Browsing by Author "Celik, Yurdunaz"

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Citation Count: 9
Comparisons of the Calculations Using Different Codes Implemented in Mcnpx Monte Carlo Transport Code for Accelerator Driven System Target
(Amer Nuclear Soc, 2012) Sarer, Basar; Şahin, Sümer; Sahin, Sumer; Gunay, Mehtap; Celik, Yurdunaz; Department of Mechanical Engineering
The MCNPX code offers options based on physics packages; the Bertini, ISABEL, INCL4 intra-nuclear models, and Dresner, ABLA evaporation-fission models and CEM2k cascade-exciton model. The study analyzes the main quantities determining ADS performance such as neutron yield, neutron leakage spectra, and neutron and proton spectra in the target and in the beam window calculated by the MCNPX-2.5.0 Monte Carlo transport code, which is a combination of LAHET and MCNP codes. The results obtained by simulating different models, cited above and implemented in MCNPX are compared with each other. The investigated system is composed of a natural lead cylindrical target and stainless steel (HT9) beam window. Target has been optimized to produce maximum number of neutrons with a radius of 20 cm and 70 cm of height. Target is bombarded with a high intensity linear accelerator by a 1 GeV, 1 mA proton beam. The protons are assumed uniformly distributed across the beam of radius 3 cm, and entering the target through a hole of 5.3 cm radius. The proton beam has an outer radius of 5.3 cm and an inner radius 5.0 cm. The maximum of the neutron flux in the target is observed on the axis similar to 10 cm below the beam window, where the maximum difference between 7 different models is similar to 15 %. The total neutron leakage out of the of the target calculated with the Bertini/ABLA is 1.83x10(17) n/s, and is about 14 % higher than the value calculated by the INCL4/Dresner (1.60x10(17) n/s). Bertini/ABLA calculates top, bottom and side neutron leakage fractions as 20 %, 2.3 %, 77.6 % of the total leakage, respectively, whereas, they become 18.6 %, 2.3 %, 79.4 % with INCL4/Dresner combination.
Citation Count: 11
Energy Multiplication and Fissile Fuel Breeding Limits of Accelerator-Driven Systems With Uranium and Thorium Targets
(Pergamon-elsevier Science Ltd, 2015) Sahin, Sumer; Şahin, Sümer; Sarer, Basar; Celik, Yurdunaz; Department of Mechanical Engineering
The study analyses the integral U-233 and Pu-239 breeding rates, neutron multiplication ratio through (n,xn)- and fission-reactions, heat release, energy multiplication and consequently the energy gain factor in infinite size thorium and uranium as breeder material in an accelerator driven systems (ADS), irradiated by a 1-GeV proton source. Energy gain factor has been calculated as M-energy = 1.67, 4.03 and 5.45 for thorium, depleted uranium (100% U-238) and natural uranium, respectively, where the infinite criticality values are k(infinity) = 0.40, 0.752 and 0.816. Fissile fuel material production is calculated as 53 Th-232(n,gamma)U-233, 80.24 and 90.65 U-238(n,gamma)Pu-239 atoms per incident proton, respectively. The neutron spectrum maximum is by similar to 1 MeV. Lower energy neutrons E < 1 MeV have major contribution on fissile fuel material breeding (>97.5%), whereas their share on energy multiplication is negligible (0.2%) for thorium, depleted uranium. Major fission events occur in the energy interval 1MeV < E < 50 MeV. Copyright (C) 2015, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.
