Risk Factor * WLM (1.8)

where the occupancy factor is the fraction of time spent indoor (Shafi, 2005).
Radon is now recognized as the second most important cause of lung cancer after smoking in the general population .Since lung cancer is rare before age 40, exposure during childhood may contribute very little to the chance of developing lung cancer. This factor may also be helpful in retrospective studies of environmental radon, since estimating childhood exposures may not be as important as estimating exposures received later in life (NCRP Commentary, 1991;Aamir, 2013).

1.8 Radioactivity:

Radioactivity is the process of the spontaneous decay and transformation of unstable atomic nuclei accompanied with the emission of nuclear particles and electromagnetic radiation.

The unit of radioactivity is Curie (Ci) which is defined as the quantity of any radioactive material gives 3.7*1010 disintegration per second (dps).

Ci = 3.7*1010 dps (1.9)

It is the SI system of units. Another unit of radioactivity is called Becquerel (Bq) which is defined as the activity of one disintegration per second.Bq = 1 disintegration / second .Therefore, we have

(1.10) Ci = 3.7*1010 Bq

1.8.1 Absorbed Dose:

Absorbed dose is a measure of energy deposited in any medium by all types of ionizing radiation. The original unit of absorbed dose was the rad and was defined as an energy deposition of 0.01 J.kg-1.
In the SI system of units, the unit of absorbed dose is called the Gray (Gy) and is defined as an energy deposition of 1 J.kg.

(1.11) Gy = 1 J.kg-1 = 100 rad

1.8.2 Dose Equivalent:

The dose equivalent is introduced to take account the relative biological effectiveness of different types of radiation. It is defined that the equal dose equivalents have an equal chance of producing the somewhat random biological effects that occur at low and moderate dose levels, independent of the type of radiation. The dose equivalent HT is related to the absorbed dose D by a dimensionless parameter commonly known as the quality factor Q, which takes on different values for different radiations

(1 . 12) HT = Q * D

1.8.3 The Decay and Growth of Radioactive Materials:

Radioactive decay is the process in which an unstable nucleus spontaneously disintegrates to emit energy in the form of ionizing particles or electromagnetic radiation or both the spontaneous decay may lead to changes in the charge ( Z ) and mass ( M ) of the unstable atomic nucleus. Radioisotopes can either be natural or artificial.
Examples of natural radioisotopes include unstable isotopes arising from the decay of primordial uranium and thorium. Artificial radioisotopes are manufactured by producing a combination of neutrons or with atomic nuclei to produce radioactive nuclei protons that does not exist in nature ( Ali, 2011 ) .

1.8.4 The Decay equation:
All radioisotopes decay at a rate obeying the radioactive decay law. The radioactive decay law states that the number of radioisotope nuclei within a population of N radioisotope nuclei decaying at any instant is proportional to N ;

N=N_(0 )×e^(-? t) (1.13)

Where ? is the radioactive decay constant that characterizes the probability of decay of any nucleus in unit time. From the above equation , the number of present nuclei in a sample decreases exponentially as the time increases.

There are three conditions that may in decay schemes: Secular, transient equilibrium, and the state of no equilibrium.

1.8.5 Transient equilibrium ( T 1 / 2 Parent >T 1 / 2 Daughter ) :

Transient equilibrium is a steady-state condition between the parent and daughter nuclides. The condition upon which transient equilibrium rests is that :
1. The parent nuclide must be longer lived than its daughter, that is, it is necessary that ?A < ?B . However,
2. The ratio ?A /?B , should fall within the limits 10 – 4 < (?A / ?B) ?B , no equilibrium is attained. Instead, the parent nuclide of shorter half-life eventually decays to a negligible extent; In this case the daughter nuclide builds up faster than it decays. Essentially all parent nuclei transform into daughter nuclei and the activity of the sample comes from the daughter nuclide only as shown in Figure( 1.11 ) (L’Annunziata , 2003).

Figure (1.11): Illustration graph of none equilibrium state.

1.9 Aim of the work :

Tourism is the most important sources of national income to any country is the backbone of the economy, especially in Egypt, so it had to be interest in them and contribute to the revitalization and protection of tourists coming thousands Mona various parts of the world from the danger of exposure to radiation sources, so it was necessary to measure background radiation and concentrations of radon and uranium. The aim of this study includes the following themes:

1-using CR-39 can-tech to measure Radon concentration in Site.
2- using CR-39 can-tech to measure Radon concentration from collected samples in lab.
3- Calculate and measuring radiation in site using Digilert 50 dosimeter .
4-measring Natural radio nuclide from collected samples using High Pure Germanium Technique (HPGe) .
5- correlation of measured Radon concentration in Site and Lab.
6- correlation of calculated and measured dose .
Chapter 2
Literature review

2.1 Overall view :

This section of the thesis, presents a description of an intensive studies and surveys carried out for measurement of radon concentration levels in various soil samples especially which collected from archaeological sites and naturally occurring radioactive materials (NORM) in Egypt and different countries all over the world up to date.

