Browsing by Author "Ersez, T"

Now showing 1 - 11 of 11
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    Calculation of the core parameters measured during the commissioning of the OPAL Reactor
    (American Nuclear Society, 2010-05-12) Villarino, EA; Hergenreder, DF; Braoudakis, G; Ersez, T
    The OPAL Research reactor is a multi-purpose open-pool type reactor. The nominal fission power of the reactor is 20 MW. It was commissioned during the second half of the year 2006. The reactor has several nuclear safety related design criteria that have to be experimentally verified during Stage B of the commissioning of the reactor. The present work presents the measurements carried out during the Stage B of the commissioning of the OPAL reactor, and the numerical verification of the calculated values using the design calculation methodology against these measured values. A brief description of the OPAL reactor, its commissioning plan, its nuclear safety related design criteria and the calculation and the experimental methodology are presented. The measured values and a comparison with the calculated is also given.
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    Contract performance demonstration tests in the OPAL
    (International Atomic Energy Agency, 2007-11-08) Hergenreder, DF; Lecot, CA; Lovotti, O; Villarino, EA; Braoudakis, G; Ersez, T
    This paper will describe the measurements and calculations that were done in the OPAL Reactor to demonstrate compliance against contractual Design Features and Performance Acceptance Criteria. The contract specifies several neutronic aspects to be fulfilled by the core, the irradiation and the beam facilities design, which have to be verified during the commissioning tests. Guaranteed flux values will be taken as being for equilibrium core conditions. The relationship between values measured during commissioning (First Core) and the guaranteed values is largely based on calculations. The calculated values are obtained modelling with full detail the measurement conditions using the INVAP traditional calculation lines: CITVAP and MCNP calculation lines. © The Authors
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    Diffuse neutron scattering studies of single crystal specimens of Fe3-x MnxSi
    (Australian and New Zealand Institutes of Physics, 1994-02-09) Ersez, T; Kennedy, SJ; Hicks, TJ; Kepa, H
    Polarized neutron diffuse scattering measurements have been made of two single crystal specimens of the ordered intermetallic compounds Fe2.45Mno.55Si (at room temperature and Fe2MnSi (above and below the re-ordering temperature). The difference between spin-flip and non-spin-flip scattering cross-sections for the (111) position gave a negative diffuse peak around a positive Bragg peak, being more pronounced for the Fe2.45Mno.55Si crystal. This is consistent with a loss of moment on the B(Fe/Mn) site with addition of Mn. Preliminary model fitting has suggested that Mn atoms cluster on their preferred B-site.
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    Radiation shielding design for neutron diffractometers assisted by Monte Carlo methods
    (Elsevier B. V., 2006-11-15) Osborn, JC; Ersez, T; Braoudakis, G
    Monte Carlo simulations may be used to model radiation shielding for neutron diffractometers. The use of the MCNP computer program to assess shielding for a diffractometer is discussed. A comparison is made of shielding requirements for radiation generated by several materials commonly used in neutron optical elements and beam stops, including lithium-6 based absorbers where the Monte Carlo method can model the effects of fast neutrons generated by this material. Crown copyright © 2006 Published by Elsevier B.V.
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    Radiation shielding design for neutron diffractometers assisted by Monte Carlo methods
    (The Bragg Institute, Australian Nuclear Science and Technology Organisation, 2005-11-27) Ersez, T; Braoudakis, G; Osborn, JC
    The absorption and scattering of neutrons by neutron optical elements, beam stops and other components present significant radiation shielding challenges due to the generation of gamma radiation. In the case of neutron absorbers incorporating lithium- 6, fast neutrons are also generated. We show how Monte Carlo simulations using the MCNP computer code may be used to model the radiation fields produced by such components, thereby assisting in the choice of materials for shutters and other elements and assisting in the design of shielding. We discuss the use of these techniques to model instrument shielding bunkers, comprised principally of lead walls with boron-containing linings, for diffractometers at the OPAL Reactor, ANSTO. © 2005 The Authors
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    Radiation shielding for neutron guides
    (Elsevier B. V., 2006-11-15) Ersez, T; Braoudakis, G; Osborn, JC
    Models of the neutron guide shielding for the out of bunker guides on the thermal and cold neutron beam lines of the OPAL Reactor (ANSTO) were constructed using the Monte Carlo code MCNP 4B. The neutrons that were not reflected inside the guides but were absorbed by the supermirror (SM) layers were noted to be a significant source of gammas. Gammas also arise from neutrons absorbed by the B, Si, Na and K contained in the glass. The proposed shielding design has produced compact shielding assemblies. These arrangements are consistent with safety requirements, floor load limits, and cost constraints. To verify the design a prototype was assembled consisting of 120 mm thick Pb(96%)Sb(4%) walls resting on a concrete block. There was good agreement between experimental measurements and calculated dose rates for bulk shield regions. Crown Copyright © 2006 Published by Elsevier B.V.
