Haluk Yücel

• Prof.Dr.
• Faculty Member at Ankara University

Purpose The objective of this study was to provide insights into the most recent responses of sediments to climate change and their capability to sequester atmospheric carbon (C). Methods Three sediment cores were collected, one from the western Black Sea, and two from the southern Adriatic Sea. Cores were extruded and sectioned into 1 cm or 0.5 c...

In this study, tissue equivalency (TE) of a newly developed epoxy-based phantom to 3–5 years child's tissue investigated in paediatric energy range. Epoxy-based TE-phantoms were produced at different glandular/adipose (G/A) ratios of 17/83%, 31/69%, 36/64% and 10/90%. A procedure was developed in which specific amounts of boron, calcium, magnesium,...

The study estimated the radiological exposure levels in a mining area for miners in the Beylikova-Sivrihisar (Turkey) complex ore site containing 238U, 226Ra and 232Th. Sixty samples were collected from the study area based on a geologic map. The radionuclide activities were measured using a 78.5% efficient n-type HPGe detector. The measured mean a...

In this study, it is aimed to investigate neutron self-shielding effect in application of k0-NAA standardization method to determine Mn contents in manganese ores. Because the neutron self-shielding correction factors are significant factors in application of k0-NAA method for large samples. To estimate these, several Mn-ore samples and Au monitor...

The radionuclide activities were measured in sea sediment and coastal sand samples taken from the Black Sea to improve the understanding on coastal pollution as sediments and sand act as a sink for inorganic contaminants from various sources. The core sediments were taken from the Black Sea near to Varna city and sand samples were collected from in...

An internal consistency test of the calculation of coincidence-summing correction factors FC for volume sources is presented. The test is based on exact equations relating the values of FC calculated for three ideal measurement configurations. The test is applied to a number of 33 sets of FC values sent by 21 teams. Most sets passed the test, but n...

In this study, the k0-NAA standardization method was applied to determine manganese concentrations in commercial manganese ores that collected different mining sites in Turkey. The samples were grinded, sieved and filled into Teflon tubes with a thickness of 1mm and then irradiated in one irradiation cell of the 37GBq ²⁴¹Am–Be isotopic neutron sour...

In this study, a new measurement method based on voltage transients in CdZnTe detectors response to low energy photon irradiations is applied to measure the electron mobility (μe) and electron mobility-lifetime product (μτ)e in a CdZnTe detector. In the proposed method, the pulse rise times are derived from low energy photon response to 59.5 keV(²⁴...

In this study, an in-house ¹⁵² Eu calibration source was produced from a custom epoxy matrix with a density of ρ = 1.14 g cm ⁻³ , which is chemically stable and durable form after its solidification. The homogeneity of ¹⁵² Eu in matrix was obtained better than 98%. For a Marinelli beaker geometry, an efficiency calibration procedure was applied to...

The aim of this study was to investigate the thermal neutron measurement capability of a CdZnTe detector irradiated in a mixed gamma-neutron radiation fi eld. A CdZnTe detector was irradiated in one of the irradiation tubes of a ²⁴¹Am-Be source unit to determine the sensitivity factors of the detector in terms of peak count rate (counts per second...

142 Pr (praseodymium-142), a potential radionuclide for brachytherapy, was produced after irradiating high purity natural Pr2O3powder in a research reactor. The irradiated powder was then dissolved in acids and diluted for measurement. Several radioactivity measurement methods were used in the standardization of142Pr radionuclide. This work reports...

Canlıların doğal yaşam ortamlarının bozulmasına neden olan etmenler; ortamda bulunan diğer canlı organizmaların uyaran etmeni olarak yanıt vermesini sağlar. Canlıların bu özelliklerini belirlemek ve izlemek için yapılan araştırmalar biyomonitöring (biyoizleme) çalışmalarını ortaya çıkarmıştır (Ellenberg 1991). Biyomonitöring; biyoindikatör (biyobel...

In this study, the practical methodologies are described for the determination of the factors for the self-absorption effect (Fs), spectral interferences (Fcsi), and true coincidence summing effects (Fcoi), which are used in direct gamma-spectrometric measurement of radionuclides such as ²¹⁰Pb, ²³⁸U, ²³⁴Th, ²²⁶Ra, ²¹⁴Pb, ²²⁸Ac, ²⁰⁸Tl, ²¹⁴Bi, ¹³⁷Cs...