2.2 literature survey for radon measurements in soil:

(Ajaj, 1999 ) Estimated the radon concentrations in Makkah. Indoor radon measurements inside bedrooms were performed in fifteen various districts in Makkah with an average value of 56±23 Bq.m-3. Measurements were also carried out inside five tunnels and inside mashayer mosques with an average values of 52±13 Bq.m-3 and 40±22 Bq.m-3, respectively.

(Abd Ali, 2002) Studied the effect of higher voltage power lines (400 kV and 132 kV) upon radon concentration and its decay results utilizing CR-39 as SSNTD. She was found that the value of weighted average of radon concentration inside the buildings which were under the effect of high voltage 400 kV is 91.77 ± 0.1122 Bq.m-3and under the effect of high voltage lines 132 kV was equal to 60.03 ± 0.266 Bq.m-3, as for the buildings which were far away from the high voltage lines, it was equal to 23.2651± 0.773 Bq.m-3.

(Al-Jarallah et al., 2003) Determined radon concentrations in dwellings of four Saudi Arabian cities. The results of the survey in those cities showed that the overall minimum, maximum and average radon concentration were 7, 137 and 30 Bq.m-3, respectively. The technique used in this survey is based on CR-39 nuclear track detectors.

(Karim, 2004) Estimated radon concentrations in soil samples taken from area situated in south east of Baghdad – Iraq (Al- Wardia, Al – Twitha and Haiy Al – Ryaid). He was found that the higher concentration of radon gas in Al – Wardia was 697.18 Bq.m-3, after it in Haiy Al-Ryaid it was163.54 Bq.m-3and in Al–Twitha it was 119.17 Bq.m-3.

(Al- Qahtani et al., 2005) Estimated indoor radon measurements in the Women College, Dammam, Saudi Arabia using CR-39 as SSNTD.The average radon concentration in the ready-made concrete buildings was 6±2 Bq.m-3 whereas for the ordinary concrete brick building was 24±2 Bq.m-3.

(Al-Mustafa et al.,2005) Determined radon concentrations in the desert caves of Al-Somman Plateau in the eastern Province of Saudi Arabia. Passive radon dosimeters based on alpha particle etch track detectors with an inlet filter, were used in this study. The results of the study showed that the average of radon concentration in different caves ranged from 74 up to 451 Bq.m-3.

(Banjanac et al, 2006) Measured radon concentrations in secondary schools in Serbia using SSNTDs. The radon concentrations ranged from 21 Bq.m-3 to 35 Bq.m-3.

(Al-Saleh, 2007) Measured radon concentrations in dwellings of Riyadh city in Saudi Arabia. The range of annual mean radon concentrations for all sites was 2 – 69 Bq/m3 with an average of 18.4 Bq.m-3.

(Amin and Eissa, 2008) Measured radon concentrations using SSNTDs in Sannur cave, Eastern desert of Egypt. They were found that the average radon concentration for the cave was 836±150 Bq.m-3.

(Mohammed. A, 2008) Estimated the concentration of radon for twentyfour samples of soil distributed in six locations on the north part of Iraq. The study regions included each of Al- Sulaimaniya and Erbil Governorates using CR-39 detector. The average radon concentrations in Al- Sulaimaniya and Erbil Governorates were 22.30 Bq.m-3 and 26.17 Bq.m-3 respectively.

(Shafi et al., 2009) Studied indoor radon measurement have been carried out in four districts, namely, Jhelum, Chakwal, Rawalpindi and Attock of the Punjab Province. In this regard, CR-39 based detectors were installed in bedrooms, drawing rooms and kitchens of 40 randomly selected houses in each district. After exposing to radon in each season, CR-39 detectors were etched in 6M NaOH at 80°C and counted under an optical microscope. Indoor radon activity concentrations in the houses surveyed ranged from 15 ± 4 to 176 ± 7 Bq.m-3 with an overall average value of 55 ± 31 Bq.m-3 . The observed annual average values are greater than the world average of 40 Bq.m-3. Maximum indoor radon concentration levels were observed in winter season whereas minimum levels were observed in summer season. None of the measured radon concentration value exceeded the action level of 200–400 Bq.m-3.

(Shafi et al., 2010) Measured radon concentrations in workplace buildings of the Rawalpindi region and Islamabad Capital area, Pakistan using CR-39 based on radon detectors. The measured indoor radon concentration in the buildings surveyed ranged from 12±5 to 293±19 Bq.m-3 with an overall mean value of 64±32 Bq.m-3.

