Person: AKYÜREK, TAYFUN
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AKYÜREK
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TAYFUN
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Publication Open Access Voltage dependent pulse shape analysis of Geiger-Muller counter(KOREAN NUCLEAR SOC, 2019-07) AKYÜREK, TAYFUN; Almutairi, B.; Akyurek, T.; Usman, S.Detailed pulse shape analysis of a Geiger-Mfiller counter is performed to understand the pulse shape dependence on operating voltage. New data is presented to demonstrate that not all pulses generated in a GM counter are identical. In fact, there is a strong correlation between the operating voltage and the pulse shape. Similar to detector deadtime, pulse shapes fall in three distinct regions. For low voltage region, where deadtime was reported to reduce with increasing voltage, pulse generated in this region was observed to have a fixed pulse width with a variable tail. The pulse width and fall time of the tail was observed to be a function of applied voltage; exponentially reducing with increasing voltage with an exponent of negative 6E-04 and 2E-03 respectively. The second region showed a pulse without any significant tail. During this time the detector deadtime was earlier reported to be at its minimum. The highest voltage region demonstrated a different deadtime mechanism where the second pulse was reduced in width. During this time the deadtime seemed to be increasing with increasing voltage. This data allows us to gain some unique insight into the phenomenon of GM detector deadtime not reported thus far. (C) 2019 Korean Nuclear Society, Published by Elsevier Korea LLC.Publication Metadata only Neutron reflector analysis for the beam-port of the Missouri S&T Reactor(SPRINGER, 2019) AKYÜREK, TAYFUN; Akyurek, Tayfun; Vaz, Warren S.; Alajo, Ayodeji B.; King, Jeffrey C.; Usman, Shoaib; Giraldo, Carlos H. C.A preliminary neutron reflector material selection and feasibility study of an inexpensive reflector replacement for the neutron beam-port at the 200 kW Missouri University of Science and Technology Research Reactor (MSTR) was conducted using Monte-Carlo techniques. The Monte-Carlo N-Particle transport code (MCNP6.1) was used to model the neutron beam-port of the Missouri S&T Reactor in order to study the effects of adding different reflector materials, in terms of the neutron flux reaching the radiography/tomography facility in front of MSTR's neutron beam-port. Aluminum, beryllium, titanium, nickel, nickel-58, lead, bismuth, tungsten and stainless steel reflectors were modeled to find the best neutron reflector for the beam-port. After examining reflector materials, it was concluded that none of them were an improvement over the current design. Experimental thermal flux was measured to be 1.0 x 10(7) +/- 3.16 x 10(3) cm(-2) s(-1) at the exit of beam port for current version of beam-port. The current ratio of beam port inlet and outlet obtained from simulations was found to be 3.37 x 10(4). The flux of beam port inlet was determined on the order of 1.0 x 10(11) cm(-2) s(-1) which is consistent with previous findings.Publication Metadata only Neutron flux characterization of the beam port of the Missouri University of Science and Technology Reactor(SPRINGER, 2019) AKYÜREK, TAYFUN; Albarqi, Mubarak; Alsulami, Raed; Akyurek, Tayfun; Graham, JosephNeutron activation analysis was used to determine the thermal and epithermal neutron flux and its spatial distribution at the beam port of the Missouri University of Science and Technology Research Reactor. Gold foil irradiations were conducted and the determined flux was compared to Monte Carlo radiation transport predictions using the Monte Carlo N-particle code. The average experimental thermal (E<0.55eV) and epithermal (0.55eVPublication Open Access Simultaneous experimental evaluation of pulse shape and deadtime phenomenon of GM detector(NATURE RESEARCH, 2021-12) AKYÜREK, TAYFUN; Almutairi, Bader; Alam, Syed; Goodwin, Cameron S.; Usman, Shoaib; Akyurek, TayfunAnalysis of several pulse shape properties generated by a Geiger Mueller (GM) detector and its dependence on applied voltage was performed. The two-source method was utilized to measure deadtime while simultaneously capturing pulse shape parameters on an oscilloscope. A wide range of operating voltages (600-1200 V) beyond the recommended operating voltage of 900 V was investigated using three radioactive sources (Tl-204, Cs-137, Na-22). This study investigates the relationship between operating voltage, pulse shape properties, and deadtime of the detector. Based on the data, it is found that deadtime decreases with increasing voltage from 600 to 650 V. At these low voltages (600-650 V), the collection time was long, allowing sufficient time for some recombination to take place. Increasing the voltage in this range decreased the collection time, and hence deadtime decreased. It is also observed that rise and fall time were at their highest at these applied voltages. Increasing the voltage further would result in gas multiplication, where deadtime and pulse width are observed to be increasing. After reaching the maximum point of deadtime (similar to 250 mu s at similar to 700 V), deadtime started to exponentially decrease until a plateau was reached. In this region, it is observed that detector deadtime and operating voltage show a strong correlation with positive pulse width, rise and fall time, cycle mean, and area. Therefore, this study confirms a correlation between detector deadtime, operating voltage, and pulse shape properties. The results will validate our hypothesis that deadtime phenomena at different operating voltages are phenomenologically different.Publication Open Access Delayed fast neutron as an indicator of burn-up for nuclear fuel elements(KOREAN NUCLEAR SOC, 