In this study, paraffin was selected as a base material and mixed with different amounts of CaSO4·2H2O and H3BO3 compounds in order to mimic breast tissue. Slab phantoms were produced with suitable mixture ratios of the additives in the melted paraffin. Subsequently, these were characterized in terms of first half-value layer (HVL) in the mammograp...

In this work, the effective resonance energy, -value for the 193Ir(n,γ)194Ir reaction was measured using cadmium ratio method. A dual monitor (197Au–98Mo), which has convenient resonance properties, was employed for characterization of the irradiation sites. Then analytical grade iridium oxide samples diluted with CaCO3 to lower neutron self-shield...

In the medical field, some protective materials incorporating lead or high- Z elements are used as lead-equivalent aprons or garments and thyroid guards for the protection of personnel against X-rays. However, in recent years, non-lead protective materials have become widespread in radiology because of their light weight and durability. Lead (Pb) h...

High energy linear accelerators are increasingly used in the medical field. However, the unwanted photo-neutrons can also be contribute to the dose delivered the patients during their treatments. In this study, neutron fluxes were measured in a solid water phantom placed at isocenter 1m distance from the head of an 18MV-linac using the foil activat...

İyonlaştırıcı radyasyona karşı radyasyonla çalışanların korunması için farklı bileşimlerde (Pb, Sb, Sn, W, Ba, vb. elementleri içeren) üretilen koruyucu malzemelerin X-ışın zayıflatma özelliklerinin belirlenmesi ve kullanım için uygunluğunun deneysel olarak gösterilmesi önemlidir. Bu çalışmada, radyolojik enerji aralığında (40-300 kVp) hasta ve hek...

Abstract. Characterization of nuclear materials is an important topic within the context of nuclear safeguards, homeland security and nuclear forensics. This paper deals with the performance of multigroup gamma-ray analysis (MGA) method using the X- and -rays in the 80–130 keV region and enrichment meter principle (EMP) based on the analysis of 18...

In this study, after the pulse shape calibration of a liquid scintillation counting (LSC) spectrometer (Quantulus 1220), the effi ciency was determined depending on sample quenching parameters. Then, gross alpha and beta activities in two spiked water samples obtained from International Atomic Energy Agency (IAEA) were used for the validation of th...

For the applicability of instrumental neutron activation analysis (NAA) technique, an irradiation unit with a 37 GBq 241Am-Be neutron source was installed at Institute of Nuclear Sciences of Ankara University. Design and configuration properties of the irradiation unit are described. It has two different sample irradiation positions, one is called...

The energy dependence of the response of BC-408 plastic scintillator (PS), an approximately water-equivalent material, has been investigated by employing standardized x-ray beams. IEC RQA and ISO N series x-ray beam qualities, in the range of 40–100 kVp, were calibrated using a PTW-type ionization chamber. The energy response of a thick BC-408 PS d...

A rapid and non-destructive assay of uranium enrichment has a great importance in various practical fields, e.g., nuclear safeguards, waste characterization, fuel fabrication plants and the tracking of illicit trafficking of the goods. For the nondestructive measurements, the multigroup γ-ray analysis method for uranium (MGAU) is widely applied in...

In this study, neutron dose occuring in radiotherapy irradiations with 18 MV photon was investigated on beam axis, treatment room and control console. PTW RW3 water equivalent solid phantom was irradiated with 18 MV, SSD 100 cm, 20x20 cm2 field size and 5000 MU using Varian Clinac DHX Dual Energy linear accelerator device located in Süleyman Demire...

The thermal neutron cross section and the resonance integral for the Gd-158(n, gamma)Gd-159 reaction were measured by the activation method with using the Mn-55(n, gamma)Mn-55 monitor reaction. The analytical grade MnO2 and Gd2O3 were mixed separately with Al2O3 powder to reduce both thermal and epithermal neutron self-shielding effects. Then, they...

