Investigation of coal samples from different regions in Turkey by nuclear techniques

The aim of this master thesis study is to increase database about the natural radioactivity and trace elements in lignite and pit coals of Turkey and analyzing the natural radiactivity level and trace element concentration diffrences between lignite and pit coals. Numerous samples of lignite and pit coals from different regions of Turkey were used for this study. On scope of this work; untreated coal samples that were taken from the coal mines of Soma İnbat, Tunçbilek, Dursunbey, Afşin Elbistan and Zonguldak Kozlu were collected and then these collected samples were analyzed with two different nuclear analysis techniques. While, for finding the amount of trace elements that are presented in samples, energy dispersive X-ray fluorescence (EDXRF) spectrometer is used; for obtaining natural radioactivity of the coal samples gama spectroscopy system were used. In this study; natural radioactivities of low calorie lignite coal and high calorie Zonguldak pit coal were measured and elemental analysis for these coals were carried out with nuclear techniques. Minor and trace elements; Al, As, Ba, Br, Cd, Cr, Ce, Cu, Fe, K Mn, Hg, Ni, S, Sb, Se, Si, Pb, Ti, U, Th, V, Zn considered as they can be present in the sample. With the usage of gama spectrometry analysis technique which enables detection of certain elements that cause the natural radioactivity, natural radioactivity of coal samples was characterized according to Uranium, Thorium and Potassium origins and by EDXRF spectrometer technique the concentrations of minor and trace elements were founded. Basically, coal is a sedimentary organic rock which is composed of organic materials (mainly carbon), minerals and water. It is formed by plants and other organics which are accumulated between the layers of earth by the effects of pressure and heat. Coal is classified by the amount of organic materials in it. Lignite, subbituminous coal, bituminous coal and anthracite are the main types of this classification. Subbituminous and bituminous coals are also named as pit coal. Besides the usage of coal for heat production by combustion, coal is also essential material for cement and steel production to complex oxidations for gas/liquid fuel production and chemical raw material producing. While heat from coal fuels were first used for domestic purposes, with the begining of industrial revolution till the 1950s coal was the main source of energy for industrial applications and transportation. And along from the usage as a fuel, coal is also widely used for production of construction materials and industrial raw materials. Coal, is the one of the main sources of energy since it was first used as an energy source. Unfortunately, coal use may cause danger for environment and humans. Elements that are dangerous to environment and humans are released by coal usage. So knowing the elemental content of coal used is important for human health and environmental safety. Therefore contents of U-238, Th-232 and K-40 elements in the coal makes the coal, naturally radioactive. The radionuclides from decay series of naturally occurring radioactive elements Uranium, Thorium and Potassium is the cause of the natural radioactivity. Within the increase in nuclear medicine applications and some industrial applications that are involved radiation, radiation from man made sources are starting to be a concern about radiation exposure, therefore exposure from natural radiation is still the biggest source of radiation exposure for mankind. These natural radioactive elements are usually present in low concentrations but human activities such as mining can enhance the amount of radioactive element content in certain places. Industrial wastes or by products enriched with radioactive elements found in nature and decay products of these elements such as radium and radon can be hazardous especially with inhalation and ingestion. Therefore natural radioactiviy of these materials that are used in activities leading to radioactive element enhancement must be known. Natural radioactivity which consists from radioactivies of U-238, Th-232 and K-40 radionuclides were measured with gamma spectrometry system. Characteristic gamma ray peaks of these radionuclides were measured in low level counting system. Then the activity of each radionuclide were calculated from these measurements hence radioactivity of coal samples were identified. Eight coal samples were collected from Soma İnbat, Tunçbilek, Dursunbey, Afşin Elbistan and Zonguldak Kozlu coal mines. These samples were investigated with two different nuclear analysis techniques. X-ray flouresans (XRF) spectrometry used for elemental anaysis whereas gamma ray spectroscopy system used for natural radioactivity analysis. Collected coal samples were grinded and inserted into cylindrical and marinelli style containers. After 40 days of waiting time these containers were measured in low level radiation detection laboratory. Gamma spectroscopic analysis of samples were conducted with .GAMMA-VISION 32 spectrum analysis software. Geometry corrections and corrections from background radiation were applied to gamma spectrometry results. After energy and efficiency calibrations with known values of calculated activities of source standards, efficiency equation was found and efficiency values for Uranium, Thorium and Potassium detections were calculated. These samples are also analyzed with a energy dispersive XRF system and element concentrations in the samples were found. Elements that are of some concern with respect to enviromental safety and health were classified according to their concern level and amount of these elements in samples were tabulated. Scope of this research covers the two main coal types, lignite and pit coal, which are extracted in coal mining facilities and used in various fields like energy production, steel manufacturing and domestic heating in Turkey. According to analyses, trace amount of As and Pb elements which are high concern because of its environmental effects were found pit coal and lignite samples as a trace element, therefore another high concern element Hg was also founded in only one sample again in trace amounts.. Other hazardous elements like Se, B, Cd and Mo were not detected in both samples. In general, natural radioactivity of pit coal samples were found lower than the lignite coal samples. While variation of activities from Th-232 are not too much in samples, big variations has been seen at activities from K-40. Also it can be seen that, if results of XRF and gamma spectroscopy assessed together, amounts of Uranium, Thorium and Potassium that are measured from XRF are not always in a good agreement with the results of gamma spectrometric measurements. Hence the XRF results alone is not enough for conclusion for natural radioactivity.