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    Radiation shielding for neutron guides
    (The Institution of Engineers Australia, 2005-11-27) Ersez, T; Braoudakis, G; Osborn, JC
    Models of the neutron guide shielding for the out of bunker guides on the thermal and cold neutron beam lines of the OPAL Reactor (ANSTO) were constructed using the Monte Carlo code MCNP 4B. The neutrons that were not reflected inside the guides but were absorbed by the supermirror (SM) layers were noted to be a significant source of gammas. Gammas also arise from neutrons absorbed by the B, Si, Na and K contained in the glass. The proposed shielding design has produced compact shielding assemblies. These arrangements are consistent with safety requirements, floor load limits, and cost constraints. To verify the design a prototype was assembled consisting of 120mm thick Pb(96%)Sb(4%) walls resting on a concrete block. There was good agreement between experimental measurements and calculated dose rates for bulk shield regions. © The Authors
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    Recent upgrades to ANSTO’s thermal neutron spectrometer, TAIPAN
    (Australian Institute of Physics, 2018-01-30) Rule, KC; Darmann, F; Oste, T; Olsen, SR; Bartlett, D; Franceschini, F; Berry, A; McGregor, A; Ogrin, A; Ersez, T; Kafes, A; Pangelis, S; Danilkin, SA; Stampfl, APJ
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    Recent upgrades to ANSTO’s thermal triple axis spectrometer ‘TAIPAN’
    (Australian Institute of Nuclear Science and Engineering, 2016-11-29) Rule, KC; Olsen, SR; Danilkin, SA; Darmann, F; Oste, T; Bartlett, D; Kafes, T; Mcgregor, A; Stampfl, APJ; Ersez, T; Orgrin, A
    The thermal triple axis spectrometer, TAIPAN, has been operational since 2010 and employs a graphite monochromator to access neutron energy transfers up to 80meV. A recent string of projects have greatly increased the capabilities of this instrument. Initially the wall shared with the cold TAS, SIKA, was modified to allow access to larger regions of Q-Energy space for TAIPAN. A more recent upgrade project has involved developing a new sapphire filter translation stage mechanism and a new Cu-200 double-focussing monochromators. The copper monochromator has been installed back to back with the previous highly ordered PG-monochromator and extends the accessible energy range of the neutrons from 70meV to 180meV.
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    Small angle and inelastic scattering investigation of nanodiamonds
    (International Conference on Neutron Scattering, 2017-07-12) Osborn, JC; Ersez, T; Lu, W
    Nanodiamond material (~5 nm diameter diamond particles) has the potential to be used in the design of the next generation of cold neutron sources (CNS). It is hoped that a blanket layer of this material surrounding the CNS moderator vessel will reflect very cold neutrons back into the moderator, thus reducing leakage through the vessel wall. In this work nanodiamonds produced by two different techniques have been studied, namely those prepared by the detonation method and by laser ablation of a carbon-hydrocarbon mixture. The analysis of experimental data from USANS, SANS and SAXS measurements performed at Australia’s OPAL reactor suggests that large scale structure such as clustering or aggregation of nanodiamond particles may be determining the scattering. The generalised density of states (GDOS) obtained at 20 K from TOF inelastic neutron scattering measurements showed no low energy states. The GDOS of heated and unheated samples at 300 K are consistent with the proposition that thermal treatment of nanodiamond samples eliminates hydrogen in the form of water absorbed on the nanoparticle surface. Hydrogen bonded to carbon is difficult to remove by thermal treatment.
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    Studies of magnetic structure of La1-xSrxMnO3 colossal magnetoresistive perovskites
    (Australian Institute of Physics, 2004-02-04) Finlayson, TR; Wu, X; Ersez, T; Schulz, JC
    This class of materials, based on the compound LaMnO3, continues to be the focus of attention because they exhibit colossal magnetoresistance (CMR) [1] which could lead to possible applications in magnetic recording and field sensors. In addition to the technological applications, the materials are important from a fundamental point of view due to the strong correlations between transport, structural and magnetic behaviour. The origin of the CMR effect has been attributed to the presence of magnetic polarons above the ferromagnetic ordering temperature, Tc. From recent research, using a combination of powder neutron diffraction, polarisation analysis and small-angle neutron scattering together with magnetic measurements, we present diffuse scattering, spin dynamics and lattice and magnetic correlations results for the La1-xSrxMnO3 (x=0.125 and 0.175) compounds. The diffuse scattering in the neutron diffraction patterns increases as the temperature approaches Tc from low temperature and continues to increase above Tc. The scattering peak in the forward direction above Tc (Tc