(Abu-Haija et al., 2010) Studied three of districts in Tafila province, which is located in the south part of Jordan and where the most important hot spa and phosphate mines are located. The main concern in these investigations is to measure the indoor radon concentration levels by means of CR-39 detectors installed in randomly selected houses during winter season. The exposure time started from December 2008 and lasted for ninety days. After exposure, the detectors were etched in a KOH solution at 70°C for 8 h. The obtained average values of indoor radon concentration in the three different districts were ranged from 20.45 to 32.41 Bq.m-3. It was found out that the Ayma district possesses the highest radon concentration. Meanwhile, the district of Aina Al-Badah possesses the lowest.

(Atia et al., 2010) Measured radon concentrations in Missan Governorate using CR-39 as SSNTD. They were found that the radon concentrations ranged from 131.5 Bq.m-3to 281.139 Bq.m-3.

(Abdelzaher, 2011) Measured radon concentration, in the atmosphere of the archaeological place, namely Catacomb of Kom El-Shuqafa, in Alexandria, Egypt, which is open to the public, using time-integrated passive radon dosimeters containing LR-115 solid-state nuclear track detector. The measurements were performed throughout winter and summer. Seasonal variation of radon concentration, with the maximum in summer ranging from 243 to 574 Bq.m-3 and minimum in winter ranging from 64 to 255 Bq.m-3 was observed.

(Muhammad .R et al., 2011) Estimated an indoor radon measurement survey has been carried out in the dwellings of Balakot city of North West Frontier Province of Pakistan using CR-39 based radon detectors. The main objective of this survey was to estimate radiation doses received by the dwellers of the Balakot city due to the indoor radon exposure. For this purpose CR-39 based radon detectors were installed in bedrooms and living rooms of 50 randomly selected houses. After 90 days of radon exposure, CR-39 detectors were etched for 9 h in 6 M NaOH at 70 0 C and the observed track densities were related to radon concentrations. The measured indoor radon concentration ranged from 15±8 to 267±3 Bq.m-3 and 15±8 to 205±3 Bq.m-3 in bedrooms and living rooms, respectively. Weighted average radon concentration varied from 16±8 to 222±3 Bq.m-3.

(Mohammed .A, 2011) Measured radon concentration for seventeen samples of soil distributed in three sulphuric springs, in addition to other regions as a background in Hit city in Al-Anbar Governorate – Iraq. Radon concentrations in soil samples were measured using CR-39 detectors. Radon concentrations in the first spring varies from 258.253 to 347.762 Bq.m-3, where as for the second spring varies from 230.374 – 305.209 Bq.m-3 and for the third spring varies from 292.002 to 336.023 Bq.m-3 and the average radon concentration in other regions was 187.821 Bq.m-3.

(Iqbal et al., 2012) Estimated an Indoor radon data were collected from the dwellings lying on the sedimentary rocks (sandstones, siltstones and clays) of the Murree Formation, Nagri Formation, Dhok Pathan Formation, Mirpur conglomerate and surficial deposits of the Kotli area in Azad Jammu and Kashmir, Pakistan. Radon measurements were made using the passive time-integrated method using Kodak CN-85 Solid-State Nuclear Track Detectors. The radon concentration in dwellings varied from 13 ± 6 Bq.m-3 to 185 ± 23 Bq.m-3, with an average of 73 ± 15 Bq.m-3.The radon concentration in the Murree Formation, Nagri Formation, river terrace and Dhok Pathan Formation were 89.7 ± 16.5, 72 ± 15, 68.5 and 69 Bq.m-3, respectively. The average value of all the measured concentrations (73 ± 15 Bq.m-3) .

(Aamir, 2013) Estimated and survey of a total of 112 locations with one dosimeter per site was carried out at the university of Baghdad- Jadiriyah site. In this study, the concentrations of radon and uranium, radon exhalation rate and background of gamma rays were estimated, and the dose due to indoor radon concentrations was calculated. The minimum, maximum and average of indoor radon concentrations were 22.399±2.182 Bq.m-3, 66.447±1.98 Bq.m-3 and 45.487±1.157 Bq.m-3 respectively.

(Kakati, 2014) Measured the radon exhalation rate of soil as well as indoor radon concentration of a few places of Karbi Anglong District of Assam. The technique of passive method has been adopted using LR-115 (type-II) plastic detector. Significant variations in radon exhalation rate and indoor radon concentration have been observed for the studied locations. The minimum and maximum values of radon exhalation rate as found for the present investigation are 348.37±17.4 mBq.m-2h-1 (10.52±0.52 mBq.kg-1h-1) and1864.2±92.7 mBqm-2h-1(56.29±2.8 mBq.kg-1h-1 ).For indoor radon concentration the minimum and maximum values as found from this study are 81.26±4.06 Bq.m-3and 277.78±13.89 Bq.m-3.