Citation Count: 7
Evaluation of Integral Quantities in an Accelerator Driven System Using Different Nuclear Models Implemented in the Mcnpx Monte Carlo Transport Code
(Pergamon-elsevier Science Ltd, 2013) Sarer, Basar; Şahin, Sümer; Sahin, Sumer; Celik, Yurdunaz; Gunay, Mehtap; Department of Mechanical Engineering
The MCNPX code offers options based on physics packages; the Bertini, ISABEL, INCL4 intra-nuclear models, and Dresner, ABLA evaporation-fission models and CEM2k cascade-exciton model. This study analyzes the main quantities determining ADS performance, such as neutron yield, neutron leakage spectra, heating and neutron and proton spectra in the target and in the beam window calculated by the MCNPX-2.5.0 Monte Carlo transport code, which is a combination of LAHET and MCNP codes. The results obtained by simulating different models cited above and implemented in MCNPX are compared with each other. The investigated system is composed of a natural lead cylindrical target and stainless steel (HT9) beam window. The target has been optimized to produce maximum number of neutrons with a radius of 20 cm and 70 cm of height. The target is bombarded with a high intensity linear accelerator by a 1 GeV, 1 mA proton beam. The protons are assumed uniformly distributed across the beam of radius 3 cm, and entering the target through a hole of 5.3 cm radius. The proton beam has an outer radius of 53 cm and an inner radius of 5.0 cm. The maximum value of the neutron flux in the target is observed on the axis similar to 10 cm below the beam window, where the maximum difference between 7 different models is similar to 15%. The total neutron leakage of the target calculated with the Bertini/ABLA is 1.83 x 10(17) n/s, and is about 14% higher than the value calculated by the INCL4/Dresner (1.60 x 10(17) n/s). Bertini/ABLA calculates top, bottom and side neutron leakage fractions as 20%, 2.3%, 77.6% of the total leakage, respectively, whereas, the calculated fractions are 18.6%, 2.3%, 79.4%, respectively, with INCL4/Dresner combination. The largest heat deposition density by considering all particles in the beam window calculated with CEM2k model is 104 W/cm(3)/mA, which is 9.0% greater than the lowest value predicted with INCL4/Dresner model (95.4 W/cm(3)/mA). The maximum average heat deposition density for all particles in the target is calculated as 6.87 W/cm(3)/mA with INCL4/ABLA. (C) 2013 Elsevier Ltd. All rights reserved.
Citation Count: 10
Neutronic Investigations of a Laser Fusion Driven Lithium Cooled Thorium Breeder
(Pergamon-elsevier Science Ltd, 2014) Sahin, Sumer; Şahin, Sümer; Sarer, Basar; Celik, Yurdunaz; Department of Mechanical Engineering
The paper investigates the main parameters of a Laser Inertial Confinement Fusion Fission Energy (LIFE) driven thorium breeder. A similar blanket to the (LIFE) engine design in Lawrence Livermore National Laboratory is chosen in order to allow mutual feedback between two geographically separated teams towards a more advanced and improved design under consideration of totally independent views. In the basic design, frozen (D,T) fusion fuel ice is shot to the center of 5 m diameter spherical fusion reactor chamber cavity in pulsed mode (10-30 Hz). Fusion fuel burns through direct or indirect laser beam irradiation. The first wall surrounds the fusion chamber and is made of S-304 steel (2 cm). The fusion reactor cavity is kept in high vacuum. It is followed by a natural lithium coolant zone. A 2nd S-304 layer (2 cm) separates the lithium zone on the right side from the graphite reflector (30 cm). The outer boundary of the graphite reflector is also covered with a 3rd S-304 layer (2 cm). The calculations have been performed for a fusion driver power of 500 MWth with the last available version of MCNP, namely with MCNPX-2.7.0. In the first calculation phase, the thickness of the natural lithium coolant-tritium breeder zone (MU has been varied as 50, 60, 70, 80, 90 and 100 cm to select the coolant thickness Delta R-Li; to have a satisfactory tritium breeding ratio (TBR) for continuous fusion reactor operation. For a pure fusion blanket without any fissionable elements in the coolant, TBR values are calculated as 1.237, 1.312, 1.370, 1.415, 1.449 and 1.476, respectively, for corresponding coolant thicknesses. A Delta R-Li value of 50 cm would keep TBR > 1.05 for self-sustaining tritium supply. These Delta R-Li values lead to blanket energy multiplication values of M = 1.209, 1.216, 1.219, 1.222, 1.223 and 1.224, respectively, and have been calculated, as a result of exoenergetic neutron absorption in Li-6. For coolant thickness values >50 cm, the increase of "M" would remain minor. In the second phase, ThO2 has been suspended in the form of micro-size tristructural-isotropic (TRISO) particles in the lithium coolant for U-233 breeding. TRISO fuel has the great advantage of high mechanical stability. Furthermore, fission products will be separated from the coolant. TRISO particles have been dispersed homogenously in the lithium coolant with volume fractions V-tr = 1, 2, 3, 4, 5 and 10 vol-%. Calculations with Delta R-Li = 50 cm and by variable V-tr result with TBR = 1.229, 1.222, 1.214, 1.206, 1.1997 and 1.1622, respectively. Parasitic neutron absorption in Thorium decreases the TBR values. For V-tr < 5 vol-% TRISO in the coolant, the increase of the neutron absorption in thorium will be compensated to a great degree through neutron multiplications via Th-232(n,f) and Th-232(n,2n) reactions so that the sacrifice on TBR remains acceptable. However, for V-tr 5 TRISO vol-%, neutron absorption in thorium reduces TBR drastically. On the other hand, the blanket energy multiplication M increases with thorium volume fraction, namely as M = 1.2206, 1.2322, 1.2426, 1.2536, 1.2636, 1.3112 for respective TRISO volume fractions due to the contribution of fission energy. Fissile fuel productions in the blanket are calculated as 17.23, 33.09, 48.66, 64.21, 79.77 and 159.71 U-233 (kg/year), respectively. (C) 2014 Elsevier Ltd. All rights reserved.