The scatter effect on the X-ray spectra was also measured under broad beam conditions by using different detectors. The scatter effect caused by the above mentioned organ phantoms such as PMMA and ANSI were investigated based on the contrast measurements with use of CdZnTe and NaI(Tl) counting detectors and a DRX digital imaging detector.

In direct measurement of some radionuclides using a gamma-ray spectrometer, there is a need to correct the measured results for self-attenuation effects (Fs) spectral interferences (Fcsi), and true coincidence summing effects (Fcoi). For testing the correction methods, lake and stream sediments were measured as certified reference materials (CRM) b...

Illicit trafficking of nuclear and radioactive materials such as uranium, plutonium, thorium, polonium poses a serious threat to not only the homeland security and but also international community when the smuggling materials are diverted by the terrorist organizations. Therefore, in case such materials are intercepted, a series of nuclear forensic...

A performance study was performed for CdZnTe coplanar grid (CPG) detectors when used as γ-ray spectrometers. The detectors have the crystal volumes of 1, 1.6875 and 2.25 cm(3), respectively. Time stability of each CdZnTe CPG detector was investigated in a long-term operation (time span of 0.25 to about 100 h). The spectroscopic performances were me...

The accuracy and precision of effective resonance energy E¯r parameter is an important point in the determination of the mass fraction of an analyte contained in the sample when NAA is used. Because the effective resonance energy E¯r is an essential parameter, which is directly introduced in the k0–NAA standardization method. Therefore, the effecti...

In the γ-ray spectrometric analysis of the radionuclides, a correction factor is generally required for the spectral interfering γ-rays in determining the net areas of the analytical peaks because some interfering γ-rays often might contribute to the analytical peaks of interest. In present study, a correction methodology for the spectral interferi...

The effective resonance energies for the (n,γ) reactions of 152Sm and 165Ho isotopes were determined by using dual monitors (55Mn–98Mo) due to their favourable resonance properties. The samples were irradiated in an isotropic neutron field obtained from 241Am–Be neutron sources. The induced activities were measured with a high efficient, p-type Ge...

In this paper, a semi-empirical method is proposed to determine true coincidence-summing (TCS) correction factors for high resolution γ-ray spectrometry. It needs the knowledge of both full energy peak (FEP) efficiency and total-to-peak (TTP) efficiency curves. The TTP efficiency curve is established from the measurements with a set of coincidence-...

In this study, true coincidence-summing (TCS) correction factors have been measured for the sources (22)Na, (60)Co, (133)Ba and (152)Eu by use of three large volume coplanar grid CdZnTe (acronym: CZT) detectors. In case of a close-in detection geometry, two different TCS calculation algorithms were used to compute the required TCS correction factor...

When the high-resolution gamma-ray spectrometry was used in the analysis of (234)U and (230)Th in samples, there is a much more need to correct for the measured activity results of (234)U and (230)Th mainly due to self-absorption effects and the interfering lines from (226)Ra, (235)U, (238)U and their decay products that often might be present in t...

In this study, the spectral interferences are investigated for the analytical peaks at 63.3 keV of (234)Th and 1001.0 keV of (234m)Pa, which are often used in the measurement of (238)U activity by the gamma-ray spectrometry. The correction methods are suggested to estimate the net peak areas of the gamma-rays overlapping the analytical peaks, due t...

In this study, the validity of the effective (virtual) point-detector concept for the CdZnTe (CZT) detector for disc-shaped radioisotope sources has been investigated in the photon energy range of 50–662 keV. It has been found that the virtual point-detector model is valid for conventional CZT detectors. The photon energy dependence of the virtual...

In this paper, the known multigroup gamma-ray analysis method for uranium (MGAU) as one of the non-destructive gamma-ray spectrometry methods has been applied to certified reference nuclear materials (depleted, natural and enriched uranium) containing (235)U isotope in the range of 0.32-4.51% atom (235)U. Its analysis gives incorrect results for th...

To study environmental samples, a 44.8% relative efficient well-type Ge detector with an active volume of 218 cm3 was calibrated in three different voluminous sample geometries. The models were tested by absolute full energy peak efficiency calibration with use of certified multinuclide standards. The efficiency results corrected for this experimen...