(Amin et al., 2015) Measured an indoor radon concentrations in the dwellings of 10 neighborhoods located on the west side of the river Tigris (Al-Karkh) in Baghdad city using passive dosimeters. CR-39 solid state nuclear track detector (SSNTD) technique was used for radon measurements. Ninety-one dosimeters were distributed in the dwellings of the study area, three dosimeters were planted in three rooms of each house depending on the usage of the room (bedroom, living or sitting room and kitchen). They were left for a period of 3 months during winter time from November 2013 to February 2014. Radon concentrations were found to range from 64.9 Bq.m-3 to 94.7 Bq.m-3 in Daoudi and Hayy Al-Jamiaa, respectively, with a mean value of 79.82±1.05 Bq.m-3.

(Ali, 2016 ) Determine the radon concentration using Solid State Nuclear Track Detector (SSNTD) type CR-39 in samples of feed grains which are available in the local market in Samawah city, Iraq. Sixteen different samples of feed grains have been collected; some of them from Iraq and others were imported. These samples well have been ground using a ceramic mortar and then dried by electric oven to get the best data (that works to increase the surface area and reduce the moisture content). Optical microscope has been used to calculate the number of tracks on the detector. The radon concentrations have been obtained by using the distribution technique within sealed-cup. The results indicate that the highest rate of radon found in the Nigella sativa (34. Bq.m-3) and the lowest rate of radon concentration was in the Vigna radiata and Medicago sativa (1 Bq.m-3).

(Meleksah et al., 2016) Measured radon ( 222Rn) concentrations in offices at the Me_selik campus of Eski_sehir Osmangazi University to estimate the effective dose of 222 Rn and its progeny for office occupants. The measurements were performed four times in 2011 over a period of 3 months using solid state nuclear track detectors (LR-115). A total of 381 LR-115 detectors were installed in 110 different offices, choosing three offices on each oor in the same building. 222Rn concentrations obtained in the _rst, second, third, and fourth measurement periods were 163.73 Bq.m-3 , 105.53 Bq.m-3 , 77.43 Bq.m-3, and 164.70 Bq.m-3 respectively.

(Asay and Bhardwaj, 2016 ) Measured an indoor radon concentration in different dwellings in Adwa using Passive techniques Solid-state nuclear track detectors (LR-115 type II plastic track detectors) in a bare mode. The detectors were properly arranged in 12 houses and collected after an exposure time of 47days. The detectors were etched using 2.5N NaOH solution at 60°C for 75 minutes. The films were studied under transmitted light microscope and counted the tracks for each film. The results show that, the indoor radon concentration in the dwellings varied from 14.22 Bq.m-3 to 161.74 Bq.m-3 with mean value of 56.72 Bq.m-3 and standard deviation of 40.43.

(Murtadha et al., 2017) Estimated concentrations of radon in agricultural soil in Cameron Highlands in Pahang, Malaysia. CR-39 plastic track detectors are used to measure concentration of radon rate in the soil samples. Results reveal that the mean radon concentrations in agricultural soil collected from Cameron Highlands are 198.44 ± 59.44 Bq.m-3. These concentrations are below than the action levels of 200 – 600 Bq m-3 as recommended by ICRP. According to the results, the areas of study are safe and do not pose health risks to the population in those areas, and thus the soil can be used for construction materials.

2.3 Literature survey for naturally occurring radioactive materials (NORM) in soil :

(Matiullah and Hussein, 1998) Measured of the natural radioactivity in different soil samples were taken from Iran. The ranges of the activity concentration of 226Ra,232Th, and 40K were 8.0 – 55.0, 6.0 – 42.0 and 250.0 – 980.0 Bq.kg-1,respectively. The average calculate D absorbed dose rates from terrestrial gamma rays in normal background areas were 64.0 nGy/hr (Sohrabi, 1997).In Jordan, The mean specific activities of 226Ra, 232Th, and 40K were 48.6(31.5 – 72.3), 27.8 (8.0 – 37.8), and 382.5 (207.6 – 467.7) Bq.kg-1, respectively.

(Nada, 2003) Estimated the variation in concentration of radionuclides in Egypt, at Um-Greifat area, Eastern desert and aftar investigation the area can be classified into A, B and C regions of high, medium, and low natural radioactivity. In region A, average concentration of 238U, 232Th, 235U and 40K ranged from 1858 – 4062, 29 – 151, 60 – 136 and 46 – 409 Bq.kg-1 ,respectively. The high activity concentration within region A points to an environmental hazard, while regions B and C have less exposure effect on human beings.

(Nour, 2005) Measured the average activity level of the natural radionuclides 226Ra, 232Th and 40K in Samples of phosphate fertilizers and farm soils were collected over the Qena governorate, Upper Egypt. For phosphate fertilizers, Activity concentration of 226Ra, 232Th and 40K were 366 ± 10.5, 66.7 ± 7.3 and 4 ± 2.6 Bq.kg-1, respectively. For farm soil and Nile island’s soil the corresponding values were 13.7 ± 7, 12.3 ± 4.6, 1233 ± 646 and 11.9 ± 6.7, 10.5 ± 6.1, 1636 ± 417 Bq.kg-1, respectively.

