Adem Acır

Application of regression and artificial neural network analysis in modelling of tool-chip interface temperature in machining

In this paper, the regression analysis (RA) and artificial neural network (ANN) are presented for the prediction of tool-chip interface temperature depends on cutting parameters in machining. The RA and ANN model for prediction tool-chip interface temperature are developed and mathematical equations derived for tool-chip interface temperature prediction are obtained. The tool-chip interface temperature results obtained from mathematical equations with RA and ANN model and the experimental results available in the literature obtained by using AISI 1117 steel work piece with embedded K type thermocouple into the uncoated cutting tool (Korkut, Boy, Karacan, & Seker, 2007) are compared. The coefficient of determination (R^2) both training and testing data for temperature prediction in the ANN model are determined as 0.999791289 and 0.997889303 whereas; R^2 for both training and testing data in the RA model are computed as 0.999063 and 0.999427, respectively. The correlation obtained by the training ANN model are better than the one obtained by training RA model. The training ANN model with the Levenberg-Marquardt (LM) algorithm provides more accurate prediction and is quite useful in the calculation of tool-chip interface temperature when compared with the trained RA method in machining. On the other hand, prediction values obtained the testing RA model is slightly better performance than the testing ANN model. The results show that the tool-chip interface temperature equation derived from RA and ANN model can be used for prediction.

Effects of spectral shifting in an inertial confinement fusion system

Abstract The main objective is to study the effects of spectral shifting in an inertial confinement system for kT/shot energy regime on the breeding performance for tritium and for high quality fissile fuel. A protective liquid droplet jet zone of 2 m thickness is used as coolant, energy carrier, and breeder. Flibe as the main constituent is mixed with increased mole-fractions of heavy metal salt (ThF4 or UF4) starting by 2 moles% up to 12 moles%. Spectrum softening within the inertial confinement system reduces the tritium production ratio (TBR) in the protective coolant to a lower level than unity. However, additional tritium production in the 6Li2DT zone of the system increases TBR to values above unity and allows a continuous operation of the power plant with a self-sustained fusion fuel supply. By modest fusion fuel burn efficiencies (40 to 60 %) and with a few mol.% of heavy metal salt in the coolant in form of ThF4 or % UF4, a satisfactory TBR of > 1.05 can be realized. In addition to that, excess fissile fuel of extremely high isotopic purity with a rate of ∼ 1000 kg/year of 233U or 239Pu can be produced. Radiation damage through atomic displacements and helium gas production after a plant operation period of 30 years is very low, namely dpa < 1 and He < 2 ppm, respectively.

Effect of Feed Rate on Tool Wear in Milling of Al-4%Cu/B4 C p Composite

The effect of feed rate on tool wear in milling of B4C p reinforced aluminum metal matrix composites (MMCs), produced by liquid phase sintering method, was investigated. Milling experiments on these composites were conducted with three different types of cementide carbide tools (uncoated, double coated (TiN + TiAlN) and triple coated (TiCN + Al2O3 + TiN)) for three different feed rates of 0.15 mm/z, 0.20 mm/z, and 0.25 mm/z. After milling experiments, an optical microscope was used to measure the magnitude of flank wear on the tools. Flank wear limit value, (V B ) = 0.3 mm was selected as a reference value for comparison of these tools. On the other hand, tool wear mechanisms were examined with the help of a scanning electron microscope (SEM). Experimental results indicated that higher feed rates led to lower tool wear for all type of tools and coated tools exhibited better performance than uncoated tool with respect to the flank wear.

Minor actinide burning in a CANDU thorium reactor

Abstract Nuclear waste actinides can be used as a booster fissile fuel material in form of mixed fuel with thorium in a CANDU reactor in order to assure the initial criticality at startup. Two different fuel compositions have been found useful to provide sufficient reactor criticality over a long operation period: 1) 95% thoria (ThO2)+5% minor actinides MAO2 and 2) 90% ThO2+5% MAO2+5% UO2. The latter allows a higher degree of nuclear safeguarding through denaturing the new 233U fuel with 238U. The temporal variation of the criticality k∞ and the burn-up values of the reactor have been calculated by full power operation for a period of 10 years. The criticality starts by k∞>1.3 for both fuel compositions. A sharp decrease of the criticality has been observed in the first year as a consequence of rapid plutonium burnout in the actinide fuel. The criticality becomes quasi constant after the 2nd year and remains close to k∞ = ∼1.06 for ∼10 years. After the 2nd year, the CANDU reactor begins to operate practically as a thorium burner. Very high burn up could be achieved with the same fuel material (up to 200000 MW.D/MT), provided that the fuel rod claddings would be replaced periodically (after every 50000 or 100000 MW.D/MT). The reactor criticality can be maintained until a great fraction of the thorium fuel is burnt up. This would reduce fuel fabrication costs and nuclear waste mass for final disposal per unit energy drastically.

Investigation of varying dead state temperatures on energy and exergy efficiencies in thermal power plant

In this study, the energy and exergy analysis of a 160 MW Cayorhan thermal power plant, which is operational in Ankara, Turkey, is performed. The effects of varying dead state temperatures on energy and exergy in the plant are investigated. Exergy destruction (irreversibility), entropy generation, per cent ratio to exergy destruction and heat loss, energy and exergy efficiencies are determined for the dead state temperatures ranging from 5 to 30uC. The varying dead state temperatures do not have an effect on the energy efficiency (first law efficiency), whereas they affect the exergy efficiency (second law efficiency). The energy efficiency is computed as 42?76% for the whole plant. The exergy efficiency values for the whole plant are obtained as 35?62 and 32?97% for varying dead state temperature values between 5 and 30uC respectively. It is observed that dead state temperatures directly affect the exergy efficiency of the thermal power plant. In addition, the comparison between heat losses and exergy destruction of the individual component of the plant shows that the maximum heat losses occur in the condenser, whereas the maximum exergy destruction occurs in the boiler for all the reference state temperatures. Furthermore, the analysis shows that the boiler is the major source of irreversibility in the plant.