The present study is concerned with the measurement of the spectroscopic properties of the CdZnTe detectors in a particular energy range since its sensitivity depends mainly on two parameters: energy resolution and detection efficiency. Thus, the energy resolution (in terms of FWHM) and the peak shape (in terms of peak-to-valley (P/V) ratio) were d...

The effective resonance energy -values for the (n, γ) reactions of 71Ga, 75As, 164Dy, 170Er were determined by the cadmium ratio method using dual monitor (55Mn–98Mo) having favorable resonance properties. The powder samples with and without a 1 mm thick Cd cylindrical box were irradiated in an isotropic neutron field obtained from three 241Am–Be n...

The thermal-neutron cross-section and the resonance integral for the 174Yb(n,γ)175Yb reaction were measured by the activation method using a 55Mn monitor as single comparator. Analytical grade MnO2 and Yb2O3 powder samples with and without a cylindrical 1 mm Cd shield box were irradiated in an isotropic neutron field obtained from three 241Am–Be ne...

ZET Bu çalışmada, dedektör hassasiyeti, temelde iki parametreye; enerji çözme gücü ve dedeksiyon verimine bağlı olduğundan, belirli bir enerji aralığında CdZnTe dedektörlerin spektroskopik özellikleri incelenmiştir. Bu amaçla, radyoaktif disk kaynaklar kullanılarak bir 5x5x5 mm 3 CdZnTe dedektörle elde edilen gama spektrumlarının analizinden enerji...

The multi-group analysis (MGA) method for the determination of uranium isotopic abundances in depleted uranium (DU) and natural uranium (NU) samples is applied in this study. A set of non-destructive gamma-ray measurements of DU and NU samples were performed using a planar Ge detector. The relative abundances of 235U and 238U isotopes were compared...

The thermal neutron cross section and the resonance integral of the reaction 170Er(n,γ)171Er were measured by the Cd-ratio method using a 55Mn monitor as single comparator. Analytical grade MnO2 and Er2O3 powder samples with and without a cylindrical 1 mm Cd shield box were irradiated in an isotropic neutron field obtained from three 241Am-Be neutr...

The activity concentrations of 232Th, 226Ra, and 40K in different pumice samples have been determined by high-resolution gamma-ray spectrometry using a 110% HpGe detector. The radium equivalent activities (Raeq), external hazard index (Hex), and internal hazard index (Hin) associated with the natural radionuclides and representative level index (Ig...

This study implies that 55Mn(n,γ)55Mn monitor reaction may be a convenient alternative comparator for the activation method and thus, it was used for the determination of thermal neutron cross section (TNX) and the resonance integral (RI) of the reaction 152Sm(n,γ)153Sm. The samples of MnO2 and Sm2O3 diluted with Al2O3 powder were irradiated within...

The bremsstrahlung radiation energy spectra were produced by hard beta-emitters the 90Sr-90Y contaminated tea sample sources placed in a copper cylinder (cylinder counting geometry) and encapsulated in two Cu discs (sandwich counting geometry). These energy spectra were directly measured by using two separate gamma-ray spectrometers with a coaxial...

The thermal neutron cross-section (σ0) and the resonance integral (I0) of the reaction 164Dy(n,γ)165Dy were measured by the activation method, using 55Mn(n,γ)55Mn monitor reaction as a single comparator. The diluted MnO2 and Dy2O3 powder samples within and without a cylindrical Cd shield case were irradiated in an isotropic neutron field obtained f...

The thermal neutron cross section and the resonance integral of the reaction 165Ho(n, γ)166gHo were measured by the activation method using 55Mn(n,γ)56Mn monitor reaction. The sufficiently diluted MnO2 and Ho2O3 samples with and without a cylindrical Cd case were irradiated in an isotropic neutron field of the 241Am–Be neutron sources. The γ-ray sp...

Phosphatic fertilizers are manufactured from phosphate ores which contain naturally occurring radionuclides such as 238U and its daughter products. Large amounts of phosphogypsum is obtained and has 226Ra. The natural radioactivity was measured by a gamma ray spectrometer. The activity concentration 226Ra was 465 Bq/kg as a mean value. The natural...