(El-Daly and Hussein, 2008) Estimated the average activity level of the natural radionuclides 226Ra, 232Th and 40K in Soil samples were collected from different locations of El Dabaa area, Northwestern desert in Egypt. Gamma spectroscopy was used to determine the concentration of naturally occurring radionuclides 226Ra (238U), 232Th and40K. The average activity concentration for soil samples were 22.12, 10.27 and 180.04 Bq.kg-1, respectively. The measurement results obtained from this study indicate that the region has background radioactivity levels within natural limits.

(El-Kameesy et al., 2008) Studied undertaken to evaluate the natural radioactivity levels in Libya, Northwest coast in the Tripoli region using gamma spectroscopy. The radioactivity concentrations for 226Ra, 232Th, 40K, and 210Pb were measured in 40 soil samples. It was observed that the activity concentrations of 226Ra, 232Th, 40K, and 210Pb in samples taken at depth 5-10 cm have an average 7.5±2.5, 4.5±1.3, 28.5±6.7, and 10.3±2.7 Bq.kg-1, respectively. The corresponding results at depths 50 – 70 cm are 6.7 ± 1.9, 4.2 ± 1, 26.6 ± 5.9 and 9.2 ± 3.9 Bq.kg-1,respectively. The range of the absorbed dose rate obtained for the soil samples is from 2.7 n Gy.h-1 to 6.1 n Gy/h with an average 4.4 ±1.3 n Gy.h-1, while the average effective dose rate is 0.0054 ±0.0016 m Sv.y-1 with the range 0.0033-0.0075 m Sv.y-1.

(Lee and Husin, 2009) Measured the natural background gamma radiation and radioactivity concentrations were investigated from 2003 to2005 in Kinta District, Perak, in Malaysia. Sample locations were distant from any „amang? processing plants. The activity concentration of 238U, 232Th and 40K ranged from 12 – 426, 19 – 1377 and ?B

Or

sin (?) >??/??

However, if we increase the angle of the incidence of the track forming particle with respect to the normal of the detector surface, a stage is reached where the etching is:

??= sin?1( ) (3.7)
where the damage trail is not developed into a track. The ratio VT/VB is called the etching rate ratio and denoted by V. The higher the value of this ratio the smaller is ?? and the faster and more efficiently is the damaged trail developed into a track. In general, due to the varying energy loss rate along the track, VT is not constant and the sharp critical angle does not exist (Abdul Ahad, 2004).

3.5.5 Track Affecting Parameters:

There are two important factors that affect the appearance of a track; the track etch rate velocity VT and the bulk etch rate velocity VB The Track Etch Rate Velocity (VT) The track etch rate can be defined as the ratio of dissolution of a detector along the line of the track. Its value depends on the detector type, etching conditions, the particle velocity and its energy. Experiments prove that VT increased with increasing the rate of ionization for different organic and inorganic detector.The relation between VT and the temperature of the etching solution is (Al-uboode, 2009).

VT (?m.h-1) = B exp (-ET / k ?) (3.8)

where: B is constant, k is Boltzmann constant = 1.38 × 10-23 J mol/ ?, ? is temperature of the etching solution (?), ET = activation energy of the track etch (J).

3.5.6 The Bulk Etch Rate Velocity (VB):

The rate of chemical etchant that attacks the undamaged region surrounding the track is termed the bulk etching velocity VB. It is defined as the thickness that is removed from one of the surfaces of the detector as per time as a result of chemical etching effect (Al- Wasity, 2010). It is an important parameter for determining the track sensitivity of SSNTD. It depends on the construction of the plastic, the constituents of the etching solution, its concentration and temperature. It is found that for a given homogenous and isotropic solid, the bulk etch rate velocity VB increases exponentially with etching temperature and concentration of the etching solution. The bulk etch rate is found to satisfy the following relation (Al-uboode, 2009).

VB (?m.h-1) = A exp (-EB / k ?) (3.9)

Where:

A = constant
EB = activation energy of the bulk etch

3.5.7 Etching Efficiency and Sensitivity:

The etching efficiency is defined as the ratio of the counted tracks and the particles flux impinging the detector surface. The efficiency ? is given by:

? =1- ( ) (3.10)
Or

? =1- ( ) (3.11)
Where: V =
This means that the value of the etching efficiency depends on the track etched rate velocity VT and the bulk etched rate velocity VB. The efficiency can also be defined in terms of the critical angle as follows:

? =1- sin ?? (3.12)

Since: sin ?? =

Another etching parameter is termed etching sensitivity S is defined as the ratio between etching velocity along the track to the etching velocity at surface and can be calculated using the following equations (Al-Wasity, 2010).

