Çeşitli Madensuyu Ve Sodaların Radyoaktivite Seviyelerinin Tayini

Abstract

Üzerinde yaşadığımız dünyamız, bir kısım radyoizotopları doğal olarak bulundurmaktadır. Bu radyoizotopların doğal çevremizde yarattığı radyasyon etkisi esas itibariyle "Doğal Çevre Radyasyonu" olarak nitelenmektedir. Süz konusu doğal çevre radyasyonunun önemli kaynağı olan doğal radyoizotoplar, toprakta bulunabileceği gibi, atmosferde de bulunabilmektedir. Toprakta var olan radyoizotoplar, toprakla temasta olan su içinde çözünebilmek t e ve çevre sularında doğal radyasyonu oluşturmaktadır. Toprakla temasta olan sular ise yerüstü suları ve yeraltı suları olarak başlıca iki grupta incelenebilir. Yeraltı suları, toprağın farklı derinliklerindeki cegitli elementlerle temas edebi lmektedi r 1er. Genellikle, toprağın derinliklerine kadar inip daha sonra yeryüzüne çıkan, özellikle dünyamızın jeolojik yapı bozukluklarının, örneğin; fay hatları dolayındaki yeraltı suları, bazı mineralleri ve bu arada radyoizotopları, diğer sulara göre daha cok ihtiva etmektedirler. îste bu tip suları "Maden Suyu" olarak nitelemekteyiz. Ayrıca, soda içeren bir grup su da bulunmaktadır ki; bunlar halk dilinde kısaca "Soda" olarak anılmaktadırlar. Öte yandan, maden suyu ve soda özelliğini beraberce gösteren içecekler de söz konusudur. Bu durumda maden suyu ve sodalarda doğal radyoaktivite seviyesi, diğer içme sularından "bir miktar" daha yüksek olabilmektedir. Maden suyu ve sodalar, içerdikleri elemanlar nedeniyle genellikle, hazmı kolaylaştıran etkileri bulunduğundan, insanlar tarafından tercih edilen içecekler olabilmektedirler. Hatta günümüzde, doğal sodalara benzer içerikte "Yapay Soda" üretimi de yapılmaktadır. Bu Yüksek Lisans Tezi çalışmasında, doğal ve yapay soda ve maden sularında radyasyon seviyesi tayini amaçlanmıştır. Bu amaçla, piyasada satılmakta olan maden suyu ve sodalar temin edilmiş ve radyasyon seviyeleri tayin edilmiştir. ITU Nükleer Enerji Enstitüsü Nükleer Uygulamalar Anabilim Dalı labratuvarları ile TAEK-CNAEM Sağlık Fiziği olanaklarından yararlanılarak madensuyu ve sodaların alfa ve beta aktivite seviyeleri tayin edilmiştir. Üzerinde çalışılan madensularınıat 10' u kaynak yerleri Türkiye'nin batısından yer alan madensuları, 3'ü ise yabancı madens uları dır. Ayrıca, 3 yapay soda da bu Yüksek Lisans Tezi kapsamında incelenmiştir. Böylelikle, ülkemizden temin edilen toplam 16 madensuyu ve soda üzerinde çalışılarak radyoaktivite seviyeleri tayini gerceklenmistir.