Neutronic analysis of a high power density hybrid reactor using innovative coolants

In this study, neutronic investigation of a deuterium-tritium (DT) driven hybrid reactor using ceramic uranium fuels, namely UC, UO2 or UN under a high neutron wall load (NWL) of 10MW/m2 at the first wall is conducted over a period of 24 months for fissile fuel breeding for light water reactors (LWRs). New substances, namely, Flinabe or Li20Sn80 are used as coolants in the fuel zone to facilitate heat transfer out of the blanket. Natural lithium is also utilized for comparison to these two innovative coolants. Neutron transport calculations are performed on a simple experimental hybrid blanket with cylindrical geometry with the help of the SCALE 4.3 System by solving the Boltzmann transport equation with the XSDRNPM code in 238 neutron groups and an S8-P3 approximation. The investigated blanket using Flinabe or Li20Sn80 shows better fissile fuel breeding and fuel enrichment characteristics compared to that with natural lithium which shows that these two innovative coolants can be used in hybrid reactors for higher fissile fuel breeding performance. Furthermore, using a high NWL of 10MW/m2 at the first wall of the investigated blanket can decrease the time for fuel rods to reach the level for charging in LWRs.

Performance analysis of 233U for fixed bed nuclear reactors

Abstract Criticality and burn up behavior of the Fixed Bed Nuclear Reactor (FBNR) are investigated for the mixed fuel 233UO2/ThO2 as an alternative to low enriched 235UO2 fuel. CERMET fuel with a zirconium matrix and cladding has been used throughout the study. The main results of the study can be summarized as follows: Reactor criticality is already achieved by ∼2% 233UO2 with the mixed 233UO2/ThO2 fuel. At higher 233U fractions, reactor criticality rises rapidly and exceeds keff > 1.5 already by 9% 233UO2. With 100% 233UO2, start up criticality can reach keff = 2.0975. Time dependent reactor criticality keff and fuel burn up have been investigated for two different mixed fuel 233UO2/ThO2 compositions, namely: 4% 233UO2 + 96% ThO2 for a reactor power of 40 MWel (120 MWth) and 9% 233UO2 + 91% ThO2 for a reactor power of 70 MWel (210 MWth). Sufficient reactor criticality (keff > 1.06) for continuous operation without fuel change can be sustained during ∼5 and 12 years with 4% and 9% 233UO2 fractions in the mixed fuel, leading to burn ups of ∼36000 and >105000MWD/t, respectively. Thorium based fuel produces no prolific uranium. Plutonium production remains negligible.

On the Surface Roughness of Al-4%Cu/B4C Metal Matrix Composites Machined by Milling Operation

In this study, the influence of cutting speed, feed rate and type of cutting tools on the surface roughness of the boron carbide particle reinforced aluminum composites in the milling operation was investigated. For this purpose, the composite samples were produced using powder metallurgy route. And then, the milling operations were carried out by using three different cutting tools at various feed rates (0.15, 0.20 and 0.25 mm/z) and cutting speeds (100, 130, 169 and 220 m/min). Experimental results showed that the surface roughness of the composites decreased significantly by increasing the cutting speed for all tools. Moreover, it was gradually increased for all tools when the feed rate was increased at the cutting speeds of 169 and 220 m/min.

Energy and exergy analyses of a new solar air heater with circular-type turbulators having different relief angles

In this study, energy and exergy analyses of a new SAHs with circular-type turbulators are performed. Experiments are conducted for 0.0023, 0.0033, 0.0044 and 0.0055 kg/s, respectively. While the energy efficiency values are obtained between 28.6% and 79.5%, the exergy efficiency values are calculated between 8.1% and 42.4%. Type II, which has 45° obstacle relief angle and 0.0055 kg/s mass flow rate, shows the highest energy and exergy efficiencies among all the considered cases. The lowest energy and exergy efficiencies are obtained in Type I case, which has no obstacles and has a 0.0023 kg/s mass flow rate. According to the uncertainty analyses that are made, uncertainties of energy efficiencies are obtained between 0.53% and 1.06% whereas uncertainties for exergy efficiencies are varied between 0.27% and 5.4% for all the investigated cases. In addition, the obtained energy and exergy efficiency results are compared with results given in the literature.

Reduction of Weapon Grade Plutonium Inventories in a Thorium Burner

Large quantities of weapon grade (WG) plutonium have been accumulated in the nuclear warheads. Plutonium and heavy water moderator can give a good combination with respect to neutron economy. TRISO type fuel can withstand very high fuel burn up levels. The paper investigates the prospects of utilization of TRISO fuel made of WG-plutonium in CANDU reactors. Three different fuel compositions have been investigated: 1: 90 % ThC + 10 % PuC, 2: 70 % ThC + 30 % PuC and 3: 50 % ThC + 50 % PuC. The temporal variation of the criticality k∞ and the burn-up values of the reactor have been calculated by full power operation up to 17 years. Calculated startup criticalities for these fuel modes are k∞,0 = 1.6403, 1.7228, 1.7662, respectively. Attainable burn up values and reactor operation times with the same fuel charge will be 94 700, 265 000, 425 000 MW.D/MT and ~ 3.5, 10, 17 years, respectively. These high burn ups would reduce fuel fabrication costs and nuclear waste mass for final disposal per unit energy drastically.