S = – 1 (3.13)

S = V – 1 (3.14)

Where: V =

S = – 1 (3.15)

The detectors track registration efficiency largely depends on the;
(a) composition and concentration of chemical etchant.
(b) temperature and.
(c) etching time.

3.5.8 Calibration of SSNTD for Radon Measurements:

Any device used for relative measurements should be calibrated in order to obtain a calibration coefficient to convert the device reading to the value of measurement, so for SSNTD the calibration coefficient will convert the track density to the unit of radon concentration. The calibration coefficient ? (Track cm-2 d-1 / Bqm-3 of radon ) for SSNTD has a wide range depending on the geometry of the using configuration and also on many parameters that affect the results during the calibration. The calibration coefficient is very important because it can be used to determine many parameters related to radon by means of SSNTD such as ; diffusion coefficient and diffusion length, mass and real exhalation rate and effective radium content.

The calibration procedure is based on exposing the detector to a known integrating concentration of radon inside a well sealed standard calibration chamber of a known volume . The used chamber is manifested by its volume and the measured decay constant of radon gas inside it . This decay constant, which is a function of the chamber shape, can be used to evaluate the chamber, where it measures the leakage of radon gas from it . The second request for the calibration is the Radon source . Many sources can be used in the calibration experiment to get the integrating concentration over the exposure period . The integrating concentration C? = Bqm-3 d ) can be achieved by integrating the Radon concentration C(t) over the exposure period (t) by using the following equation (Abo-Elmagd, 2001 ).
C? = Co t – ( 3.16 )
Where, Co is the radon equilibrium concentration can be calculated from the equation (3.17 ), t and ? are the exposure time and decay constant .

Co = C (t) / {1- exp (-?t )}. ( 3.17)

In our experiment to determine the calibration coefficient of CR-39 for radon, the radon source and SSNTD’S ( in a diffusion cup with fiberglass filter ) were equipped in Alpha-Guard chamber . The concentration of radon C (t) is measured during experiment by using the Alpha-Guard monitor, which was used to calculate the equilibrium concentration (Co) of radon from eq (3.17) and then calculating the integrating concentration of Radon from eq.(3.16 ). The SSNTD’S were registered the alpha track density (?o) track cm-2. The calibration coefficient can be calculated from the following equation .

? = ?o /C? ( 3.18 )

3.6 Radon Measurement Techniques.
3.6.1 Passive Technique.
Passive techniques are more suitable for the assessment of radon exposure over long time scales and can be used for scale surveys at moderate cost (Ahn and Lee, 2005).

3.6.1.1 CR-39 Technique In Lab:

This technique has been implemented in several stages, including collecting soil samples, then Preparation them and then measuring them.

3.6.1.1.1 Sampling in Container:

After collecting and processing the samples, they are placed in a container in the laboratory in a dry place for at least 30 days in order to equilibrium the radon gas. This container is a cylinder made of a thick plastic material about 20 cm long and a diameter about 3 cm and placed in front of it in a tight container. A sample of the bolt is placed above it CR-39 Dimensions 1 cm * 1 cm as shown in the illustration figure (3.12). The container is also numbered and the CR-39 samples are stored and stored in the laboratory as shown in Figure(3.13).

Figure (3.12): Diagram for soil sample with CR-39.

Figure (3.13): Samples soil with CR-39 in the lab.

3.6.1.1.2 Eaching of CR-39:

The chemical etching of CR-39 detectors is usually carried out in thermostatically controlled bath . using aqueous solution of NaOH , with concentrations ranging from a Molarity of 1-12 (~ 6 M being the most popular) and the temperatures usually employed ranging from ~ 40 to 70 °C. putting the samples with the solution in the beaker as shown in Figure(3.14)
Figure(3.14): Chemical etching of CR-39 samples.

3.6.1.1.3 Counting Tracks with Optical microscope:

Optical microscope is capable of giving magnifications of (400 X) where the object piece (40X) and eye piece (10X). The track density is equal to the average of the total tracks divided by area of the field view. The tracks are shown in Figure (3.15) and the optical microscope is shown in Figure (3.16).

Figure(3.15) Tracks in sample which appear with Optical microscope.

Figure(3.16):The optical microscope with digital camera( Aamir, 2013).

3.6.1.1.4 Calibration of CR-39 :

Calibration of CR-39 was done using a device (AlphaGuard)and its Composition and components shown in section 3.4 and figure (3.8). In the next paragraph we will discuss how calibration works.