2021-10) AKYÜREK, TAYFUN; Akyurek, T.; Shoaib, S. B.; Usman, S.Feasibility study of burn-up analysis and monitoring using delayed fast neutrons was investigated at Missouri University of Science and Technology Reactor (MSTR). Burnt and fresh fuel elements were used to collect delayed fast neutron data for different power levels. Total reactivity varied depending on the burn-up rate of fuel elements for each core configuration. The regulating rod worth was 2.07E-04 Dk/k/in and 1.95E-04 Dk/k/in for T121 and T122 core configurations at 11 inch, respectively. Delayed fast neutron spectrum of F1 (burnt) and F16 (fresh) fuel elements were analyzed further, and a strong correlation was observed between delayed fast neutron emission and burn-up. According to the analyzed peaks in burnt and fresh fuels, reactor power dependency was observed and it was determined that delayed neutron provided more reliable results at reactor powers of 50 kW and above. (c) 2021 Korean Nuclear Society, Published by Elsevier Korea LLC. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).Publication Open Access Determination of plutonium and uranium content and burnup using six group delayed neutrons(KOREAN NUCLEAR SOC, 2019-07) AKYÜREK, TAYFUN; Akyurek, T.; Usman, S.In this study, investigation of spent fuel was performed using six group delayed neutron parameters. Three used fuels (F1, F2, and F11) which are burnt over the years in the core of Missouri University of Science and Technology Reactor (MSTR), were investigated. F16 fresh fuel was used as plutonium free fuel element and compared with irradiated used fuels to develop burnup and Pu discrimination method. The fast fission factor of the MSTR was calculated to be 1.071 which was used for burnup calculations. Burnup values of F2 and F11 fuel elements were estimated to be 1.98 g and 2.7 g, respectively. Pu-239 conversion was calculated to be 0.36 g and 0.50 g for F2 and F11 elements, respectively. (C) 2019 Korean Nuclear Society, Published by Elsevier Korea LLC.Publication Open Access A new dead-time determination method for gamma-ray detectors using attenuation law(KOREAN NUCLEAR SOC, 2021-12) AKYÜREK, TAYFUN; Akyurek, T.This study presents a new dead-time measurement method using the gamma attenuation law and generalized dead-time models for nuclear gamma-ray detectors. The dead-time of the Nal(TI) detection system was obtained to validate the new dead-time determination method using very thin lead and polyethylene absorbers. Non-paralyzing dead-time was found to be 8.39 mu s, and paralyzing dead-time was found to be 8.35 mu s using lead absorber for Nal(TI) scintillator detection system. These dead-time values are consistent with the previously reported dead-time values for scintillator detection systems. The gamma build-up factor's contribution to the dead-time was neglected because a very thin material was used. (C) 2021 Korean Nuclear Society, Published by Elsevier Korea LLC.Publication Metadata only Characterization of different reactor parameters of TRIGA Mark II, PWR and VVER under various conditions(2022-06-30) AKYÜREK, TAYFUN; AKYÜREK T., AÇIKGÖZ D.Publication Open Access Experimental evaluation of the deadtime phenomenon for GM detector: deadtime dependence on operating voltages(NATURE RESEARCH, 2020-12) AKYÜREK, TAYFUN; Almutairi, Bader; Alam, Syed; Akyurek, Tayfun; Goodwin, Cameron S.; Usman, ShoaibA detailed analysis of Geiger Mueller counter deadtime dependence on operating voltage is presented in the manuscript using four pairs of radiation sources. Based on two-source method, detector deadtime is calculated for a wide range of operating voltages which revealed a peculiar relationship between the operating voltage and the detector deadtime. In the low voltage range, a distinct drop in deadtime was observed where deadtime reached a value as low as a few microseconds (22 mu s for Tl-204, 26 mu s for Cs-137, 9 mu s for Na-22). This sharp drop in the deadtime is possibly due to reduced recombination with increasing voltage. After the lowest point, the deadtime generally increased rapidly to reach a maximum (292 mu s for Tl-204, 277 mu s for Cs-137, 258 mu s for Na-22). This rapid increase in the deadtime is mainly due to the on-set of charge multiplication. After the maximum deadtime values, there was an exponential decrease in the deadtime reaching an asymptotic low where the manufacturer recommended voltage for operation falls. This pattern of deadtime voltage dependence was repeated for all sources tested with the exception of Mn-54. Low count rates leading to a negative deadtime suggested poor statistical nature of the data collected for Mn-54 and the data while being presented here is not used for any inference.Publication Open Access Effective multiplication factor and fuel temperature coefficient calculations of PWR assembly under different temperatures(2018-04-02) AKYÜREK, TAYFUN; TAYFUN AKYÜREKThis paper presents effective multiplication factor (keff) with different burnable absorbers and weight percentages at different temperatures as well as doppler coefficient results and number density calculations for Westinghouse type pressurized water reactor (PWR) Assembly. Integral fuel burnable absorber rods coated with ZrB2 and Gadolinia-Uranium (UO2-Gd2O3) integral burnable absorbers were considered to calculate reactor parameters (keff and doppler coefficient). The results compared with base fuel which does not contain burnable absorber at different temperatures. The results show that reactivity was decreased with increased temperature and doppler coefficients increased with temperatures but remained negative at all temperatures. At 1500 K, the effective multiplication factor for base fuel was found to be 1.46985 while the effective multiplication factors for 2% with Gd2O3, 8% with Gd2O3, and IFBA rods were 1.38976, 1.37574, and 1.30337 respectively.