Citation Count: 2
Radiation Source Terms of Myrrha Reactor Components and Equipment
(Pergamon-elsevier Science Ltd, 2016) Celik, Yurdunaz; Şahin, Sümer; Stankovskiy, Alexey; Engelen, Jeroen; Van den Eynde, Gert; Sarer, Basar; Sahin, Sumer; Department of Mechanical Engineering
In-vessel structural components of nuclear reactors are subject to prompt and residual neutron and photon activation. The MYRRHA fast spectrum facility, when operated in sub critical mode, suffers additional activation due to a wide range of energetic particles produced in the interactions of 600 MeV-primary protons with matter. The purpose of this work was to assess the source term (activation, heating and induced radiation level) of ex core equipment and components located inside the reactor vessel. Numerous stainless steel samples uniformly distributed inside the vessel have been used to simulate the activation of equipment in order to take into account the perturbation of the neutron spectrum caused by structural materials of components and equipment. The calculated quantities were prompt and residual activation, heating, radiation dose and radiation damage. The calculations were carried out with the ALEPH2 depletion code which invokes the MCNPX code for radiation transport. Copyright (C) 2016, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.
Citation Count: 11
Utilization of Nuclear Waste Plutonium and Thorium Mixed Fuel in Candu Reactors
(Wiley, 2016) Sahin, Sumer; Şahin, Sümer; Sarer, Basar; Celik, Yurdunaz; Department of Mechanical Engineering
Spent nuclear fuel out of conventional light water reactors contains significant amount of even plutonium isotopes, so called reactor grade plutonium. Excellent neutron economy of Canada deuterium uranium (CANDU) reactors can further burn reactor grade plutonium, which has been used as a booster fissile fuel material in form of mixed ThO2/ PuO2 fuel in a CANDU fuel bundle in order to assure reactor criticality. The paper investigates incineration of nuclear waste and the prospects of exploitation of rich world thorium reserves in CANDU reactors. In the present work, the criticality calculations have been performed with 3-D geometrical modeling of a CANDU reactor, where the structure of all fuel rods and bundles is represented individually. In the course of time calculations, nuclear transformation and radioactive decay of all actinide elements as well as fission products are considered. Four different fuel compositions have been selected for investigations: 95% thoria (ThO2) + 5% PuO2,. 90% ThO2 + 10% PuO2,. 85% ThO2 + 15% PuO2 and. 80% ThO2 + 20% PuO2. The latter is used for the purpose of denaturing the new U-233 fuel with U-238. The behavior of the criticality k8 and the burnup values of the reactor have been pursued by full power operation for similar to 10 years. Among the investigated four modes, 90% ThO2 + 10% PuO2 seems a reasonable choice. This mixed fuel would continue make possible extensive exploitation of thorium resources with respect to reactor criticality. Reactor will run with the same fuel charge for similar to 7 years and allow a fuel burnup similar to 55 GWd/ t. Copyright (C) 2016 John Wiley & Sons, Ltd.