AlphaGuard operates in two modes, diffusion mode and flow through mode. The diffusion mode measures continuously in 10 or 60 minutes cycle,while the flow through mode operates in 1 or 10 minutes cycle. In the present study, the 60 minutes cycle was used where 222Rn gas gets in diffusion mode via a large surface glass filter into an ionization chamber. AlphaGuard is used to study the temporal variation in the Radon activity concentration as a function of temperature, air pressure and relative humidity. The radon concentration emanated from each sample inside the emanation container was monitored hourly and measured for an average period of 96 hour. The concentration of radon exhaled from Soil, Granit and Phosphate sample loaded inside the emanation container was allowed to build up with time in that period. Moreover, A PC Software support allows a graphic presentation and calculation of the average concentration in the measured period as seen in figure (3.17)

The detection process of radon in the AlphaGuard system is based on a designed optimized pulse ionization chamber. Each sample from Soil, Granit and Phosphate was powdered and put in a plate of surface area 0.04 m2 and placed into the bottom of the emanation container which was tightly sealed for the mentioned duration in order to measure the concentration of the exhaled radon from samples which fill the container due to the decay of parent 226Ra emitting ?- particles and ?-rays in the same time fixed CR-39 in can and Cover the other side with a chemical filter paper and then fix the can with silicone material inside the cylinder and then close the lock and leave them for about one week for each of the three samples. The radon 222Rn gas gets in diffusion mode via large-surface glass fiber filter into the ionization chamber where only the gaseous 222Rn may pass, while the Radon progeny products are prevented to enter the ionization chamber . Also at the same time the filter protects the interior of the chamber from contamination of dusty particles. The alpha particles emitted in the decay of radon and its daughter will ionize the air in the chamber. Due to the presence of applied voltage the electrons and ions are moved towards their respective electrodes. The resulting current is a measure of the quantity of decayed radon atoms. Counting is started after reaching equilibrium between radon and its progenies and the radon concentration can be obtained from the number of pulses. After about a week we open the closed container and then take the reading of AlphaGuard from the monitor and then take the can and get out CR-39 samples of them and we do the eaching to them and variation between density of tracks in samples of granite, waste soil, phosphate and backgrond are shown under the optical microscope as shown in Figures (3.18;a,b,c,d) then counting tracks using the optical microscope and then draw a graphic relationship between the data from alphaGuard (the integrating concentration of radon CT) and number of track Cm-2 as shown in figure (3.19) and take slope then compensate for the relationship (3.18) we get value The calibration coefficients ( ? )
Figure (3.17): Experimental built up of radon concentration with time in Granite, Waste soil, phosphate and Background samples.

Figure (3.18,a):Tracks in granite sample.

Figure (3.18,b):Tracks in waste soil sample.

Figure (3.18,c):Tracks in phosphate sample.

Figure (3.18,d):Tracks in background sample.

The calibration coefficients ? for CR-39 detector obtained from the calibration experiment were 0.189±0.002 (Track cm-2 per Bq m-3 d) of Radon. These values were found to be in good agreement with that reported by other investigators as in Table 3.4 .

Figure(3.19):The relation between integrating concentration of radon C? and density of tracks(Track Cm-2).

Table 3.4: Review of important calibration coefficients ? results of CR-39 (Hassan, 2004).
? Detail of exposure References

0.20 Placed in a diffusion chamber with
a hyperphopic fiber glass filter . (Urban,
1986)

0.1800±0.02 Aerosol load provided to simulated dwelling condition . (Khan,
1990)
0.170
to
0.132 Placed in a diffusion chamber with
a filter (filtrak no.390 GDR) exposed
to RaCl2 source in Radon chamber counted under many magnification powers . (Avramovic, 1995)

0.138
& 0.133 Placed in karlsruhe plastic diffusion
cup with polyethylene filter and use
two CR-39 (Chang Bing , 1993)

0.181 ±0.015 Placed in a diffusion cup with fiberglass filter exposed to Radon gas from Uranium ore stone and in bare mode configuration inside NIS Radon chamber with F=0.841 ± 0.109
(Abo-Elmagd, 1997)

0.18±0.01
Placed in a diffusion cup with
fiberglass filter exposed To radon gas from uranium ore stone and in bare
mode configuration inside NIS Radon chamber with F=0.841 ± 0.109
(Hafez et al.,
2001)
0.154±0.003 CR-39 in a diffusion chamber covered with filter paper exposed to high Radon level . (Nikezic,
1994)

0.17±0.03
Placed in a diffusion cup with fiberglass filter exposed to radon source inside Alpha-Guard chamber (Hassan, 2004)
0.189±0.002
CR-39 in a diffusion chamber covered with filter paper exposed to three Radon level .exposed to radon source inside Alpha-Guard chamber. This work
3.6.1.1.5 Calculation of radon concentration & Radon emanation coefficient:

To calculate the concentration of radon we can determine the value of the calibration coefficients (?) of the relationship (3.18) after knowing the storage time of the samples and counting the number of track in CR-39 samples using the optical microscope and when compensation in the relationship (3.16) can be calculated radon concentration .

