الفهرس 
IntroductionOnly 14 pages are availabe for public view
 |  | from | 16 |  |  |
| | | from | 16 | | |
Abstract
Recently, there is an increase of awareness and concern about the effects of radiation dose received from the exposure to ionization radiation emitted from environmental materials (natural origin, waste and by-products). High level of radionuclide concentrations were maintained in those environmental materials (ceramic and marble tiling). Thus, more attention should be paid to control and regulate the radiation dose delivered to public from environmental materials (ceramic and marble tiling). Therefore, studying the main cause of increasing radiation dose is very important from point of view of radiation protection. Nowdays, Egyptians used ceramic and marble tiling in all fashion houses. So, this work emerged from the potential use of marble and ceramic tiles as decorative building materials used in Egyptian dwellings and their contributions to the radioactivity exposure and indoor radon causing various hazards. As a result, we measured the radiation dose released from them that especial several authors reported that those materials maintain high level of radionuclide concentrations. Controls on the radioactivity concentration of these materials are based on dose criteria and on exemption levels.
The thesis was focused on the study of natural radioactivity and radionuclide concentrations of 226Ra, 232Th and 40K in some marble and ceramic tiles commonly used in Egypt for construction or decoration of dwellings using gamma spectrometric techniques. Moreover, study the release of radon gas from such materials and its concentration as well as the associated parameters such as radon emanation and exhalation rate using AlphaGuard technique. More detailed,
This thesis includes four chapters:
Chapter 1: Introduction
This chapter presents the main goals of the work:
The use of marble and ceramic tiles as decorative building materials in Egyptian dwellings and the production cycle of ceramic tiles from natural contents which considered as an important source of radioactivity exposure.
The description of natural radioactivity, sources of radiation and its associated environmental issues as well as the levels of radionuclides in the environment.
Discussion of external radiation exposure due to NORM and its associated health hazards for human.
Presenting radon gas sources, isotopes and progenies as well as the decay series where radon and its isotopes are delivered.
Discussion of radon gas and its short lived progenies role in radiation exposure and the health risks due to accumulation in homes and then inhalation or ingestion by human.
Chapter 2: Literature review
This chapter presents a description of an intensive studies and surveys carried out for measurement of both naturally occurring radioactive materials (NORM) and radon concentration levels in various building materials especially, marble and ceramic materials used for decoration purposes in Egypt and different countries all over the world.
Chapter 3: Experimental procedures & Analytical methods
This chapter contains three items discussed:
Sample collection and preparation
Types and locations of the selected samples are indicated in this part as well as the methodology of preparing the samples for the required measurements. About 30 types of marble and ceramic tile samples were collected from different companies. All are locally produced except for 6 types of marble samples imported from Turkey, Greece, china, India and Italy and two ceramic tile samples imported from China.
Gamma-ray spectra measuring technique
This part presents the type of the technique used in gamma ray spectra measurements (high purity germanium detector, HPGe) and its characteristics. The detection system components, device set up, energy and efficiency calibrations, the principles of measurement and the method of analysis and calculation of radionuclide activity are all discussed as well.
Radon gas measuring technique
The type of the device used in measuring radon gas process is introduced (AlphaGuard radon monitor) in this part and its components are discussed. Moreover, the set up and operation of the device are indicated and a database software package is applied.
Chapter 4: Results & Discussion
This chapter of the thesis discusses the results of different measurements carried out in this work and analysis of the obtained data and contains:
Measurement of radionuclide concentrations of 226Ra, 232Th and 40K in 15 type of marble and 15 type of ceramic tiles samples collected from different companies and factories around Egypt commonly used as decorative materials using high purity germanium detector. The activity values observed in marble samples are in the range (ND - 49.92±7.74)Bqkg-1 with average value of (21.07±3.32) Bqkg-1 for 226Ra, for 232Th found to be in the range (8.30±1.70 - 119.52 ±16.00) Bqkg-1 with average value of (33.00±5.01) Bqkg-1 and for 40K are in the range (32.60±4.25 - 2238.33±242.66) Bqkg-1with average value of (666.54±74.88) Bqkg-1. While for ceramic tiles samples, the activity values of 226Ra are in the range (28.42±5.41 - 118.70±20.34)Bqkg-1 with an average value of (59.65 ± 9.08) Bqkg-1 and values of 232Th are in the range (30.65±5.49 - 114.15±18.78)Bqkg-1 with an average value of (47.06±7.77) Bqkg-1, while the activities for 40K are in the rang (389.54±49.57 - 1069.83±124.50) Bqkg-1with an average value of (703.23 ± 87.21) Bqkg-1.
The maximum acceptable values for radium, thorium and potassium are 50, 50 and 500 BqKg-1, respectively according (UNSCEAR, 1993, 2000) which indicates that for all studied marble and ceramic samples, all activity values of 226Ra are under the accepted limit except for some ceramic samples (EC2), (EC3),(EC7), (EC8), (EC12), (CC14) and (CC15). For 232Th, all values are less than the accepted value except for samples (EM2), (EM3), (EM8), (EC12), (CC14) and (CC15). But for 40K, all the values exceed the world wide acceptable limit except for (EM2), (EM3), (EM6), (EM7), (EM8), (EM9), (EC3), (EC6) and (EC12).
Calculation of radiological indices based on the obtained results of activity concentration such as radium equivalent activities (Raeq) which are in the range (23.20±3.75 - 355.81±45.56) Bqkg-1 with an average value of (118.17±16.22) Bqkg-1 for marble samples and the values for ceramic tiles samples are in the range (117.57±17.65 - 349.15±56.17) Bqkg-1with an average value of (181.08±26.91) Bqkg-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) in all samples under study and all samples show indices less than unity, proposed by the European commission (Ec, 1999) except for two samples (EM8) and (CC15) which show internal hazard indices Hin more than unity.
Calculation of activity level indices (Iγ& Iα) for all samples, also all values are less than unity except for (EM3), (EM8), (EM9) and (CC15) showing gamma indices Iγ higher than unity.
Estimation of absorbed gamma ray dose (nGyh-1) and five marble and 13 ceramic tiles samples show high values of absorbed dose which exceed the world wide recommended value (59 nGyh-1) reported by (UNSCEAR, 2000). Like the adsorbed dose, the annual effective dose equivalent (mSvy-1) is calculated for all marble and ceramic tiles samples under investigation and all the obtained values are less than the permissible limit of unity.
Assessment of radon concentration in the selected samples using AlphaGuard radon monitor with an average value of (120.91±7.14) Bqm-3 for marble samples and (193.74±5.59) Bqm-3 for ceramic tile samples.
Calculation of radon emanation coefficient (f)% and radon exhalation rate (ERn)(Bqm-2s-1) with an average value of (30.51±2.15) % and(2.33±0.14)Bqm-2s-1 for marble samples and (13.34±0.87) % and (3.23±0.27) ×10-4Bqm-2s-1 for five studied ceramic tiles samples.
Estimation of alpha equivalent dose using two methods based on radon emanation coefficient and radon exhalation rate and obtaining average value of (12.80±2.04) µSvy-1 for marble and (29.98±4.44) µSvyr-1 for ceramic samples by first method (Bruzzi method) and having average value of (21.15±1.24) µSvy-1 for marble samples and (29.37±2.44) µSvy-1 for ceramic tiles samples by the second method (Chen method).