A prompt gamma neutron activation analysis (PGAA) setup installed at ANRTC has been used to analyze boron. It consists of a 22.6% REGe detector and a 740 GBq 241Am-Be neutron source moderated with water and paraffin. At the sample irradiation position, the thermal neutron fluence rate measured was 2.36. 104 n. m-2 . s-1 and the corresponding Cd-rat...

The thermal neutron cross-section (σ0) and the resonance integral (I0) of the reaction 186W(n,γ)187W were measured by the activation method using 55Mn as a single comparator. The diluted MnO2 and WO3 samples within and without a cylindrical Cd shield case were irradiated in an isotropic neutron field of the 241Am–Be neutron source. The γ-ray spectr...

The a-shape factor of real, non ideal 1/E 1+ epithermal neutron spectrum in an isotropic neutron field of 241 Am–Be isotopic neutron sources was determined by dual monitor method using measured cadmium ratios of 197 Au(n,g) 198 Au and 98 Mo(n,g) 99 Mo(b À) 99m Tc reactions. The irradiations of Gold (Au) and Molybdenum (Mo), chosen as suitable monit...

Comprehensive Quality Control (QC) and Quality Assurance (QA) Program is stated on the quality policy, organization, methods and records for nuclear analytical laboratories which are necessary for improvement of productivity, to upgrade the performance, credibility and reputation. The proper and complete identification of quality elements for manag...

Thermal neutron cross-sections and resonance integrals for the 71Ga(n,gamma)72Ga and 75As(n,gamma)76As reactions were measured by the activation method. The experimental samples with and without a cylindrical Cd shield case in 1mm wall thickness were irradiated in an isotropic neutron field of the 241Am-Be neutron source. The induced activities in...

The 1001 keV g-ray emission from 234mPa as an analytical peak has ever increasing importance in direct g-ray spectrometric measurements of 238U content in samples with the development of high pure Ge detectors of larger crystal volumes and higher efficiency. In this study, -ray spectrometric measurement for the determination of the absolute intensi...

More than 40 years after its launching, the gamma-ray spectrometry with especially high pure Germanium detectors developed in the last 30 years, is nowadays applied to measure quantitatively gamma emitting radionuclides for various research purposes and environmental problems in numerous laboratories world-wide. Since the gamma-ray spectrometry is...

For the direct gamma-ray spectrometric measurements of uranium concentrations in the samples, the use of 1001 keV peak of 234mPa, second daughter of 238U is emphasized. This “clean” peak is well resolved by HPGe detectors and gives accurate indication of uranium concentration in the samples without any self-absorption correction. The 1001 keV peak...

An automated sample transfer system associated with a 3 × 592 GBq AmBe neutron source has been constructed at the Ankara Nuclear Research and Training Center (ANRTC) for Instrumental Neutron Activation Analysis (INAA) and Cyclic Instrumental Neutron Activation Analysis (CINAA). The pneumatic transfer system is controlled by an IBM PS/1 personal co...

The present work is concerned with the construction of a semiempirical function de(μ, Eγ) of the effective photon interaction depth depending upon both the linear attenuation coefficient of Ge and γ-ray energy. The interaction depth results obtained from the measurements in two high purity germanium crystals, which are nearly equal in volume, have...

The effect of the organic material of tea on the adsorption behavior of 137Cs on the silty clay soil has been examined by batch experiments, using 137Cs extracted from tea, contaminatd by the Chernobyl accident, with water. The variation of Kd values was studied as a function of contact time and a volume-solid ratio (V/m). The equilibration time of...

The migration behavior of 137Cs extracted from the contaminated tea at Chernobyl accident in sandy clay soil has been studied by batch and column experiments. Time dependent sorption behavior of 137Cs extracted from the tea reaches equilibrium slower by 6.5 times than 137Cs+ ions. However, the distribution coefficient of 137Cs extracted from the te...

The migration behavior of 137Cs extracted from the contaminated tea at Chernobyl accident in sandy clay soil has been studied by batch and column experiments. Time dependent sorption behavior of 137Cs extracted from the tea reaches equilibrium slower by 6.5 times than 137Cs+ ions. However, the distribution coefficient of 137Cs extracted from the te...