A fraction of radon atoms will escape to the pore space among the material’s grains, When they are generated upon decay of radium atom. The ratio between the radon that escapes into pore space to the total amount of radon generated (equivalent to the radium concentration in the case of secular radioactive equilibrium between radon and radium) is called the emanation coefficient. It was calculated from the measured equilibrium radon concentration in AlphaGuard radon monitor using the following expression (Morawska, 1989)

f = (3.19)
Where; f is the radon emanation coefficient, CRa the radium activity
concentration in (Bqkg-1), Ceq : the equilibrium radon concentration (Bq.m-3), V the gas empty volume (the container volume minus the sample volume) in (m3), and M the sample mass in (kg).

3.6.1.1.6 Calculation of radon exhalation rate:

The radon exhalation rate per unit area for each soil
samples, which is defined as the flux of radon released from the surface of material, is computed using the following formula (Mustonen, 1984; Hassan, 2011;Samar, 2015 ).

(3.20) ERn =
Where; ERn : radon exhalation rate (Bqm-2s-1), Ceq : the equilibrium
radon concentration (Bqm-3), V : the volume of the radon emanation
container (6.89858 *10-05 m-3) of the studied samples, and S : the total surface area (m2).

3.6.1.2 CR-39 Technique In Site:

The second passive method to measure radon concentrations was used radon dosimeter in this work to determine the indoor radon concentrations of the archaeological site(Tanis). Radon dosimeter geometry is a closed plastic container into which radon diffuses. CR-39 detector is fixed at the bottom of the container; its area is 1*1cmP2P. The cover contains a hole covered with a layer of a sponge (filter) which only allows for radon gas to enter into a plastic container. Radon dosimeter is shown in Figure. (3.20).

Figure(3.20): Radon dosimeter using to measure the indoor radon.

After formation Radon dosimeter as shown in last figure then fixed 13 dosimeter with 13 samples of CR-39 In enclosed places such as tombs, especially royal tombs and Nilometers, which are found in the two maps in Figures (1.1,a),(1.1,b) and then left in place for a period not less than 30 days as shown in figure (3.21) and then after this period we remove them from their places and we do the same steps previous from eaching of CR-39 and Counting Tracks with Optical microscope To compensate in equations (3.16),(3.18) for the density tracks to calculate the value of radon concentrations.

Figure(3.21):Fixed dosimeter with CR-39 sample in Poetry Nilometer
3.6.2 Active Techniques:

Active techniques are those that require power for their operation and are used normally for short term measurement. There are some active methods used to measure radon concentration.

3.6.2.1 Digilert 50 Nuclear Radiation Monitor :

The Digilert 50 uses a Geiger tube to detect radiation. Alpha and low energy beta radiation does not penetrate most solid materials, so this Geiger tube has on one end, a thin disk of mica. The screened opening at the top of the Digilert 50 is called the window. It allows alpha and low-energy beta and gamma radiation through so it can penetrate the mica end of the tube .Installation and content as shown in Figure( 3.22).

Figure(3.22): Digilert 50 Monitor.

3.6.2.2 Starting the Digilert 50:

To start the Digilert 50, set the top switch to the mode you want, and set the bottom switch to On or Audio. The Digilert 50 then does a three-second system check, displaying all the indicators and numbers
After the system check, the radiation level is displayed in the selected mode. In mR/hr and CPM mode, the display shows the accumulated reading for the first minute and the hourglass icon to show that the first minute’s reading is not yet complete. One minute after you start the Digilert 50, the hourglass disappears.

3.6.2.3 Operating Modes:

When the mode switch is set to mR/hr or CPM, the numeric display is updated every minute.CPM and total counts are the most direct methods of measurement; mR/hr is calculated using a conversion factor optimized for Cesium-137, so this mode is less accurate for other radionuclides. It is more appropriate to measure alpha and beta activity using CPM than using mR h-1. Conversion for alpha and beta emitters is calculated differently, and the Digilert 50’s reading in mR/hr may not be exact.
The most immediate indicators of the radiation level are the count light, the audio beep, and the alert. Updated readings are shown every 60 seconds on the numeric display in the CPM and mR/hr modes.(Digilert 50 Nuclear Radiation Monitor Operation Manual ).
3.6.2.4 Calibration of Digilert 50 dosimeter:
Each device used in the measurement process must undergo a calibrating process even if it is used and its results are accurate. A device Digilert 50 dosimeter was used in this study. It was calibrated at the Nuclear Research Center of the Egyptian Atomic Energy Agency using gamma radiation from a standard source of 60Co. The calibration process is carried out under special conditions so that the equipment and radiation source are surrounded by a thick layer of lead to protect against gamma leakage.
3.6.2.5 Measurement method by Digilert 50 Monito:
The measurement and determination of the amount of alpha particles radiation produced directly from the decomposition of radon gas by the Digilert 50 device is done by applying several readings for an equal duration of at least three minutes at a time and for a fixed distance away from the material or wall to measure the emissions of alpha particles. Radon gas and taking the mean of these readings were three readings in each of the places specified in the maps shown in the figures (1.1,a),(1.1,b).