It is well known that the human body normally contains small quantities of naturally occuring radioactive elements; but to what extent these materials are derived from foodstuffs, drinking waters, or other ingested substances has been largely unknown for a particular individual. The knowledge of the natural radioactivity of our environment is so scanty that it seemed possible that a number of natural sources of irradiation of human beings. Although largely unknown, these levels of radioactivity have been assumed to be of rather academic importance. For example, the natural background of gamma rays gives us a standard by which we may judge the possible effects of increased radiation on the genetic material of the race. But, natural gamma ray sources are less than the others occasionally. Since many of the natural occuring radioactive nuclides emit alpha paricles it seemed worth while to look again for such alpha activities both within the human body and its environment. Another important radioactive materials are beta emitters that are also important for human body and his natural radioactivity level. - xiii - Four types of radiation are especially important for human body. These are; - Alpha particles - Beta particles - Electromagnetic radiation C X-rays and gamma rays) - Neutrons Alpha particles are high velocity nuclei of helium atoms emitted from some radioactive nuclei. Each alpha particle is made up of two protons and two neutrons, thus having a double positive charge. All naturally occur ing alpha particles are below 7 MeV and these can be stopped with small amounts of material. This heavy particle with a relatively large charge loses enrgy rapidly as it passes through matter by creating a dense path of ions. Since the range of alpha particles is so small, they do not usually create an external radiation hazard, but a serious hazard occurs when alpha emitters find their inside body by ingestion» inhalation or through wounds. Consequently, the healh physicist's detection of alpha particles is usually concerned with the assaying of various samples such as smears, water samples and dust samples for radioactivity evaluation. Since alpha particles are so easily stopped, detectors must have thin windows or be "window less". In this thesis, a proportional counter is used for detection of alpha particles. Beta particles which found as products of almost all radioactive decay shemes are electrons or positrons carrying a single charge. A few isotopes disintegrate with only emission of a beta particle and a few exist which do not give off beta paricles, but the large majority of the natural and man-made radioactive isotopes are beta emitters. - xiv - Although beta particles are not as easily stopped as alpha particles, they do not possess great penetrating power until high energies are reached. The energies normally encountered from isotopes are all below 5 MeV. When passing through matter the beta particle will give up its energy along its path length by ionizing the medium and by producing soft X-rays or Brehmsstrahlen. This an important effect while studing with beta sources. Almost any source will exhibit some self absorption causing the beta particles to exhibit an energy spread, the maximum energy of which will be the tabulated beta particle energy of the isotope. The range of beta particles can be calculated according to maximum energy of beta particles. In this study a sintillation detector is used for beta counting. X and gamma rays are electromagnetic radiation. In general, the energy of X-rays is lower than that gamma rays in the radiation applications. But an overlap exists which is becoming larger as time goes on. Gamma-emitting isotopes have been found which give off low energy gamma rays and X-ray machines are being made which produce ever increasing energy X-rays. The difference between X and gamma rays rests in the origin of the radiation. Both are electromagnetic in nature and both can have the same nominal energy, but a subtle difference exists. In the case of gamma rays, the gamma-emitting isotope produces gamma rays which are characteristic of a nuclear transition and which are all of the same energy for any given transition. Many isotopes exhibit complicated decay shemes which may call for more than one gamma ray, but the gamma rays are produced with discreet energies. X-rays, however, are produced by impinging a beam of accelerated electrons against a target. The energy of the X-ray is directly dependent on the energy of the electron, which may lose some of its energy in passing through the target material before producing an X-ray. X-ray machines produce X-rays with a continous energy spectrum. The importance of this difference between X and gamma rays which may be described as a continuous spectrum of X-rays as opposed to a line spectrum of gamma rays. When passing through matter, X and gamma rays are absorbed in an exponential manner - xv - The neutron has approximately the mass of a photon and carries no electrical charge. Neutrons are not produced by normal radioactive decay, but by the fission reaction. Since these particles are neutral, they react weakly with atoms and can penetrate matter freely. Neutrons are informally classed by their energy; as thermal neutrons, epi thermal neutrons and fast neutrons. Thermal neutrons interact in neutron capture and other nuclear reactions. Epi thermal and fast neutrons interact to great extent in sacattering process which reduce the energy of the neutron. The intensity of nuclear radiation originating from a point source obeys the common inverse square law. Radiation evaluation can be made according to measurement of it and according to radiation units that are seen below: - Activity unit - Irradiation dose rate - Absorbed dose rate - Biological dose rate Useful radiation detection instruments must embrace wide limits os sensitivity. An order of magnitude of desired sensitivity can be obtained by a review of the present standarts of radiation exposure. The maximum permissible exposures CMPE3 and maximum permissible concentrations CMPC5 of radioactive material in air and water are recommended by national and international authorities. But no special regulations for mineral waters and sodas. The limits imposed on the amount of radioactive material deposited in the body by inhalation, ingestion, or thorough wounds are based on the dose that the material delivers to the organs. Almost all health physics work must take into consideration the inherent background radiation caused by naturally occuring radioactive materials, cosmic rays and man-made low level contamination. Mineral waters and sodas can be account in this type materials. - xvi - In this thesis» it is aimed to determination of radiation levels in the mineral waters and sodas that are bought from Turkey market. Experiments related on determination of alpha and beta activity levels have been done in labrotories of Nuclear Application Division of ITU Institute For Nuclear Energy and Health Physics Division of TAEA-CNRTC. Ten of mineral waters belong to west Anatolia and three of them are import mineral waters. Moreover, three artificial sodas are also investigated in this thesis. Therefore, determination of radiation levels for mineral waters and sodas have been observed with sixteen samples totally. As the conclusion of the studies, the results obtained by the calculation according to the measurements, have been given as totally and groups according to their originate, e.i. turkish mineral waters, import mineral waters and sodas. Radioactivity levels of mineral waters and sodas are determined and mentioned comperatively each other and radioactivity limits for drinking waters.